Article

The evolution of a submarine landform record following recent and multiple surges of Tunabreen glacier, Svalbard

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Abstract

This study focuses on the glacial landform record associated with recent surge events of Tunabreen - a calving tidewater glacier in Tempelfjorden, Spitsbergen. Submarine geomorphology and recent terminal fluctuations of Tunabreen's glacier front were studied using high-resolution multibeam-bathymetric data and a range of published and remote-sensing sources, including topographic maps, satellite images and aerial photographs. The retreat moraines in the inner part of Tempelfjorden have been correlated with glacier terminus positions during retreat from the 2004 surge maximum. Glacier surface velocity and ice-front positions derived from high-resolution TerraSAR-X satellite data show ice movements at the glacier front during minor advances of the front in winter when calving is suppressed. This suggests that the moraines have formed annually during quiescent phase winter advances. Tunabreen has experienced three surges since the Little Ice Age (LIA). This is in contrast with most Svalbard surging glaciers which have long quiescent phases and have typically only undergone one or two surges during this time. The landform record in Tempelfjorden is distinguished from previously studied glacier-surge landsystems by four, well-preserved sets of landform assemblages generated by the LIA advance and three subsequent surges, all of which partly modify earlier landform records. Based on the unique landform record in Tempelfjorden, a new conceptual landsystem model for frequently surging glaciers has been put forward improving our understanding of the dynamics of the surging glaciers and, most importantly, how they can be distinguished from the climatically-controlled glaciers in the geological record.

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... The eastern part of the Wijdefjorden catchment has a glacier coverage of 41-50 % (Nuth et al., 2013). Sixty-eight percent of the total glaciated area in Svalbard is drained by tidewater glaciers, all highly vulnerable to increased submarine melt due to increasing ocean temperatures (Nuth et al., 2013;Luckman et al., 2015). The thermal regime of glaciers range from entirely cold based, polythermal to temperate with few frozen patches. ...
... Due to their transverse orientation and symmetric cross profiles, these ridges are interpreted as moraine ridges formed during stillstands and/or re-advances of the grounding line, similar to observations from other Spitsbergen fjords (e.g. Ottesen & Dowdeswell 2006;Kempf et al. 2013;Flink et al. 2015;Streuff et al. 2017). ...
... The thermal state of Svalbard glaciers has been documented to switch from polythermal to cold-based during retreat and thinning, as thinning allows for penetration of cold atmospheric temperatures to the bed of the ice (e.g., Hagen et al., 1993;Lovell et al., 2015;Farnsworth et al., 2020). Midtsundstadbreen could have switched from warm to cold after the LGM, and as the ice sheet in the northern sector had already started thinning c. 25 ka ago it is not unlikely that this switch occurred early . ...
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The Arctic regions are affected by the modern climate change to a greater extent than the global average. This effect is called the Arctic amplification and is reflected in air temperatures rising with double rate and increased precipitation compared to the global average. The climate of Svalbard is strongly related to variations in the atmospheric and oceanic circulation patterns, and the archipelago is, therefore, ideal location to study the climate sensitivity of the Arctic. This dissertation presents research on the Late Pleistocene and Holocene glacial history of Svalbard. Marine, lacustrine and terrestrial archives are assessed in a confined geographical area in northern Wijdefjorden, northern Spitsbergen, and the regional timing of the deglaciation, Holocene Thermal Maximum, Holocene Glacial Minimum as well as the onset of the Neoglacial are identified (Papers I-III). The research focus is on Wijdefjorden, Femmilsjøen and the NW part of the Åsgardfonna ice cap. The results are placed in a regional context and compared to studies across Svalbard. A review of the Holocene glacial history of Svalbard is presented in Paper IV, where all Holocene chronological data from Svalbard are re-calibrated or calculated and gathered in one database. The landforms in the fjord (Paper I) and the lowermost acoustic and sedimentary facies (Papers I-II) are interpreted to be indicative of grounded, warm-based ice occupied the fjord during the Last Glacial. By contrast, Paper III speculates that parts of the terrestrial terrain are similar to forelands of cold-based glaciers in Antarctica, which may have been covered by cold-based and little erosive glacier ice during the Last Glacial. Among the findings are that northern Svalbard deglaciated early. Wijdefjorden is inferred to deglaciate at least prior to 12.4 ± 0.3 cal. ka BP and potentially prior to 14.5 ± 0.3 cal. ka BP. Femmilsjøen deglaciated potentially prior to 16.1 ± 0.3 cal. ka BP. Deglaciation occurred in a stepwise manner and was characterised by fluctuating water temperatures and sea ice cover. Overarching, the Svalbard fjords deglaciated rapidly during the first half of the Early Holocene, however the overall retreat was punctuated by dynamic ice-advances of smaller tributary glaciers. Femmilsjøen was isolated from the marine environment c. 11.4 cal. ka BP. The regional Holocene glacial minimum coincided with the Holocene thermal maximum (between 10.1 ± 0.4 and 3.2 ± 0.2 cal. ka BP), during which time the ice cap Åsgardfonna was small or close to absent. Collectively in Svalbard, the Holocene glacial minimum most likely occurred between 8.0 and 6.0 cal. ka BP. Thus, the Holocene thermal maximum and Holocene glacial minimum in northern Wijdefjorden seems extended compared to the rest of Svalbard. In the fjord, seawater temperatures show a gentle decrease and the sea-ice proxy a gentle increase from c. 6.0 cal. ka BP, but values do not accelerate until c. 0.5 cal. ka BP. In Svalbard, Neoglacial glacier advances occurred generally from 4.0 to 0.5 cal. ka BP and with the Little Ice Age representing the last cold-spell of the Neoglacial. In Femmilsjøen, glacial influence recommenced from 3.2 ± 0.2 cal. ka BP, and glaciers in the catchment reached sizes no smaller than their current extent within c. 1.0 ka. The Holocene climate and glacial variability of Svalbard are strongly coupled to atmospheric and oceanic forcings.
... Evidence from these events shows that the active surge phase initiates after a frontal destabilization (Strozzi and others, 2017; Sevestre and others, 2018; Willis and others, 2018; Nuth and others, 2019). During the destabilization, crevassing often initiates or intensifies close to the terminus and propagates up-glacier (Flink and others, 2015; Sevestre and others, 2018). Crevasses have been shown to be able to cause a cycle of positive feedbacks in glacier dynamics by increasing surface melt-water input to the glacier bed, a feedback that was documented in detail during the surge on Basin-3 of Austfonna (Dunse and others, 2015), and has been observed on other glaciers (e.g. ...
... This area could be representative of such a source of ice, and similar thinning might have occurred elsewhere on the upper basin of Lomonosovfonna. However, this specific area touches the drainage divide of the upper basin of Tunabreen, another known surgetype tidewater glacier (Flink and others, 2015). Therefore, it is unclear if the outflow from this specific area contributed completely to the bulge of Negribreen, flowing east, or partly to Tunabreen, flowing south. ...
... Also, any pre-surge eskers are likely to be erased with the passage of the surge front. This may explain why such depositions are not seen in front of the surge glaciers Blomstrandbreen and Tunabreen, as sea-floor surveys were conducted too soon after their respective surges (Flink and others, 2015; Burton and others, 2016). ...
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Negribreen, a tidewater glacier located in central eastern Svalbard, began actively surging after it experienced an initial collapse in summer 2016. The surge resulted in horizontal surface velocities of more than 25 m d ⁻¹ , making it one of the fastest-flowing glaciers in the archipelago. The last surge of Negribreen likely occurred in the 1930s, but due to a long quiescent phase, investigations of this glacier have been limited. As Negribreen is part of the Negribreen Glacier System, one of the largest glacier systems in Svalbard, investigating its current surge event provides important information on surge behaviour among tidewater glaciers within the region. Here, we demonstrate the surge development and discuss triggering mechanisms using time series of digital elevation models (1969–2018), surface velocities (1995–2018), crevasse patterns and glacier extents from various data sources. We find that the active surge results from a four-stage process. Stage 1 (quiescent phase) involves a long-term, gradual geometry change due to high subglacial friction towards the terminus. These changes allow the onset of Stage 2, an accelerating frontal destabilization, which ultimately results in the collapse (Stage 3) and active surge (Stage 4).
... Three glaciers drain into Tempelfjorden: two land-terminating glaciers (von Postbreen and Bogebreen; Figs 1b and c), and a tidewater glacier, Tunabreen, which is also a surge-type glacier (Flink and others, 2015). Surging is a cyclical process in which a glacier alternates between quiescent periods with low velocities and frontal retreat, and short periods with high velocities, during which ice is transferred from the upper basin, and the front advances significantly into the fjord. ...
... All three glaciers are the major sediment sources in the northern basin of our study area; here, the bedrock is dominated Annals of Glaciology 3 by carbonate and evaporitic rock (Dallmann and others, 2002). Tunabreen has surged four times since the first observations were made in the early 1900s (Hagen and others, 1993), most recently in 2002-04 (Flink and others, 2015) and now again, in 2016-18 (Sevestre and others, 2018). Consequently, this means that Tempelfjorden has received varying amounts of freshwater and glacier sediment. ...
... Indeed, the high [Si(OH) 4 ] in sea ice were only observed at the glacier front in 2012, coinciding with the lowest δ 18 O values and the highest content (68%) of frozen-in freshwater. Flink and others (2015) found that ...
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The effect of freshwater sources on wintertime sea-ice CO 2 processes was studied from the glacier front to the outer Tempelfjorden, Svalbard, in sea ice, glacier ice, brine and snow. March-April 2012 was mild, and the fjord was mainly covered with drift ice, in contrast to the observed thicker fast ice in the colder April 2013. This resulted in different physical and chemical properties of the sea ice and under-ice water. Data from stable oxygen isotopic ratios and salinity showed that the sea ice at the glacier front in April 2012 contained on average 54% of frozen-in glacial meltwater. This was five times higher than in April 2013, where the ice was frozen seawater. In April 2012, the largest excess of sea-ice total alkalinity (A T), carbonate ion ([CO 3 2− ]) and bicarbonate ion concentrations ([HCO 3 − ]) relative to salinity was mainly related to dissolved dolomite and calcite incorporated during freezing of mineral-enriched glacial water. In April 2013, the excess of these variables was mainly due to ikaite dissolution as a result of sea-ice processes. Dolomite dissolution increased sea-ice A T twice as much as ikaite and calcite dissolution, implying different buffering capacity and potential for ocean CO 2 uptake in a changing climate.
... After the termination of the last major glacier advance marking the peak of the LIA in Svalbard some 100 years ago, glaciers have undergone overall retreat and negative mass balance, exposing extensive areas of formerly glaciated landscape, in both terrestrial and submarine environments (Hagen et al., 1993(Hagen et al., , 2003Nuth et al., 2013). The sedimentlandform assemblages at the recently deglaciated forefields in front of surge-type glaciers on Svalbard have been of interest for numerous studies of glacial dynamics and paleoclimate reconstructions (e.g., Boulton et al., 1996;Glasser et al., 1998;Evans, 2003;Ottesen and Dowdeswell, 2006;Ottesen et al., 2008;Flink et al., 2015Flink et al., , 2017Streuff et al., 2018). However, only a few studies have integrated data from terrestrial and submarine forefields for a holistic view of the icemarginal environment and better understanding of glacial dynamics (Boulton, 1986;Kristensen et al., 2009;Farnsworth et al., 2017;Allaart et al., 2018;Lovell et al., 2018). ...
... This highlights the importance of identifying surge-type glaciers and understanding the reason behind individual glacier advances (Lefauconnier and Hagen, 1991;Yde and Paasche, 2010;Farnsworth et al., 2016). Landsystem models have been developed to help identify undocumented surge-type glaciers (Evans andRea, 1999, 2003;Ottesen and Dowdeswell, 2006;Ottesen et al., 2008) and then modified to better depict the preservation potential and formation of sediments and landforms (Brynjólfsson et al., 2012(Brynjólfsson et al., , 2014Schomacker et al., 2014;Brynjólfsson, 2015;Flink et al., 2015;Lønne, 2016). ...
... The formation of the frontal terminal moraine is connected to bulldozing of marine muds and subglacial sediments in front of an advancing glacier terminus and/or by sediment accumulation during periods of longer terminal still stands (Solheim, 1991;Boulton et al., 1996;Kristensen et al., 2009). Similar submarine terminal moraines have been described from both non-surging and surge-type glaciers in Svalbard (Plassen et al., 2004), where the latter are often multicrested (e.g., Solheim, 1991;Boulton et al., 1999;Ottesen and Dowdeswell, 2006;Ottesen et al., 2008;Flink et al., 2015Flink et al., , 2017. The orientation of the ridge, difference in dimension and non-continuous SW part is probably because Harriet-and Kjerulfbreen were more active during the time of its formation, influencing the ridge morphology. ...
... Glacier surges pre-dating this are usually identified from aerial photographs (1930s onwards) or historical observations/written accounts (since the Little Ice Age (LIA) maximum~1900) of characteristic surge evidence, such as widespread surface crevassing and/or rapid terminus advances (e.g. Liestøl, 1969;Hagen et al., 1993;Bennett et al., 1999;Ottesen et al., 2008;Flink et al., 2015). Very little is known about surge behaviour prior to the LIA maximum. ...
... For tidewater glacier surges, this evidence is typically recorded on the sea floor (e.g. Solheim and Pfirman, 1985;Plassen et al., 2004;Ottesen et al., 2008Ottesen et al., , 2017Forwick et al., 2010;Flink et al., 2015Flink et al., , 2017Streuff et al., 2015Streuff et al., , 2018Burton et al., 2016;Farnsworth et al., 2017). Field observations of the active phase of glacier surges are rare (e.g. ...
... Lovell et al., 2015); and (iv) annual retreat moraines, marking minor winter readvances during terminus retreat in the quiescent phase (e.g. Flink et al., 2015). This landform assemblage, or slight variations of it, is found at the marine margins of several other known surge-type glaciers in Svalbard and is suggested to be diagnostic of tidewater glacier surging (Ottesen et al., 2008(Ottesen et al., , 2017Flink et al., 2015). ...
Article
Most large tidewater glaciers in Svalbard are known to have surged at least once in the last few hundred years. However, very little information exists on the frequency, timing or magnitude of surges prior to the Little Ice Age (LIA) maximum in ∼1900. We investigate the sediment-landform assemblages produced by multiple advances of the Nathorstbreen glacier system (NGS) in order to reconstruct its Late Holocene surge history. The glacier has recently undergone one of the largest surges ever observed in Svalbard, advancing ∼16 km from 2008 to 2016. We present flow velocities and ice-marginal observations (terminus change, proglacial geomorphological processes) from the later stages of this surge. A first detailed assessment of the development of a glaciotectonic mud apron within the fjord during a surge is provided. Geomorphological and sedimentological examination of the terrestrial moraine areas formed prior to the most recent surge reveals that at least two advances were responsible for their formation, based on the identification of a previously unrecognised ice-contact zone recorded by the distribution of sediment facies in coastal exposures. We distinguish between an outer, older advance to the distal part of the moraine system and an inner, younger advance to a position ∼2 km upfjord. Radiocarbon dating of shells embedded in glaciotectonic composite ridges formed by the onshore bulldozing of marine mud during the outer (older) of the two advances shows that it occurred at some point during the interval 700–890 cal. yr BP (i.e. ∼1160 AD), and not during the LIA as previously assumed. We instead attribute the inner (younger) advance to the LIA at ∼1890. By combining these data with previous marine geological investigations in inner and outer Van Keulenfjorden, we demonstrate that NGS has advanced at least four times prior to the recent 2008–2016 surge: twice at ∼2.7 kyr BP, at ∼1160 AD, and in ∼1890. This represents a unique record of the timing and magnitude of Late Holocene tidewater glacier surges in Svalbard.
