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An ExcelTM spreadsheet program for reconstructing the surface profile of former mountain glaciers and ice caps
Abstract
A new Excel™ spreadsheet program is introduced, which calculates the surface profiles of former glaciers using an exact solution of a ‘perfectly plastic’ glacier model. Two versions of the model are presented. The basic model requires only bed topography along a flowline and a yield stress for ice as inputs. The latter can be tuned using ‘target ice elevations’ derived from geomorphological mapping. A more sophisticated form of the model allows the yield stress to vary along the flowline, and incorporates the effect of valley-side drag on the glacier profile.
... Their geomorphological record has been described in a few areas, both through geological mapping campaigns (Barbieri & Grandesso, 2007;Zanferrari et al., 2013) and through studies that specifically aimed at reconstructing former ice extents and ELAs (Fuchs, 1970;Carraro and Sauro, 1979;Baratto et al., 2003;Monegato, 2012;Rettig et al., 2021). However, only few of these studies have applied numerical approaches (Benn and Hulton, 2010;Pellitero et al., 2016) to acquire palaeoglacier geometries, and the reported ELAs were calculated using different methods (including the Accumulation-Area-Ratio (AAR), Area-Altitude Balance Ratio and Toe to Headwall Altitude Ratio (THAR) methods), thus making a potential comparison at a regional scale unreliable. Additionally, no numerical datings have yet been reported from isolated glaciers in the south-eastern Alps, partially due to the difficulty of applying surface exposure dating in carbonate catchments (cf. ...
... Reconstructions of palaeoglacier 3D surfaces were carried out using the semi-automated GIS toolbox "GlaRe" developed by Pellitero et al. (2016). This toolbox calculates the thickness of a former glacier along user-defined flowlines, assuming perfectly plastic ice rheology (Nye, 1952;Schilling and Hollin, 1981;Benn and Hulton, 2010). The flowlines were manually digitised following the thalweg of the major valleys and according to ice-flow directions indicated on glacially moulded bedrock. ...
... In a first modelling step, shear stress along the flowlines was set to 100 kPa (Pellitero et al., 2016) and then partially adjusted so that the reconstructed ice thickness better matched the geomorphological evidence, in particular the elevation of lateral moraine ridges. Where glaciers were topographically constrained, an Ffactor correction was applied to account for lateral drag exerted by the valley walls (Nye, 1965;Benn and Hulton, 2010). Owing to the complexity of the glacier network with multiple outlets, ice thickness had to be modelled separately along several flowlines before the 3D glacier surface could be interpolated across the entire area. ...
... First, key landforms and deposits within the DB catchment ( Fig. 1 and Table S1) were grouped to define distinct stages of ice retreat or stillstand/re-advance, based on their radiometric age ( 10 Be surface-exposure and luminescence burial dating), spatial distribution and geomorphological significance. Second, for each defined ice-front position, 2D ice-surface profiles were generated using the Excel™ spreadsheet program Profiler v.2 (Benn and Hulton, 2010), which is based on a steady-state solution of a 'perfectly plastic' ice model. We propagated the 2D ice profiles into the DB valley and its major tributaries, using as ice-front and icesurface constraints the identified landforms/deposits grouped into the same paleoglacial stage (Fig. 6, Table S1). ...
... Present-day topography along the main hydrographic channels was used as input for glacier bed topography (Fig. 6A). Shape-factor (f) values were calculated along the DB valley and its tributaries as input in the Profiler v.2 model, in order to include the valley side-drag effects on ice thickness (Benn and Hulton, 2010). We calculated f according to Eq. (12) from Benn and Hulton (2010) for a total of 62 crosssections (13 in DB valley and 49 in tributaries; Fig. 6A). ...
... Inputs and fitting of Profiler v.2(Benn and Hulton, 2010) for paleoglacial reconstructions. A) Location of modern hydrographic channels (black lines) used as glacier bed input, and of the cross sections in the DB valley (blue segments) and tributaries (red segments) for which shape factors (f) were calculated. ...
Paleoglacial reconstructions in the European Alps have mainly focused on specific climatic periods such as the Last Glacial Maximum (LGM) or the Younger Dryas, with few studies investigating post-LGM Alpine glacier fluctuations encompassing broader temporal periods. In this study, we present a detailed reconstruction of the post-LGM glacial history of the Dora Baltea catchment, which hosted one of the main Quaternary glacial systems of the western European Alps. By combining existing and new chronological constraints from glacial and postglacial landforms/deposits into 2D and 3D ice surface reconstructions, we quantitatively reproduce the timing and ice-configuration of six LGM to early Holocene paleoglacial stages. Our deglaciation sequence along the Dora Baltea valley can be correlated with specific Lateglacial to Holocene paleoclimatic periods, in line with post-LGM glacier reconstructions from other Alpine areas. We estimated paleo equilibrium-line altitudes (ELAs) for each ice stage, using empirical ice-geometric methods. Our results indicate a low ELA sensitivity to ice decay during the early stages of deglaciation, despite significant glacier retreat from the piedmont into the massifs, suggesting a major role of catchment topography in controlling ELA estimates of large glacial systems. Finally, we provide chronological constraints for two major valley-slope collapse events, both postdating the Dora Baltea glacier withdrawal but implying different landscape response time to deglaciation as well as different triggering factors.
... Finally, a simple 2D ice surface model reconstructed paleoglacier behavior for 22-16 ka in the study area. First, we created small initial glacial surface profiles for both valleys using the 2D ice surface model developed by Benn and Hulton (2010). We computed the ice surface elevation (ice thickness) along the profiles in both valleys with this model. ...
... Accordingly, variations in paleo-ELAs were calculated with respect to the ice thickness change. Eventually, we used the simple quadratic function formula (f (x) = ax 2 + bx + c) to determine the location of the glacial toe based on the ELA and headwall altitude values (Benn and Hulton, 2010). Using the glacial toe location, we could evaluate the paleoglacier advance and retreat at any time of interest. ...
Mountain glacier mass balance is affected by factors other than climate, such as topography, slope, and aspect. In midlatitude high-mountain regions, the north–south aspect contrast can cause significant changes in insolation and melt, resulting in local asynchrony in glacial dynamics. This study documents the asynchronous response of two paleoglaciers in southwestern Mongolia to the local topoclimatic factors using 10Be exposure age dating and 2D ice surface modeling. 10Be surface exposure age dating revealed that the Ikh Artsan south-facing valley glacier culminated (MIA1) at 20.1 ± 0.7 ka, coinciding with the global Last Glacial Maximum (gLGM). In contrast, the north-facing Jargalant paleoglacier (MJ1) culminated at 17.2 ± 1.5 ka, around Heinrich Stadial 1 and during the post-gLGM Northern Hemisphere warming. Our temperature-index melt model predicts that ablation will be substantially lower on the north-facing slope, as it is exposed to less solar radiation and cooler temperatures than the south-facing slope. The 2D ice surface modeling also revealed that the south-facing Ikh Artsan Glacier abruptly retreated from its maximum extent at 20 ka, but the Jargalant Glacier on the shaded slope consistently advanced and thickened due to reduced melt until 17 ka. The timing of the modeled glacier culmination is consistent within ± 1σ of the 10Be exposure age results. Extremely old ages ranging from 636.2 to 35.9 ka were measured for the inner moraines in the Jargalant cirque (MJ2–MJ4), suggesting a problem with inheritance from boulders eroded from the summit plateau.
... Using calculations for ice sheet profiles and using average surface elevation plots from the present Antarctic and Greenland ice sheets as analogs ( Fig. 11B; cf. Nye, 1952;Sugden, 1977;Benn and Hulton, 2010;Cuffey and Paterson, 2010;Ng et al., 2010), glacial ice at least 1600 to 2500 m thick would have overlain the study site during glacial maxima, which is more than enough to allow for the development of whalebacks (Figs. 11B and 12A). ...
