Article

# Fifty Years of Mass Balance and Glacier Front Observations at the Tarfala Research Station

Authors:
• Swedish Polar Research Secretariat, Stockholm, Sweden
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## Abstract

In 1945 Storglaciären located in the Kebnekaise massif, northern Sweden, was selected for a long term study of the climatic impact on glaciers and an annual mass balance programme was initiated. Since the mass balance year 1945–1946 the average annual winter precipitation has increased by 0.53 m water equivalent (w. eq.), the annual average ablation has decreased by 0.58 m w. eq., and the annual average net balance has increased from -0.80 m w. eq./year to +0.30 m w. eq./year. The decrease in ablation is caused by a decrease in summer temperature of about 1°C. In addition, frontal retreat has decreased the low altitude area of the glacier and hence contributed to this decrease in ablation. A comparison with results from mass balance studies at three additional glaciers in the Kebnekaise area show that Storglaciären is representative for the area. The mass balance of Storglaciären is also positively correlated with each of four Norwegian glaciers, although accumulation and net balance are better correlated than ablation. Correlations become less positive with increasing distance between sites. Glacier front measurements provide filtered and delayed indications of climatic changes. Small glaciers are at present in balance with the climate. However, retreating fronts of large glaciers show that they are still adjusting to the major warming of the first half of the 1900s.

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... The proglacial area of Storglaciären consists of a till sheet ~ 0.3 km 2 in area which has been exposed by the retreat of Storglaciären since 1910 (Bronge, 1996;Holmlund et al., 1996a). The proglacial area of Storglaciären has been studied in detail by Etienne et al. (2003) who identified seven sediment lithofacies within the proglacial area. ...
... The value of these measurements is enhanced by the high spatial resolution of the data: Snow depth is measured at ~ 300 points (~ 100 points km -2 ) and ~ 50 ablation stakes are distributed across the entire glacier surface (~15 stakes km -2 ) . The quality of snow depth measurements has been increased in recent years by the use of snow radar, which allows depth measurements to be collected to an accuracy of ±10 cm (Holmlund et al. 1996a). ...
... Radar and thermistor measurements collected by Moore et al. (2011) suggest that the cold layer meets the glacier bed ~ 100 m from the terminus (referred to as the basal thermal transition), with basal freezing occurring where the layer thins at the glacier margin. It is estimated that around 16% of the total glacier area is frozen to the bed (Holmlund et al., 1996a). The scarcity of studies of proglacial hydrology has largely been attributed to the difficulties of collecting discharge data in the Tarfala valley as a result of frequent changes in size and position of proglacial streams (Bronge, 1996;Bronge and Openshaw, 1996;Schneider and Bronge, 1996). ...
Thesis
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In glacierised regions, suspended sediment fluxes are highly responsive to climate‐driven environmental change and can provide important information regarding the relationships between glacier variations, climate and geomorphic change. As a result, understanding patterns of suspended sediment transport and their relationship with meltwater delivery is of critical importance. However, studies of glacial suspended sediment transport are often limited by interpreting patterns of suspended sediment transfer based on whole-season data, allowing precise patterns to become masked. This thesis aims to contribute to the understanding of suspended sediment transfer in glacierised basins through the investigation of patterns of suspended sediment delivery to the proglacial area of Storglaciären, a small polythermal valley glacier located in the Tarfala valley, Arctic Sweden. High temporal resolution discharge and suspended sediment concentration data were collected during two summer field campaigns at Storglaciären. Interpretations of suspended sediment transport data were made using diurnal hysteresis and sediment availability data, combined with suspended sediment ‘shape’ and ‘magnitude’ data classified by applying principal component and hierarchical cluster analyses. Analysis of the dominant discharge generating processes at Storglaciären was also conducted using principal component analysis, allowing patterns of discharge to be better understood. This was complemented by analysis of the structure and evolution of the glacier drainage system by linear reservoir modelling and flow recession analysis. The results suggest that patterns of discharge and suspended sediment transport at Storglaciären are complex, with distinct processes and magnitudes of transport evident at both proglacial outlet streams, Nordjåkk and Sydjåkk. These processes are intrinsically linked to meteorological variables, with both ablation-driven and precipitation-driven discharge exerting influence over patterns of suspended sediment transport in the proglacial area of Storglaciären.
... Intense research on glacier mass balance has been conducted at Storglaciären since 1946 (Grudd and Schneider 1996;Holmlund, Karlén, and Grudd 1996;Holmlund and Jansson 1999), but Lake Tarfala has received considerably less attention. Pioneering investigations focusing on the bathymetry and thermal state of Lake Tarfala were made in 1959 and 1966/1967 (Larje and Nyberger 1960;Björklund 1967). ...
... It is remarked that comparably low winter (1966/1967) lake water temperatures were observed in April 1967 by Björklund (1967) but that a comparison with the 2018/ 2019 winter state remains speculative because of a scarcity of relevant external environmental data for both periods. Available data comprise average June-July-August air temperatures from TRS (7.4°C in 2018 and5.7°C in 1966) 1965-31 August 1966Holmlund, Karlén, and Grudd 1996;World Glacier Monitoring Service 2020). Both support the notion that cold winter thermal regimes may be related to elevated influx of glacial meltwater into Lake Tarfala during the late summer and fall, under the assumption that similar mass balances held for the glaciers draining into Lake Tarfala. ...
Article
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Arctic lakes are exposed to warming during increasingly longer ice-free periods and, if located in glaciated areas, to increased inflow of meltwater and sediments. However, direct monitoring of how such lakes respond to changing environmental conditions is challenging not only because of their remoteness but also because of the scarcity of present and previously observed lake states. At the glacier-proximal Lake Tarfala in the Kebnekaise Mountains, northern Sweden, temperatures throughout the water column at its deepest part (50 m) were acquired between 2016 and 2019. This three-year record shows that Lake Tarfala is dimictic and is overturning during spring and fall, respectively. Timing, duration, and intensity of mixing processes, as well as of summer and winter stratification, vary between years. Glacial meltwater may play an important role regarding not only mixing processes but also cooling of the lake. Attribution of external environmental factors to (changes in) lake mixing processes and thermal states remains challenging owing to for example, timing of ice-on and ice-off but also reflection and absorption of light, both known to play a decisive role for lake mixing processes, are not (yet) monitored in situ at Lake Tarfala.
... [29] Storglaciären reached quasi-steady state in mid-1970s after adapting to climate warming in northern Europe at the beginning of the century [Holmlund et al., 1996a]. During the 12 years spanning the two cold surface layer surveys, the net mass balance of Storglaciären was close to equilibrium [Holmlund and Jansson, 1999]. ...
... A possible weaker temperature gradient will limit the upward transport of released latent heat and diminish the freezing rate at the CTS. This may also be reinforced by the observed increase in winter accumulation [Holmlund et al., 1996a] insulating the ice surface. The suggested decrease in the downward migration of the CTS, and no similar decrease in the net loss of ice at the surface, should result in a thinning of the cold surface layer. ...
Article
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A characteristic feature of ground penetrating radar (GPR) surveys on polythermal glaciers is an internal reflection presumably caused by the cold temperate transition surface (CTS), hence providing a possible tool for mapping thermal structure with high accuracy. Comparison of detailed temperature measurements in bore holes and GPR profiles at 345 MHz and 800 MHz center frequencies on Storglaciären, Sweden, show that the CTS can be detected and mapped with an accuracy of about ±1 m at both frequencies. A comparison between comprehensive GPR surveys of the cold surface layer, separated by 12 years (1989–2001), shows a substantial and complex thinning of the cold layer. An overall decrease of 8.3 m (22% of average thickness) of the CTS depth is much larger than uncertainties in CTS depth determinations. The stability of the cold surface layer depends on the net ice ablation at the surface and the downward migration of CTS. There is no evidence of substantial increased net ablation between the survey dates that could explain the observed thinning. However, small increase in average winter air temperature, a limiting factor for the temperature gradient through the cold surface layer, may provide a partial explanation. The weaker temperature gradient reduces the transport of latent heat from the CTS, thus slowing down its downward migration.
... The glaciers in the west of the study area are mostly of the plateau icefield type (Karlén 1973;Goodfellow et al. 2008). Glaciers across the study area have been retreating since reaching a 'Little Ice Age' maximum extent c. 1916, although positive mass balance years have occurred at Storglaciaren (Kebnekaise), particularly between the mid-1970s to mid-1990s (Karlén 1973;Holmlund et al. 1996;Holmlund and Holmlund 2019). ...
Article
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Proglacial lakes have increased in number and extent in Arctic Sweden since the 1950s/1960s as glaciers have retreated dramatically. Interrogation of Rapid Eye imagery highlights that some lake terminating glaciers had substantial (>100 m) rates of retreat between 2010 and 2018, with one other land terminating glacier also retreating at a similar rate. However, analysis of a regional remote sensing time series suggests that proglacial lake formation in this period across the area has not been uniform. Despite glacier accumulation areas having similar maximum elevations (∼2,000 m) and similar alpine topography, proglacial lakes in the southern area (Sarek) were found to be significantly smaller than proglacial lakes in the northern area (Kebnekaise), which had smaller glaciers within corries and more prominent terminal moraines. Therefore, it cannot be assumed that proglacial lake formation will occur as glaciers retreat in response to elevated air temperature, particularly as only 33% of glaciers had proglacial lakes in their forefield. Thus, whilst it cannot be assumed that proglacial lakes will accommodate water currently held in glaciers, the 108 lakes mapped here present a substantial area (4.767 ± 0.377 km²) of fresh water that has not previously been included in the Global Lakes and Wetlands Database (GLWD). This inventory therefore provides an important dataset that can be used to underpin our understanding of the role of proglacial lakes within the hydrological system in this area of the Arctic.