... There is a change in the ridge orientation, from approximately northerly (~ 0°) trending ridges on the ice-distal side of the bay to north-westerly (~ 350°) about 1500 m from the modern glacier margin (Fig. 2a). These ridges are interpreted as De Geer moraines formed during an episodic retreat associated with periods of sea ice cover supressing calving at the ice margin and instead causing the glacier to push sediment during small readvances [43]. The irregularly arcuate shape of the ridges, their height as well as the asymmetry of the stoss and lee sides support the interpretation of De Geer moraines over crevasse-squeezed ridges (CSR), but in a surge-type setting the latter cannot be entirely excluded. ...
... The advance of Dahlbreen to 5 km (Feature 5, Fig. 2a) from its modern terminus is thus possibly also of neoglacial age but requires verification. On the basis of this complex assemblage of related glacial landforms including moraines and MSGLs in Dahlbrebukta and by analogy with similar landform assemblages in Svalbard fjords, the De Geer moraines probably formed during stepwise (potentially annual) retreat following an advance of a fast-flowing glacier [see 40,43]. ...
... Therefore, we interpret the features in Forlandsundet to have formed as ice occupied the area, probably during the transitional phase following the initial retreat of the SBSIS from its LGM extent and during the break-up of ice streams [see 5]. The smaller lineations in St. Jonsfjorden (Fig. 3c) formed at a later stage of ice retreat and potential readvance, as they are confined to the topography of this tributary fjord and terminate at the retreat moraines in the area [43]. ...
Article
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The last glacial maximum (LGM) and post-glacial Quaternary history of Forlandsundet, the strait between western Spitsbergen and Prins Karls Forland, are enigmatic. Previous terrestrial field studies report contradicting evidence for an ice sheet either overriding the entire strait or completely absent during the LGM. Here, we present a multi-proxy investigation of marine sediments, high-resolution bathymetric data and aerial imagery from Forlandsundet. We reveal glacial till present at 15 cal. ka BP and geomorphological landforms characteristic to an inter-ice-stream glaciated margin. This new evidence implies that the Forlandsundet region was fully glaciated during the LGM. This glaciation was followed by a stepwise retreat of glacial ice during the Bølling–Allerød (14.7–12.7 cal. ka BP) and Younger Dryas (12.7–11.7 cal. ka BP). The Holocene record from the marine sediments is incomplete, with a hiatus from approximately 11.8 to 7.4 cal. ka BP, interpreted as an erosive event. By the mid-Holocene (7.4 cal. ka BP), more temperate, Atlantic conditions based on the benthic foraminiferal assemblages prevailed, and are followed by gradual cooling into the late Holocene (< 4 cal. ka BP). This study provides new data to resolve the LGM extent of the Svalbard–Barents Sea ice sheet in the Forlandsundet region and sheds light on the deglacial ice dynamics in a palaeo-inter-ice-stream area driven by the inflow of warm Atlantic water.
... Forwick & Vorren 2007;Dowdeswell et al. 2016). Glacier surging is believed to be particularly widespread in Svalbard, where up to 90% of glaciers are suggested to have exhibited surge-type behaviour (Lefauconnier & Hagen 1991;Flink et al. 2015;Lovell et al. 2015Lovell et al. , 2018bFarnsworth et al. 2016Farnsworth et al. , 2017. Many surge-type glaciers drain into the fjords (or have drained in the past) in Svalbard forming tidewater margins (cf. ...
... Many surge-type glaciers drain into the fjords (or have drained in the past) in Svalbard forming tidewater margins (cf. Lefauconnier & Hagen 1991;Howe et al. 2010;Burton et al. 2015;Flink et al. 2015Flink et al. , 2016Flink et al. , 2017. Fjords preserve signatures of glacier fluctuations (both climate-induced and surge-type) as well as slope processes, resulting in a complex landform and sedimentary record. ...
... Due to the less persistent sea-ice conditions controlled by the relatively warm West Spitsbergen current, the fjords along the west coast of Spitsbergen are comparatively easier accessible and therefore better studied than their counterparts in the northern and eastern parts of Svalbard (Andersson et al. 2000;Vieli et al. 2002;Hald et al. 2004;Plassen et al. 2004;Ottesen & Dowdeswell 2006;Kristensen et al. 2009;Forwick et al. 2010;Mansell et al. 2012;Rasmussen et al. 2012;Blaszczyk et al. 2013;Flink et al. 2015;Burton et al. 2016;Ottesen et al. 2017;Butschek et al. 2019;Farnsworth et al. 2020). The first written scientific records of the extent and dynamics of the glaciers in Svalbard originate from expedition diaries of the late 19th to early 20th century (Nordenski€ old 1875;Vassiljev 1907;De Geer 1910;Gripp 1927). ...
Article
The submarine landforms and shallow sediment record are presented from Hambergbukta, southeastern Spitsbergen using swath‐bathymetric, subbottom acoustic, and sediment core data. The mapped landforms include large terminal and end‐moraines with associated debrisflow aprons on their distal flanks, drumlinized till surface, glacial lineations, medial and retreat moraines, crevasse squeeze ridge networks, eskers, as well as iceberg‐produced terraces and plough‐marks. Analysis of the landforms and landform assemblages in combination with the sediment core data and aerial imagery studies reveal a complex and dynamic glacial history of Hambergbukta. We present a detailed history of Hambergbreen glacier indicating two previously unknown surges as well as new details on the nature of the subsequent ice‐margin retreat. The results from two gravity cores combined with the shallow acoustic stratigraphy and high‐resolution bathymetry suggest that the c. AD 1900 surge was less extensive than previously thought and the retreat was most likely rapid after the c. AD 1900 and 1957 surges of the Hambergbreen. Mixed benthic foraminifera collected from the outer fjord basin date to 2456 cal. a BP, suggesting older sediments were re‐worked by the c. AD 1900 surge. This highlights the importance of exercising caution when using foraminifers for dating surge events in fjord basins enclosed by prominent end‐moraines.
... Glaciers are important indicators of climate change, with variations in flow behaviour and mass balance contributing directly to global sea level (Kodde et al., 2007;Strozzi et al., 2008;Schubert et al., 2013;Flink et al., 2015). Calving of icebergs is an important process of mass loss in many glaciers and ice sheets, and contributes significantly to the losses of high--and mid--latitude ice masses Nick and Oerlemans, 2006;Benn et al., 2007a;Benn and Evans, 2010). ...
... The focus of this study is Tunabreen, a grounded tidewater glacier located in Spitsbergen (Figure 1), part of the High--Arctic archipelago of Svalbard (Flink et al., 2015). ...
... Tunabreen drains from the Filchnerfonna and Lomonosovfonna ice caps, with its calving margin located in Tempelfjorden (Fleming et al., 2013). As is often the case in Svalbard, Tunabreen is a 'surge--type' glacier (Nuth et al., 2010;Fleming et al., 2013), meaning that it undergoes short periods of rapid flow, usually accompanied by a terminus advance (Mansell et al., 2012;Flink et al., 2015), followed by a long period of quiescent flow (Pritchard et al., 2005). During a surge event, up--glacier propagation of crevasses is often observed (Flink et al., 2015) and the iceberg calving flux may also increase dramatically (Mansell et al., 2012). ...
Thesis
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The formation and development of crevasses provides great insight into the overall dynamics of a calving glacier, in particular because the formation of crevasses reflects glacier stretching, the same process that leads to calving. If a crevasse opens to the water-line then a calving event normally occurs. Thus outlining where and when crevasses form and how fast they open up, can be very important in detecting pre- conditions for calving events. Detecting crevasses from satellite imagery is an efficient way of tracking their movement, but manual techniques for identifying individual features and monitoring their evolution are time-consuming. In addition, most optical data is subject to inconsistent illumination due to time of day or season, long periods of darkness during winter, and cloud cover. High-resolution radar imagery provides an alternative that does not rely on illumination by the sun and is independent of weather constraints. This study uses a series of TerraSAR-X images of Tunabreen, a grounded calving glacier in Svalbard, taken between February 2013 and July 2014, to automatically detect and delineate crevasses close to the calving front. Feature tracking techniques are used to measure the relative strain taken up by these crevasses in relation to the ‘inter-crevasse’ ice between them, as the glacier approaches the calving margin. Strain rates follow a surface velocity gradient that increases as the glacier approaches the calving margin, but both velocity and strain rates level off and, in some cases, decrease in the final ~300m before the terminus. Seasonal fluctuations are also observed.
... Svalbard tidewater glaciers have been observed to exhibit surge behavior that is inconsistent with the traditional model (Sevestre et al. 2018). For example, numerous marine-terminating glaciers in Svalbard have exhibited a snout destabilization where surge-type behavior initiates at the terminus and propagates upward through the glacier system (Rolstad et al. 1997;Luckman et al. 2002;Dowdeswell & Benham 2003;Murray et al. 2012;Flink et al. 2015;Dunse et al. 2015;Strozzi et al. 2017;Sevestre et al. 2018). Furthermore recent studies have highlighted a connection between surge cyclicity and mass balance (Dowdeswell et al. 1995;Striberger et al. 2011), as well as surge-type glacier distribution and climatic conditions . ...
... Thus, during a period of prolonged positive mass balance, typical glaciers advance, while surge-type glaciers accumulate mass and exhibit gradual steepening of surface profiles. Additionally, studies suggest that surge-type glacier behavior can be interpreted based on a distinguishable landform assemblage with specific landforms indicative of rapid ice flow (Evans & Rea 1999, 2003Ottesen et al. 2008;Brynjólfsson et al. 2012;Schomacker et al. 2014;Flink et al. 2015;Ingólfsson et al. 2016). Landform assemblages include streamlined features (flutes, drumlins and mega-scale glacial lineations) as well as deposits oriented oblique or perpendicular to ice flow (crevasse squeeze ridges, concertina eskers and glaciotectonized end moraines; Ingólfsson et al. 2016). ...
... In phase with climatic favorability, several glacier re-advances constrained to the Neoglacial -LIA have been characterized as surges based on size, extent of glacial deposits and preservation of landforms (related to rapid ice advances) corresponding to associated ice-margins (Ottesen et al. 2008;Kristensen et al. 2009;Kempf et al. 2013;Lovell & Boston 2017;Flink et al. 2017;Lyså et al. 2018). While the most extensive Late Holocene glacier deposits have been associated with surge-type behavior especially near the culmination of the LIA (Kristensen et al. 2009;Kempf et al. 2013;Flink et al. 2015;Lyså et al. 2018), an increasing number of studies have identified both complete and fragmented moraine ridges outboard of the LIA maxima (Werner 1993;Sletten et al. 2001;Reusche et al. 2014;Philipps et al. 2017;. The classical perspective of the (Late) Holocene glacial maximum occurring during the culmination of the LIA is being challenged (Svendsen & Mangerud 1997;Snyder et al. 2000). ...
Thesis
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Identifying the key factors that influence the global cryosphere and eustatic sea level are critical in today’s populated world characterized by a changing climate. Within the Arctic, which has recently experienced amplified warming, and located between the Polar Northern Atlantic and the Arctic seasonal sea-ice, the Svalbard archipelago experiences a heightened sensitivity to climate change. Studying the processes, dynamics and historic fluctuations of Svalbard’s glaciers and climate is critical. Understanding these elements allows us to place current rates of change into longer-term perspective and ultimately to better model future climatic conditions. This study synthesizes the state of the art of Svalbard’s Holocene glacial and climate history. Chapters (i) introduce new findings of Holocene glaciers and climate; (ii) discuss the factors influencing Svalbard ice margins; (iii) summarize accumulated knowledge in the perspective of today’s paradigm; and (iv) outline potential approaches to address further unknowns regarding the Holocene on Svalbard. Through the Holocene, Svalbard glaciers have exhibited at least two phases of widespread re-advances, one during the Early Holocene and another throughout the entire Late Holocene. No geomorphological features have been identified corresponding to glacier re-advances between 9.0 – 4.5 ka BP. The Early Holocene glacier re-advances are identified across Svalbard and correspond to a diverse range of glacier sizes. With our current level of age constraint, these ice marginal fluctuations do not appear synchronous. Furthermore, the Early Holocene climate is believed to have been warm, unfavorable for glacier growth, and characterized by deglaciation. Early Holocene glacier re-advances appear to relate to the time-transgressive nature of deglaciation. Thus, the re-advances correspond to glacio-dynamics (not mass balance) and reflect the complex style of icemass-loss during a changing climate. Landforms and deposits from glaciers re-advancing during the Late Holocene have been the primary focus of Holocene glacial studies. Glacier re-advances and corresponding deposits have been attributed to episodic Neoglacial cooling and the Little Ice Age (LIA). The majority of Late Holocene glacier re-advances have been dated to between 4.0 – 0.5 ka BP with the highest frequency of re-advances constrained to 1.0 – 0.5 ka BP, during the first half of the LIA. It has been suggested that glacial landforms and deposits from LIA re-advances indicate rapid and dynamic glacier behavior, and in some cases surge-type events. During the 20th century (i.e. post-LIA), Svalbard glaciers have exhibited widespread negative mass balance, ice marginal retreat, and glacier thinning. This phase of retreat has had a direct influence on glacier thermal regime, hydrologic system and surface profile. Through the 20th century, some Svalbard glaciers have continued to exhibit surge-type re-advances. Several glaciers have surged numerous times. These glacio-dynamic re-advances have been un-sustained and each subsequent surge has been less extensive then prior surges. Consequently, and despite re-advance, glaciers reflect a continual phase of ice-mass-loss in a periodic fashion. Our understanding of Svalbard’s Holocene glaciers and climate has progressed but critical components remain obscure. For example, although our understanding of the timing of the Holocene glacial minimum has improved, we lack detailed constraints on the extent of ice retreat across Svalbard during the Mid-Holocene. As reconstructions of palaeo-temperatures develop, the improvement of palaeo-precipitation proxies (e.g., leaf wax hydrogen isotopes) should continue. Additionally, as we approach further unknowns of Svalbard’s Holocene history, it is evident that studies must take a holistic approach. Combining a mixture of archives, geochronological methods and emerging techniques will enhance the accuracy of reconstructions detailing Svalbard’s glacial history.
... While surges of land-terminating glaciers in Svalbard follow the stages described above (Dowdeswell & Benham, 2003;Mansell et al., 2012;Murray et al., 1998;Sund et al., 2009), there are numerous reports of tidewater glacier surges initiating at the terminus and propagating up-glacier. Remote sensing analyses of surges of Osbornebreen (Rolstad et al., 1997), Perseibreen (Dowdeswell & Benham, 2003), Tunabreen (Flink et al., 2015), Monacobreen (Luckman et al., 2002;, and Fridtjovbreen Murray et al., 2012) have clearly demonstrated this pattern, with an up-glacier propagation of the surge accompanied by extensional crevassing. Analyses of crevasse patterns show the absence of a compressive surge bulge in all cases. ...
... Few velocity data are available, and surges are often already in progress before the start of observations. In the absence of comprehensive velocity data, patterns of surge propagation are largely inferred from proxy data, such as the analysis of crevasse patterns (Flink et al., 2015). ...