... (B) Reconstruction of ice sheet surface elevation using theoretical calculations for ice sheets and actual profiles from the East Antarctic and Greenland ice sheets. Data and theoretical equations are from Nye (1952), Sugden (1977), Benn and Hulton (2010), Cuffey and Paterson (2010), and Ng et al. (2010). The gray boxes show the range of ice thicknesses and the range of distances that Estancia Las Moras was located behind the assumed ice margin during formation of the whalebacks and later during formation of the roches moutonnées based on the different reconstruction method. ...
Whalebacks, roche moutonnées, and S-forms carved on Ediacaran granitoids near Cerro de las Cuentas, Uruguay, along with overlying diamictites, siltstones, and sandstones displaying soft-sediment grooved and striated surfaces in the Pennsylvanian San Gregorio Formation, record the glacial to post-glacial transition in the linked Norte, southern Paraná and Chaco-Paraná basins of Uruguay, Brazil, and Argentina respectively. Early authors reported these features resulted from subglacial abrasion and deposition as lodgement tills and glaciotectonites. Our re-examination reveals a nuanced setting with changing ice thicknesses, subglacial kinematics, and ice proximal glaciomarine dynamics associated with advance and retreat of an ice stream, or multiple advances of the Uruguayan Ice lobe, during glaciation of the Late Paleozoic Ice Age (LPIA) in these basins. The preserved landforms indicate temperate glacial conditions. Whalebacks form under 1.6 to 2.5 km-thick ice and likely formed when the lobe extended across the Uruguayan and Rio Grande do Sul shields into the adjacent Paraná Basin. Previously unidentified m-scale roches moutonnées cut into one whaleback developed under thinner ice where reduced basal pressure allowed for the opening of air and water-filled cavities, thus facilitating quarrying on the lee side of basement bumps. S-forms provide additional evidence for the occurrence of subglacial waters, indicating that the basal ice was at or above its pressure melting point. The lower meter of the overlying strata consists of interstratified trace fossil-bearing, laminated siltstones; thin-bedded diamictites; and current-rippled sandstones. Trace fossils belonging to the Mermia ichnofacies within the basal siltstones, as well as acritarchs in the overlying siltstones, suggest that these sediments were deposited in ice-proximal subaqueous settings with contributions from meltwater discharge. Graded siltstone laminae suggest settling from suspension likely from meltwater plumes, while thin-bedded diamictites were deposited either as debris flows or as two-component sedimentation with fines settling from suspension and coarser particles introduce as iceberg-rafted dropstones. Current-rippled sandstones indicate the occurrence of underflow currents. Soft-sediment troughs, grooves, and striations cutting these sediments display curved and sinuous paths with some features oriented perpendicular, and one oriented opposite to the overall trend. They contain marginal and terminal berms typical of iceberg scour marks suggesting transit across the area by icebergs calving from a tidewater ice front located to the SE.
... Plus précisément, la toolbox permet de calculer une épaisseur de glace à partir de la topographie sous-glaciaire, en suivant les lignes de flux de glace du paléoglacier. La toolbox considère une rhéologie de la glace parfaitement plastique (Benn & Hulton, 2010). La modélisation des paléoglaciers utilise plusieurs données d'entrée : 1-le modèle numérique de terrain (MNT) de la topographie sous-glaciaire, 2-les lignes de flux de glace du paléoglacier, 3-la contrainte de cisaillement basale et 4-le facteur de forme F. ...
... Dans le cas de glaciers de vallée, une trainée latérale liée aux frottements du glaciers contre les versants va s'ajouter au cisaillement basal (Nye, 1952b;Shilling & Hollin, 1981;Benn & Hulton, 2010). Pour prendre en compte cette trainée latérale, le modèle de reconstitution glaciaire utilise le facteur de forme F. Ce facteur est un coefficient décrivant la forme d'une section transversale d'une vallée. ...
Dans les Alpes occidentales françaises, de nombreuses morphologies et dépôts issus d’environnements glaciaires et proglaciaires sont hérités des glaciations du Quaternaire. Depuis plus d’un siècle, deux complexes morainiques ont été reconnus dans la zone de piémont et attribués aux dernières glaciations du Quaternaire. A partir d’analyses géomorphologiques et géologiques sur le piémont et dans les vallées internes, différentes avancées glaciaires ont été identifiées. Ces avancées glaciaires ont été définies par une approche morphostratigraphique, mais le cadre chronologique absolu basé principalement sur des datations 14C reste très fragmentaire. Ainsi, l’âge absolu du complexe des moraines internes (CMI) se trouvant sur le piémont et mis en place par le lobe glaciaire lyonnais reste encore débattu. De même, la dynamique et la chronologie du retrait glaciaire, depuis le dernier maximum glaciaire jusque dans les vallées alpines restent très parcellaires. Le but de cette thèse est donc de définir un meilleur cadre chronologique du dernier maximum glaciaire et des différents stades de retrait dans les Alpes occidentales françaises. Ce travail de thèse se focalise sur le piémont des Alpes occidentales françaises et plus précisément sur le CMI et sur les dépôts fluvioglaciaires associés. Ce travail se concentre également sur la dynamique de retrait depuis le piémont jusqu’en amont de la vallée de la Maurienne. Pour la première fois sur ce secteur, les méthodes de datation absolue par radionucléides cosmogéniques 10Be et par luminescence (OSL) ont été utilisées. Cette étude est basée sur une nouvelle caractérisation géomorphologique et sédimentologique des dépôts glaciaires et proglaciaires, afin de mettre en évidence et de dater les fluctuations (avancées et retraits) des glaciers des Alpes occidentales françaises depuis le front montagneux jusqu’en amont de la vallée de la Maurienne. Dans le piémont, les analyses géomorphologiques et sédimentologiques des systèmes fluvioglaciaires localisés au front du CMI ont mis en évidence une corrélation topographique entre les terrasses fluvioglaciaires et les différents ensembles de moraines. Ces systèmes fluvioglaciaires ont été ensuite datés par luminescence. Les résultats indiquent une activité fluvioglaciaire à 75-60 ka au cours du MIS 4 à l’origine du dépôt des terrasses corrélées aux moraines du maximum d’extension du lobe lyonnais. Une seconde activité fluvioglaciaire à 30-40 ka au MIS 3 est à l’origine des terrasses fluvioglaciaires corrélées aux moraines laissées par une extension du lobe lyonnais géométriquement proche de celle du MIS 4. Pour compléter cette chronologie OSL, nous avons réalisé des datations par âges d’exposition 10Be sur 9 blocs glaciaires localisés sur le complexe morainique et sur 12 blocs erratiques situés sur le reste du piémont. Les résultats montrent un retour du lobe glaciaire sur le piémont au LGM à 24-21 ka. Cette extension LGM est légèrement moins étendue que les extensions du MIS 4 et du MIS 3. En arrière de ces moraines, une réavancée / stabilisation a été mise en évidence à 19 ka. Enfin, les âges d’exposition indiquent que le piémont est déglacé à 16,5 ka. En amont du piémont, des âges d’exposition 10Be ont permis de reconstituer la dynamique de déglaciation dans les Alpes occidentales françaises au Tardiglaciaire. Ces âges d’exposition sont issus de datations inédites sur blocs erratiques ainsi que de datations sur blocs erratiques et glaciaires publiées. Ces résultats ont permis de retrouver des positions glaciaires de l’entrée du piémont (Culoz) jusqu’en amont de la Maurienne (Bessans) entre ~16,5 et ~12,5 ka. Entre l’entrée du piémont et la partie aval de la Maurienne (Pas du Roc), des âges d’exposition proches les uns des autres suggèrent un retrait rapide à environ 16,5 ka sur ~120 km, probablement favorisé par un vêlage dans de grands lacs proglaciaires. En Maurienne, des analyses sédimentologiques de deux affleurements (Verney et Lanslebourg) ont permis de mettre en évidence deux avancées glaciaires n’ayant pas laissé de moraines. La première avancée glaciaire est marquée par des déformations retrouvées dans un dépôt deltaïque au Verney. ALanslebourg, des faciès de plus en plus proximaux vers le haut de la succession sédimentaire et des déformations de cônes proglaciaires sous-aquatiques attestent de la seconde avancée glaciaire. Les analyses sédimentologiques, les datations par exposition et les âges par luminescence, permettent de reconstituer six fluctuations du glacier de l’Arc. Trois étapes de retrait glaciaire ont été mises en évidence à 16,7-14,6 ka ; 15,3 et 14,5 ka respectivement. Puis, deux stades de réavancée du glacier de l’Arc mis en évidence par les analyses sédimentologiques dont l’âge est estimé entre 14,5 et 13,6 ka. Enfin le dernier stade est marqué par des moraines frontales issues d’une réavancée à 12,5 ka au Dryas récent. Pour les six fluctuations glaciaires identifiées en Maurienne, une modélisation géométrique glaciaire a été réalisée et a permis d’estimer les variations de la ligne d’équilibre glaciaire (ELA) entre 16,7 et 12,5 ka. Ces modèles ont également permis de quantifier les variations de volume de glace et le bilan de masse moyen entre 16,7 et 14,5 ka, pendant la période de réchauffement climatique au début du Bølling-Allerød. Les variations de l’altitude de la ELA suggèrent des conditions de plus en plus sèches en Maurienne. Le bilan de masse moyen a été comparé aux bilans de masse des glaciers actuels soumis au réchauffement climatique anthropique. Ces comparaisons montrent que les bilans de masse moyens des glaciers actuels sont 10 à 100 fois supérieurs aux valeurs calculées pour le glacier de l’Arc pendant le Bølling-Allerød.