... Glaciers started to grow again during the mid-Holocene cooling c. 6000-5000 cal a BP, as a response to a wetter and colder climate and have since been continuously present in the Scandes Mountains. Swedish glaciers respond primarily to changes in summer temperature (Holmlund et al. 1996) in contrast to glaciers in western Norway that are more influenced by changes in the winter precipitation . Glacier growth is also affected by postglacial land uplift, which is believed to have been around 150 m in the mountains of northern Sweden since the early Holocene deglaciation (Karlén & Kuylenstierna 1996). ...
Article
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This paper presents a review on more than hundred years of palaeoenvironmental research in Sweden; from early descriptions of peat and tufa deposits in the late nineteenth and early twentieth centuries to multiproxy transfer function studies in the late twentieth and early twenty-first centuries CE. Research on Holocene climate variability has a long history in Sweden and many ideas and concepts about changes in temperature and precipitation during the Holocene originated in Fennoscandia. The Holocene climate evolution in Sweden follows a pattern in common for many northern latitude records with a rapid warming starting at the Pleistocene–Holocene boundary at c. 11 650 cal a BP, followed by the middle Holocene thermal maximum between c. 8000 and 5000 cal a BP. A change to colder and wetter conditions starts c. 4000 cal a BP and lasts until the late 1800 s CE. There is evidence for climatic anomalies such as the 8.2 and 4.2 ka BP events and the Little Ice Age (LIA) but only inconclusive evidence for other events, such as the 10.3 ka BP event. The main pattern of Holocene climate and environmental evolution is well known for most parts of Sweden, but the present review also shows that several research questions remain to be addressed.
... Figure 3.3 displays recent mass balance. Storglaciären thus provides an almost unique prospect for examining the cryosphere's temporal response to climate change and for studies requiring extensive empirical data (e.g., Holmlund et al., 1996Holmlund et al., , 2005Brugger, 2007). ...
Thesis
There is a need for more studies in glacier hydrology that integrate numerical models with detailed empirical data collected over one/multiple summer(s). This is especially true for physically based models whose main advantage lies in ability to predict basal water pressure because of its significance for ice dynamics, thus helping inform knowledge of runoff and ultimately sea-level rise both presently and, when forced with climate projections, into the future. This study helped fulfill this requirement by applying a physically based glacier-hydrology model to the predominantly temperate ~3.22km$^{2}$ Storglaciären, Sweden, forced with 2012 empirical data. The model has three subelements: a high temporal (hourly) and spatial (20-m) resolution surface-energy-balance model to generate meltwater across Storglaciären’s surface for the entire summer, a surface-routing model to route this meltwater (and precipitation) across the surface either until it runs off Storglaciären’s edges or is intercepted by moulins extending into the internal system, and a subglacial-hydrology model where inflow from moulin hydrographs is routed in R-channels from moulins to the terminus to produce proglacial discharge. The surface-energy-balance model was validated using Storglaciären’s summer mass-balance data and measurements of surface lowering at an automatic weather station on its surface. It performed well, though slightly (~4%) underestimated melt. The surface-routing model was qualitatively evaluated using estimates of direct supraglacial runoff derived from previous studies and reproduced these to within 2%. The subglacial-hydrology model’s outputs of proglacial discharge and subglacial flow-routing times were quantitatively compared with empirical discharge measurements in the three proglacial streams Nordjåkk, Centerjåkk and Sydjåkk, and with flowrouting times from ~25 tracer injections across Storglaciären in 2012 and 2013. To replicate these data, the subglacial model required high conduit roughnesses to be specified (Manning’s $\textit{n}$ = 0.125 for conduits leading to Centerjåkk/Sydjåkk and $\textit{n}$ = 0.075 for the conduit producing outflow at Nordjåkk). However, this is encouraging and follows postulations of braided, broad and low Hchannels beneath Storglaciären, which cannot be explicitly accounted for by the model, so rough Rchannels are instead required. Overall, the subglacial model performed well, though slightly underestimated discharge and overestimated flow-routing times. The internal drainage system was reevaluated, with suggestion that the englacial network in the upper ablation and firn areas may feed Centerjåkk/Sydjåkk, not Nordjåkk, contrasting with suggestions in previous studies. The physically based model performed less favourably than simpler linear-reservoir models applied to Storglaciären; however, its key worth was in generating continuous basal water pressure for the entire summer, the first data of this kind to be generated for this glacier. These data compared well with suggestions from empirical borehole measurements in previous years. Specifically, the ‘Spring Event’ (marked by a high-pressure period at the end of May), continuously high pressures (at/above ice-overburden) within the overdeepened (up to ~230m) area and the response of water pressures to major meteorological forcings were captured. The fact that continuously high pressures within the overdeepening were reproduced despite the model’s inherent specification of R-channels suggests this flow morphology is possible here, informing our understanding of processes within overdeepenings.
... The glaciers of the Kebnekaise region have been subject to significant glaciological research (e.g. Schytt 1962Schytt , 1966Holmlund et al. 1996;Holmlund & Jansson 1999;Zemp et al. 2010;Rippin et al. 2011;Gusmeroli et al. 2012;Brugger & Pankratz 2015). However, despite considerable research also investigating moraine development (e.g. ...
Article
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Despite a long history of glaciological research, the mode of formation and palaeo-environmental significance of moraine systems in the Kebnekaise Mountains, Sweden has remained uncertain. These landforms offer the potential to elucidate glacier response prior to the period of direct monitoring and provide an insight into the ice-marginal processes operating at polythermal valley glaciers. This study sets out to test existing interpretations of Scandinavian ice-marginal moraines which invoke ice stagnation, pushing, stacking/dumping, and push-deformation as important moraine forming processes. Moraines at Isfallsglaciären were investigated using ground-penetrating radar to document the internal structural characteristics of the landform assemblage. Radar surveys revealed a range of substrate composition and reflectors, indicating a debris-ice interface and bounding surfaces within the moraine. The moraine is demonstrated to contain both ice-rich and debris-rich zones, reflecting a complex depositional history and a polygenetic origin. As a consequence of glacier overriding, the morphology of these landforms provides a misleading indicator of glacial history. Traditional geochronological methods are unlikely to be effective on this type of landform as the fresh surface may post-date the formation of the landform following reoccupation of the moraine rampart by the glacier. This research highlights that the interpretation of geochronological datasets from similar moraine systems should be undertaken with caution.
... Some exist from interior valley glaciers such as Storglaciären in Sweden (e.g. Holmlund et al. 1996). However, little is known about glacier positions, and hence glacier volumes, at the end of the nineteenth century. ...
Article
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This paper outlines some significant visits made to north Norway by geologists and mountaineers from Britain and Ireland from the early to late nineteenth century. These visitors wrote up their travels and climbing experiences in a region in north Norway that was difficult to get to other than by sea: øksfjordjøkelen and Lyngen. Early travellers revealed the sights of the fjord areas and thereby promoted the region for subsequent travellers. Leopold von Buch's Travels though Norway and Lapland during the Years 1806, 1807, and 1808 probably prompted J. D. Forbes to visit and produce Norway and Its Glaciers and Archibald Geikie's Geological Sketches at Home and Abroad as part of the contemporary discussions about the 'glacial theory'. In the latter years of the nineteenth century the British climbers William Cecil Slingsby and George Hastings, with local climber Josef Caspari, explored the Lyngen Peninsula. Elizabeth Main (Mrs Aubrey Le Blond) also climbed in Lyngen. As well as providing written summaries of their exploits, the early explorers included photographs in their books. Some of these images are helpful in the reconstruction of the glacierized landscapes at the end of the Little Ice Age. It is suggested that present-day travellers might leave their observations available, in digital media, for future investigators.
... From the similarity between the δ 18 O record derived from diatoms and the proxy record for Holocene glacier activity in Vuolep Allakasjaure we conclude in paper III that the coinciding of all isotope depletion minima with glacier advances indicates that changes in atmospheric circulation affected both δ 18 O lakew and the mass balance of the glacier. The mass balance of present-day glaciers in this area primarily responds to summer air temperatures, but winter precipitation amounts are also important (Holmlund et al., 1996). Weaker westerlies and a more southerly polar front would allow colder and isotopically more depleted air from the north to influence the region in summer. ...
... The earliest known long-term mass balance study was launched in 1946 on the Storglaciären in Sweden. This study continues today (Holmlund et al., 1996). The study of glaciers grew rapidly in the 1960s, spurred by the International Hydrological Decade, 1965Decade, -1974, and the development of hydroelectric power, particularly in Norway (Collins, 1984). ...
Article
A combination of field work, modeling, and remote sensing was used to determine mass balances for the Quelccaya Ice Cap in Peru and for parts of the Greenland Ice Sheet. A 40-year history of deglaciation on Quelccaya derived from satellite is presented. Automatic Weather Station and snow pit data throughout Greenland were utilized to determine a mass balance profile for the ice sheet which will serve as a baseline for future comparison. Finally, a series of models were tested in west-central Greenland for their ability to accurately simulate measured melt conditions given hourly observations of the surface meteorology. A new analytical melt model, SOSIM, was developed and tested for this study.