Article
There have been numerous reports that surges of tidewater glaciers in Svalbard were initiated at the terminus and propagated up-glacier, in contrast with downglacier-propagating surges of land-terminating glaciers. Most of these surges were poorly documented, and the cause of this behavior was unknown. We present detailed data on the recent surges of two tidewater glaciers, Aavatsmarkbreen and Wahlenbergbreen, in Svalbard. High-resolution time series of glacier velocities and evolution of crevasse patterns show that both surges propagated up-glacier in abrupt steps. Prior to the surges, both glaciers underwent retreat and steepening, and in the case of Aavatsmarkbreen, we demonstrate that this was accompanied by a large increase in driving stress in the terminal zone. The surges developed in response to two distinct processes. (1) During the late quiescent phase, internal thermodynamic processes and/or retreat from a pinning point caused acceleration of the glacier front, leading to the development of terminal crevasse fields. (2) Crevasses allowed surface meltwater and rainwater to access the bed, causing flow acceleration and development of new crevasses up-glacier. Upward migration of the surge coincided with stepwise expansion of the crevasse field. Geometric changes near the terminus of these glaciers appear to have led to greater strain heating, water production, and storage at the glacier bed. Water routing via crevasses likely plays an important role in the evolution of surges. The distinction between internally triggered surges and externally triggered speedups may not be straightforward. The behavior of these glaciers can be understood in terms of the enthalpy cycle model.
... The second area of interest is the Tunabreen/Tempelfjorden system (see Fig. 1 for location). Tunabreen is a surge-type glacier which has experienced three surges since the Little Ice Age 24 . Recent observations of Tunabreen have found low velocities (less than 1 md −1 during winter) and a trend of retreat interspersed with small winter re-advances 24 . ...
... Tunabreen is a surge-type glacier which has experienced three surges since the Little Ice Age 24 . Recent observations of Tunabreen have found low velocities (less than 1 md −1 during winter) and a trend of retreat interspersed with small winter re-advances 24 . Tempelfjorden is part of the Isfjorden system and is around 14 km long with a width of between 3 and 5 km. ...
Article
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Fjord-terminating glaciers in Svalbard lose mass through submarine melt and calving (collectively: frontal ablation), and surface melt. With the recently observed Atlantification of water masses in the Barents Sea, warmer waters enter these fjords and may reach glacier fronts, where their role in accelerating frontal ablation remains insufficiently understood. Here, the impact of ocean temperatures on frontal ablation at two glaciers is assessed using time series of water temperature at depth, analysed alongside meteorological and glaciological variables. Ocean temperatures at depth are harvested at distances of 1 km from the calving fronts of the glaciers Kronebreen and Tunabreen, western Svalbard, from 2016 to 2017. We find ocean temperature at depth to control c. 50% of frontal ablation, making it the most important factor. However, its absolute importance is considerably less than found by a 2013–2014 study, where temperatures were sampled much further away from the glaciers. In light of evidence that accelerating levels of global mass loss from marine terminating glaciers are being driven by frontal ablation, our findings illustrate the importance of sampling calving front proximal water masses.
... Its drainage area is approximately 174 km 2 (Nuth et al., 2013). This glacier is known to have surged in 1930, 1970 and more recently in 2002-2005, experiencing multiple retreats and advances and leaving submarine footprints (Forwick et al., 2010;Flink et al., 2015). It was retreating from its maximum extent, reached in 2004, until 2016 when it started to surge again. ...
... It was retreating from its maximum extent, reached in 2004, until 2016 when it started to surge again. The 3 km wide terminus is roughly 70 m thick and grounded in 40 m deep water (Flink et al., 2015). At the front of Tunabreen, there is one main subglacial drainage portal (see Fig. 1) that can also be seen in the pictures (see Figs. 10 and 1b). ...
Article
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Calving is an important process in glacier systems terminating in the ocean, and more observations are needed to improve our understanding of the undergoing processes and parameterize calving in larger-scale models. Time-lapse cameras are good tools for monitoring calving fronts of glaciers and they have been used widely where conditions are favourable. However, automatic image analysis to detect and calculate the size of calving events has not been developed so far. Here, we present a method that fills this gap using image analysis tools. First, the calving front is segmented. Second, changes between two images are detected and a mask is produced to delimit the calving event. Third, we calculate the area given the front and camera positions as well as camera characteristics. To illustrate our method, we analyse two image time series from two cameras placed at different locations in 2014 and 2015 and compare the automatic detection results to a manual detection. We find a good match when the weather is favourable, but the method fails with dense fog or high illumination conditions. Furthermore, results show that calving events are more likely to occur (i) close to where subglacial meltwater plumes have been observed to rise at the front and (ii) close to one another.
... The lower Borgarfj€ orður region does not exhibit a complete sediment-landform assemblage diagnostic of surge-type glacier behaviour (Ottesen et al. 2008;Flink et al. 2015). However, large moraines exhibiting heavily tectonized sediments associated with elevated water pressures and meltwater runoff, like those seen in the moraine series in Melasveit, are usually associated with glacier surges due to rapid application of glacial stress (Huddart & Hambrey 1996;Boulton et al. 1999;Evans & Rea 1999;Bennett et al. 2004;Benediktsson et al. 2008Benediktsson et al. , 2010Benediktsson et al. , 2015Ing olfsson et al. 2016;Lovell & Boston 2017;Sigf usd ottir et al. 2019). ...
... A comparable retreat pattern as seen in the Melabakkar-Asbakkar cliffs is common in front of terrestrial surge-type glaciers in Iceland that had their greatest surges during the Little Ice Age maximum but have since then had successively smaller surges due to an overall warming climate (Bennett et al. 2004;Benediktsson et al. 2008Benediktsson et al. , 2009Benediktsson et al. , 2010Benediktsson et al. , 2015Striberger et al. 2011). Such patterns are also common in front of modern retreating, surgetype, marine-terminating glaciers, e.g. on Svalbard (Ottesen & Dowdeswell 2006;Ottesen et al. 2008;Flink et al. 2015;Larsen et al. 2018). Therefore, we surmise that the oscillations recorded in the Melabakkar-Asbakkar cliffs in Melasveit represent successively smaller advances/surges of the Borgarfj€ orður glacier due to gradually decreasing mass balance during the Younger Dryas. ...
Article
The lower Borgarfjörður region, western Iceland, has been central to the reconstructions of the dynamics and collapse of the Icelandic Ice Sheet during the deglaciation. Here, extensive stratigraphical sections and landforms provide a rare opportunity to study past glacier dynamics in this part of Iceland. Previous studies reveal that a large outlet glacier in Borgarfjörður advanced during the Late Weichselian resulting in large‐scale deformation of glaciomarine sediments and the formation of a series of ice‐marginal moraines. However, the events recorded by these sediments and landforms are poorly constrained in time. We present and discuss 22 new radiocarbon dates in the context of recent reconstructions of the regional glacier dynamics in order to constrain the timing of the glacier oscillations. The results show that a dynamic, marine‐terminating glacier advanced out of Borgarfjörður sometime after c. 13.0 cal. ka BP, resulting in the formation of an extensive moraine complex. The timing indicates that the advance occurred during climate cooling and widespread glacier expansions within the Younger Dryas. Followed by the first initial advance, the glacier exhibited at least five re‐advances punctuated by phases of retreat. Each re‐advance terminated proximal (within 5 km) to the outermost moraine complex although the extent of periodic retreat and the exact timing of these oscillations are unknown. All these phases of re‐advance occurred prior to the onset of the Holocene (around 11.7 cal. ka BP), during which marine fauna re‐colonized the area and the Borgarfjörður glacier retreated from the moraines. During the Early Holocene (sometime after c. 11.3 cal. ka BP), the Borgarfjörður glacier re‐advanced to a position within ~5 km of the YD ice limit. This is the first recorded Early Holocene large‐scale glacier advance in western Iceland and suggests that glacier expansion in this region coincided with widespread advances elsewhere in Iceland.
... Geometrical (rectilinear) ridge networks represented as crevasse squeeze ridges (CSRs) are widely distributed at the forelands of surging glaciers (e.g. Rea, Evans 2011;Schomacker et al. 2014;Flink et al. 2015;Ingólfsson et al. 2016;Aradóttir et al. 2019) and have been regarded as diagnostic landforms of glacier surging for a long while (e.g. Sharp 1985a, b), although Evans, Rea (2003) have noted that "they cannot be regarded independently as diagnostic features of palaeo-glacier surging even though widespread development of crevasse-squeeze networks clearly requires extensive fracturing of the glacier, normally associated with surging". ...
... A total of 7067 small rectilinear ridges were mapped in the Kursa lowland, within the topographic low hosting MSGL flow set 2 (Figs 1-2). We interpret the rectilinear ridges as CSRs based on their resemblance to and common characteristics with such ridges revealed in numerous investigations at modern and paleo-ice stream and/or ice lobe beds (Sharp 1985a, b;Evans et al. , 2008Evans et al. , 2016Evans et al. , 2020Rea, Evans 2011;Bjarnadóttir et al. 2014;Schomacker et al. 2014;Ankerstjerne et al. 2015;Cline et al. 2015;Flink et al. 2015;Farnsworth et al. 2016;Greenwood et al. 2016;Ingólfsson et al. 2016;Delaney et al. 2018;Aradóttir et al. 2019;Kurjanski et al. 2019;Ponce et al. 2019). Measurements of the orientation of the crests of CSRs reveal a dominant W-E align-ment ( Fig. 2) reflecting transverse ice fractures during their formation, although other variations exist as well, for example, a system of NNE-SSW, WNW-ESE and W-E oriented ridges occur in close proximity to each other (Fig. 3A). ...
Article
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Glacial geomorphological mapping of western Latvia using a 1-m-resolution digital elevation model generated from airborne LiDAR data has revealed two sets of mega-scale glacial lineations (MSGLs), one of which is superimposed by crevasse-squeeze ridges (CSRs). CSRs occur as a dense ridge network with a dominant orientation of ridges perpendicular to the ice flow direction. The landform assemblage is interpreted as evidence for two separate phases of fast ice flow with different ice flow directions during the overall deglaciation of the Fennoscandian Ice Sheet (FIS). The first fast ice flow phase occurred from the northwest by the Usma Ice Lobe that extended in the Eastern Kursa Upland. The second fast ice flow occurred from the north by the Venta Ice Tongue in a narrow flow corridor limited mainly to the Kursa Lowland. Active ice streaming caused ice crevassing perpendicular to the ice flow direction and formation of CSRs by squeezing of subglacial till into basal crevasses. A good preservation of the CSRs and general lack of recessional moraines suggest widespread stagnation and ice mass melting after the shutdown of the Venta Ice Tongue followed by the formation of the Venta-Usma ice-dammed lake and glaciolacustrine deposition in the lowest areas of lowland. Our data provide the first evidence of CSRs in the southeastern terrestrial sector of the FIS suggesting the dynamic ice streaming or surging behaviour of the ice lobes and tongues in this region during deglaciation.
... Tunabreen is one of a few glaciers in Svalbard that has been observed to undergo multiple surge cycles, with surge maxima occurring in 1930, 1971, 2004(Flink and others, 2015 and most recently in 2016 (A. Luckman, pers. ...
... The glacier terminates in a relatively shallow part of Tempelfjorden which is 30-50 m deep, and the ∼70 m thick ice front is grounded on the sea bed (Flink and others, 2015). Two turbid meltwater plumes surface in the fjord adjacent to the glacier, coinciding with two pronounced embayments in the calving front (noted in Fig. 1b). ...
Article
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Here, we present a highly detailed study of calving dynamics at Tunabreen, a tidewater glacier in Svalbard. A time-lapse camera was trained on the terminus and programmed to capture images every three seconds over a 28-hour period in August 2015, producing a highly detailed record of 34,117 images from which 358 individual calving events were distinguished. Calving activity is characterised by frequent events (12.8 events per hour) that are small relative to the spectrum of calving events observed, demonstrating the prevalence of small-scale calving mechanisms. Five calving styles were observed, with a high proportion of calving events (82%) originating at, or above, the waterline. The tidal cycle plays a key role in the timing of calving events, with 68% occurring on the falling limb of the tide. Calving activity is concentrated where meltwater plumes surface at the glacier front, and a ∼5 m undercut at the base of the glacier suggests that meltwater plumes encourage melt-undercutting. We conclude that frontal ablation at Tunabreen may be paced by submarine melt rates, as suggested from similar observations at glaciers in Svalbard and Alaska. Using submarine melt rate to calculate frontal ablation would greatly simplify estimations of tidewater glacier losses in prognostic models.
... 3a, b, 6), and the typically symmetric form of the moraines in the western Ross Sea (Figs. 5a, 9a) contrasts with similar features elsewhere whose steeper proximal sides have been interpreted as a product of push from short-lived margin fluctuations (e.g. Bennett, 2001;Winkelmann et al., 2010;Flink et al., 2015). Conversely, sub-bottom acoustic profiles only occasionally show deposition onto a preserved lower surface represented by an acoustic reflection horizon (Fig. 9a). ...
... This idea is perhaps difficult to reconcile with asymmetric moraines (e.g. Larsen et al., 1991;Flink et al., 2015), although these are typically proximal asymmetric, resulting from the magnitude of push, rather than asymmetry being a consequence of time and growth. It is more difficult to reconcile moraines as a proto-feature with the occurrence of much larger terminal moraines globally (e.g. ...
Article
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The resilience of a marine-based ice sheet is strongly governed by the stability of its grounding lines, which are in turn sensitive to ocean-induced melting, calving, and flotation of the ice margin. Since the grounding line is also a sedimentary environment, the constructional landforms that are built here may reflect elements of the processes governing this dynamic and potentially vulnerable environment. Here we analyse a large dataset (n = 6275) of grounding line landforms mapped on the western Ross Sea continental shelf from high-resolution geophysical data. The population is divided into two distinct morphotypes by their morphological properties: recessional moraines (consistently narrow, closely spaced, low amplitude, symmetric, and straight) and grounding zone wedges (broad, widely spaced, higher amplitude, asymmetric, sinuous, and highly variable). Landform morphotypes cluster with alike forms that transition abruptly between morphotypes both spatially and within a retreat sequence. Their form and distribution are largely independent of water depth, bed slope, and position relative to glacial troughs. Similarly, we find no conclusive evidence for morphology being determined by the presence or absence of an ice shelf. Instead, grounding zone wedge construction is favoured by a higher sediment flux and a longer-held grounding position. We propose two endmember modes of grounding line retreat: (1) an irregular mode, characterised by grounding zone wedges with longer standstills and accompanied by larger-magnitude retreat events, and (2) a steady mode, characterised by moraine sequences that instead represent more frequent but smaller-magnitude retreat events. We suggest that while sediment accumulation and progradation may prolong the stability of a grounding line position, progressive development of sinuosity in the grounding line due to spatially variable sediment delivery likely destabilises the grounding position by enhanced ablation, triggering large-magnitude retreat events. Here, the concept of stability is multifaceted and paradoxical, and neither mode can be characterised as marking fast or slow retreat. Diagnosing grounding line stability based on landform products should be considered for a wider geographic range, yet this large dataset of landforms prompts the need to better understand the sensitivity of marine-based grounding lines to processes and feedbacks governing retreat and what stability means in the context of future grounding line behaviour.
... In addition, archival satellite data afford time-series of multi-spectral images that may facilitate assessments of geomorphological changes through time; for example, fluctuations in highly dynamic (surging or rapidly retreating) glacial systems (e.g. Flink et al., 2015;Jamieson et al., 2015). Conversely, for smaller research areas (e.g. for a single valley or foreland), high-resolution satellite imagery is becoming an increasingly viable option, with prices for georeferenced and orthorectified products comparable to those for digital aerial photographs (see Section 3.2.2.2). ...