... There have been several phases of research regarding ice surface modeling, from the first moments in which a simple mapping of the shapes was carried out to others that used new techniques to obtain 2D models [9,10]. In the last decades, the number of researchers focused on improving these studies has grown considerably. ...
... The glacier surface reconstruction was performed using the GlaRe toolbox [11], available as an add-on for ArcGIS. It is based on the glacier reconstruction approach designed by Benn and Hulton [9]. This technique has been used extensively in multiple locations [14,[52][53][54][55][56][57][58]. ...
The Trevinca Massif is in the northwestern Iberian Peninsula, on the border between Galicia and Castilla-León. Its highest elevation is 2124 m at the Trevinca peak. During the Pleistocene, an extensive icefield developed in this area, occupying the flattened surfaces in the high massif zones, and generating several glacier valleys. In the occidental sector, the identified paleoglaciers reached 187 km 2 , and glacier tongues up to 30 km in the Bibei valley, where the ice thickness came to 527 m. The glacial forms and deposits were mapped and analyzed in the entire Trevinca massif, whereas the paleoglacial reconstruction was carried out in the occidental sector (previous works analyzed the oriental sector). The reconstruction was performed by using high-resolution orthophotography, digital elevation models with a spatial resolution of 2 m, and fieldwork surveys to identify the primary forms and estimate the ice cover in the past through the GlaRe methodology. Moreover, the paleo-ELA was estimated for this sector, and the values of the ice thickness, the ELA position, and the moraines were related to other nearest sectors to analyze their similarities and differences. Three main paleoglaciers were identified in the occidental Trevinca massif (Xares, Canda, and Bibei-Barxacova). Bibei showed the highest ice thickness and ice extension, occupying more than 140 km 2 and with a thickness above 500 m in some areas. Concerning the ELA, the values varied between the minimum at Xares with 1427 m and the maximum at Bibei-Barxacova with 1839 m. Four groups were identifying based on moraine ridges and were related to the different climatic phases in that sector.
... The geomorphology comprises a geomorphological map supplemented by the active landslide inventory, map of flood-prone areas, geometric 2D reconstruction of ancient palaeoglaciers and the karst cave inventory (Table 3). Also included is topographic restitution of the A Seara palaeoglacier based on field evidence and applying the numerical model described in Benn and Hulton (2010) and the ArcGIS GLARE toolbox (Pellitero et al. 2016). Karst caves were 3D modelled and integrated into GIS based on cave survey data following Ballesteros et al. (2019). ...
... Global changes occurred in the UGGp highlands since the maximum advance of glaciers before 21 cal ka BP (Muñoz Sobrino et al. 2001) to areas occupied by native forests and villages at present. a Maximum expansion of paleoglaciers reconstructed from previous works (Supplementary information 2). b 3D reconstruction of the A Seara palaeoglacier using the ArcGIS GLARE toolbox (Benn and Hulton 2010;Pellitero et al. 2016) and displayed in ArcScene. c Current distribution of villages and forests (derived from the MFE - Table 2) The GIS database was used for planning and technical designing of touristic resources, such as routes, activities, touristic information documents and interpretation centres. ...
The management of a UNESCO Global Geopark (UGGp) requires a vast wealth of miscellaneous scientific knowledge that
can be successfully organised using a Geographical Information System (GIS). This paper presents a pragmatic GIS database
to assist in the suitable governance of the Courel Mountains UGGp (2017) in Northwest Spain. The database is structured in
66 coverages compiled from public sources and previous works or produced through traditional mapping (combining fieldwork
and photointerpretation) and GIS tools. The acquired data was later homogenised and validated by a multidisciplinary
team and archived in independent coverages. Forty thematic maps illustrate the broad range of cartographic information
included in the GIS database. Among them, 25 basic maps provide an overview of the UGGp and 15 new maps focus on
crosscutting and technical issues. All maps illustrate the huge potential of GIS to create new resources combining coverages
and adapting the legend according to their purpose and audience. The database facilitates the suitable publishing of consistent
outputs (e.g., brochures, books, panels, webpages, web serves), as well as the elaboration of technical data to assist the
park management. The database furnishes information on the design of education actions, touristic routes, activities and
Geopark facilities. The GIS database is also a supportive tool for scientific research and provides the necessary knowledge
to conduct geoconservation actions based on land use, geological hazards and the occurrence of natural and cultural heritages.
Altogether, the GIS database constitutes a powerful instrument for policy-making, facilitating the identification and
evaluation of alternative strategy plans.
... A three-dimensional palaeoglacier reconstruction was performed for the different glacial phases using the 'GLaRe' ArcGIS toolbox devised by Pellitero et al. (2016). Former ice thickness was estimated by applying a perfect-plasticity physical-based rheological model along flowlines from the termini to the headwall (Veen Van der, 1999;Benn and Hulton, 2010). Such a toolbox requires only a flowline, a tentative palaeoglacier geometryapproximated from lateral or frontal morainesand a digital elevation model. ...
... Such a toolbox requires only a flowline, a tentative palaeoglacier geometryapproximated from lateral or frontal morainesand a digital elevation model. Ice thickness was modelled by using a constant shear stress of 100 kPa (Paterson, 1994;Benn and Hulton;. The effect of lateral side drag was corrected by integrating shape factors (F-factor) obtained from cross-sections (Schilling and Hollin, 1981). ...
The Upper Garonne Basin included the largest glacial system in the Pyrenees during the last glacial cycle. Within the long‐term glacial retreat during Termination‐1 (T‐1), glacier fluctuations left geomorphic evidence in the area. However, the chronology of T‐1 glacial oscillations on the northern slopes of the Central Pyrenees is still poorly constrained. Here, we introduce new geomorphological observations and a 12‐sample dataset of 10Be cosmic‐ray exposure ages from the Ruda Valley. This U‐shaped valley, surrounded by peaks exceeding 2800 m a.s.l., includes a sequence of moraines and polished surfaces that enabled a reconstruction of the chronology of the last deglaciation. Following the maximum ice extent, warmer conditions prevailing at ~15–14 ka, during the Bølling–Allerød (B–A) Interstadial, favoured glacial retreat in the Ruda Valley. Within the B–A, glaciers experienced two phases of advance/stillstand with moraine formation at 13.5 and 13.0 ka. During the early Younger Dryas (YD), glacial retreat exposed the highest surfaces of the Saboredo Cirque (~2300–2350 m) at 12.7 ka. Small glaciers persisted only inside the highest cirques (~2470 m), such as in Sendrosa Cirque, with moraines stabilising at 12.6 ka. The results of this work present the most complete chronology for Pyrenean glacial oscillations from the B–A to the YD.