... To track or estimate glacier volume change requires some kind of monitoring program. Historically, glacier-monitoring programs were based on intensive measurements at each glacier to understand the links between glacier mass balance, meteorology and runoff (Reinwarth, 1993; Holmlund, 1996; Krimmel, 1999b). However, such intensive measurements were limited to one glacier within a region, with the expectation that those changes represented the processes on all the glaciers across the region. ...
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The spatial characteristics for all glaciers in the North Cascades National Park Complex, USA, were estimated in 1958 and again in 1998. The total glacier area in 1958 was 117.3 ± 1.1 km2; by 1998 the glacier area had decreased to 109.1 ± 1.1 km2, a reduction of 8.2 ± 0.1 km2 (7%). Estimated volume loss during the 40 year period was 0.8 ± 0.1 km3 of ice. This volume loss contributes up to 6% of the August-September stream-flow and equals 16% of the August-September precipitation. No significant correlations were found between magnitude of glacier shrinkage and topographic characteristics of elevation, aspect or slope. However, the smaller glaciers lost proportionally more area than the larger glaciers and had a greater variability in fractional change than larger glaciers. Most of the well-studied alpine glaciers are much larger than the population median, so global estimates of glacier shrinkage, based on these well-studied glaciers, probably underestimate the true magnitude of regional glacier change.
... In the vicinity of all these three drill sites exist glaciers with long continuous mass balance records. The glacier austre Brøggerbreen on western Spitsbergen, 130 km from Janssonhaugen, has such records since 1967 (Liestøl 1990, Hagen & Liestøl 1990, and the glacier Storglaciären in northern Sweden, situated some 2.5 km away from Tarfalaryggen, has mass balance measurements since 1945/1946 (Schytt 1947, Holmlund et al. 1996, Holmlund & Jansson 1999. This is the longest continuous mass balance record in the world. ...
Article
The first deep permafrost boreholes (>10 m) ever drilled in Scandinavia for climatic studies constitute part of a transect of deep mountain permafrost boreholes through the mountains of Europe established under the EU PACE (Permafrost and Climate in Europe) Project. In Scandinavia, PACE boreholes are located at Juvvasshøe, southern Norway, Tarfalaryggen in northern Sweden, and northernmost in the transect at Janssonhaugen, western Svalbard. This paper outlines the aims and objectives of the PACE programme, and describes in detail the Svalbard and Scandinavian permafrost boreholes.
... Storglaciären was chosen due to its relative accessibility and simple geometry (Schytt 1947;Ahlmann 1951). The mass balance work on Storglaciären started in 1945 and is still running today (Holmlund et al. 1996a; Fig. 1). From 1981 through to today a number of glaciers have been studied, either as part of the long-term monitoring programme or as shorter time-span studies ( Table 1 summarises the work done in Sweden since 1941; Holmlund 1995). ...
Article
The Tarfala mass balance programme currently comprises seven glaciers distributed in two, one southerly and one northerly, east-west trending profiles. Of the studied glaciers, Storglaciären has the longest record spanning 1945 to present. The purpose of the programme is to study gradients in mass balance parameters across the northern Scandinavian mountains. The measurements of both winter and summer balance are carried out with significant redundancy each year. In order to maintain such a large programme with limited personnel, different measurement techniques and strategies are applied to the different glaciers according to a priority scale. Storglaciären is the most important glacier in the network and is measured with high accuracy and measurement density. Storglaciren is also used as a reference for all other glaciers in the programme. The other glaciers have sparser measurement systems and are sometimes measured using alternative methods such as snow radar. In general, Swedish glaciers are still responding to the major climatic warming around 1910–1920 by retreat, and the effect of very long response times. However, measured volume change indicates that most glaciers are close to or varying around a quasi-steady state.
... Glaciers 1, 2, 3, 6, 7 and 8 are located in southern Norway, glacier 4 in northern Norway, 5 in northern Sweden, and 9 and 10 on western Svalbard (for location, see Figs 1 and 2). Glacier mass-balance data for glaciers on the Norwegian mainland from Kjøllmoen (1998), the two Svalbard glaciers from Jania and Hagen (1996; and later updated by J.O. Hagen, personal communication) and Storglaciären in northern Sweden from Holmlund et al. (1996) Glacier including melting, wind deflation, avalanching from the front, calving of icebergs, melting from runoff, evaporation and sublimation. The amount of snow and ice stored in glaciers is subject to systematic changes during a year, which are the result of cycles of accumulation and ablation. ...
Article
The North Atlantic Oscillation (NAO) is one of the modes of climate variability in the North Atlantic region. The atmospheric circulation during the winter season in this region commonly displays a strong meridional (north–south) pressure contrast, with low air pressure (cyclone) centred close to Iceland and high air pressure (anticyclone) near the Azores. This pressure gradient drives the mean surface winds and the mid-latitude winter storms from west to east across the North Atlantic, bringing mild moist air to northwest Europe. The NAO index is based on the difference of normalised sea-level pressures (SLP) between Ponta Delgada, Azores and Stykkisholmur, Iceland. The SLP anomalies at these stations are normalised by division of each monthly pressure by the long-term (1865–1984) standard deviation. Interannual atmospheric climate variability in northwest Europe, especially over Great Britain and western Scandinavia has, during the last decades, been attributed mainly to the NAO, causing variations in the winter weather over the northeast North Atlantic and the adjacent land areas. A comparison between the NAO index and the winter (December–March) precipitation between ad 1864 and 1995 in western Norway shows that these are strongly linked (correlation coefficient 0.77). Variations in the NAO index are also reflected in the mass balance records of glaciers in western Scandinavia. The NAO index is best correlated with mass balance data from maritime glaciers in southern Norway (e.g. Ålfotbreen R2 = 0.51). The record of Holocene (last ca. 11 500 cal. yr) glacier variations of maritime glaciers in western Scandinavia is thus a proxy of pre-instrumental NAO variations. Copyright © 2000 John Wiley & Sons, Ltd.
... The longest, continuous glacier mass-balance record in the world comes from Storglaciä ren, northern Sweden, and was started by Valter Schytt in the spring of 1946 (Schytt, 1947;Holmlund et al., 1996Holmlund et al., , 2005Klingbjer et al., 2005) (Fig. 13A). The next longest continuous mass-balance record, initiated in 1948/1949 by Olav Liestøl, is from Storbreen, Jotunheimen, central-southern Norway (Fig. 13B). ...
Article
During the early Holocene abrupt, decadal to centennial-scale climate variations caused significant glacier variations in Norway. Increased freshwater inflow to the North Atlantic and Arctic Oceans has been suggested as one of the most likely mechanisms to explain the abrupt and significant Lateglacial and early Holocene climatic events in NW Europe. The largest early Holocene glacier readvances occurred ∼11,200, 10,500, 10,100, 9700, 9200 and 8400–8000 cal. yr BP. The studied Norwegian glaciers apparently melted away at least once during the early/mid-Holocene. The period with the most contracted glaciers in Scandinavia was between 6600 and 6000 cal. yr BP. Subsequent to ∼6000 cal. yr BP the glaciers started to advance and the most extensive glaciers existed at about ∼5600, 4400, 3300, 2300, 1600 cal. yr BP, and during the ‘Little Ice Age’. Times with overall less glacier activity were apparently around 5000, 4000, 3000, 2000, and 1200 cal. yr BP. It has been proposed that several glacier advances occurred in Scandinavia (including northern Sweden) at ∼8500–7900, 7400–7200, 6300–6100, 5900–5800, 5600–5300, 5100–4800, 4600–4200, 3400–3200, 3000–2800, 2700–2000, 1900–1600, 1200–1000, and 700–200 cal. yr BP. Glaciers in northern Sweden probably reached their greatest ‘Little Ice Age’ extent between the 17th and the beginning of the 18th centuries. Evidence for early Holocene glacier advances in northern Scandinavia, however, has been questioned by more recent, multi-disciplinary studies. The early to mid-Holocene glacier episodes in northern Sweden may therefore be questioned.
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Geodetic volume estimates of Storglaciären in Sweden suggest a 28% loss in total ice mass between 1910 and 2015. Terrestrial photographs from 1910 of Tarfala valley, where Storglaciären is situated, allow for an accurate reconstruction of the glacier's surface using Structure-from-Motion photogrammetry, which we used for past volume and mass estimations. The glacier's yearly mass balance gradient and net mass balance was also estimated back to 1880 using weather data from Karesuando, 170 km north-east of Storglaciären, through neural network regression. These combined reconstructions provide a continuous mass change series between the end of the Little Ice Age and 1946, when field data become available. The resultant reconstruction suggests a state close to equilibrium between 1880 and the 1910s, followed by drastic melt until the 1970s, constituting 76% of the 1910–2015 ice loss. More favourable conditions subsequently stabilized the mass balance until the late 1990s, after which Storglaciären started losing mass again. The 1910 reconstruction allows for a more accurate mass change series than previous estimates, and the methodology can be used on other glaciers where early photographic material exists.
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Timing of cirque formation and the climate necessary to initiate glaciation are fundamental to the understanding of the landscape of the northern Scandinavian mountains. Empty cirques in the Rassepautasjtjåkka massif are located near a glaciated area and thus appear near the glaciation limit. In order to investigate the climate conditions necessary for glacier formation in the cirques, we applied a spatially distributed temperature index melt model. After calibration under present climate conditions, the model was run with different combinations of increased initial winter snow cover and lowered summer air temperatures to assess the climate conditions needed for snow to survive summer and hence form a base for glaciation. Results indicate that a significant increase in precipitation or decrease in summer air temperature or a combination of both is necessary to initiate glaciation. Thus current climate conditions are far from favorable for glaciation. If summer temperature is decreased by 4°C or winter snow cover is more than doubled, only 10% of cirque areas remain snow covered, which is considered as a minimum condition for glacier formation. According to climate reconstructions such conditions have not occurred during the Holocene suggesting that the cirques have not been glaciated during this period. Consequently glaciation of the cirques must have occurred during other parts of the glacial cycles.