... Ottesen et al., 2005Ottesen et al., , 2008aOttesen et al., , 2016Bradwell et al., 2008;Winsborrow et al., 2010Winsborrow et al., , 2012Livingstone et al., 2012;Ó Cofaigh et al., 2013;Hodgson et al., 2014;Stokes et al., 2014;Margold et al., 2015a, b;Greenwood et al., 2017) and modern tidewater (often surging) glaciers (e.g. Ottesen and Dowdeswell, 2006a, b;Ottesen et al., 2008bOttesen et al., , 2017Robinson and Dowdeswell, 2011;Dowdeswell and Vazquez, 2013;Flink et al., 2015;Streuff et al., 2015;Allaart et al., 2018). In addition, recent years have seen the production of DEMs of sub-ice topography from geophysical datasets (radar and seismics) at spatial resolutions suitable for identifying and mapping bedforms (see King et al., 2007King et al., , 2009King et al., , 2016aSmith and Murray, 2009). ...
Article
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Geomorphological mapping is a well-established method for examining earth surface processes and landscape evolution in a range of environmental contexts. In glacial research, it provides crucial data for a wide range of process-oriented studies and palaeoglaciological reconstructions; in the latter case providing an essential geomorphological framework for establishing glacial chronologies. In recent decades, there have been significant developments in remote sensing and Geographical Information Systems (GIS), with a plethora of high-quality remotely-sensed datasets now (often freely) available. Most recently, the emergence of unmanned aerial vehicle (UAV) technology has allowed sub-decimetre scale aerial images and Digital Elevation Models (DEMs) to be obtained. Traditional field mapping methods still have an important role in glacial geomorphology, particularly in cirque glacier, valley glacier and icefield/ice-cap outlet settings. Field mapping is also used in ice sheet settings, but often takes the form of necessarily highly-selective ground-truthing of remote mapping. Given the increasing abundance of datasets and methods available for mapping, effective approaches are necessary to enable assimilation of data and ensure robustness. This paper provides a review and assessment of the various glacial geomorphological methods and datasets currently available, with a focus on their applicability in particular glacial settings. We distinguish two overarching ‘work streams’ that recognise the different approaches typically used in mapping landforms produced by ice masses of different sizes: (i) mapping of ice sheet geomorphological imprints using a combined remote sensing approach, with some field checking (where feasible); and (ii) mapping of alpine and plateau-style ice mass (cirque glacier, valley glacier, icefield and ice-cap) geomorphological imprints using remote sensing and considerable field mapping. Key challenges to accurate and robust geomorphological mapping are highlighted, often necessitating compromises and pragmatic solutions. The importance of combining multiple datasets and/or mapping approaches is emphasised, akin to multi-proxy approaches used in many Earth Science disciplines. Based on our review, we provide idealised frameworks and general recommendations to ensure best practice in future studies and aid in accuracy assessment, comparison, and integration of geomorphological data. These will be of particular value where geomorphological data are incorporated in large compilations and subsequently used for palaeoglaciological reconstructions. Finally, we stress that robust interpretations of glacial landforms and landscapes invariably requires additional chronological and/or sedimentological evidence, and that such data should ideally be collected as part of a holistic assessment of the overall glacier system.
... Megascale glacial lineations have been described from the Bellsund Trough, inner van Keulenfjorden, the mouth of Isfjorden, Borebukta, Yoldiabukta, the Kongsfjorden trough, Woodfjorden and Woodfjorden crossshelf trough, Wijdefjorden, Hinlopen trough and fjord system, Ginevrabotnen, Olgastretet, Erik Eriksenstretet, Hartogbukta, inner Storfjorden and Bakanbukta (Ottesen & Dowdeswell 2006;Ottesen et al. 2007Ottesen et al. , 2008Ottesen et al. , 2017Dowdeswell et al. 2010;Robinson & Dowdeswell 2011;Streuff et al. 2015). Smaller scale submarine glacial lineations have been described from Billefjorden, Tempelfjorden, Ymerbukta, St. Jonsfjorden, Kongsfjorden, Lomfjorden, Mohnbukta, Hinlopenstretet, Vaigattbogen, Wahlenbergfjorden and Palanderbukta (Baeten et al. 2010;Flink et al. 2015;Flink et al. 2017a;Flink et al. 2017b;Streuff et al. 2015Streuff et al. , 2017aBurton et al., 2015;Farnsworth et al. 2017;. Furthermore, streamlined landforms initiating from drumlin features have been described from the submarine forefield of Koristkabreen (Ottesen et al. 2017). ...
... Units of poorly sorted sands and gravels -unit 2 at site 1 and unit 1 at site 3 -are also interpreted to be glaciofluvial sediments. The poor sorting, the occurrence of lenses of planar cross-bedded and on identifying glaciers that exhibit surge-behaviour (Jiskoot et al. 2000;Murray & Porter 2001;Hansen 2003;Christoffersen et al. 2005;Ottesen et al. 2008;Flink et al. 2015;Farnswoth et al. 2016). Another reason can be that drumlins form some distance inside the ice margin and the recent retreat of Svalbard glaciers has only recently begun to expose this drumlin zone (Fig. 15). ...
Article
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The study of glacial landforms is important for understanding past subglacial processes and dynamics. The Nordenskiöldbreen forefield hosts numerous streamlined landforms resulting from a late Holocene glacier advance. Here, we present a geomorphological map constructed from remotely sensed imagery of both the marine and terrestrial environments. Sixteen drumlin bedforms have been identified in the mapped forefield – ten terrestrial and six submarine. A sedimentological investigation of drumlins in the Nordenskiöldbreen forefield shows that they are composed of pre-existing sediments draped by a thin layer of till which formed during the most recent advance of the glacier. Analysis of recent (2008–2012), high-resolution aerial imagery of all the glacier forelands in Svalbard suggests drumlin features are widespread. Here, we have identified 49 previously undocumented terrestrial glacier forefields, where subglacially streamlined landforms occur within the margins of the late Holocene glacier extent. Additionally, the location of 53 previously published submarine sites with streamlined landscape have been mapped. Thirty of these are sites with streamlines of late Holocene origin and 18 with Last Glacial Maximum (LGM) origin. Based on our detailed case study at the Nordenskiöldbreen forefield, and remote sensing survey, we suggest that drumlins in Svalbard form predominantly in forefields of glaciers with low-elevation termini, in areas with abundant fine-grained sediments, and where the glaciers are able to advance into an area of unconstrained topography.
... The seminal description of CSRs came from land-terminating surging glaciers in Iceland by Sharp (1985), and they have subsequently been investigated in many other areas in contemporary and deglaciated landscapes, for example: Svalbard (e.g. Boulton et al., 1996;Christoffersen et al., 2005;Flink et al., 2015;Streuff et al., 2015); Canada (Johnson, 1975;Clarke et al., 1984;; and Iceland (e.g. Evans et al., 2009;Waller et al., 2008). ...
Article
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Marine-based ice streams are responsible for a significant proportion of the ice mass loss from the present-day Greenland Ice Sheet, East Antarctic Ice Sheet (EAIS) and West Antarctic Ice Sheet (WAIS) but the processes controlling their initiation, evolution and shutdown remain elusive, hindering our understanding of how existing ice masses will respond to predicted future warming. The exposed beds of palaeo-ice streams offer a unique opportunity to study subglacial processes, which are largely inaccessible in contemporary settings. We use high resolution multibeam swath bathymetry data from the Barents Sea to map the geomorphology of a palaeo-ice stream bed, located in Olgastretet (Olga Trough), approximately 75 km southeast of Kong Karls Land and 200 km east of central Svalbard. This reveals evidence for shut down of a marine-based ice stream, followed by a phase of passive retreat or lift-off of the ice stream facilitating preservation of crevasse-squeeze ridges (CSRs). Subsequently, active retreat of the ice margin was re-established and is marked by recessional moraine ridges located upstream of the CSRs. Previously, CSRs have been mainly associated with surging land-terminating ice margins, however our work adds to recent observations of CSRs on the beds of marine-based ice streams, implying that they may be more common than previously thought. It also indicates that marine-based ice streams may switch on- and off in a surge-like manner which has important implications for our understanding of ice stream life cycles and the modelling of ice sheets.
... This type of surging has been observed at several surge-type glaciers in YukonAlaska, including Bering ( Roush and others, 2003), Trapridge (Clarke and others, 1984;Frappé and Clarke, 2007) and Variegated ( Kamb and others, 1985) Glaciers, as well various glaciers in Svalbard ( Murray andothers, 1998, 2000;Dowdeswell and Benham, 2003;Sund and others, 2009;Mansell and others, 2012), East Greenland (Jiskoot and Juhlin, 2009) and the Karakoram (Quincey and others, 2015). However, some tidewater glacier surges in Svalbard have been observed to propagate up-glacier (Rolstad and others, 1997;Luckman and others, 2002;Dowdeswell and Benham, 2003;Murray and others, 2003;Dunse and others, 2015;Flink and others, 2015;Sevestre and others, 2018). Up-glacier surge propagation has been observed elsewhere as well, including at Sabche Glacier, Nepal (Lovell and others, 2018). ...
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Donjek Glacier has an unusually short and regular surge cycle, with eight surges identified since 1935 from aerial photographs and satellite imagery with a ~12 year repeat interval and ~2 year active phase. Recent surges occurred during a period of long-term negative mass balance and cumulative terminus retreat of 2.5 km since 1874. In contrast to previous work, we find that the constriction where the valley narrows and bedrock lithology changes, 21 km from the terminus, represents the upper limit of surging, with negligible surface speed or elevation change up-glacier from this location. This positions the entire surge-type portion of the glacier in the ablation zone. The constriction geometry does not act as the dynamic balance line, which we consistently find at 8 km from the glacier terminus. During the 2012–2014 surge event, the average lowering rate in the lowest 21 km of the glacier was 9.6 m a ⁻¹ , while during quiescence it was 1.0 m a ⁻¹ . Due to reservoir zone refilling, the ablation zone has a positive geodetic balance in years immediately following a surge event. An active surge phase can result in a strongly negative geodetic mass balance over the surge-type portion of the glacier.
... The geomorphology of fiords has consequently been the object of numerous studies, which uncovered a number of landforms and processes linked to glacial and postglacial environments (e.g., Syvitski et al., 1987;Syvitski and Shaw, 1995;Howe et al., 2010;Dowdeswell et al., 2016). The seabed geomorphology of fiords has also been documented using high-resolution bathymetric imagery (e.g., Ottesen and Dowdeswell, 2009;Dowdeswell and Vásquez, 2013;Hjelstuen et al., 2013;Dowdeswell et al., 2014;Hodgson et al., 2014;Flink et al., 2015;Batchelor et al., 2017). From these studies, different glacial landsystems, in the form of schematic models, have been proposed to identify processes and conditions that prevailed in fiords (Powell, 2003;Dowdeswell and Vásquez, 2013;Dowdeswell et al., 2016;Batchelor et al., 2017). ...
Article
Fiord morphology plays a fundamental role in glacier flow dynamics and on ice-margin stability. As most of the present-day margins of the Greenland Ice Sheet lays in fiords, there is a need for understanding short- and long-term glacial dynamics in fiord settings. We investigate ice-sheet retreat patterns in previously glaciated submarine terrain of northeastern Baffin Island fiords to provide analogues for modern and future ice-sheet response to climate change and sea-level rise. Geomorphological maps constructed from the interpretation of swath bathymetry imagery in fiords of northeastern Baffin Island reveal a wide range of glacial to postglacial landforms that allow the reconstruction of past ice-sheet retreat dynamics. Ice-flow landforms such as mega-scale glacial lineations, crag-and-tails, and meltwater channels reveal the direction and behaviour of late-Foxe ice flow through the fiords. The presence of undisturbed elongated landforms within the fiords suggests that ice streams have probably been active until the late stage of deglaciation. Landforms transverse to ice-flow direction include grounding-zone wedges, frontal moraines, grounding-line fans, recessional moraines and De Geer moraines. These landforms are interpreted as the result of former standstills of the ice margin during deglaciation. The occurrence of grounding zones in deep (>800 m) part of the fiords contrasts with studies suggesting instability and rapid retreat of outlet glaciers over deep fiord basins. Sediment-filled basins, often characterised by the presence of turbidity channels, gullies and mass movement scars occur in-between the moraines. Sediment-filled basins with a ponded architecture between sills illustrate that most of the sediment accumulation was ice-proximal during deglaciation and characterised by gravity-driven flows. The proposed landform-assemblage model for northeastern Baffin fiords includes landforms typical of different fiord landsystems.
... Based on mass-balance estimates (Holmlund and Holmlund, 2019), photographic documentation (Fig. 2), and comparison with submarine glacial landforms observed in front of fjord-terminating glaciers (Flink et al., 2015), ridges R3 and R4 are interpreted as end moraines of the Kebnepakte Glacier that have formed during minor halts or re-advances of the glacier terminus. Still-stands or retreat can occur during summer, when calving rates at the glacier front may exceed or equal ice flow, while cessation of summer melt and lake ice cover during winter may lead to advances of the glacier front because calving is suppressed. ...
Article
In Arctic alpine regions, glacio‐lacustrine environments respond sensitively to variations in climate conditions, impacting, for example,glacier extent and rendering former ice‐contact lakes into ice distal lakes and vice versa. Lakefloors may hold morphological records of past glacier extent, but remoteness and long periods of ice cover on such lakes make acquisition of high‐resolution bathymetric datasets challenging. Lake Tarfala and Kebnepakte Glacier, located in the Kebnekaise mountains, northern Sweden, comprise a small, dynamic glacio‐lacustrine system holding a climate archive that is not well studied. Using an autonomous surface vessel, a high‐resolution bathymetric dataset for Lake Tarfala was acquired in 2016, from which previously undiscovered end moraines and a potential grounding line feature were identified. For Kebnepakte Glacier, structure‐from‐motion photogrammetry was used to reconstruct its shape from photographs taken in 1910 and 1945. Combining these methods connects the glacial landform record identified at the lakefloor with the centennial‐scale dynamic behaviour of Kebnepakte Glacier. During its maximum 20th century extent, attained c. 1910, Kebnepakte Glacier reached far into Lake Tarfala, but had retreated onto land by 1945, at an average of 7.9 m year –1.
... Subglacial till extruded from the grounding line as GFDs formed the acoustically-homogenous units (Facies V) extending and tapering down-slope in front of the GZW (Fig. 9d). Where such flow deposits are prolific and occur at the seafloor, they are easily identified as smooth, lobate features in front of known grounding-zone positions marked 320 by terminal moraines (e.g., Ottesen and Dowdeswell, 2006;Flink et al., 2015) et al., 2017). Here, they may reflect local shifts in the location of the grounding zone during a phase of ice-shelf instability interpreted from core records (Jennings et al., 2018) prior to further grounding-zone retreat. ...