... For the ELA calculations, there have been several methods developed over the past century [43][44][45]. The use of the Maximum Elevation of Lateral Moraines (MELM) and the Accumulation Area Ratio (AAR) were the two most commonly used approaches for calculating ELA [46][47][48][49][50] until the development of the more current method, the Area/Altitude Balance Ratio (AABR) [51]. ...
... For the ELA calculations, there have been several methods developed over the past century [43][44][45]. The use of the Maximum Elevation of Lateral Moraines (MELM) and the Accumulation Area Ratio (AAR) were the two most commonly used approaches for calculating ELA [46][47][48][49][50] until the development of the more current method, the Area/Altitude Balance Ratio (AABR) [51]. ...
Soajo Mountain is located in the northwestern Iberian Peninsula near the border between Portugal and Spain. Its highest elevation is 1416 m at the Pedrada summit. During the Pleistocene, the cascade cirques on the east flank and the icefield that covered the flattened surface of the high plateau generated several glacier valleys. This study presents a paleoglacial reconstruction of the relict glacial landscape in Soajo Mountain for the Glacial Maximum Extent (GME) through the following methods: (1) a detailed geomorphological map supported by high-resolution orthophotography, digital elevation models with a spatial resolution of 70 cm, and field surveys; (2) the delineation of the glacial surface, and the calculation of the glacial flowlines to obtain the numerical model of the ice thickness; and (3) an estimation of the paleoELA altitudes. The paleoglacial reconstruction, using GlaRe methodology, reveals a glacial surface of 16 km 2 , including an icefield on the Lamas de Vez plateau (mean elevation of 1150 m) and a radial glacial flow to the east and north. The arrangement of the glaciated area attests to the topographic, lithological, and structural conditioning on the development of small glacial tongues, with an emphasis on the ice tongue flowing northwards, with a thickness of 173 m and a length of 2.92 km. The Soajo GME paleoglacier comprises three main glacial sectors: Lamas de Vez Icefield, Vez and Aveleira Valleys, and the Eastern Glacial Sector. These paleoglaciers have achieved maximum ice volumes of 214.4 hm 3 , 269.2 hm 3 , and 115.8 hm 3 , respectively, with maximum ice thicknesses of 127 m, 173 m, and 118 m, respectively. On the west flank, a smaller paleoglacier named Branda da Gémea recorded an ice volume of 24.3 hm 3 and a maximum ice thickness of 110 m. According to the ELA-AABR method, Soajo Mountain has one of the lowest ELA values in the Iberian NW, ranging from 1085 to 1057 m. This is due to its oceanic location, an orographic barrier effect, and the influence of the polar front.
... The surface profiles of former glaciers reconstructed entirely from geomorphological evidence were compared with theoretical glacier profiles based on a glacier flow law, using the Profiler program of Benn & Hulton (2010). This program permits two-dimensional reconstruction of ice-surface configuration along a former flowline based on either a known terminus position or an ice divide of known or assumed altitude, or both. ...
The upper Henson Gletscher Formation (Cambrian, Miaolingian Series, Wuliuan Stage) of southern Lauge Koch Land and Løndal, south-western Peary Land, North Greenland (Laurentia) yields diverse assemblages of phosphatised Small Shelly Fossils after treatment with weak acetic acid. The occurrence merits description as a fossil Lagerstätte on account of the exceptional preservation of soft parts in some specimens, although the phosphatisation itself is generally rather coarse. Bradoriid and phosphatocopid arthropods are common and display substantial variation in their preservational history. Some specimens retain traces of internal morphology, although details are generally obscured by indifferent preservation. Rare specimens extend the range of stem-group pentastomid arthropods back by more than 10 million years. A unique hatching larva demonstrates the same early developmental stage of a stem-group priapulan worm to that described in some present-day priapulans. The preservation of an in place operculum has demonstrated that the widespread, supposed mollusc Protowenella is actually an unusual, strongly coiled hyolith. Abundant coprolites and cololites provide additional evidence of early phosphatisation. In terms of morphology, Cambrocoryne lagenamorpha gen. et sp. nov. superficially resembles wiwaxiid and some annelid sclerites, thelodont scales and the foraminiferan Lagena, but its true identity is obscure.
... The removal of moraines by slope processes ("external censoring") may be problematic as the practice of palaeoglacier reconstruction benefits from complete moraine assemblages, which are often used to calibrate the lateral and vertical extent of former glacier models (e.g. Benn & Hulton, 2010;Ng et al., 2010;Pellitero et al., 2015Pellitero et al., , 2016. Here, it is highlighted that it is not only high-Arctic moraines that are considerably altered during deglaciation (e.g. ...
Within Alpine catchments, glacial landforms are subject to post-depositional reworking during and following deglaciation. Ice-marginal moraines are thought to rapidly stabilise within ~200 years in this topographic context, although ice-proximal slopes are particularly prone to alteration by debris flows and solifluction. This study investigates landform transformation, documenting geomorphological change at the Bas Glacier d’Arolla, Switzerland. Gully development on a moraine slope was assessed using archive image sets obtained in 1977, 1988 and 2009 to derive historical elevation models. Raster differencing suggests that the mean rate of surface lowering on the upper moraine slope was 7.15 ± 1.83 m (± minimum level of detection) over the observation period (1977–2009), a rate of 0.22 m yr−1. The erosion of the landform resulted in an incontiguous moraine crestline. Whilst some landforms may undergo limited transformation upon deglaciation, selected sites are subject to rapid geomorphologic change, involving crestline retreat via the initial dissection by gullies, followed by the removal of inter-gully slopes.
... The 3D surface position was reconstructed in a GIS environment based on the mapped distribution of the landforms of glacial accumulation (frontal and lateral moraines, scattered erratic boulders and glacial till covers) and erosional features (trimlines) (Benn et al. 2005). Ice thickness was assessed along the flowline using glacier profile models (Benn & Hulton 2010) provided in the Pellitero et al. (2015) toolbox with the use of 50-100 kPa basal shear stress values (Cuffey & Paterson 2010). ...
In the Western Carpathians, clear evidence of the Pleistocene glaciations only occurs in two mountain massifs – the Tatra and Low Tatra Mountains. The Low Tatra Mountains (2043 m a.s.l.), contrary to the higher and more strongly glaciated Tatra Mountains (2654 m a.s.l.), have previously been much less attractive for scientific research. Hence, in these mountains, both glacial landforms and chronology, together with a detailed reconstruction of glacier geometry and resulted equilibrium line altitude (ELA), are poorly documented. The aim of this paper is to characterize the glacial relief and reconstruction of geometry and ELA of the Zadná voda glacier in the Demänovská Valley system which belongs to the category of the largest Pleistocene glaciers on the northern slope of the Low Tatra Mountains. The mapping results show that a freshly shaped, massive terminal moraine of maximal ice extent (MIE, likely formed during the global Last Glacial Maximum – LGM) occurs 4.3 km distance down-valley from the glacial cirque backwalls. There is no evidence of deposits from older glaciations beyond the terminal moraine down the valley. The terminal zone of the MIE features a fresh morainic landscape with hummocky topography with kettle hollows and the only known morainic lake in the Low Tatra Mountains – Vrbické pleso. During the MIE, the Zadná voda glacier covered 7 km2 of the area and featured a mean thickness of 48 m. The ELA of this glacier was 1433 m, determined by the area-altitude balance ratio (AABR) 1.6 method, which is a similar value to the LGM ELA calculated in the Western Tatra Mountains. The recessional stages were only recognized in the cirques area, where one or two generations of debris-covered glaciers and rock glaciers mark the final deglaciation of the study area.