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Storglaciären is a small valley glacier in northern Sweden. Detailed studies of surface velocity, glacier hydrology and ice dynamics between 1981 and 1995 have revealed unexpected details of dynamic behaviour of the glacier. The glacier accelerates and decelerates, frequently on a diurnal basis, in direct response to subglacial water pressure variations. Furthermore longitudinal coupling effects are evident where the glacier flows across irregularities on the bed. This coupling is caused by a change in the hydraulic system underneath the glacier as the glacier flows across a bedrock ridge. Since the properties of the drainage system can change over small distance, the dynamics of the glacier is also spatially highly variable. Thus, small glaciers, such as Storglaciären, are not as sluggish as may be expected but exhibit behaviour similar to that of larger glaciers. This means that features of large glaciers and ice sheets can be studied on smaller glaciers where logistics and experimental set-ups are easier to establish.
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Photogrammetrical studies of volume changes of glaciers are a helpful complementary tool to field studies of mass balance. Map data give an indication as to what has happened and field data provide possibilities to interpret why it happened. Photogrammetric studies are thus well suited for monitoring programmes, especially in remote areas such as in the Arctic. Photogrammetrically surveyed volume changes can also be used to validate field measured mass balances.
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The robustness of a simple flow-line model has been tested against new data from Storglaciären. The model appears robust for given subglacial geometry. A realistic longitudinal profile and acceptable ice surface velocities were generated. The model has been tested in a series of sensitivity experiments, and was found to react strongly to changes in climatic parameters (ΔELA of 25 m, ∼0.25 meters water equivalent). Due to the uneven subglacial topography underlying Storglaciären, its behavior is non-linear and prone to considerable hysteresis. From these experiments it appears that Storglaciären was not in balance with its climate when it reached its maximum historic extent in 1915.
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Ice cores obtained from cold glaciers are known to contain detailed archives on past climates. So far, no such data-set has been retrieved from Scandinavia, in part because most Scandinavian glaciers are largely of a temperate type, thus having a less well preserved climatic signal. However, within the more continental parts of the Scandinavian mountain range, glaciers often have a substantial cold surface layer in the ablation area. Past climate variations may be reconstructed from studies of crystallography and stratigraphy of ice from the cold surface layer. The thicknesses of such cold layers at two closely situated sites in northern Sweden have been mapped by a ground based high resolution radar. The best results were obtained by using the frequency interval 700–900 MHz. The two investigated glaciers Storglaciären and Mårmaglaciären are situated 20 km from each other in an area with a strong east-west climatic gradient. The annual average air temperature is similar at the two sites, whilst the precipitation rate on Storglaciären is almost double that of Mårmaglaciären. The radar soundings show that Mårmaglaciären has a significantly thicker cold surface layer, 65 m on average compared with 30 m on Storglaciären. The difference is caused by less snow cover insulation from winter cold and less net ablation on Mårmaglaciären. The measured thicknesses of the cold surface layer therefore seem to correlate well with the degree of continentality at the sites. Radar sounding is a highly useful tool for locating glaciers containing a potential relatively well preserved climatic signal. Such glaciers may be found within the more continental parts of the Scandinavian mountain range.
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Air temperatures at Tarfala Research Station have been measured during the summers of 1946 to 1995. Since 1965 several different types of automatic systems have been used for measurements throughout the entire year. Mean annual temperature for the period 1965 to 1995 was -3.9°C. Mean summer (June-August) and mean winter temperatures (October-April) were +5.5°C and -8.9°C respectively. The mean annual temperature shows a weak warming trend which is caused by increasing winter temperatures and slightly decreasing summer temperatures. The amplitude between the temperature of the coldest winter month and that of the warmest month of the following summer decreased by 0.8°C per decade during the period from 1965 to 1995, indicating a change towards a more maritime climate in the Tarfala Valley.
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Hourly melt and discharge of Storglaciären, a small glacier in Sweden, were computed for two melt seasons, applying temperature-index methods to a 30 m resolution grid for the melt component. The classical degree-day method yielded a good simulation of the seasonal patient of discharge, but the pronounced melt-induced daily discharge cycles were not captured. Modelled degree-day factors calculated for every hour and each gridcell from melt obtained from a distributed energy-balance model varied substantially, both diurnally and spatially. A new distributed temperature-index model is suggested, attempting to capture both the pronounced diurnal melt cycles and the spatial variations in melt due to the effects of surrounding topography. This is accomplished by including a radiation index in terms of potential clear-sky direct solar radiation, and thus, without the need for other data besides air temperature. This approach improved considerably the simulation of diurnal discharge fluctuations and yielded a more realistic spatial distribution of melt rates. The incorporation of measured global radiation to account for the reduction in direct solar radiation due to cloudiness did not lead to additional improvement in model performance.
Chapter
This chapter compiles and assesses information on recent and current change within the terrestrial cryosphere of the Baltic Sea drainage basin. Findings are based on long-term observations. Snow cover extent (SCE), duration and amount have shown a widespread decrease although there is large interannual and regional variation. Few data are available on changes in snow structural properties. There is no evidence for a recent change in the frequency or severity of snow-related extreme events. There has been a decrease in glacier coverage in Sweden and glacier ice thickness in inland Scandinavia. The European permafrost is warming, and there has been a northward retreat of the southern boundary of near-surface permafrost in European Russia.
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Glacier mass balance and mass balance gradient are fundamentally affected by changes in glacier 3D geometry. Few studies have quantified changing mountain glacier 3D geometry, not least because of a dearth of suitable spatiotemporally distributed topographical information. Additionally, there can be significant uncertainty in georeferencing of historical data and subsequent calculations of the difference between successive surveys. This study presents multiple 3D glacier reconstructions and the associated mass balance response of Kårsaglaciären, which is a 0.89 ± 0.01 km2 mountain glacier in sub-arctic Sweden. Reconstructions spanning 101 years were enabled by historical map digitisation and contemporary elevation and thickness surveys. By considering displacements between digitised maps via the identification of common tie-points, uncertainty in both vertical and horizontal planes were estimated. Results demonstrate a long-term trend of negative mass balance with an increase in mean elevation, total glacier retreat (1909–2008) of 1311 ± 12 m, and for the period 1926–2010 a volume decrease of 1.0 ± 0.3 × 10–3 km3 yr–1. Synthesising measurements of the glaciers’ past 3D geometry and ice thickness with theoretically calculated basal stress profiles explains the present thermal regime. The glacier is identified as being disproportionately fast in its rate of mass loss and relative to area, is the fastest retreating glacier in Sweden. Our long-term dataset of glacier 3D geometry changes will be useful for testing models of the evolution of glacier characteristics and behaviour, and ultimately for improving predictions of meltwater production with climate change.
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During the summer of 2010 the surface elevation of Storglaciären in northern Sweden was measured using high-precision GNSS and reflectorless Total Station surveys. The DEM created from these data contain less noise than those created from orthophotographic methods over snow covered glaciers and is therefore smoother, with fewer erroneous features in the data. The principal, though not sole, intended use for the DEM is in the calculation of surface mass balance, which has influenced decisions on what constitutes a functional part of a glacier, leading to the exclusion of features such as snow aprons and perennial ice above the bergschrund. Other peripheral features have changed since the previous, aerial survey from 1999 leading to a reduction in size of approximately 0.17 km2.
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The mechanisms controlling the spatial distribution and temporal fluctuations of the thermal structure in polythermal glaciers have, to date, been poorly investigated and are not fully understood. We have investigated the sensitivity of the cold surface layer thickness to different forcing parameters and the causes for an observed thinning of the cold surface layer on Storglaciären, northern Sweden, between 1989 and 2001 using a one-dimensional thermomechanical model and measurements of ice surface temperature, vertical velocity and net mass balance. Similarities between the spatial patterns of the cold surface layer, net mass balance and emergence velocity together with modelled high sensitivity to variations in emergence velocities suggest that the net ablation and vertical ice advection are the dominant forcing parameters. Results from transient model experiments suggest that the cold surface layer reaches a new equilibrium after a perturbation in the forcing within a few decades. No significant change in ice flow or mass balance has been observed at Storglaciären in recent decades. Instead, an increase of 18C in winter air temperature since the mid-1980s is probably the cause of the observed thinning of the cold surface layer. Increased winter temperatures at the ice surface result in a reduced formation rate of cold ice at the base of the cold surface layer and lead to a larger imbalance between net loss of ice at the surface and freezing of temperate ice at the cold–temperate transition surface. Model results indicate that the cold surface layer is more sensitive to changes in ice surface temperature in areas with lower emergence velocity, which explains the observed complex thinning pattern of the cold surface layer.