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Petermann Fjord is a deep (> 1000 m) fjord that incises the coastline of northwest Greenland and was carved by an expanded Petermann Glacier, one of the six largest outlet glaciers draining the modern Greenland Ice Sheet (GrIS). Between 5–70 m of unconsolidated glacigenic material infills in the fjord and adjacent Nares Strait, deposited as the Petermann and Nares Strait ice streams retreated through the area after the Last Glacial Maximum. We have investigated the deglacial deposits using seismic stratigraphic techniques and have correlated our results with high-resolution bathymetric data and core lithofacies. We identify six seismo-acoustic facies in more than 3500 line-km of sub-bottom and seismic-reflection profiles throughout the fjord, Hall Basin and Kennedy Channel. Seismo-acoustic facies relate to: bedrock or till surfaces (Facies I); subglacial deposition (Facies II); deposition from meltwater plumes and icebergs in quiescent glaciomarine conditions (Facies III, IV); deposition at grounded ice margins during stillstands in retreat (grounding-zone wedges; Facies V); and the redeposition of material down slopes (Facies IV). These sediment units represent the total volume of glacial sediment delivered to the mapped marine environment during retreat. We calculate a glacial sediment flux for the former Petermann Ice Stream as 1080–1420 m³ a−1 per meter of ice stream width and an average deglacial erosion rate for the basin of 0.29–0.34 mm a−1. Our deglacial erosion rates are consistent with results from Antarctic Peninsula fjord systems but are several times lower than values for other modern GrIS catchments. This difference is attributed to fact that large volumes of surface water do not access the bed in the Petermann system and we conclude that glacial erosion is limited to areas overridden by streaming ice in this large outlet glacier setting. Erosion rates are also presented for two phases of ice retreat and confirm that there is significant variation in these rates over a glacial-deglacial transition. Our new fluxes and erosion rates show that the Petermann Ice Stream was approximately as efficient as the palaeo-Jakobshavn Isbrae at eroding, transporting and delivering sediment to its margin during early deglaciation.
... This pattern is typical of Svalbard tidewater glaciers, and reflects longitudinal extension of the ice in response to the force imbalance at the terminal ice cliff (cf. Flink and others, 2015). No crevasses are visible farther up-glacier on Landsat imagery until July 2014, when crevasses appeared along the margins of the central trunk, aligned obliquely up-glacier towards the centre line, and in the upper tributaries where they were oriented transverse to ice flow (Fig. 5b). ...
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Analysis of a recent surge of Morsnevbreen, Svalbard, is used to test predictions of the enthalpy balance theory of surging. High-resolution time series of velocities, ice thickness and crevasse distribution allow key elements of the enthalpy (internal energy) budget to be quantified for different stages of the surge cycle. During quiescence (1936–1990), velocities were very low, and geothermal heat slowly built-up enthalpy at the bed. Measurable mass transfer and frictional heating began in 1990–2010, then positive frictional heating-velocity feedbacks caused gradual acceleration from 2010 to 2015. Rapid acceleration occurred in summer 2016, when extensive crevassing and positive air temperatures allowed significant surface to bed drainage. The surge front reached the terminus in October 2016, coincident with a drop in velocities. Ice plumes in the fjord are interpreted as discharge of large volumes of supercooled water from the bed. Surge termination was prolonged, however, indicating persistence of an inefficient drainage system. The observations closely match predictions of the theory, particularly build-up of enthalpy from geothermal and frictional heat, and surface meltwater, and the concomitant changes in ice-surface elevation and velocity. Additional characteristics of the surge reflect spatial processes not represented in the model, but can be explained with respect to enthalpy gradients.
... Crevasses can also be difficult to separate from other linear glacier features and patterns such as ogives or meltwater runnels. Precise mapping of the patterns and propagation of surface crevasses has also been conducted using manual techniques ( others, 2011, 2016; Flink and others, 2015). ...
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Finely resolved geodetic data provide an opportunity to assess the extent and morphology of crevasses and their change over time. Crevasses have the potential to bias geodetic measurements of elevation and mass change unless they are properly accounted for. We developed a framework that automatically maps and extracts crevasse geometry and masks them where they interfere with surface mass-balance assessment. Our study examines airborne light detection and ranging digital elevation models (LiDAR DEMs) from Haig Glacier, which is experiencing a transient response in its crevassed upper regions as the glacier thins, using a self-organizing map algorithm. This method successfully extracts and characterizes ~1000 crevasses, with an overall accuracy of 94%. The resulting map provides insight into stress and flow conditions. The crevasse mask also enables refined geodetic estimates of summer mass balance. From differencing of September and April LiDAR DEMs, the raw LiDAR DEM gives a 9% overestimate in the magnitude of glacier thinning over the summer: −5.48 m compared with a mean elevation change of −5.02 m when crevasses are masked out. Without identification and removal of crevasses, the LiDAR-derived summer mass balance therefore has a negative bias relative to the glaciological surface mass balance.
... De Geer moraines are typically thought to occur at the grounding-line of calving glaciers (e.g. Ottesen & Dowdeswell, 2006;Flink et al., 2015), which is consistent with their occurrence only in areas below 80 m a.s.l., well within the proposed maximum marine limit of the Tyrrell Sea along the 195 west coast of Hudson Bay (Shilts et al., 1979;Shilts, 1986;Simon et al., 2014;Randour et al. 2016). In addition, the v-shaped arrangement of the moraine ridges around the esker beads is consistent with embayments forming at the mouth of subglacial conduits (see also Hoppe, 1957;Strömberg, 1981;Lindén & Möller, 2005;Bouvier et al., 2015;Dowling et al., 2016) due to plume-enhanced melting and calving (e.g. ...
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We identify and map chains of esker beads (series of aligned mounds) up to 15 m high and on average ~ 65 m wide across central Nunavut, Canada from the high-resolution (2 m) ArcticDEM. Based on the close one-to-one association with regularly spaced, sharp crested ridges interpreted as De Geer moraines, we interpret the esker beads to be quasi-annual ice-marginal deposits formed time-transgressively at the mouth of subglacial conduits during deglaciation. Esker beads therefore preserve a high-resolution record of ice-margin retreat and subglacial hydrology. The well-organised beaded esker network implies that subglacial channelised drainage was relatively fixed in space and through time. Downstream esker bead spacing constrains the typical pace of deglaciation in central Nunavut between 7.2 and 6 ka 14C BP to 165–370 m yr−1, although with short periods of more rapid retreat (> 400 m yr−1). Under our time-transgressive interpretation, the lateral spacing of the observed eskers provides a true measure of subglacial conduit spacing for testing mathematical models of subglacial hydrology. Esker beads also record the volume of sediment deposited in each melt season, thus providing a minimum bound on annual sediment fluxes, which is in the range of 103–104 m3 yr−1 in each 6–10 km wide subglacial conduit catchment. We suggest the prevalence of esker beads across this predominantly marine terminating sector of the former Laurentide Ice Sheet is a result of sediment fluxes that were unable to backfill conduits at a rate faster than ice-margin retreat. Esker ridges, conversely, are hypothesised to form when sediment backfilling of the subglacial conduit outpaced retreat resulting in headward esker growth close to but behind the margin. The implication, in accordance with recent modelling results, is that eskers in general record a composite signature of ice-marginal drainage rather than a temporal snapshot of ice-sheet wide subglacial drainage.
... The Svalbard archipelago is situated in the Barents Sea and was chosen for this case study because the recent retreat of Svalbard glaciers since their Little Ice Age (LIA) maximum extent has exposed a wide range of glacial trimlines, representing many different trimline expressions. The trimlines are relatively young, with the local LIA maximum ice margin position thought to have been reached between 1850and 1940(Ziaja, 2005Mangerud and Landvik, 2007;Flink et al., 2015;Farnsworth et al., 2020). The relatively recent nature of trimlines on Svalbard mean that these features are generally clear, well-defined and often closely associated with a modern ice margin, making them more straightforward to identify and map than older trimlines. ...
Article
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Glacial trimlines are important features for constraining 3-dimensional palaeoglaciological reconstructions, but relatively little is known about the processes of their formation and preservation. A new classification scheme for the expression of glacial trimlines was presented by Rootes and Clark (2020), with the aim to encourage further research into the processes of formation and preservation for trimlines. Here we present the first application of the trimline classification scheme to a case study location in central western Spitsbergen, Svalbard. Little Ice Age trimlines were mapped using remotely sensed imagery and the classification scheme applied. These data are presented and used to examine the factors that may influence the distribution and expression of trimlines in order to explore controls on their formation and preservation. Preliminary analysis suggests that the type of glacier, and geology, particularly the bedrock erodibility, may have an influence over the location and expression of glacial trimlines in Svalbard. These findings open the potential for trimlines to be used as part of diagnostic landsystems for specific types of glacier, such as marine-terminating tidewater glaciers, terrestrial glaciers or surge-type glaciers, and indicates that further research into glacial trimlines may enable these landforms to yield additional information about palaeo-ice masses than has previously been the case.
... Accumulations of retreat moraines have repeatedly been referred to as "annual moraines" correlated with annual cycles including winter advances and summer retreats during the overall deglaciation (Baeten et al., 2010;Boulton, 1986;Kempf et al., 2013;Ottesen and Dowdeswell, 2006) (Fig. 9: Stage 3). While annual formation of moraines can be studied in situ in, e.g., Svalbard (Flink et al., 2015;Ottesen and Dowdeswell, 2006), the interpretation of a series of evenly spaced recessional moraines as annual features in the paleo-record is debated (e.g., Chandler et al., 2020). However, assuming that accumulations of retreat moraines reflect annual moraines, we propose the following deglaciation velocities in the study area: following the formation of grounding zone wedge A at the shelf edge, the grounding line (1) retreated with an average of 80 m yr −1 , (2) readvanced and (3) retreated again, accelerating to 200-400 m yr −1 in the outer trough ( Fig. 9: Stage 6). ...
Article
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The presence of a grounded Greenland Ice Sheet on the northeastern part of the Greenland continental shelf during the Last Glacial Maximum is supported by new swath bathymetry and high-resolution seismic data, supplemented with multi-proxy analyses of sediment gravity cores from Store Koldewey Trough. Subglacial till fills the trough, with an overlying drape of maximum 2.5 m thick glacierproximal and glacier-distal sediment. The presence of megascale glacial lineations and a grounding zone wedge in the outer part of the trough, comprising subglacial till, provides evidence of the expansion of fast-flowing, grounded ice, probably originating from the area presently covered with the Storstrømmen ice stream and thereby previously flowing across Store Koldewey Island and Germania Land. Grounding zone wedges and recessional moraines provide evidence that multiple halts and/or readvances interrupted the deglaciation. The formation of the grounding zone wedges is estimated to be at least 130 years, while distances between the recessional moraines indicate that the grounding line locally retreated between 80 and 400 m yr−1 during the deglaciation, assuming that the moraines formed annually. The complex geomorphology in Store Koldewey Trough is attributed to the trough shallowing and narrowing towards the coast. At a late stage of the deglaciation, the ice stream flowed around the topography on Store Koldewey Island and Germania Land, terminating the sediment input from this sector of the Greenland Ice Sheet to Store Koldewey Trough.
... The majority of these data are gridded with a cell size of 5 m, which is suitable for identifying and mapping subdued glacial landforms (e.g. Ottesen et al., 2008;Flink et al., 2015;Fransner et al., 2017). Although multi-beam echosounder data within Norwegian territorial waters (within 12 nautical miles (~22 km) of the coastline) are shown here with a grid-cell size of 50 m, glacial landforms were mapped from these data using a high-resolution grid (typically 5 m). ...
Article
The analysis of glacial landforms preserved on mid- and high-latitude continental margins provides insights into the patterns and processes of sedimentation beneath contemporary ice sheets and aids predictions of the future resilience of ice sheets to ocean and atmospheric drivers of change. However, most previous high-resolution investigations of submarine glacial landforms have utilised data that are focused only on relatively small areas of the seafloor. Here we use an extensive database of high-resolution marine-geophysical data to map and interpret the distribution of glacial landforms over an 80,000 km² area along a ∼600 km-long section of the mid-Norwegian margin. Our glacial-geomorphological mapping shows that the Scandinavian Ice Sheet displayed highly dynamic behaviour, including readvances and changes in ice-flow direction, during the last glacial-interglacial cycle. The shallow banks briefly became dynamic centres of ice flow during deglaciation, with ice readvances from these banks linked to the loss of ice-sheet buttressing through the early deglaciation of grounded ice in the deeper troughs. The geometry of the continental shelf, especially its troughs and banks, exerted an important control on the pattern of ice-sheet retreat. The distribution of small grounding-zone wedges shows that frequent, small-magnitude still-stands or readvances within overall ice-stream retreat were prevalent on prograding slopes that limited the flux of ice across the grounding zone. Although the pattern of ice-sheet retreat along the mid-Norwegian margin is now relatively well-understood, future marine sediment coring efforts are needed to better constrain the timing of these deglacial events.
... During the sampling, the color of the sediments in the outer fjord was black (indicating reduced conditions), and near the glacier red-yellow (indicating oxic conditions). We can hypothesize that the sediment in the outer fjord is enriched with organic matter compared with the sediment near the glacier that opened to exchange with the water column after the last Tunabreen glacier surge event in 2004 [41]. Mineralization of organic matter requires oxygen, and when oxygen is depleted, denitrification starts and nitrate is consumed [42,43]. ...
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Observations and predictions show that consequences of climate warming such as declining summer sea ice cover, melting glaciers, thawing permafrost, and increased river runoff to the Arctic Ocean will likely modify processes relevant to the freshwater and carbon budget, which in turn affect high-latitude marine ecosystems. There is a knowledge gap in terms of understanding the seasonal variability of biogeochemical characteristics in coastal environments, first of all due to a lack of winter data. More data are also needed on the biogeochemical composition of different environmental media, i.e., sediments, snow, and ice. The aim of this work was to assess the current biogeochemical regime of a fjord system exposed to coastal runoff and glacial melting and discuss the possible consequences connected with climate warming. We used data from five expeditions to the Templefjord, West Spitsbergen, obtained in different seasons (February 2011, September 2011, March 2014, June 2015, and June 2017). In all the expeditions, the distributions of dissolved oxygen, nutrients, and carbonate system parameters in the water column were studied. The principal environmental media, i.e., seawater, bottom sediments, river water, sea ice, river ice, glacier ice, and snow, were sampled. The collected data allowed us to describe seasonal dynamics in the water column and to estimate the concentrations of the parameters under study in different environmental media. Our observations revealed the glacial and river footprints in the water column biogeochemistry; the glacial influence can be traced both in summer and in winter season. The results demonstrated the significant influence of coastal runoff and melted glacier water on the carbonate system and nutrient regime in the Templefjord, and can be extrapolated to other Arctic fjord systems.
... Crevasse-squeezed ridges are present in the modern-day forefield and are noted as a sign of historic surging (Farnsworth et al., 2016). The glacier was historically confluent with Tunabreen with a continuous calving front in Tempelfjorden, but has steadily retreated throughout the twentieth century and is now entirely land-terminating (Flink et al., 2015;Sweeting & Groom, 1956). While Von Postbreen has been long quiescent, neighboring Tunabreen has surged regularly and is well-studied (How et al., 2019). ...
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Ground‐penetrating radar (GPR) is widely used on polythermal glaciers to image bed topography and detect internal scatter due to water inclusions in temperate ice. The glaciological importance of this is twofold: bed topography is a primary component for modeling the long‐term evolution of glaciers and ice sheets, and the presence of temperate ice and associated englacial water significantly reduces overall ice viscosity. Englacial water has a direct influence on radar velocity, which can result in incorrect observations of bed topography due to errors in depth conversion. Assessment of radar velocities often requires multi‐offset surveys, yet these are logistically challenging and time consuming to acquire, hence techniques to extract velocity from common‐offset data are required. We calculate englacial radar velocity from common offset GPR data collected on Von Postbreen, a polythermal glacier in Svalbard. We first separate and enhance the diffracted wavefield by systematically assessing data coherence. We then use the focusing metric of negative entropy to deduce a migration velocity field and produce a velocity model which varies spatially across the glacier. We show that this velocity field successfully differentiates between areas of cold and temperate ice and can detect lateral variations in radar velocity close to the glacier bed. This velocity field results in consistently lower ice depths relative to those derived from a commonly assumed constant velocity, with an average difference of 4.9 ± 2.5% of local ice depth. This indicates that diffraction focusing and velocity estimation are crucial in retrieving correct bed topography in the presence of temperate ice.