... The shape and maximum extent of the Jupania glacier was reconstructed in the GIS environment based on the mapped distribution of lateral and frontal moraines and glacial deposits. Ice thickness was assessed along the flowline using a glacier profile model (Benn & Hulton, 2010) provided in the GlaRe, a semi-automated GIS-based method (Pellitero et al., 2015) with the use of basal shear stress values 50 to 100 kPa (Cuffey & Paterson, 2010) and a calculated valley shape factor. Ice thickness was adjusted to the mapped glacial landforms by fine-tuning their thickness using the basal shear stress values. ...
The Late Pleistocene Jupania palaeoglacier (area 0.85 km2, 1.7 km long) was reconstructed in the headwaters of the Ceremuşul Alb/Bilyj Cheremosh valley (Maramureş Mountains). The study area represents one of the most inaccessible natural areas in the Romanian part of the Eastern Carpathians where the legacy of the
Pleistocene glaciation has recently been discovered. Based on mapping of glacial landforms and deposits, we reconstruct glacier dimension and ice-surface geometry, as well as estimate equilibrium line altitude (ELA) during the maximal ice extent (MIE). Well-preserved terminal moraines mark the extent of glacier front
at ~1400 m a.s.l. Sedimentological analysis documents that the lateral moraines are sometimes overbuilt by 1-1.5 m thick colluvial deposits. The ELA for the Jupania palaeoglacier calculated with the Area-Altitude-Balance-Ratio (AABR) 1.6 was 1630 m. However, the gentle-sloping mountain-top could serve as an important
snow contribution area to glacier mass balance; therefore, the ELA could potentially exist even higher at 1676 m. The resulting climatic ELA (1630-1676 m) in the south-eastern part of the Maramureş Mountains fits well with the rising trend of ELA towards the southeast observed between Chornohora (ELA = 1516 m) and Rodna Mountains (ELA = 1697 m). The SE rising trend of the ELA corresponds well with the dominant palaeowind
direction suggested in the Carpathian region and supports the prevalence of zonal circulation pattern in Central Eastern Europe during the culmination of the last glaciation.
... The surface profiles of former glaciers reconstructed entirely from geomorphological evidence were compared with theoretical glacier profiles based on a glacier flow law, using the Profiler program of Benn & Hulton (2010). This program permits two-dimensional reconstruction of ice-surface configuration along a former flowline based on either a known terminus position or an ice divide of known or assumed altitude, or both. ...
This paper presents a new complete field mapping of glacial landscapes, landforms and sediments in the Faroe Islands, supplemented by observations from bathymetric maps of the Faroe Shelf. In addition, previous investigations of Quaternary and espe-cially the Weichselian glaciation of the archipelago are reviewed. New cosmogenic nuclide exposure ages indicate that the last extensive glaciation of the Faroe Islands occurred during the Late Weichselian, most likely during the Last Glacial Maximum (LGM; c. 26.5–19.0 cal. ka BP), although a Younger Dryas (c. 12.9–11.7 cal. ka BP) age cannot be entirely excluded. Geomorphological mapping provides a background for reconstructing the extent and type of the glaciation of the Faroe Islands. The reconstructed Weichselian glaciation appears to have had the character of an exten-sive valley glaciation, with several marine glacier termini. The present glaciation of southern Spitsbergen, Svalbard, represents a modern analogue of the reconstructed Weichselian glaciation in the Faroe Islands. The lack of raised coastal features in the Faroe Islands, also at protected sites, suggests that postglacial isostatic uplift was smaller than post-LGM eustatic sea level rise. Numerical glacier reconstructions carried out for different extents of the last extensive Faroese glaciation suggest that such limited postglacial isostatic crustal uplift requires that the Faroe Shelf was not extensively glaciated during the Late Weichselian, but it doubtless was so during at least one of the previous Quaternary glaciations.
... Mapped distributions of latero-frontal moraines and glacial deposits were used to reconstruct the maximum extent and icesurface geometry of the former glaciers. Detailed ice thickness was modelled along the glacier center lines using a glacier profile model (Benn and Hulton, 2010) provided by GlaRe, a GIS-based tool (Pellitero et al., 2015). The model was run with the use of basal shear stress values of 50 to 100 kPa, typical of valley glaciers (Cuffey and Paterson, 2010) and an estimated valley shape factor. ...
The Eastern Carpathians are the northeasternmost sector of the European Alpine Mountain system and comprise 14 formerly glaciated massifs that stretch over 300 km into the territories of Ukraine and Romania. In this study we provide a regional overview on Late Pleistocene glaciation in the Eastern Carpathians integrating recently published and new geomorphological data which include mapped glacial landforms and glacier reconstruction of the maximal ice extent (MIE) which is assigned to the global Last Glacial Maximum (LGM). Thus we obtain a complete inventory of glaciation in the Eastern Carpathians, including the documentation of 214 glacial cirques and 147 small mountain glaciers with a total area of 153.2 km2. The estimated LGM equilibrium line altitude (ELA) shows a strong rise of 2.4 m/km from the northwest (1270 m asl) to the southeast (1870 m asl), as well as a consistent eastward rise on several W-E transects (2–3.4 m/km). Similar patterns are shown by the palaeoglaciation level and the cirque floor altitude trend, which mimic the pattern of modern temperature-precipitation ELA (tpELA) in the region. Reconstructed palaeoglacial trends reflect dominant W-NW precipitation-wind regime and an enhanced zonal North Atlantic circulation pattern in the far interior of Europe in full glacial climate. This is consistent with both regional palaeoclimatic simulations and wind regime proxies which indicate that the pattern of LGM circulation was similar to the present circulation, although the magnitude may have increased during glacial conditions. Additionally, based on the wide array of glacial landscapes inventoried in this study, ranging from traces of small niche/cirques to about 7 km long valley glaciers, we propose a quantitative approach to define the distinct stages of glacial landscape development based on the relationship between the Pleistocene ELA and mountain hypsometry
... -Although the marginal moraines M1, M3 and M4 (Fig. 2) allow for very accurate reconstructions of the glacier fronts, there is no geomorphological evidence indicating the glacier surface profile further upvalley. To overcome this problem, the surface profiles of the glaciers G1, G3 and G4 were reconstructed using the steady-state model of Benn & Hulton (2010). This model calculates the ice-surface elevation along the central flowline, based on the relationship between the shear stress and rate of ice deformation, and by assuming a perfect ice plasticity with an ice density of 900 kg m À3 (Nye 1952;Schilling & Hollin 1981). ...
Continuous glacier margin and equilibrium‐line altitude fluctuations of a former glacier on central Andøya, northern Norway, are reconstructed during the Lateglacial based on moraines and AMS 14C‐dated sediments from the distal glacier‐fed lake Ner‐Finnkongdalsvatnet. The results indicate that a valley glacier occupied the entire valley during the Last Glacial Maximum (before 21 970±620 cal. a BP). The glacier remained large throughout the early Lateglacial until a significant glacier retreat took place about 14 300±330 cal. a BP. Major advances occurred during the Older Dryas (OD) and during the Younger Dryas (YD), while minor advances are suggested to have taken place during the Intra Allerød Cold Period and the Late Allerød Cooling. Additionally, three smaller glacier retreats/re‐advances within the YD are suggested to have taken place, the latter being the largest. The glacier re‐formations/advances during the Lateglacial are consistent with increases in temperature, and they are thus suggested to be the result of increased winter precipitation. Comparing the results with relevant glacier and sea‐surface temperature records, a south–north migration of storm tracks may have occurred between 12 100–11 810±220 cal. a BP. The high temporal resolution of local glacier activity in Finnkongdalen improves our understanding of the climate forcing of the regional glacier fluctuations of the northwestern sector of the Scandinavian Ice Sheet during the Skarpnes‐ (OD) and Tromsø‐Lyngen (YD) re‐advances.