Article
Hourly melt and discharge of Storglaciaren, a small glacier in Sweden, were computed for two melt seasons, applying temperature-index methods to a 30 m resolution grid for the melt component. The classical degree-day method yielded a good simulation of the seasonal pattern of discharge, but the pronounced melt-induced daily discharge cycles were not captured. Modelled degree-day factors calculated for every hour and each gridcell from melt obtained from a distributed energy-balance model varied substantially, both diurnally and spatially. A new distributed temperature-index model is suggested, attempting to capture both the pronounced diurnal melt cycles and the spatial variations in melt due to the effects of surrounding topography. This is accomplished by including a radiation index in terms of potential clear-sky direct solar radiation, and thus, without the need for other data besides air temperature. This approach improved considerably the simulation of diurnal discharge fluctuations and yielded a more realistic spatial distribution of melt rates. The incorporation of measured global radiation to account for the reduction in direct solar radiation due to cloudiness did not lead to additional improvement in model performance.
Thesis
In dieser Arbeit werden Berechnungen zur klimatischen Sensitivität der Eiskappe von Devon Island (Nunavut, Kanada) durchgeführt, die auf einem mit Wärmesummen arbeitenden Massenbilanzmodell basieren. Wichtigste Datenbasis für die Modellrechnungen sind dabei höhenabhängige Massenbilanzreihen der Devon-Eiskappe sowie tägliche Klimadaten der WMO-Station Resolute Bay. Durch die Bestimmung geeigneter Modellparameter (Temperaturgradienten, Wärmesummenkoeffizienten) ist es möglich, das mittlere Massenbilanzprofil gut zu simulieren. Das auf diese Weise kalibrierte Modell kann dann – als einfache Alternative zu Energiebilanzmodellen – zur Berechnung der Sensitivität der Massenbilanz auf Veränderungen von Temperatur und Niederschlag genutzt werden. Anwendungen des Modells verdeutlichen, dass die Massenbilanz der Devon-Eiskappe stark abhängig von der Entwicklung der Sommertemperaturen und die klimatische Sensitivität im Vergleich mit anderen Eismassen aus feuchteren Klimaten sehr klein ist. Die Einbeziehung der saisonalen Abhängigkeit der Massenbilanz kann schließlich helfen, eine mit Schwierigkeiten verbundene Rekonstruktion der jährlichen Massenbilanz zu verbessern.
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. Ground-penetrating radar has been widely used to map the thermal structure of polythermal glaciers. Hitherto, the cold–temperate transition surface (CTS) in radargrams has been identified by a labour-intensive and subjective manual picking method. We introduce a new automatic approach for picking the CTS that uses the difference in signal power exhibited by the cold and temperate ice layers. We compare our automatically computed CTS depths with manual picks. Our results show very good agreement between the two methods in most areas (r 2 > 0.7). RMSEs computed at each trace in two-way travel-time from three test sites range from 14 to 19 ns (2.4–3.2 m). The proposed automated method mostly fails in areas showing a rather gradual transition in signal power at the CTS. In some areas, high power originating from non-water sources is misinterpreted by the automatic picking method as 'temperate ice'.
Article
A passive seismology experiment was conducted across the main overdeepening of Storglaciären in the Tarfala valley, northern Sweden, to investigate the spatial and temporal distribution of basal microseismic waveforms in relation to known dynamics of this small polythermal sub-arctic glacier. The high ablation rate made it difficult to keep geophones buried and well coupled to the glacier during the experiment and reduced the number of days of good-quality data collection. The characterization of typical and atypical waveforms showed that the dominant waveforms were from near-surface events such as crevassing. Waveforms resembling basal microseismic signals were very rare, and seldom observed on more than two seismic stations simultaneously. The analysis of waveforms, amplitudes and particle motions suggested a near-field origin for most events. Even though basal sliding is known to occur in the overdeepening, no convincing examples of basal waveforms were detected, suggesting basal microseismic signals are rare or difficult to detect beneath polythermal glaciers like Storglaciären. We discuss the reasons for failing to locate basal signals, consider the origin of common waveforms and make recommendations for setting up passive seismology experiments on glaciers with high ablation rates.
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The mass balance and associated work on Scandinavian glaciers is probably as extensive as anywhere in the world. The utility of these glacio-climatic records plus glacial chronological investigations allows not only comparisons from different climatic conditions in Scandinavia but testing of models of behaviour. Such models may relate to the behaviour of the glacier flow itself as perturbed by mass balance changes or they may be ways of modelling the mass balance itself in terms of meteorological/climatic parameters. All such modelling relies upon good field data and the papers reviewed briefly above show the importance of the longevity as well as quality of the Scandinavian data sets. With new techniques being added to the glaciological armoury and the ability to use them on an increasingly diverse range of glaciers, both spatially and with respect to size, the Scandinavian glaciers will remain a most important means of elucidating both past and future climate change. Furthermore, it is now becoming evident that the wide range of various ‘proxy’ data from both terrestrial and oceanic sources is also becoming better integrated with the mass balance data and the modelling of climate change. The glaciers of Scandinavia, by their nature, do not provide good ice-core records which go well back in time but the quality data which the glaciers do preserve in moraines, historical records as well as mass balance and snout retreat data for the last 150 years will continue to be important in elucidating climate change and climate variability.
Article
Glacier fluctuations constitute an important indicator for climate change, both current and past. Glacier mass balance measurements are made to correctly reflect the state of the glacier. Very few studies have been made to study the representability of each point measurement to the average mass balance of a particular glacier, an exercise that requires a large number of measurements. Such studies are rare due to the practical constraints and costs involved in collecting data. On Storglaciaren, Sweden, a very dense system of measurements of both distributed winter (similar to 100 points km) and summer (similar to 15 points km(-2)) balance allows a spatial analysis of the mass balance components. The results Show that local summer balance values are strongly correlated to the average summer balance value of the glacier. Local winter balance values are also generally well correlated to the average winter balance value, but small areas on the glacier exhibit no correlation. These areas correspond to wind-eroded areas of low accumulation on the glacier. The local net balance values are also well correlated to the average net balance value, indicating that the effect of the summer balance is strong and, at least partly, counter-balancing the spatial inhomogeneities in the local spatial winter balance values. These results show that detailed knowledge of both mass balance components and their spatial variability may be necessary to safely use a sparse system of measurements points. On Storglaciaren, this is especially true for winter balance measurements since the spatial snow distribution is highly variable and not necessarily representative of the glacier average at each measurement point. The results strictly apply to Storglaciaren but similar effects should be present on most glaciers in a similar setting; the results thus serve as an example of conditions that can be expected on a typical mid-latitude to subarctic glacier.
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This work presents historical data on glacier mass balance. Until now, these data have been scattered throughout many publications, limiting their utility in the geosciences. The main objective of this contribution is to summarize data available in the digital data base of Dyurgerov (2002), and to discuss in some detail their quality and limitations. This paper is intended for glaciologists, climatologists, hydrologists, and other specialists interested in high-mountain and polar environments. Other potential users include those interested in the state of modern glaciers, their change on a global scale, or in changes occurring in any particular region.
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We use a pro-glacial oxygen isotope record of diatom silica (δ18Odiatom) and a sedimentary proxy for glacier fluctuations to determine centennial–millennial scale climate change during the last 5000 years in northern Sweden. We show that the lake water isotopic composition predominantly reflects the isotopic composition of the precipitation. Superimposed on a general depletion trend of 3.5‰ over the past 5000 years we found that the isotopic composition of precipitation became depleted (>1‰ excursions) during four occasions centered at 4400, 3000, 2000, and after 1200calyr BP. Climate simultaneously sustained a positive glacier mass balance, that caused the catchment glacier to advance. A persistent change in the atmospheric circulation pattern could potentially have caused the registered changes in δ18Odiatom because different air masses hold characteristic δ18O signatures of their precipitation. The glacier mass balance primarily responds to the influence of summer temperature on ablation. We suggest that the most likely cause for the recorded changes in both these proxies is a steadily increasing but fluctuating dominance of colder and δ18O depleted air masses from the north/northeast during the past 5000 years. The δ18Odiatom depletion and glacier events all occur at times of relative ice-rafted-debris maxima in the North Atlantic, consistent with cold conditions and changes in surface wind directions. Our results confirm that changes towards a predominance of north/northeasterly winds occurred at these time intervals.
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The subarctic environment of northernmost Sweden has changed over the past century, particularly elements of climate and cryosphere. This paper presents a unique geo-referenced record of environmental and ecosystem observations from the area since 1913. Abiotic changes have been substantial. Vegetation changes include not only increases in growth and range extension but also counterintuitive decreases, and stability: all three possible responses. Changes in species composition within the major plant communities have ranged between almost no changes to almost a 50 per cent increase in the number of species. Changes in plant species abundance also vary with particularly large increases in trees and shrubs (up to 600%). There has been an increase in abundance of aspen and large changes in other plant communities responding to wetland area increases resulting from permafrost thaw. Populations of herbivores have responded to varying management practices and climate regimes, particularly changing snow conditions. While it is difficult to generalize and scale-up the site-specific changes in ecosystems, this very site-specificity, combined with projections of change, is of immediate relevance to local stakeholders who need to adapt to new opportunities and to respond to challenges. Furthermore, the relatively small area and its unique datasets are a microcosm of the complexity of Arctic landscapes in transition that remains to be documented.