... Blaszczyk et al. [6] specifically described Svalbard's tidewater glaciers with emphasis on flow velocity, calving fluxes, and mass loss. Many tidewater glaciers in Svalbard have experienced surge events during the last 150 years [13,[35][36][37][38][39][40]. Such activity is described for most of the glaciers in this study [6,13], even though there is only one reported surge event on Markhambreen from around 2010. ...
Article
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Tidewater glaciers on the east coast of Svalbard were examined for surface elevation changes and retreat rate. An archival digital elevation model (DEM) from 1970 (generated from aerial images by the Norwegian Polar Institute) in combination with recent ArcticDEM were used to compare the surface elevation changes of eleven glaciers. This approach was complemented by a retreat rate estimation based on the analysis of Landsat and Sentinel-2 images. In total, four of the 11 tidewater glaciers became land-based due to the retreat of their termini. The remaining tidewater glaciers retreated at an average annual retreat rate of 48 m year􀀀1, and with range between 10–150 m year􀀀1. All the glaciers studied experienced thinning in their frontal zones with maximum surface elevation loss exceeding 100min the ablation areas of three glaciers. In contrast to the massive retreat and thinning of the frontal zones, a minor increase in ice thickness was recorded in some accumulation areas of the glaciers, exceeding 10 m on three glaciers. The change in glacier geometry suggests an important shift in glacier dynamics over the last 50 years, which very likely reflects the overall trend of increasing air temperatures. Such changes in glacier geometry are common at surging glaciers in their quiescent phase. Surging was detected on two glaciers studied, and was documented by the glacier front readvance and massive surface thinning in high elevated areas.
... Although efforts have been made to conceptualise glacimarine sedimentation and glacier dynamics (e.g. Powell 1981;Ottesen et al. 2008;Forwick & Vorren 2011;Streuff 2013;Flink et al. 2015), most such publications provide evidence from only limited geographical areas and consider local or regional environmental factors at best. It is therefore difficult to fully comprehend the large-scale dynamics of former and contemporary ice sheets despite their relevance for future sea level (Nick et al. 2010;Meredith et al. 2019;Fox-Kemper et al. 2021). ...
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A digital database for submarine glacial landforms and sediments formed in the Arctic during and since the Last Glacial Maximum was created in order to facilitate and underpin new research on palaeo-ice sheets and tidewater glacier dynamics. The glacimarine database (GlaciDat) documents and standardises evidence of previous glacial activity as visible on the contemporary seafloor of fjords and continental shelves around Svalbard, Greenland, Alaska, northern Russia and north of 66°30′N in Canada and Norway. An extensive literature search was conducted to create GlaciDat, which compiles nearly 60 000 individual submarine landforms, more than 1000 sediment cores and 232 radiocarbon dates. Glacial landforms included are cross-shelf troughs, trough-mouth fans, grounding-zone wedges, lateral moraines, overridden moraines, (mega-scale) glacial lineations, drumlins, crag-and-tails, medial moraines, terminal moraines, debris-flow lobes (including glacier-contact fans), recessional moraines, De Geer moraines, crevasse-fill ridges, eskers, hill-hole pairs, crescentic scours, and submarine channels. They were digitised as point, line and polygon features alongside a list of their individual characteristics. Sediment core locations are attributed with a description of the sampled lithofacies and sedimentation rates where available. Landforms and sediments have been standardised according to predefined nomenclatures to make the glacial evidence as consistent as possible. Marine radiocarbon dates were included when thought to be relevant for constraining the timing of large-scale palaeo-ice dynamics. Outlines of bathymetric data sets, which have previously been used for glacial geomorphological mapping, were also included to give an overview of already investigated research areas. GlaciDat is available for download (https://doi.pangaea.de/10.1594/PANGAEA.937782) and will aid researchers in the reconstruction of past ice dynamics and the interpretation of Arctic glacial landform–sediment assemblages. Moreover, as well as providing a comprehensive bibliography on Arctic glacial geomorphological and sedimentological research, it is intended to serve as a basis for future modelling of Arctic glacier and ice-sheet dynamics.
... Additionally, at Tunabreen we do not find any clear seasonal velocity pattern during the pre-and post-surge phases. The special characteristics of the surge of Tunabreen with its short duration, the relatively low maximum velocities and the absence of a clear seasonal velocity pattern may be linked to its short temporal distance to the glacier's last surge in 2004 (Flink et al., 2015). Whereas the velocity time series of Negribreen and Tunabreen show that the surges initiated in the lower areas of the glacier and then spread upstream, for Strongbreen the time series reveals that the surge started from the upper areas, followed by a surge front of fast-moving ice propagating down the glacier. ...
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Consistent and continuous data on glacier surface velocity are important inputs to time series analyses , numerical ice dynamic modeling and glacier mass flux computations. Since 2014, repeat-pass synthetic aperture radar (SAR) data have been acquired by the Sentinel-1 satellite constellation as part of the Copernicus program of the EU (European Union) and ESA (European Space Agency). It enables global, near-real-time-like and fully automatic processing of glacier surface velocity fields at up to 6 d temporal resolution, independent of weather conditions, season and daylight. We present a new global data set of glacier surface velocities that comprises continuously updated scene-pair velocity fields, as well as monthly and annually averaged velocity mosaics at 200 m spatial resolution. The velocity information is derived from archived and new Sentinel-1 SAR acquisitions by applying a well-established intensity offset tracking technique. The data set covers 12 major glacier-ized regions outside the polar ice sheets and is generated in an HPC (high-performance computing) environment at the University of Erlangen-Nuremberg. The velocity products are freely accessible via an interactive web portal that provides capabilities for download and simple online analyses: http://retreat.geographie.uni-erlangen.de (last access: 6 October 2021). In this paper, we give information on the data processing and how to access the data. For the example region of Svalbard, we demonstrate the potential of our products for velocity time series analyses at very high temporal resolution and assess the quality of our velocity products by comparing them to those generated from very high-resolution TerraSAR-X SAR and Landsat-8 optical (ITS_LIVE, GoLIVE) data. The subset of Sentinel-1 velocities for Svalbard analyzed in this paper is accessible via the GFZ Potsdam Data Services under the DOI https://doi.org/10.5880/fidgeo.2021.016 (Friedl et al., 2021). We find that Landsat-8 and Sentinel-1 annual velocity mosaics are in an overall good agreement, but speckle tracking on Sentinel-1 6 d repeat acquisitions derives more reliable velocity measurements over featureless and slow-moving areas than the optical data. Additionally, uncertainties of 12 d repeat Sentinel-1 mid-glacier scene-pair velocities have less than half (< 0.08 m d −1) of the uncertainties derived for 16 d repeat Landsat-8 data (0.17-0.18 m d −1).
... The large dimensions and the rugged appearance of R1eR3 indicate that a purely glacial origin is unlikely (cf. Ottesen and Dowdeswell, 2006;Ottesen et al., 2008;Hogan et al., 2011;Flink et al., 2015;Streuff et al., 2015), and the sub-bottom profiler data show that the majority of the topographically distinct highs are formed in bedrock (e.g. Fig. 4d). ...
Article
Fast-flowing outlet glaciers currently drain the Greenland Ice Sheet (GIS), delivering ice, meltwater and debris to the fjords around Greenland. Although such glaciers strongly affect the ice sheet's mass balance, their glacimarine processes and associated products are still poorly understood. This study provides a detailed analysis of lithological and geophysical data from Disko Bay and the Vaigat Strait in centralWest Greenland. Disko Bay is strongly influenced by Jakobshavn Isbræ, Greenland's fastest-flowing glacier, which currently drains ~7% of the ice sheet. Streamlined glacial landforms record the former flow of an expanded Jakobshavn Isbræ and adjacent GIS outlets through Disko Bay and the Vaigat Strait towards the continental shelf. Thirteen vibrocores contain a complex set of lithofacies including diamict, stratified mud, interbedded mud and sand, and bioturbated mud deposited by (1) suspension settling from meltwater plumes and the water column, (2) sediment gravity flows, and (3) iceberg rafting and ploughing. The importance of meltwater-related processes to glacimarine sedimentation in West Greenland fjords and bays is emphasised by the abundance of mud preserved in the cores. Radiocarbon dates constrain the position of the ice margin during deglaciation, and suggest that Jakobshavn Isbræ had retreated into central Disko Bay before 10.6 cal ka BP and to beyond Isfjeldsbanken by 7.6e7.1 cal ka BP. Sediment accumulation rates were up to 1.7 cm a^-1 for ice-proximal glacimarine mud, and ~0.007 - 0.05 cm a^-1 for overlying distal sediments. In addition to elucidating the deglacial retreat history of Jakobshavn Isbræ, our findings show that the glacimarine sedimentary processes in West Greenland are similar to those in East Greenland, and that variability in such processes is more a function of time and glacier proximity than of geographic location and associated climatic regime.
... Unlike terrestrial surge-type glaciers that typically ablate by downwasting during quiescence, tidewater glaciers undergo frontal retreat interrupted by minor annual readvances . Rapid frontal retreat can occur in summer by melting below the waterline and calving, and when melting is suppressed during the winter months, minor advances of the glacier terminus bulldoze sea-floor sediments, forming sequences of annual recessional moraines (Flink et al., 2015;Ottesen & Dowdeswell, 2006). The contrast in style of deglaciation between terrestrial and fjord-terminating sectors of surge-type glaciers is well illustrated by Aradóttir et al. (2019). ...
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Glacier surges are cyclic oscillations of velocity and mass resulting from internal dynamic instabilities. For surge-type glaciers, cycles of advance and retreat are decoupled from climate forcing, so it is important to consider the possibility that former glaciers may have been surge-type when making climatic inferences from their dimensions and chronologies. In this paper, climatic and glacier geometric data are used to show that Scotland was likely the location of a surge cluster during the Loch Lomond Stade (∼12.9–11.7 ka), with high probabilities of surging for outlets of the West Highland Icefield and the larger glaciers in the Inner Hebrides and Northern Highlands. Terrestrial and marine landforms consistent with surging occur in all of these areas, and it is proposed that surge-type glaciers existed on the Islands of Skye and Mull, in the Northern Highlands, and in a ‘surging arc’ along the western, southern and south-eastern margins of the West Highland Icefield. The possibility that surge-type glaciers were widespread in Scotland during the Loch Lomond Stade offers a fresh perspective on some long-standing issues, including the relationship between style of deglaciation and climate change, the climatic significance of glacial chronologies, palaeoclimatic reconstructions, and the interpretation of numerical model results.
... Few glacier reconstructions predating the 1936 aerial photography campaign have been performed on Svalbard. Topographic maps older than 1936 have been used to draw profiles or to calculate (Liestøl, 1969;Nuttall and others, 1997;Pälli and others, 2003;Flink andothers, 2015, 2018). However, the associated errors are large and sometimes difficult to quantify, although the workflow suggested by Weber and others (2020) may help in standardising these errors. ...
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Photogrammetric reconstructions of the Aldegondabreen glacier on Svalbard from 17 archival terrestrial oblique photographs taken in 1910 and 1911 reveal a past volume of 1373.7 ± 78.2 · 106 m3; almost five times greater than its volume in 2016. Comparisons to elevation data obtained from aerial and satellite imagery indicate a relatively unchanging volume loss rate of − 10.1 ± 1.6 · 106 m3 a−1 over the entire study period, while the rate of elevation change is increasing. At this rate of volume loss, the glacier may be almost non-existent within 30 years. If the changes of Aldegondabreen are regionally representative, it suggests that there was considerable ice loss over the entire 1900s for the low elevation glaciers of western Svalbard. The 1910/11 reconstruction was made from a few of the tens of thousands of archival terrestrial photographs from the early 1900s that cover most of Svalbard. Further analysis of this material would give insight into the recent history and future prospects of the archipelago's glaciers. Photogrammetric reconstructions of this kind of material require extensive manual processing to produce good results; for more extensive use of these archival imagery, a better processing workflow would be required.
... Several glacier re-advances constrained to the Neoglacial -LIA have been characterized as surges based on size, landsystem, extent of glacial deformation and preservation of landforms (related to rapid ice advances) corresponding to associated ice-margins Ottesen et al., 2008;Kristensen et al., 2009;Kempf et al., 2013;Farnsworth et al., 2016Farnsworth et al., , 2017Flink et al., 2017;Lovell and Boston, 2017;Lyså et al., 2018;Lovell et al., 2018;Aradóttir et al., 2019). While the most extensive Late Holocene glacial deposits have been associated with surge-type behavior during, or at, the culmination of the LIA (Schomacker and Kjaer, 2008;Kristensen et al., 2009;Kempf et al., 2013;Flink et al., 2015;Lyså et al., 2018) an increasing number of studies have identified both complete and fragmented moraine ridges outboard of the LIA maxima (Werner, 1993;Sletten et al., 2001;Reusche et al., 2014;Sharin et al., 2014;Philipps et al., 2017;Larsen et al., 2018). Fig. 16. ...
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We synthesize the current understanding of glacier activity on Svalbard from the end of the Late Pleistocene (12,000 yrs. before present) to the end of the Little Ice Age (c. 1920 AD). Our glacier history is derived from the SVALHOLA database, the first compilation of Holocene geochronology for Svalbard and the surrounding waters, including over 1,800 radiocarbon, terrestrial cosmogenic nuclide and optically stimulated luminescence ages. Data have been categorized by geological setting, uniformly (re-)calibrated, quality assessed and ultimately used to constrain glacier fluctuations (deglaciation, ice free conditions, glacier re-advances and ice marginal positions). We advance existing knowledge by mapping the extent and distribution of ice-cover during the Holocene glacial maximum and the glacial minimum, as well as present retreat rates (and percentages) within Early Holocene fjord-systems. We discuss the complexities of glacier systems and their dynamics in response to changes in climate. This review provides a holistic state of the art of Holocene glaciers on Svalbard, suitable for orienting future works which address gaps in our current knowledge.
... Due to their transverse orientation and symmetric cross profiles, these ridges are interpreted as moraine ridges formed during stillstands and/or re-advances of the grounding line, similar to observations from other Spitsbergen fjords (e.g. Ottesen & Dowdeswell 2006;Baeten et al. 2010;Kempf et al. 2013;Flink et al. 2015;Streuff et al. 2017). ...
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The deglaciation history and Holocene environmental evolution of northern Wijdefjorden, Svalbard, are reconstructed using sediment cores and acoustic data (multibeam swath bathymetry and sub-bottom profiler data). Results reveal that the fjord mouth was deglaciated prior to 14.5AE0.3 cal. ka BP and deglaciation occurred in a stepwise manner. Biomarker analyses show rapid variations in water temperature and sea ice cover during the deglaciation, and cold conditions during the Younger Dryas, followed by minimum sea ice cover throughout the Early Holocene, until c. 7 cal. ka BP. Most of the glaciers in Wijdefjorden had retreated onto land by c. 7.6AE0.2 cal. ka BP. Subsequently, the sea-ice extent increased and remained high throughout the last part of the Holocene. We interpret a high Late Holocene sediment accumulation rate in the northernmost core to reflect increased sediment flux to the site from the outlet of the adjacent lake Femmilsjøen, related to glacier growth in the Femmilsjøen catchment area. Furthermore, increased sea ice cover, lower water temperatures and the re-occurrence of ice-rafted debris indicate increased local glacier activity and overall cooler conditions in Wijdefjorden afterc. 0.5 cal. ka BP. We summarize our findings in a conceptual model for the depositional environment in northern Wijdefjorden from the Late Weichselian until present. Lis Allaart (lis.allaart@uit.no),
... Where such flow deposits are prolific and occur at the seafloor, they are easily identified as smooth, lobate features in front of known grounding-zone positions marked by terminal moraines (e.g. Ottesen and Dowdeswell, 2006;Flink et al., 2015) or GZWs (e.g. Bjarnardóttir et al., 2013;Esteves et al., 2017). ...