... The geometry of the former Cère glacier was modelled in 3D using the GlaRe ArcToolBox for ArcGIS (Pellitero et al., 2016) for the three glacial stadials recognised in the field (Fig. 4). This model assumes a perfect plasticity behaviour for glacier ice and applies the numerical iterative solution to the Van der Veen's equation (Benn and Hulton, 2010). The basal shear stress value generally lies between 50 kPa and 150 kPa (Benn and Evans, 2010). ...
The landform assemblage in the Cère Valley (Cantal, France) provides one of the most complete sequences for Late Pleistocene glacial fluctuations in the French Massif Central. However, the associated glacial chronology has been debated since the 1980s. This paper aims to improve the glacial chronology of the Cère Valley using 36Cl surface exposure ages. Geomorphological results define two glacier stadials with reconstructed equilibrium line altitudes of 1078 ± 43 and 1152 ± 34 m above sea level. These results are comparable to those obtained in the Alps or the Pyrenees during the Last Glacial Maximum (26–19.5 ka). However, 36Cl surface exposure ages are centred around the Younger Dryas (YD), between 13 and 11 ka (n = 4). We suggest that these 36Cl ages are not related to a standstill during the YD but rather to the effects of the postglacial evolution of the Cère Valley. We investigate two geomorphological end‐member scenarios to explain the postponed exposure of sampled boulders: the Aurillac Lake scenario and the later fluvial incision scenario. While the nature of the geomorphological events leading to the boulder exhumation is not fully resolved, we highlight a long phase of postglacial evolution in the Cère Valley.
... The 30-m-resolution ALOS (Advanced Land Observing Satellite) DEM was used for the model domain. To obtain the valley bed topography, we subtracted the ice thicknesses of the modern glaciers using a simple method, which assumed a uniform basal shear stress (τ = 100 kPa) and yielded ice thicknesses (H) from H = τ/(ρgsinα), where ρ is ice density (917 kg m -3 ), g is gravitational acceleration (9.81 m s -2 ), and α is surface slope of ice in degrees (Benn and Hulton, 2010;Xu et al., 2013;2014). The calculated net mass balance was then inputted to the ice flow model, which was run iteratively until the calculated ice thickness attained a steady state. ...
This study outlines the paleoglacial history and paleoclimatic conditions that were present during the Last Glacial Maximum (LGM) and Lateglacial (LG) in the Songlong and Zhuxi valleys in the eastern Nyainqêntanglha Range, southeastern Tibet. Two sets of moraines were identified at the valley mouths, and were dated using cosmogenic 10Be exposure and optically stimulated luminescence (OSL) dating. The ages suggest that two glaciations occurred at ~20–21 and ~14–16 ka, respectively, coinciding with the LGM and LG. Using glacier–climate modeling, temperature drops were calculated to have ranged from 6.3 to 7.8 °C during the LGM–LG, with precipitation being 40–60% of the present‐day value. The results in the modeled domain appear generally consistent with other climatic records from the Tibetan Plateau. Glacial advances in monsoon‐dominated southeastern Tibet during the LGM–LG were probably driven by low temperatures rather than by high precipitation, which was usually produced by an enhanced Indian Summer Monsoon during periods of climatic warming.
... Mapped distributions of latero-frontal moraines and glacial deposits were used to reconstruct the maximum extent and ice-surface geometry of the former glaciers. Detailed ice thickness was modelled along the glacier center lines using a glacier profile model (Benn and Hulton, 2010) provided by GlaRe, a GIS-based tool (Pellitero et al., 2015). The model was run with the use of basal shear stress values of 50 to 100 kPa, typical of valley glaciers (Cuffey and Paterson, 2010) and an estimated valley shape factor. ...
... To estimate the reach of viscous flow-features possibly buried beneath the surface of unit NHt (see section 9.2) we used a 2D model of perfect plasticity calculate ice thickness on Earth (e.g. Ng and al., 2010;Benn and Hulton 2010) and Mars on (e.g. Parsons et al., 2011;Fastook et al., 2014;Karlsson et al., 2015;Schmidt et al., 2019;Hepburn et al., 2020a). ...
The long-term cyclicity and temporal succession of glacial-periglacial (or deglacial) periods or epochs are keynotes of Quaternary geology on Earth. Relatively recent work has begun to explore the histories of the mid- to higher-latitudinal terrain of Mars, especially in the northern hemisphere, for evidence of similar cyclicity and succession in the Mid to Late Amazonian Epoch. Here, we carry on with this work by focusing on Protonilus Mensae [PM] (43-490 N, 37-590 E). More specifically, we discuss, describe and evaluate an area within PM that straddles a geological contact between two ancient units: [HNt], a Noachian-Hesperian Epoch transition unit; and [eHT] an early Hesperian Epoch transition unit. Dark-toned terrain within the eHt unit (HiRISE image ESP_028457_2255) shows continuous coverage by structures akin to clastically-sorted circles [CSCs]. The latter are observed in permafrost regions on Earth where the freeze-thaw cycling of surface and/or near-surface water is commonplace and cryoturbation is not exceptional. The crater-size frequency distribution of the dark-toned terrain suggests a minimum age of ~100 Ma and a maximum age of ~1 Ga. The age estimates of the candidate CSCs fall within this dispersion. Geochronologically, this places the candidate CSCs amongst the oldest periglacial landforms identified on Mars so far.
... We used a geographic information system (GIS) approach to semi-automatically reconstruct thickness and extent of the former glaciers that deposited the frontal moraines (Pellitero et al., 2016). The GIS tool creates a 3D glacier surface based on the lateral interpolation of a 2D glacier equilibrium profile, which is calculated by using a plastic rheology glacier model along user-defined flowlines (Benn et al., 2010;Paterson, 1994;Shilling and Hollin, 1981). Glaciers are reconstructed by extrapolating the ice thickness along defined flowlines, after applying a default shear stress of 100 kPa and shape (F) factors to account for variation in the width of the glacial valley. ...
We combined data from geomorphologic surveys, glacial modelling, and ¹⁰Be exposure ages of boulders on moraines, to investigate the Last Glacial Maximum (LGM) and the early retreat glacial phases in the Stura Valley of the Maritime Alps. We used the exposure ages to reconstruct the timing of standstills or readvances which interrupted the post-LGM withdrawal, initiated ∼24 ka. We mapped and dated the frontal moraines of a first glacial standstill/readvance at a short distance (∼7 km) from the maximum external limit of the LGM, which occurred at ∼22 ka, and a second one at ∼19 ka (Bühl stadial). This morpho-chronologic succession is congruent with that obtained in the adjacent Gesso Valley and, combined with the similarity of Equilibrium Line Altitude values, demonstrates a consistent glacial response in the Maritime Alps to climatic forcing.
Our data are chronologically consistent with those of the southern flank of the European Alps, stressing not only a general synchroneity of the LGM across the various sectors, but also that of a LGM recessional standstill or readvance at ∼22 ka. The short distance between the LGM moraines and the recessionary phase moraines, and minimal difference in ELA indicate a modest variation in the mass balance of the Maritime Alps glaciers during this time interval. A similar modest variation between LGM and the first recessional phase glacier mass balance is also found throughout the western sector of the Southern Alps but is considerably more pronounced for the glaciers of the central-eastern sectors. This behaviour can be explained by the interplay between the moisture supplied by southern currents sourced in the Western Mediterranean and that advected by the westerlies sourced in the North Atlantic, which affected the various sectors of the Southern Alps differently.
... GlaRe requires several inputs: the paleoglacier extent (i.e., a polygon bounded by moraine and trimline locations); a DEM to characterize local topography; and userdefined glacier flowlines. Using these inputs and several other user-defined parameters (described in Supplementary Information and in Pellitero et al., 2016), the tool uses a numerical approach based on an iterative solution to the perfect plasticity assumption for ice rheology (Nye, 1952a(Nye, , 1952bBenn and Hulton, 2010;Li et al., 2012;Van der Veen, 2013) to reconstruct the paleoglacier thickness along the flowlines. The 3-D paleoglacier surface is then computed via interpolation. ...