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The spatial and temporal variability of seasonal snow cover in glacierized catchments has important implications for the net mass balance of alpine glaciers. This study examines the relationship between changing snowpack volume, the resulting winter balance and the net mass balance of Storglaciären, northern Sweden. Using a conceptual model, the net seasonal snow input to the glacier is simulated daily for 16 years from 1990. From this the annual snow accumulation and winter balance are calculated. The model outputs are compared with snowlines delineated from classified aerial photographs, ASTER and Landsat 7 ETM+ satellite imagery, and with measured Storglaciären winter balances. The results of the model indicate variability in the winter balance over the study period, though there is a slightly negative trend overall. The highest winter balances and seasonal snow volumes occurred in the early 1990s and correspond with positive net mass balances. However, the slightly negative trend in winter balance and decreased net seasonal snow volumes suggested by the model, combined with the measured increasing trend in mass lost due to ablation, have resulted in decreasing glacier net mass balances and a corresponding rise in ELA over the study period.
Article
Measurements of summer and winter mass balances have been carried out over the past 53 years on Storglaciären, northern Sweden. Repeated surveys of the glacier have resulted in several maps of surface topography, as well as a map of the bed topography. A new time-dependent ice flow model allows us to compare the observed surface evolution of the glacier with that computed by the model using measured mass-balance maps as input. The computed volume change compares well with the measured change: the model replicates the distribution of surface elevation to within ±10 m over 30 years of integration. On the model side, these deviations can be attributed to the low-resolution discretization of the model domain as well as to the limited accuracy of the ice rheology and omitted basal sliding. On the other hand, the uncertainties of the topography and mass-balance maps match the model uncertainties. In this sense, the experiments are a validation of both model and observations.
Article
Rabots Glaciär and Storglaciären, two small valley glaciers in the Swedish Arctic, have not behaved synchronously in response to recent climate change. Both glaciers advanced late in the 19th century and then began to retreat in response to a ∼1°C warming that occurred around 1910. By the mid-1980s the terminus and volume of Storglaciären had essentially stabilized, so it may have completed its response to the earlier warming. In contrast, ongoing thinning and retreat of Rabots Glaciär are substantial and suggest its response time is considerably longer. A time-dependent numerical model was used to investigate each glacier's response to perturbations in mass balance. This modeling suggests that, for small perturbations, volume timescales for Storglaciären and Rabots Glaciär are ∼125 and ∼215 years, respectively. Another measure of response time (i.e. length response time) yields somewhat lower values for each glacier; however, what is significant is that by either measure and accounting for uncertainties, the response time for Rabots Glaciär is consistently about 1.5 times longer than that for Storglaciären. This implies that their non-synchronous behavior is likely due to differences in response times. The latter ultimately result from markedly different longitudinal geometries (particularly near the termini), velocity profiles and specific net balance gradients.
Article
We present a Seasonal Sensitivity Characteristic (SSC) of Vatnajökull (Iceland), which consists of the sensitivity of the mean specific mass balance to monthly perturbations in temperature and precipitation. The climate in Iceland is predominantly maritime (high precipitation) although often the polar air mass influences the area. This results in temperature sensitivities that are high in summer and nearly zero during the winter months. In contrast, precipitation sensitivities are high in winter and low in summer. We use the SSC of Vatnajökull as a reduced mass balance model, with which we reconstruct the mass balance of Vatnajökull since 1825. The reduced model shows that changes in temperature and precipitation like the ones observed both have a significant impact upon the mass balance. The reconstructed mass balance records for two Icelandic glaciers correlate very well with mass balance records that are extracted from length records with a linear inverse model. This places confidence in both the reduced (forward) mass balance model and in the inverse model, although the forward method produces larger mass balance variations than the inverse method. For the south of Vatnajökull we find that after 1900, the length record is well explained by temperature variations alone, while another Icelandic glacier (Sólheimajökull) was also influenced by precipitation variations.
Article
Mapping and laboratory analysis of the sediment—landform associations in the proglacial area of polythermal Storglaciären, Tarfala, northern Sweden, reveal six distinct lithofacies. Sandy gravel, silty gravel, massive sand and silty sand are interpreted as glaciofluvial in origin. A variable, pervasively deformed to massive clast-rich sandy diamicton is interpreted as the product of an actively deforming subglacial till layer. Massive block gravels, comprising two distinctive moraine ridges, reflect supraglacial sedimentation and ice-marginal and subglacial reworking of heterogeneous proglacial sediments during the Little Ice Age and an earlier more extensive advance. Visual estimation of the relative abundance of these lithofacies suggests that the sandy gravel lithofacies is of the most volumetric importance, followed by the diamicton and block gravels. Sedimentological analysis suggests that the role of a deforming basal till layer has been the dominant factor controlling glacier flow throughout the Little Ice Age, punctuated by shorter (warmer and wetter climatic) periods where high water pressures may have played a more important role. These results contribute to the database that facilitates discrimination of past glacier thermal regimes and dynamics in areas that are no longer glacierized, as well as older glaciations in the geological record.
Article
The paper reviews various kinds of geoecological change in the tree-limit ecotone of the Scandes Mountains during the period 1970–95. The focus of the study is a part of a regional network of sites intended for long-term tree-limit monitoring, with special stress on effects of climatic variability. The elevational tree-limits of Betula pubescens sp. Sortuosa, Picea abies and Pinus sylvestris, which rose in response to the climatic amelioration earlier this century, now show clear symptoms of increasing climatic stress and disturbance. This manifests as defoliation, growth recession and reproductive failure, locally leading to some initial elevational tree-limit retraction (unbalanced mortality). Defoliation was preceded by decades of weak summer cooling and an increasingly maritime climate, but recently it correlates significantly with low winter soil temperatures, causing death of needles, shoots and buds. In some habitats, Betula pubescens has suffered from mechanical stress and disturbance by increased snow accumulation. Tree-limit decline is paralleled by analogous responses of high-elevation boreal forests as well as the ground cover, encompassing elevational range-limit retraction of certain plant species, deterioration of alpine/subalpine dwarf-shrub heaths and terricolous lichen mats. These processes coincide with indications of enhanced periglacial activity, chiefly wind deflation of frost-heaved top-soils at exposed sites. Presumably, reindeer trampling and grazing play a certain role in the latter context, although this disturbance interacts with climate cooling and increased storminess. Short-term extreme events, particularly concerning winter climate (e.g. ground frost), represent previously underrated disturbance mechanisms in cold-stressed, high-altitude boreal forest. The results suggest mechanisms of tree-layer regression, which lag behind the most severe stresses and disturbances by decades and make cold-marginal trees increasingly sensitive to climatic extremes and, in addition, unable to respond progressively to later positive weather anomalies, due to major defoliation and hypothetical xylem cavitation. The recorded changes are logical in consequence of the irregular climatic cooling and a more maritime climate since the late 1930s. In a wider perspective, the results fit a current pattern of natural geoecological destabilization and rapid vegetation change in the North Atlantic region. In addition, the results are discussed in the perspective of global climate change and biogeographical records over the past few decades.
Article
We have studied a 33.7 m deep ice core from a small polythermal Scandinavian ice cap to determine whether it is possible to recover pre-20th century climatic information from the glacier. Ice structural studies show a significant change from clear ice above 11 m depth (superimposed ice indicating refreezing) to bubbly ice below 11 m depth, indicating this is the transition between Little Ice Age (LIA) and 20th century ice. Calculations with a Nye-age model, along with a mass balance reconstruction, show that this structural boundary likely formed in the last part of the LIA, which in this region ended about 1910. The ice below this boundary was sampled and analysed for stable isotopic composition and ionic content, which both show significant variations with depth. The stable isotope record likely contains cycles of annual duration during the LIA. The chemistry in the ice core indicates that the information is useful, and can be used to interpret climatic and environmental variables during the LIA. A comparison of Riukojietna ion chemistry and oxygen isotope records with similar records from other glaciers in this region reveals a clear continental-maritime gradient. Changes in this gradient with time may be possible to resolve using such ice core records. Results from this study demonstrate that ice cores from glaciers in this climatic environment can be useful in revealing environmental conditions from climatically colder periods and yield pre-industrial benchmark values for chemical loading and oxygen isotopes, but that hiatuses complicate the depth-age relationship.
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Seasonal glaciological mass balances have been measured on Storglaciären without interruption since 1945/46. In addition, aerial surveys have been carried out on a decadal basis since the beginning of the observation program. Early studies had used the resulting aerial photographs to produce topographic glacier maps with which the in-situ observations could be verified. However, these maps as well as the derived volume changes are subject to errors which resulted in major differences between the derived volumetric and the glaciological mass balance. As a consequence, the original photographs were re-processed using uniform photogrammetric methods, which resulted in new volumetric mass balances for 1959–69, 1969–80, 1980–90, and 1990–99. We compared these new volumetric mass balances with mass balances obtained by standard glaciological methods including an uncertainty assessment considering all related previous studies. The absolute differences between volumetric and the glaciological mass balances are 0.8 m w.e. for the period of 1959–69 and 0.3 m w.e. or less for the other survey periods. These deviations are slightly reduced when considering corrections for systematic uncertainties due to differences in survey dates, reference areas, and internal ablation, whereas internal accumulation systematically increases the mismatch. However, the mean annual differences between glaciological and volumetric mass balance are less than the uncertainty of the in-situ stake reading and stochastic error bars of both data series overlap. Hence, no adjustment of the glaciological data series to the volumetric one is required.