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In this study, 110 tidewater glaciers from Spitsbergen were studied to characterize the frontal zone using morphometric indicators. In addition, their time variability was also determined based on features of the active phase of glacier surges. Landsat satellite imagery and topographic maps were used for digitalization of the ice-cliffs line. In recent years (2014–2017) all the glaciers studied can be thus classified as: stagnant (33%), retreating and deeply recessing (33%), starting to move forward/fulfilling the frontal zone (23%), and surging (11%). Indicators of the glacier frontal zone (CfD and CfE) allow to identify the beginning and the end of the active phase through changes in their values by ca. 0.05–0.06 by the year and get even bigger for large glaciers as opposed to typical interannual differences within the limits of ±0.01 to 0.02. The active phase lasted an average of 6–10 years. The presence of a “glacier buttress system” and the “pointed arch” structure of the ice-cliff seem to be an important factor regulating the tidewater glacier stability.
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Climate warming in Svalbard since the end of the ‘Little Ice Age’ early in the 20th century has reduced glacier extent in the archipelago. Previous attempts to reconstruct ‘Little Ice Age’ glacier limits have encountered problems in specifying the area of tidewater glacier advances because it is difficult to estimate the past positions of their marine termini. Multibeam echo-sounding data are needed to map past glacier extent offshore, especially in open-marine settings where subaerial lateral moraines cannot be used due to the absence of fjord walls. We use the submarine glacial landform record to measure the recent limits of advance of over 30 marine-terminating northeastern Svalbard glaciers and ice caps. Our results demonstrate that previous work has underestimated the ice-covered area relative to today by about 40% for northeastern Svalbard (excluding southeast Austfonna) because marine-geophysical evidence in the form of submarine terminal moraines was not included. We show that the recent ice extent was 1753 km ² larger than today over our full area of multibeam data coverage; about 5% of the total modern ice cover of Svalbard. It has often been assumed that moraine ridges located within a few kilometres of modern ice fronts in Svalbard represent either a ‘Little Ice Age’ maximum or relate to surge activity over the past century or so. In the marine environment of northeastern Svalbard, this timing can often be confirmed by reference to early historical maps and aerial photographs. Assemblages of submarine glacial landforms inshore of recently deposited terminal moraines suggest whether a recent advance may be a result of surging or ‘Little Ice Age’ climatic cooling relative to today. However, older terminal moraines do exist in the archipelago, as shown by radiocarbon and ¹⁰ Be dating of Holocene moraine ridges.
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Major glaciations or ‘ice ages’ are known to have affected the Earth's surface over the past three billion years. The best preserved records of these glaciations are often found in high-latitude continental margin settings where sediment has been delivered to, and then accumulated at, the edge of the ice sheet in thick glacier-influenced marine sequences. The composition and geometry of these deposits and the related assemblages of glacial landforms provide a wealth of information about the environmental setting during successive cycles of glaciation and deglaciation, including ice-dynamic and oceanographic processes. Here, we discuss modern (present day), Quaternary (last 2.6 myr) and ancient (last 1 gyr) high-latitude continental margin settings, and then contrast the methodologies used and glacier-influenced deposits and landforms most often identified for each time period. We use examples from the literature to identify synergies, as well as to note differences, between studies of glacier-influenced sediments from ancient to modern environments.
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We identify and map chains of esker beads (series of aligned mounds) up to 15 m high and on average ∼ 65 m wide in central Nunavut, Canada, from the high-resolution (2 m) ArcticDEM. Based on the close 1 : 1 association with regularly spaced, sharp-crested ridges interpreted as De Geer moraines, we interpret the esker beads to be quasi-annual ice-marginal deposits formed time-transgressively at the mouth of subglacial conduits during deglaciation. Esker beads therefore preserve a high-resolution record of ice-margin retreat and subglacial hydrology. The well-organised beaded esker network implies that subglacial channelised drainage was relatively fixed in space and through time. Downstream esker bead spacing constrains the typical pace of deglaciation in central Nunavut between 8.1 and 6.8 cal kyr BP to 165–370 m yr−1, although with short periods of more rapid retreat (> 400 m yr−1). Under our time-transgressive interpretation, the lateral spacing of the observed eskers provides a true measure of subglacial conduit spacing for testing mathematical models of subglacial hydrology. Esker beads also record the volume of sediment deposited from conduits in each melt season, thus providing a minimum bound on annual sediment fluxes, which is in the range of 103–104 m3 yr−1 in each 6–10 km wide subglacial conduit catchment. We suggest that the prevalence of esker beads across this predominantly marine-terminating sector of the Laurentide Ice Sheet is a result of sediment fluxes that were unable to backfill conduits at a rate faster than ice-margin retreat. Conversely, we hypothesise that esker ridges form when sediment backfilling of the subglacial conduit outpaced retreat, resulting in headward esker growth close to but behind the margin. The implication, in accordance with recent modelling results, is that eskers in general record a composite signature of ice-marginal drainage rather than a temporal snapshot of ice-sheet-wide subglacial drainage.
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Recent studies have highlighted the need to improve our understanding of the relationship between glacial-front bathymetry and oceanography in order to better predict the behaviour of tidewater glaciers. The glaciomarine fjords of western Svalbard are strongly influenced by temperate Atlantic Water advected from the West Spitsbergen Current. Marine terminating (tidewater) glaciers locally influence many Svalbard fjords through fluxes of sediments, nutrients and freshwater, however their response to ocean warming and the imprint left by their recent retreat on the seabed remains unresolved. Here we present glacial front data collected by an autonomous underwater vehicle (AUV) from four tidewater glaciers; Fjortende Julibreen (Krossfjorden), Conwaybreen, Kongsbreen and Kronebreen (Kongsfjorden). The seabed adjacent to the glacial terminus has been mapped providing high-resolution bathymetry (0.5 m–1.0 m grid cell size), side-scan and photographs with additional simultaneous oceanographic observations. The aim being to survey the glacial front submarine landforms, to identify the water mass structure and to observe any melt water plume activity. The bathymetry data displays a diverse assemblage of glacial landforms including numerous retreat moraines, glacial lineations, crevasse-squeeze ridges and sediment debris flows reflecting the dynamic depositional environment of the glacial front. The age of the features and the annual rate of retreat have been estimated using satellite remote sensing imagery to digitise the glacial front positions over time. The glacial landforms have been produced by the last few years of retreat as these glaciers gradually become land-terminating. The AUV also observed in-situ subglacial meltwater plumes at the two most active glaciers (Kongsbreen and Kronebreen) and an associated signature of warm Atlantic Water occurring at the glacier face. The presence of relatively warm, oceanic waters enhances subsurface melting, accelerating the ablation rate, while fresh (melt) water injection at depth influences local water mass structure and the wider fjord circulation. At the glacial fronts of Kongsbreen and Kronebreen sedimentation from subglacial meltwater plumes dominate the ice-proximal zone and settling from suspension is more prevalent away from the glacier. This study shows how sensitive dynamic glaciomarine systems are to change in the local marine environment and how the use of autonomous vehicles can greatly aid in the monitoring of glacial change by collecting simultaneous high-resolution in-situ datasets where vessel based observations are lacking.
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The recession of the Hornbreen-Hambergbreen glaciers (Hornsund, Svalbard) will lead to the formation of a strait between the Greenland and Barents Seas within a few decades. We provide evidence for the earlier existence of this strait, in the Early–Middle Holocene and presumably since 1.3 ka cal. BP until glacier advance 0.7 ± 0.3 ka or earlier. Radiocarbon dating of mollusc shells from the ground moraines in the Hornbreen forefield indicate the existence of the marine environment at the contemporary glacierized head of Hornsund since 10.9 ka cal. BP or earlier due to glacier retreat. The gap in the radiocarbon dates between 3.9 and 1.3 ka cal. BP and the published results of 10Be exposure dating on Treskelen suggest the strait’s closure after glacier advance in the Neoglacial. Subsequent re-opening occurred around 1.3 ka cal. BP, but according to 10Be dates from Treskelen, the strait has again been closed since ca. 0.7 ± 0.3 ka or earlier. The oldest known surge of Hornbreen occurred around 1900. Analysis of Landsat satellite images, morphometric indicators characterizing the glacier frontal zones and previous studies indicate one surge of Hambergbreen (1957–1968) and five re-advances of Hornbreen in the 20th century (after 1936, between 1958 and 1962, in 1986–1990, 1998–1999, 2011). While the warmer Holocene intervals might be a benchmark for the effects of future climate change, glacier dynamics in post-Little Ice Age climate warming seems to be an analogue of glacier retreats and re-advances in the earlier periods of the Holocene.
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Glacier surges are short periodic episodes of rapid glacier flow that are driven by internal instabilities and bracketed by longer periods of slow flow. These glaciers are important to understand because they are vital to predicting future sea level rise, mitigating glacier hazards, and understanding basal glacial processes. Donjek Glacier, located in the Yukon, Canada has an unusually short and regular surge cycle, with eight surges identified since 1935 from aerial photographs and satellite imagery with a ~12 year repeat interval and ~2 year active phase. Recent surges occurred during a period of long-term negative mass balance and cumulative terminus retreat of 2.5 km since 1874. In contrast to previous work, we find that the constriction where the valley narrows and bedrock lithology changes, 21 km up-glacier of the terminus, represents the upper limit of surging, with negligible surface speed or elevation change up-glacier from this location. This positions the entire surge-type portion of the glacier in the ablation zone. The constriction geometry does not act as the dynamic balance line, which we consistently find at 8 km up-glacier from the glacier terminus. During the 2012–2014 surge, the average lowering rate in the lowest 21 km of the glacier was 9.6 m a-1, while during quiescence it was 1.0 m a-1. Due to reservoir zone refilling, the ablation zone has a positive geodetic balance in years immediately following a surge event. An active surge phase can result in a strong negative geodetic mass balance over the surge-type portion of the glacier. Potential links between climate and glacier surges are not well understood, but are required to enable prediction of glacier surges and mitigation of associated hazards. This thesis investigates the role of snow accumulation and atmospheric temperature on surge periodicity, glacier area changes, and surge initiation since the 1930s for Donjek Glacier. Three ice cores from Eclipse Icefield, at the head of the glacier, indicate that a total accumulation of 13.1 to 17.7 m w.e. of snow occurred in the 10-12 years between each of its last eight surges. This suggests that a threshold must be passed before the initiation of a surge event, although it remains unclear whether the relationship between cumulative snowfall and surging is due to the consistency in repeat surge interval and decadal average precipitation, or if it is indeed related to surging. The 1968 to 2017 climate record from Burwash Landing tests if there is a relationship between surge periodicity and an increase of 2.5°C in mean annual air temperature over this period. No such relationship was found, although each of the past 8 surge events has been less extensive than the previous, with the maximum terminus extent approximately 8 km2 smaller in the most recent 2012-2014 surge event than the ~1947 surge event.
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The 26 km long tidewater glacier Tunabreen is the most frequently surging glacier in Svalbard, with four documented surges in the past 100 years. We model the evolution of this glacier with a minimal glacier model (MGM), in which ice mechanics, calving, and surging are parameterized. The model geometry consists of a flow band to which three tributaries supply mass. The calving rate is set to the mean observed value for the period 2012–2019 and kept constant. For the past 120 years, a smooth equilibrium line altitude (ELA) history is reconstructed by finding the best possible match between observed and simulated glacier length. There is a modest correlation between this reconstructed ELA history and an ELA history based on meteorological observations from Longyearbyen. Runs with and without surging show that the effect of surging on the long-term glacier evolution is limited. Due to the low surface slope and associated strong height–mass-balance feedback, Tunabreen is very sensitive to changes in the ELA. For a constant future ELA equal to the reconstructed value for 2020, the glacier front will retreat by 8 km during the coming 100 years. For an increase in the ELA of 2 m a−1, the retreat is projected to be 13 km, and Tunabreen becomes a land-terminating glacier around 2100. The calving parameter is an important quantity: increasing its value by 50 % has about the same effect as a 35 m increase in the ELA, with the corresponding equilibrium glacier length being 17.5 km (as compared to 25.8 km in the reference state). Response times vary from 150 to 400 years, depending on the forcing and on the state of the glacier (tidewater or land-terminating).
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We assess the evolution of glaciological structures during the 2003–05 surge in the Paulabreen glacier system, Svalbard. Glaciological structures on the glacier surface were mapped using aerial photographs captured in the early stages of the surge (2003) and 5 years after surge termination (2011). Three-dimensional measurements of glaciological structures were collected at the tidewater front in 2013. These datasets document the physical changes during (1) the late quiescent phase; (2) the early phase of the surge as the surge front propagated down Skobreen and advanced into Paulabreen and (3) the final stages of the surge following the surge front reaching the glacier terminus. Crevasse patterns and clusters of arcuate shear planes record zones of compressive and extensional flow associated with the downglacier progression of the surge front. The transfer of surging ice from Skobreen into Paulabreen caused lateral displacement of the medial moraines to the northeast. At the ice front, this movement tilted glaciological structures in the same direction. Structures at the southwest margin record strike–slip faulting and the elevation of debris into the ice in a zone of compression and transpression. We summarise these observations in a schematic reconstruction of structural evolution during the surge.
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The deglaciation of the continental shelf to the west of Spitsbergen and the main fjord, Isfjorden, is discussed based on sub-bottom seismic records and sediment cores. The sea floor on the shelf to the west of Isfjorden is underlain by less than 2 m of glaciomarine sediments over a firm diamicton interpreted as till. In central Isfjorden up to 10m of deglaciation sediments were recorded, whereas in cores from the innermost tributary, Billefjorden, less than a meter of ice proximal sediments was recognized between the till and the 'normal' Holocene marine sediments. We conclude that the Barents Sea Ice Sheet terminated along the shelf break during the Late Weichselian glacial maximum. Radiocarbon dates from the glaciomarine sediments above the till indicate a stepwise deglaciation. Apparently the ice front retreated from the outermost shelf around 14.8 ka. A dramatic increase in the flux of fine-grained glaciomarine sediments around 13ka is assumed to reflect increased melting and/or current activity due to a climatic warming. This second stage of deglaciation was interrupted by a glacial readvance culminating on the mid-shelf area shortly after 12.4 ka. The glacial readvance, which is correlated with a simultaneous readvance of the Fennoscandian ice sheet along the western coast of Norway, is attributed to the so-called 'Older Dryas' cooling event in the North Atlantic region. Following this glacial readvance the outer part of Isfjorden became rapidly deglaciated around 12.3 ka. During the Younger Dryas the inner fjord branches were occupied by large outlet glaciers and possibly the ice front terminated far out in the main fjord. The remnants of the Barents Sea Ice Sheet melted quickly away as a response to the Holocene warming around 10 ka.