Alpine glaciers are sensitive responders to climate fluctuations, especially to changes in summer temperature, and thus their past extents are invaluable indicators of past climate. Here, we leverage geomorphological evidence of past glacier extent to reconstruct the three-dimensional surfaces of 42 land-terminating paleoglaciers in southernmost Greenland and calculate their equilibrium-line altitudes (ELAs) during the presumed coldest interval of the Little Ice Age (LIA). We compare LIA paleoglacier ELAs with observed modern glacier ELAs (i.e. snowlines) to estimate the LIA summer temperature depression relative to present. On average, we find that ELAs rose 122 ± 64 m since the LIA, which corresponds to a summer temperature change of 1.1± 0.6 ° C, assuming no change in precipitation. Because there are minimal constraints on LIA precipitation anomalies in southernmost Greenland, we also report summer temperature changes for precipitation values ranging from a substantially drier to substantially wetter than modern LIA. When compared with independent temperature evidence, our results suggest LIA precipitation was similar to or slightly less than today. The alpine glaciers studied lost (on average) 56± 16% of their area and 44± 13% of their centerline length between the LIA culmination and 2019 CE. In general, smaller and lower elevation glaciers lost larger fractions of their area. We find no clear geographic patterns in the magnitudes of ELA, area, or length changes across the 9000 km² study area despite its heterogeneous climate. This study demonstrates a workflow for regional-scale paleoglacier reconstruction and provides the first quantitative LIA summer paleotemperature estimate for southernmost Greenland via region-wide glacial evidence. Our work also suggests the need for reconstruction of a large number of glaciers to infer past regional climatic information, as individual glaciers may respond heterogeneously to climate perturbations leading to variable changes in their ELA and length.
... To estimate the reach of viscous flow-features possibly buried beneath the surface of unit NHt (see Section 9.2) we used a 2D model of perfect plasticity calculate ice thickness on Earth (e.g. Ng and al., 2010;Benn and Hulton, 2010) and Mars on (e. g. Parsons et al., 2011;Fastook et al., 2014;Karlsson et al., 2015;Schmidt et al., 2019;Hepburn et al., 2020a). ...
The long-term cyclicity and temporal succession of glacial-periglacial (or deglacial) periods or epochs are keynotes of Quaternary geology on Earth. Relatively recent work has begun to explore the histories of the mid-to higher-latitudinal terrain of Mars, especially in the northern hemisphere, for evidence of similar cyclicity and succession in the Mid to Late Amazonian Epoch. Here, we carry on with this work by focusing on Protonilus Mensae [PM] (43-49 0 N, 37-59 0 E). More specifically , we discuss, describe and evaluate an area within PM that straddles a geological contact between two ancient units: [HNt], a Noachian-Hesperian Epoch transition unit; and [eHT] an early Hesperian Epoch transition unit. Dark-toned terrain within the eHt unit (HiRISE image ESP_028457_2255) shows continuous coverage by structures akin to clastically-sorted circles [CSCs]. The latter are observed in permafrost regions on Earth where the freeze-thaw cycling of surface and/or near-surface water is commonplace and cryoturbation is not exceptional. The crater-size frequency distribution of the dark-toned terrain suggests a minimum age of ~100 Ma and a maximum age of ~1 Ga. The age estimates of the candidate CSCs fall within this dispersion. Geochronologically, this places the candidate CSCs among the oldest periglacial landforms identified on Mars so far, by at least one and possibly two orders of magnitude. Unit HNt is adjacent to unit eHt and shows surface material that is relatively light in tone. The coverage is topographically irregular and, at some locations, discontinuous. Amidst the light-toned surface, structures are observed that are akin to clastically non-sorted polygons [NSPs] and polygonised thermokarst-depressions on Earth. Terrestrial polygon/thermokarst assemblages occur in permafrost regions where the freeze thaw cycling of surface and/or near-surface water is commonplace and the permafrost is ice-rich. The crater-size frequency distribution of the light-toned terrain suggests a minimum age of ~10 Ma and a maximum age of ~100 Ma. The age estimates of the candidate ice-rich assemblages fall within this dispersion. Geochronologically, this places them well beyond the million-year ages associated with most of the other candidate ice-rich assemblages reported in the literature. Stratigraphically intertwined with the two possible periglacial terrains are landforms and landscape features (observed or unobserved but modelled) that are indicative of relatively recent glaciation (~10 Ma-100 Ma) and glaciation long past (≥~ 1 Ga) to decametres of depth: glacier-(cirque) like features; viscous-flow features, lobate-debris aprons; moraine-like ridges at the fore, sides and midst of the aprons; and, patches of irregularly shaped (and possibly volatile-depleted) small-sized ridge/trough assemblages. Collectively, this deeply-seated intertwining of glacial and periglacial cycles suggests that the Mid to Late Amazonian Epochs might be more Earth-like in their cold-climate geology than has been thought hitherto.
... The glacier geometry of the ice field and outlet glaciers was reconstructed by the GlaRe, a semi-automated GIS-based method (Pellitero et al., 2016), using the 9 m DEM of the study area (Milevski et al., 2013). The ice thickness from the current bed topography was generated by the GlaRe toolbox applying the parametrisation used by Profiler v.2 (Benn and Hulton, 2010). The glacier thickness was adjusted to geomorphic markers by varying the basal shear stress value (τ b ). ...
... As the geomorphological evidence (terminal moraine and cirque walls) define sufficiently the limits of this palaeoglacier it was possible to use a geographical information systems approach (GIS) to calculate its palaeo-ELA at 2090 m above modern sea level. In particular, the surface, thickness and ELA of the former glaciers were reconstructed using the semi-automated GIS tools based on the numerical technique of Benn and Hulton (2010) and developed by Pellitero et al. (2015;2016). The ELA was calculated with the adaptation of the classic area-altitude balance ratio (AABR) method (Osmaston, 2005) using a balance ratio (BR) of 1.6, which is the average obtained on present-day glaciers in other Mediterranean mountains (Rea, 2009). ...
A glacial geomorphological analysis of three valleys on Mt. Mavrovouni (North Pindus Mountains, Greece) is presented alongside a pilot study using cosmogenic ³⁶Cl to obtain surface exposure ages from iron-rich ophiolite glacial and periglacial boulders. At least three distinct morphostratigraphic units of glacial (moraines) and periglacial (relict pronival ramparts) origin have been identified. Four ³⁶Cl surface exposure ages were obtained from the stratigraphically youngest glacial and periglacial deposits. Although this limited dataset with relatively large uncertainties cannot support a robust geochronology, the ages are consistent with the ³⁶Cl-based chronologies of limestone-derived moraines on Mt. Tymphi (NW Greece) and Mt. Chelmos (S Greece), confirming that the last glaciers on this massif formed during the Last Glacial Maximum as also indicated by other studies in the Pindus mountains. At the same time it provides confidence in the suitability of ³⁶Cl dating for iron-rich samples, such as ophiolites, using an updated ³⁶Cl model that incorporates improved production rates for iron spallation. The presented preliminary chronology of moraines and pronival ramparts is based on those ages as well as on local and regional morphostratigraphic correlations. The stabilisation of the most extensive Late Pleistocene glaciers took place during the Last Glacial Maximum, at 27.0 ± 6.5 ka whereas the presence of pronival ramparts dated at 20.2 ± 4.8 ka suggests persisting cold and arid conditions. Older, still undated glacial deposits exist lower in the valleys which can be attributed to the Middle Pleistocene major glaciation phases (MIS 12/MIS 6), based on their relative morphostratigraphic position within the glacial sedimentary sequence.
... The GLARE GIS toolbox Glacier flowlines were defined from snout to source and the 'flowline ice thickness' tool was used to calculate ice thickness along the flowline, following Benn and Hulton (2010). A default shear stress of 100 kPa was used in the flowline thickness construction for Mount Tymphi and the cirques of Durmitor . ...