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Storglaciären, located in the Kebnekaise massif in northern Sweden, has a long history of glaciological research. Early photo documentations date back to the late 19th century. Measurements of front position variations and distributed mass balance have been carried out since 1910 and 1945/46, respectively. In addition to these in-situ measurements, aerial photographs have been taken at decadal intervals since the beginning of the mass balance monitoring program and were used to produce topographic glacier maps. Inaccuracies in the maps were a challenge to early attempts to derive glacier volume changes and resulted in major differences when compared to the direct glaciological mass balances. In this study, we reanalyzed dia-positives of the original aerial photographs of 1959, -69, -80, -90 and -99 based on consistent photogrammetric processing. From the resulting digital elevation models and orthophotos, changes in length, area, and volume of Storglaciären were computed between the survey years, including an assessment of related errors. Between 1959 and 1999, Storglaciären lost an ice volume of 19×106 m3, which corresponds to a cumulative ice thickness loss of 5.69 m and a mean annual loss of 0.14 m. This ice loss resulted largely from a strong volume loss during the period 1959–80 and was partly compensated during the period 1980–99. As a consequence, the glacier shows a strong retreat in the 1960s, a slowing in the 1970s, and pseudo-stationary conditions in the 1980s and 1990s.
Article
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Seasonal glaciological mass balances have been measured on Storglaciären without interruption since 1945/46. In addition, aerial surveys have been carried out on a decadal basis since the beginning of the observation program. Early studies used the resulting aerial photographs to produce glaciological maps with which the in-situ observations could be verified. However, these maps as well as the derived volume changes are subject to errors which resulted in major differences between the derived volumetric and the glaciological mass balance. As a consequence, the original photographs were re-processed using uniform photogrammetric methods, which resulted in new volumetric mass balances for 1959–1969, 1969–1980, 1980–1990, and 1990–1999. We compare these new volumetric mass balances with mass balances obtained by standard glaciological methods including an uncertainty assessment considering all related previous studies. The absolute differences between volumetric and the glaciological mass balances are 0.9 m w.e. for the period of 1959–1969 and 0.3 m w.e. or less for the other survey periods. These deviations are slightly reduced when considering corrections for systematic uncertainties due to differences in survey dates, reference areas, and internal ablation, whereas internal accumulation systematically increases the mismatch. However, the mean annual differences between glaciological and volumetric mass balance are less than the uncertainty of the in-situ stake reading and, hence, do not require an adjustment of the glaciological data series.
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This paper reports recent changes in the mass balance record from the Djankuat Glacier, central greater Caucasus, Russia, and investigates possible relationships between the components of mass balance, local climate, and distant atmospheric forcing. The results clearly show that a strong warming signal has emerged in the central greater Caucasus, particularly since the 1993/1994 mass balance year, and this has led to a significant increase in the summer ablation of Djankuat. At the same time, there has been no compensating consistent increase in winter precipitation and accumulation leading to the strong net loss of mass and increase in glacier runoff. Interannual variability in ablation and accumulation is partly associated with certain major patterns of Northern Hemisphere climatic variability. The positive phase of the North Pacific (NP) teleconnection pattern forces negative geopotential height and temperature anomalies over the Caucasus in summer and results in reduced summer melt, such as in the early 1990s, when positive NP extremes resulted in a temporary decline in ablation rates. The positive phase of the NP is related to El Nino-Southern Oscillation, and it is possible that a teleconnection between the tropical Pacific sea surface temperatures and summer air temperatures in the Caucasus is bridged through the NP pattern. More recently, the NP pattern was predominantly negative, and this distant moderating forcing on summer ablation in the Caucasus was absent. Statistically significant correlations are observed between accumulation and the Scandinavian (SCA) teleconnection pattern. The frequent occurrence of the positive SCA phase at the beginning of accumulation season results in lower than average snowfall and reduced accumulation. The relationship between the North Atlantic Oscillation (NAO), Arctic Oscillation, and accumulation is weak, although positive precipitation anomalies in the winter months are associated with the negative phase of the NAO. A stronger positive correlation is observed between accumulation on Djankuat and geopotential height over the Bay of Biscay unrelated to the established modes of the Northern Hemisphere climatic variability. These results imply that the mass balance of Djankuat is sensitive to the natural variability in the climate system. Distant forcing, however, explains only 16% of the variance in the ablation record and cannot fully explain the recent increase in ablation and negative mass balance.
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The length of time τM over which a glacier responds to a prior change in climate is investigated with reference to the linearized theory of kinematic waves and to results from numerical models. We show the following: τM may in general be estimated by a volume time-scale describing the time required for a step change in mass balance to supply the volume difference between the initial and final steady states. We suggest that τM for mountain glaciers can be substantially less than the 102-103 years commonly considered to be theoretically expected. -from Authors
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The main perturbation in the mass balance of Storglaciären during the twentieth century was caused by a sudden 1°C increase in the summer mean temperature around 1910. Later perturbations of the climate have been of minor importance in relation to the mass balance. Annual field surveys suggest that the mass budget on Storglaciären has been in near balance for the last 15 years. Because of this major step-like change, we can establish the validity of theoretical models giving response times for Storglaciären of the order of 50 years. According to these models, Storglaciären could by now have reached a profile in balance with the present climate. To study this problem, the emergence velocity was calculated and compared with the net balance. The result shows that the emergence velocity either balances or exceeds the net balance for the entire tongue except for the lowermost part, where it decreases to about half of the net balance. A slight further recession of the front position would thus be expected with today’s climate. Calculated balance velocities also suggest that most of the present profile is close to a steady-state profile, if the mean annual sliding velocity is about 50% of the surface velocity. Lower sliding velocities would imply a thickening of the tongue and a thinning of the accumulation area during years of balanced mass budget.
Article
The robustness of a simple flow-line model has been tested against new data from Storglaciären. The model appears robust for given subglacial geometry. A realistic longitudinal profile and acceptable ice surface velocities were generated. The model has been tested in a series of sensitivity experiments, and was found to react strongly to changes in climatic parameters (ΔELA of 25 m, ∼0.25 meters water equivalent). Due to the uneven subglacial topography underlying Storglaciären, its behavior is non-linear and prone to considerable hysteresis. From these experiments it appears that Storglaciären was not in balance with its climate when it reached its maximum historic extent in 1915.
Article
The mass balance of Storglaciären is well correlated with the summer temperature at Tarfala and at other climatic stations in northern Sweden. By using regression models, Storglaciärens net balance has been estimated back to 1878. Based on this estimate the cumulative net increase in mass from 1878 to 1910 is estimated to have been 2 · 10¹⁰ kg. Since 1910 the mass loss has been 1.1 · 10¹¹ kg, or 26% of its mass in 1910. The volume change of Storglaciären has also been calculated, from comparison of maps dating from 1949,1959,1969 and 1980, all of which are based upon aerial photographs. This change is compared with the mass balance measured in the field to determine whether there are systematic errors in the field method and if so whether they are large enough to influence the annual mass balance significantly. The volume change based on the map study is in good agreement with field measurements. This means that the systematic errors in field surveys are not larger than those in the maps, which are estimated to be about ± 10% of the cumulative mass change over the 31-year period.
Article
The glacial chronology, obtained from proglacial lacustrine sediments, shows that Riukojietna, a small ice cap. disappeared or was small and inactive in the early-mid Holocene. A reactivation of the ice cap occurred around 2000 B.P. Riukojietna has retreated rapidly after a distinct maximum in extent in the beginning of the twentieth century. Measurements yielded negative net balances between 1985 and 1988. Differences in net balance seem to be caused primarily by fluctuating summer balances. Since Riukojietna has a relatively small vertical extent and is relatively low lying compared with cirque glaciers, it is much more sensitive to changes in the climate. Riukojietna is far from being in balance with the existing climate and will, if present trends continue, finally disappear.
Article
Mass balance measurements for the balance years 1985/86, 1986/87 and 1987/88 and calculations of the volume changes since the last maximum around 1915 have been carried out for Sydöstra Kaskasatjäkkoglaciären and Tarfalaglaciären in the Kebnekaise massif, Northern Sweden. A measure of the sensibility to climatic changes is given by the relationship between the mass balance volumes and the volumes of the glaciers. A comparison with Storglaciären and Rabots glaciär shows that Sydöstra Kaskasatjåkkoglaciären and Tarfalaglaciären are much more sensitive to climatic changes.
Article
The main perturbation in the mass balance of Storglaciären during the twentieth century was caused by a sudden 1°C increase in the summer mean temperature around 1910. Later perturbations of the climate have been of minor importance in relation to the mass balance. Annual field surveys suggest that the mass budget on Storglaciären has been in near balance for the last 15 years. Because of this major step-like change, we can establish the validity of theoretical models giving response times for Storglaciären of the order of 50 years. According to these models, Storglaciären could by now have reached a profile in balance with the present climate. To study this problem, the emergence velocity was calculated and compared with the net balance. The result shows that the emergence velocity either balances or exceeds the net balance for the entire tongue except for the lowermost part, where it decreases to about half of the net balance. A slight further recession of the front position would thus be expected with today’s climate. Calculated balance velocities also suggest that most of the present profile is close to a steady-state profile, if the mean annual sliding velocity is about 50% of the surface velocity. Lower sliding velocities would imply a thickening of the tongue and a thinning of the accumulation area during years of balanced mass budget.
Article
Preliminary analysis of 452 determinations of end-of-summer glacier snowline altitudes (ELAs) made over 17 yr on up to 47 glaciers show good correlation with major climatic events, and conform well with fluctuations of glacier termini when reaction times are taken into consideration. With snowline altitudes used as surrogates for annual mass balance values, there is a recent trend to increased mass balances, i.e. a climate {open_quotes}cooling,{close_quotes} which follows a long period of predominantly glacial recession. Snowline trend surfaces plotted for the Southern Alps of New Zealand show considerable warping with variable departures from the steady-state equilibrium-line altitude each year. The current resurgence of the more active glaciers should continue in the near future. 39 refs., 10 figs., 1 tab.