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The tectonic effects of a glacier surge differ from those of steady state because flow is driven by longitudinal stresses rather than shear stresses. The orientations of recently formed crevasses, indicating the directions of the principal stresses, have been used to investigate tectonic processes in glacier surges recorded by repeat aerial photography. Long-term, large-magnitude shifts in stress regime are demonstrated, as are short-term propagation features. Two types of tide-water glacier advance are identified, depending on the position of the surge front relative to a low effective-pressure zone at the glacier terminus. -Authors
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We present observations of a surge of the glaciers Skobreen-Paulabreen, Svalbard, during 2003-05, including a time-lapse movie of the frontal advance during 2005, Advanced Spaceborne Thermal Emission (ASTER) imagery and oblique aerial photographs. The surge initiated in Skobreen, and then propagated downglacier into the lower parts of Paulabreen. ASTER satellite images from different stages of the surge are used to evaluate the surge progression. Features on the glacier surface advanced 2800 m over 2.4 yr, averaging 3.2 m/day, while the front advanced less (ca. 1300 m) due to contemporaneous calving. The surge resulted in a lateral displacement of the medial moraines of Paulabreen of ca. 600 m at the glacier front. The time-lapse movie captured the advance of the frontal part of the glacier, and dramatically illustrates glacier dynamic processes in an accessible way. The movie documents a range of processes such as a plug-like flow of the glacier, proglacial thrusting, incorporation of old, dead ice at the margin, and calving into the fjord. The movie provides a useful resource for researchers, educators seeking to teach and inspire students, and those wishing to communicate the fascination of glacier science to a wider public.
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Abstract – The geomorphology and sedimentology of the Teigarjökull and Búrfellsjökull, two small surge-type cirque glaciers at the Tröllaskagi peninsula, northern Iceland was explored for improved understanding of their surge imprints. Geomorphological, geological and remote sensing data on sediments and landforms were used for developing a geomorphological model for surge-type cirque glaciers in Iceland. Most surge moraines identified are in the form of uneven small ridges or debris sheets that constitute a boulder-rich hummocky terrain. The size and structures of two moraines in front of Teigarjökull are interpreted as suggesting that the glacier has in the past switched between surge and non-surge behavior. Hummocky surfaces, small medial moraines and crevasse-fill ridges are common, as are landforms suggesting dead-ice melting, such as backslumping, extension cracks and sinkholes. The surface sediments are rich in subangular and angular pebbles, cobbles, and boulders. This distinct geomorphology of the glacier forefields results from ample supply of coarse and angular sediments originating from the steep mountain slopes bordering the glaciers and subsequently carried to the marginal zone via englacial and supraglacial transport. Key words: Surge-type glaciers, glacial geomorphology, Búrfellsjökull, Teigarjökull
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[1] Anisotropy of magnetic susceptibility (AMS) has been shown to provide specific useful information regarding the kinematics of deformation within subglacially deformed sediments. Here we present results from debris-rich basal glacier ice to examine deformation associated with glacier motion. Basal ice samples were collected from Tunabreen, a polythermal surge-type glacier in Svalbard. The magnetic fabrics recorded show strong correlation with structures within the ice, such as sheath folds and macroscopic stretching lineations. Thermomagnetic, low-temperature susceptibility, varying field susceptibility, and isothermal remanent magnetism acquisition experiments reveal that the debris-rich basal ice samples have a susceptibility and anisotropy dominated by paramagnetic phases within the detrital sediment. Sediment grains entrained within the basal ice are inferred to have rotated into a preferential alignment during deformation associated with flow of the glacier. An up-glacier directed plunge of magnetic lineations and subtle deviation from bulk glacier flow at the margins highlight the importance of noncoaxial strain during surge propagation. The results suggest that AMS can be used as an ice petrofabric indicator for investigations of glacier deformation and interactions with the bed.
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Multiproxy analyses including hydrographical, geochemical, foraminferal, lithological and geophysical data reveal variable influences of the glaciers Tunabreen and von Postbreen as well as the river Sassenelva on the sedimentary environment in two Spitsbergen fjords during the Late Weichselian and the Holocene. Grounded ice covered the study area during the last glacial. The glacier fronts retreated stepwise during the latest Weichselian/earliest Holocene, and the glaciers were probably small during the early Holocene. A growth of Tunabreen occurred between 6 and 4 cal ka BP. Reduced input from Tunabreen from c. 3.7 cal ka BP was probably a result of suppressed iceberg rafting related to the enhanced formation of sea ice and/or reduced meltwater runoff. During the past two millennia, the glacier fronts advanced and retreated several times. The maximum Holocene glacier extent was reached at the end of a surge of von Postbreen in AD 1870. Characteristics of the modern glaciomarine environment include: (1) different colours and bulk-mineral assemblages of the turbid waters emanating from the main sediment sources; (2) variable locations of the turbid-water plumes as a consequence of wind forcing and the Coriolis effect; (3) stratified water masses during summers with interannual variations; (4) increasing productivity with increasing distance from the glacier fronts; (5) foraminifera-faunal assemblages typical for glacierproximal settings; and (6) periodical mass-transport activity.
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The glaciotectonic architecture and sequential evolution of the Eyjabakkajökull 1890 surge end moraines in Iceland were studied for understanding better the formation and evolution of glaciotectonic end moraines and their relation to glacier dynamics. Based on morphological, geological and geophysical data from terrain cross-profiles, cross-sections and ground penetrating radar profiles, we demonstrate that three different qualitative and conceptual models are required to explain the genesis of the Eyjabakkajökull moraines. Firstly, a narrow, single-crested moraine ridge at the distal end of a marginal sediment wedge formed in response to decoupling of the subglacial sediment from the bedrock and associated downglacier sediment transport. Secondly, large lobate end moraine ridges with multiple, closely spaced, narrow asymmetric crests formed by proglacial piggy-back thrusting. Thirdly, a new model shows that moraine ridges with different morphologies may reflect different members of an end moraine continuum. This is true for the eastern and western parts of the Eyjabakkajökull moraines as they show similar morphological and structural styles which developed to different degrees. The former represents an intermediate member with décollement at 4–5m depth and 27–33% shortening through multiple open anticlines that are reflected as moderately spaced symmetric crests on the surface. The latter represents an end member with décollement at about 27m depth and 39% horizontal shortening through multiple high amplitude, overturned and overthrusted anticlines, appearing as broadly spaced symmetric crests. We propose that the opposite end member would be a moraine of multiple symmetric, wide open anticlinal crests of low amplitude. Our data suggest that the glacier coupled to the foreland to initiate the end moraine formation when it had surged to within 70–190m of its terminal position. This indicates a time frame of 2–6days for the formation of the end moraines.
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1] During the 1990s, Monacobreen, a 40-km-long tidewater glacier in Svalbard, underwent a major surge. We mapped the surge dynamics using ERS synthetic aperture radar images, differential dual-azimuth interferometry and intensity correlation tracking. A series of 11 three-dimensional (3-D) velocity maps covering the period 1991–1997 show a months-long initiation and years-long termination to the surge, with no indication of a surge front travelling downglacier. During the surge, the front of the glacier advanced $2 km, the velocity and derived strain rate increased by more than an order of magnitude, and maximum ice flow rates measured during 1994 were $5 m d À1 . The spatial pattern of both velocity and strain rate was remarkably consistent and must therefore be controlled by spatially fixed processes operating at the glacier bed. We combine these results with those published in the literature to construct a typical Svalbard glacier surge cycle and compare this to surge dynamics of glaciers from other cluster regions, especially those of Variegated Glacier in Alaska. The strong contrast in dynamics suggests that there exist at least two distinct surge mechanisms.
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The climate history of western Spitsbergen, Svalbard is deduced from variations of glaciers during the last 20 000 years. A major depression of the regional equilibrium line altitude (ELA) occurred during the Late Weichselian glacial maximum (18000–13000y ago) when low summer temperatures may have caused year-round snow accumulation on the ground. This rapid expansion of the glaciers also indicates nearby moisture sources, suggesting partly open conditions in the Norwegian Sea during the summers. A rapid glacial retreat around 13 000–12 500 y BP was caused by a sudden warming. During the Younger Dryas the ELA along the extreme western coast of Spitsbergen was not significantly lower than at present. In contrast to Fennoscandia, the British Isles and the Alps, there is no evidence for readvance of local glaciers during Younger Dryas on western Spitsbergen. This difference is attributed to a much dryer climate on Spitsbergen and probably only slight changes in sea surface temperatures. In addition, summer melting in this high arctic area is more sensitive to orbitally increased insolation. Around 10 000 y BP another rapid warming occurred and during early and mid Holocene the summer temperatures were significantly higher than at present. A temperature decline during the late Holocene caused regrowth of the glaciers which reached their maximum Holocene position during the last century.
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The glacier Sefstrombreen in Spitsbergen surged across an arm of the sea between 1882 and 1886 and rode up onto the island Coraholmen. Marine and terrestrial geological observations and archive records show that the glacier advanced on a deforming carpet of marine mud which was eroded from its original location, transported, and smeared over the sea bed and Coraholmen as a deformation till. The glacier emplaced about 2108M3 (0.2 km3) of drift in the terminal 2 km of its advance in a maximum of 14 years, leaving a thickness of up to 20 m on Coraholmen, which was doubled in size as a result.During the surge, subglacial muds were characterised by high water pressures, low effective pressures and low frictional resistance to glacier movement. Original sedimentary inhomogenities permit fold structures to be identified, but repeated refolding and progressive remoulding produce mixing and homogenisation of deformation tills.The surge was probably shortlived, and as the heavily crevassed glacier stagnated, underlying water saturated muds were intruded into crevasses and then extruded on the glacier surface. Reticulate “crevasse-intrusion” ridges on Coraholmen and the sea floor reflect the orientation of surge generated crevasses. Water and sediment was also extruded beyond the glacier at its maximum extent, to form extensive flows producing “till tongues” both on Coraholmen and the sea floor extending over 1.3 km from the glacier.It is argued that subglacial deformation of pre-existing sediment will almost invariably be associated with glaciation of marine areas and that this process will not only produce deformation tills through remoulding of pre-existing sediments, but will also play a fundamental role in glacier dynamics. Criteria which permit glacial tills produced by such events from marine and glaciomarine muds are discussed.
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Most discharge from large ice sheets takes place through fast-flowing ice streams and their speed is strongly modulated by interactions between the ice and the underlying sediments. Seismic surveys and investigations through boreholes have revealed a spatial association between fast ice flow and saturated deformable sediments. Nevertheless, our knowledge of the morphology of the interface between ice and sediments is still limited, resulting in only rudimentary understanding of the basal boundary conditions beneath ice streams and the generation of subglacial bedforms. Here we present radar data from the bed of a West Antarctic ice stream that reveal the presence of mega-scale glacial lineations. We combine these data with previously published seismic data and show that these lineations develop in areas of dilatant deforming till and are part of a dynamic sedimentary system that undergoes significant change by erosion and deposition on decadal timescales. We find that the mega-scale glacial lineations are indistinguishable from those found on beds of palaeo-ice streams, providing conclusive evidence for the hypothesis that highly elongate bedforms are a characteristic of fast-flow regions in ice sheets.
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Many glaciers in Svalbard and in other glacierized areas of the world are known to surge. However, the time series of observations required to assess the duration of fast motion is very restricted. Data on active-phase duration in Svalbard come from aerial photographs, satellite imagery, field surveys and airborne reconnaissance. Evidence on surge duration is available for eight Svalbard ice masses varying from 3 to 1250 km2. Worldwide, active-phase duration is recorded for less than 50 glaciers. Few observations are available on high polar ice masses. The duration of the active phase is significantly longer for Svalbard glaciers than for surge-type glaciers in other areas from which data are available. In Svalbard, the active phase may last from 3 to 10 years. By contrast, a surge duration of 1–2 years is more typical of ice masses in northwest North America, Iceland and the Pamirs. Ice velocities during the protracted active phase on Svalbard glaciers are considerably lower than those for many surge-type glaciers in these other regions. Mass is transferred down-glacier more slowly but over a considerably longer period. Svalbard surge-type glaciers do not exhibit the very abrupt termination of the active phase, over periods of a few days, observed for several Alaskan glaciers. The duration of the active phase in Svalbard is not dependent on parameters related to glacier size. The quiescent phase is also relatively long (50–500 years) for Svalbard ice masses. Detailed field monitoring of changing basal conditions through the surge cycle is required from surge-type glaciers in Svalbard in order to explain the significantly longer length of the active phase for glaciers in the archipelago, which may also typify other high polar ice masses. The finding that surge behaviour, in the form of active-phase duration, shows systematic differences between different regions and their environments has important implications for understanding the processes responsible for glacier surges.
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It has been suggested that extremely long subglacial bedforms (e.g. attenuated drumlins and mega-scale glacial lineations) record former areas of fast-flowing ice and that bedform elongation ratio is a useful proxy for ice velocity. Despite the availability of much data pertaining to the measurement and analysis of subglacial bedforms, these assumptions have rarely been explicitly addressed in detail. In this paper, we demonstrate that long subglacial bedforms (length:width ratios S10:1) are indicative of fast ice flow. Using satellite imagery, we mapped over 8000 lineaments associated with a highly convergent flow pattern near Dubawnt Lake, District of Keewatin, Canada. This flow pattern is unusual in that it displays a large zone of convergence feeding into a main 'trunk' and then diverging towards the inferred ice margin. The 'bottleneck' pattern is taken to record an increase and subsequent decrease in ice velocity and we analysed transverse and longitudinal variations in bedform morphometry. The main trunk of the flow pattern (down-ice of the convergent zone) is characterized by mega-scale glacial lineations of great length (up to 13 km) and high elongation ratios (up to 43:1). The down-ice variations in elongation ratio reflect exactly what we would expect from a terrestrial ice stream whose velocity increases in the onset zone passes through a maximum in the main trunk and slows down as the ice diverges at the terminus. It is suggested that any unifying theory of drumlin formation must be able to account for the association between long subglacial bedforms and fast ice flow, although it is not assumed that fast ice flow always produces attenuated bedforms. A further implication of this work is that many more ice streams may be identified on the basis of attenuated subglacial bedforms, radically altering our views on the flow dynamics of former ice sheets.
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The englacial entrainment of basal debris during surges presents an opportunity to investigate processes acting at the glacier bed. The subsequent melt-out of debris-rich englacial structures during the quiescent phase produces geometrical ridge networks on glacier forelands that are diagnostic of surge activity. We investigate the link between debris entrainment and proglacial geomorphology by analyzing basal ice, englacial structures, and ridge networks exposed at the margins of Tunabreen, a tidewater surge-type glacier in Svalbard. The basal ice facies display clear evidence for brittle and ductile tectonic deformation, resulting in overall thickening of the basal ice sequence. The formation of debris-poor dispersed facies ice is the result of strain-induced metamorphism of meteoric ice near the bed. Debris-rich englacial structures display a variety of characteristics and morphologies and are interpreted to represent the incorporation and elevation of subglacial till via the squeezing of till into basal crevasses and hydrofracture exploitation of thrust faults, reoriented crevasse squeezes, and preexisting fractures. These structures are observed to melt-out and form embryonic geometrical ridge networks at the base of a terrestrially grounded ice cliff. Ridge networks are also located at the terrestrial margins of Tunabreen, neighboring Von Postbreen, and in a submarine position within Tempelfjorden. Analysis of network characteristics allows these ridges to be linked to different formational mechanisms of their parent debris-rich englacial structures. This in turn provides an insight into variations in the dominant tectonic stress regimes acting across the glacier during surges.
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Many glaciers in Svalbard and in other glacierized areas of the world are known to surge. However, the time series of observations required to assess the duration of fast motion is very restricted. Evidence on surge duration is available for eight Svalbard ice masses varying from 3 to 1250km2. In Svalbard, the active phase may last from 3 to 10 yr. By contrast, a surge duration of 1-2 yr is more typical of ice masses in northwest North America, Iceland and the Pamirs. The finding that surge behaviour, in the form of active-phase duration, shows systematic differences between different regions and their environments has important implications for understanding the process responsible for glacier surges. -from Authors