Article
Maps are presented for the subglacial topography of Storglaciären, Isfallsglaciären and Rabots glaciär in northern Sweden. The maps are results of radio-echo soundings. Isfallsglaciären consists of one isolated basin above the ice fall, whereas Storglaciären is situated in a valley which is divided into three basins. No depressions were found in Rabots glaciär. The distribution with elevation was obtained for ice thickness, bedrock and ice surface areas, and ice volumes. Data for Storglaciären: area A = 3.1 km2, ice volume V = 306 106 m3, average ice depth h̄ = 99 m, maximum ice depth hmax=250 m. Data for Isfallsglaciären: A = 1.3 km2, V = 93 106 m3, h̄ = 72 m, hmax=220 m. Rabots glaciär: A = 4.1 km2, V = 346 106 m3, h̄ = 84 m, hmax=175 m.
Article
Land rent assessments from western Norway and documents concerned with applications for their reduction provide detailed information about the incidence of landslides, rockfalls, and avalanches, as well as floods, during the period of the Little Ice Age. The nature and reliability of the available data is discussed and is shown to be adequate to demonstrate a much increased incidence of major mass movements and floods which started in the late 17th century and continued into the 19th century in valleys adjacent to Jostedalsbre. This environmental change began abruptly and there was a striking concentration of disastrous incidents between 1650 and 1760 and in certain years during that period, such as 1687, 1693, and 1702.
Article
The glacial chronology, obtained from proglacial lacustrine sediments, shows that Rjukojietna, a small ice cap, disappeared or was small and inactive in the early-mid Holocene. A reactivation of the ice cap occurred around 2000 B.P. Riukojietna has retreated rapidly after a distinct maximum in extent in the beginning of the twentieth century. Measurements yielded negative net balances between 1985 and 1988. Differences in net balance seem to be caused primarily by fluctuating summer balances. Since Riukojietna has a relatively small vertical extent and is relatively low lying compared with cirque glaciers, it is much more sensitive to changes in the climate. Riukojietna is far from being in balance with the existing climate and will, if present trends continue, finally disappear.
Article
In this paper Holocene climatic changes recorded in Lappland, northern Sweden, are described. Recorded changes are dated in three different ways: (1) moraines fronting alpine glaciers are dated lichenometrically, (2) lacustrine sediments, in which the silt content varies with size fluctuations of a small glacier, are C14 dated, and (3) variations in altitude of the pine tree limit are C14 dated. The advantages and limitations of the three techniques are discussed and the results of the studies are compared. In general, the results obtained in these three ways are consistent and are interpreted in climatic terms. The area around Vuolep Allakasjaure probably became deglaciated just before 9000 B.P. About 8600 B.P. climate began an improvement which culminated between 7000 and 6000 B.P. Shorter fluctuations are superimposed on this long-term climatic change. The most pronounced periods of relatively cold climate occurred about 7500-7300 B.P., 4500 B.P., 2800-2200 B.P., and during recent centuries. Variations in the composition of sediments in cores from Vuolep Allakasjaure indicate that the glacier in the drainage basin fluctuated frequently in size.
Article
The study deals with the ablation gradient and not with the budget gradient, wich has been treated by several other authors. An analysis of the 20 year long series of ablation measurements on Storglaciären, Sweden, shows that the ablation gradient varies considerably from one year to another, that the ablation gradient is dependent upon certain meteorological parameters but that this relationship is very complicated. Observations from the Arctic, from Scandinavia and from Canada show that there is no clear relation between ablation gradient and latitude, but that the ablation gradient is strongly dependent upon the degree of continentality.
Article
Detailed mapping of well-preserved moraine systems fronting 23 small glaciers in the Kebnekaise Mountains in Swedish Lapland reveals that the Holocene was punctuated by four prolonged intervals of glacier expansion. The youngest interval corresponds to the well-known Little Ice Age and lasted from at least A. D. 1500 until the 20th century. Minor fluctuations superimposed on this broad interval of expansion are dated by lichenometry and historical records; they culminated about A. D. 1916, 1890, 1850, 1780, 1710, and 1500 to 1640. The next youngest interval, which also involved a number of minor fluctuations spread over several centuries, is associated with C14 dates of 2320± 160 years B. P. (St-3811) and 2460± 90 years B. P. (I-6854) (Corrected for variation in atmospheric C14: 2370 and 2475-2720 years B. P., respectively). The two oldest glacial intervals center around tentative lichenometric dates of 5000 and 8000 years B. P., respectively. Advances of the two older intervals were the least extensive. Advances of the two youngest intervals were approximately equal in magnitude although the relative extents of drift sheets suggest that in many cases the older of these two intervals may have been slightly more intense. Within the Little Ice Age the advances between A. D. 1500 and 1640 were commonly the most extensive. Two features commonly encountered in the Kebnekaise Mountains point to the complexity of moraine construction. The first involves large moraine ridges that were built up over a time span of up to 8000 years by proximal enlargement of an original moraine obstruction by drift related to successively younger advances. The second feature involves numerous moraines that have survived documented glacier overriding essentially intact.
Article
Annual mass-balance measurements have been made at a number of glaciers in Norway since the beginning of the 1960s, A detailed and reliable map is necessary as a base for field work and more than twenty glacier maps have been constructed photogrammetrically at scales of 1:10 000 or 1:20 000 since 1952. For some of the glaciers more than one map has been constructed and changes in glacier volume can be calculated, provided the maps have sufficient accuracy. For the glaciers, Nigardsbreen, Hellstugubreen, and Gråsubreen, two or more good maps are available and these form a good basis for comparisons and calculations of changes in volume between the years when the air photographs were taken. Comparisons have been made for Gråsubreen between 1968 and 1984, for Hellstugubreen between 1968 and 1980, and for Nigardsbreen between 1964 and 1984. The calculations are made by placing a 100 m grid on the glacier maps and comparing the altitude for corresponding points. The changes in height are regarded as representative for the 0.01 km ² glacier areas represented by each point. Results from the investigation have been used to check the accuracy in cumulative mass balance for corresponding periods. Repeated air photography, at intervals of 5—10 years, can be used in the future to find the cumulative mass balance for a great number of glaciers at lower cost than “normal” mass-balance work.
Article
Austria. Here, we discuss the interpretation of detailed ablation measurements on the tongue. Two profiles are considered: one along the glacier axis and one across the glacier tongue. At the crossing, an energybalance station was operated, providing the necessary meteorological data. At all stakes the albedo was measured several times with a simple light-weight instrument (described separately in the Appendix). The absorption of solar radiation was calculated for all stake positions, taking into account local albedo, slope, aspect and shading effects. It appears that the differences in ablation can be explained almost entirely by the differences in surface albedo, both along and across the glacier tongue.
Article
Mass balance measurements for the balance years 1985/86, 1986/87 and 1987/88 and calculations of the volume changes since the last maximum around 1915 have been carried out for Sydostra Kaskasatjakkoglaciaren and Tarfalaglaciaren in the Kebnekaise massif, Northern Sweden. A measure of the sensitivity to climatic changes is given by the relationship between the mass balance volumes and the volumes of the glaciers. A comparison with Storglaciaren and Rabots glaciar shows that Sydostra Kaskasatjakkoglaciaren and Tarfalaglaciaren are much more sensitive to climatic changes. -Author
Article
Geostatistics provides a suite of methods, summarized as kriging, to analyze a finite data set to describe a continuous property of the Earth. Kriging methods consist of moving window optimum estimation techniques, which are based on a least-squares principle and use a spatial structure function, usually the variogram. Applications of kriging techniques have become increasingly wide-spread, with ordinary kriging and universal kriging being the most popular ones. The dependence of the final map or model on the input, however, is not generally understood. Herein we demonstrate how changes in the kriging parameters and the neighborhood search affect the cartographic result. Principles are illustrated through a glaciological study. The objective is to map ice thickness and subglacial topography of Storglaciren, Kebnekaise Massif, northern Sweden, from several sets of radio-echo soundings and hot water drillings. New maps are presented.
Accelerated glacier and permafrost changes in the Alps
• W Haeberli
Der Kårsa-Gletscher in Schwedish-Lappland
• H Ahlmann
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Glaciologiske undersökelser i Norge
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The bottom topography of Storglaciären. A new map based on old and new ice depth measurements, analyzed with geostatistical methods
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• W Haeberli
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Glaciologiske undersökelser i Norge
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Bremålning och brevariasjoner. Den Norske Turistförenings Årbok
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Massebalansemåliger på norske breer 1988, og 1989
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Die Gletscher Schwedens im Jahre 1908 Sveriges Geologiska Undersökningar (SGU) serie Ca part I: 1-54
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Gletscherstudien im Kebnekaise-Gebiet (Schwed. Lappland)
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Mass balance studies in northern Sweden
• P Holmlund
A snow radar measurement of the accumulation gradient from the coast to 3000 meter elevation, Dronning Maud Land. Filchner-Ronne Ice Shelf Programme (FRISP)
• P Holmlund
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Massebalansemåliger på norske breer
• T Laumann
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Storglaciärens tillbakagång i Kebnekaise
• C Mannerfelt
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Scientific investigations in the Kebnekaise massif, Swedish Lapland. III. Kartografiska arbeten i Kebnekaise
• E Woxnerud
Die Gletscher des Sarekgebirges und ihre Untersuchung
• A Hamberg