The Mediterranean mountains were glaciated during cold stages of the Pleistocene. This glacial record is often well preserved, providing an important archive of past temperature and moisture conditions that extends deep into the Middle Pleistocene. The most extensive glaciations occurred during the Middle Pleistocene, when large ice caps developed in the upland karsts of the Balkans. It is now clear that glaciers were present throughout the Late Pleistocene across the Mediterranean. Some small glaciers remain today, sustained by favourable topoclimatic factors, although many have declined in recent decades due to rising global temperatures. This thesis presents an up-to-date meta-analysis of the geochronological record for the Mediterranean, which highlights greater complexity in the timing of Pleistocene glaciation across the region than hitherto recognised. Key aspects of the glacial record lie outside the moraines in downstream river systems and in marine settings. Despite a wealth of dates for the Late Pleistocene, the timing of glacier maxima and deglaciation in the Balkans is poorly understood. New geomorphological mapping, 52 36Cl terrestrial cosmogenic nuclide exposure ages, and palaeoglacier modelling address a geographical gap in the Mediterranean record and a temporal gap in the previously undated Late Pleistocene and Holocene records at two sites in Greece and Montenegro. Late Pleistocene glaciers were restricted to the upper valleys and cirques at Mount Tymphi in the Pindus Mountains of northwest Greece and in the Durmitor Massif, in the Dinaric Alps of northern Montenegro. The timing of moraine formation and glacier retreat at Mount Tymphi is consistent with the Voidomatis River record downstream and the Ioannina basin pollen record. Glaciers were present in the high cirques of the Durmitor Massif during the Younger Dryas. In contrast, evidence of Younger Dryas glaciation is absent from Mount Tymphi. At Durmitor, Late Holocene moraines that pre-date the Little Ice Age have been identified for the first time in the Dinaric Alps and correspond with the Late Antique Little Ice Age at c. 600 CE. This research also examines the Late Pleistocene terrestrial cosmogenic nuclide (TCN) record for the wider Mediterranean region and demonstrates that mountain glaciers responded to repeated temperature and precipitation changes in the North Atlantic during the Late Pleistocene. While 36Cl dating has enhanced our understanding of the Late Pleistocene and Holocene record, challenges still remain that inhibit our geochronological and palaeoclimatic interpretations. A key conclusion from this research is that it is preferable to use multiple radiometric and relative dating methods in limestone glaciokarst settings.
... The glacier geometry of the ice field and outlet glaciers was reconstructed by the GlaRe, a semi-automated GIS-based method (Pellitero et al., 2016), using the 9 m DEM of the study area (Milevski et al., 2013). The ice thickness from the current bed topography was generated by the GlaRe toolbox applying the parametrisation used by Profiler v.2 (Benn and Hulton, 2010). The glacier thickness was adjusted to geomorphic markers by varying the basal shear stress value (τ b ). ...
In the Jakupica Mts a plateau glacier was reconstructed (max. area ∼45 km², max thickness: ∼260 m). The study area comprises six formerly glaciated valleys, five of which were fed by the plateau glacier and one had an independent cirque when local glaciation reached its maximum ice extent (MIE). The equilibrium line altitude (ELA) of the most extended glacial phase was at 2075⁺³⁷/-25 m asl. The ¹⁰Be cosmic ray exposure (CRE) age of this phase was estimated at 19.3+1.7/-1.3 ka, conformable with the Last Glacial Maximum (LGM). CRE ages from the next moraine generation placed the first phase of deglaciation to 18.2+1.0/-3.0 ka. The samples from the moraine of the penultimate deglaciation phase provided CRE ages with large scatter and biased towards old ages, which is probably the result of inherited cosmogenic nuclide concentrations within the rock.
Glacio-climatological modelling was performed for the MIE, which has a well-established LGM age. The degree-day model was used to calculate the amount of accumulation required to sustain the glaciological equilibrium assuming a certain temperature drop at the ELA. The degree-day model constrained by the pollen-based July paleo-temperature reconstructions yielded an annual total melt at the LGM ELA comparable to or slightly higher than the current mean annual precipitation at the same elevation. These wetter LGM conditions inferred from the paleo-glaciological evidence in Jakupica Mts suggest an enhanced moisture advection in the region.
... The subglacial topography was determined based on the GPR data. A default shear stress value of 100 kPa (Benn and Hulton, 2010;Pellitero et al. 2016;Rea and Evans 2007) was used to run the GlaRe model. The moraine ridges' position was considered an indication of the downslope maximum ice extent during the LIA. ...
Snezhnika and Banski Suhodol glacierets in the Pirin Mountains are the southernmost surface ice accumulations in Europe. Apart from direct snowfall, substantial inputs from avalanching feed both glacierets. Both glacierets appear to be more stable than any other small glacier in the Mediterranean region. Although accurate knowledge of ice thickness distribution and bedrock topography is essential to understand the long-term dynamics of these ice bodies, such data are lacking for the Balkan Peninsula glaciers. Detailed GPR measurements conducted in 2018 using a 100 MHz frequency antenna revealed a maximum thickness of 17 m at Banski Suhodol and 12 m at Snezhnika. Two distinct main layers revealed by density variations were inferred at Snezhnika and several clear internal reflections observed on the radargrams were associated with thin debris layers. Based on the morphological evidence of the former ice extents and high-resolution digital elevation models, 3D reconstructions of ice thickness distribution during the Little Ice Age (LIA) were generated. The results revealed that since LIA the volume of Snezhnika dropped by 123%, and that of Banski Suhodol by 83%. Both glacierets reached maximum thickness values 5 m greater than the present ones during LIA. For the first time, ERT measurements and miniature thermistors were used to investigate ground ice occurrence in the vicinity of the Pirin's glacierets. The ERT measurements revealed no glacial ice in the proglacial area of Banski Suhodol nor in the frontal moraine. Ice-rich frozen debris and frozen sediments without massive ice occur downslope the glacieret on a slope covered by loose rock deposits. Based on the ground surface thermal data, permafrost appears likely on this scree slope, where persistent or late lying snow cover occurs regularly. Our investigation revealed that permafrost is not necessarily related to rock glaciers occurrence in the Balkan Peninsula.
... The choice of the basal shear stress is thus considered the major source of uncertainty in our glacier reconstructions. Since it is unrealistic that the driving stress of topographically constrained glaciers is entirely supported by the basal shear stress (Benn and Hulton, 2010), the ice thickness at points along glacier flowlines in topographically constrained areas was recalculated by incorporating a dimensionless shape factor (f). It was derived from automatically created cross-sections using the 'automatic ice thickness recalculation with f factor' tool in GlaRe. ...
During the Late Pleistocene, an ice cap temporarily rested on the highest summit of the Black Forest, Feldberg, and on the surrounding region. Moraines inside the last glaciation maximum ice extent document subsequent glacial standstills and/or re-advances, but the chronology of the deglaciation remains largely unknown. In Sankt Wilhelmer Tal, moraines were mapped, and suitable moraine boulders were sampled for ¹⁰Be cosmic ray exposure (CRE) dating. Equilibrium line altitudes (ELAs) during moraine formation were reconstructed to evaluate whether these can be used for local stratigraphical correlations. Geomorphological mapping revealed numerous ice-marginal positions in the main valley and in two tributary valleys. CRE ages and ELAs indicate two discrete phases of glacial standstills and/or re-advances by 17–16 ka at the latest and no later than 14 ka, respectively. Differing ELAs across the study area preclude the use of ELAs for local stratigraphical correlations. Recalculated ¹⁰Be CRE ages from other localities in Central Europe indicate similar periods of moraine formation, thus raising the question of a common climatic forcing. Additional sets of CRE ages are needed to answer this question. In addition, future studies should concentrate on determining the age of the last glaciation maximum in the Black Forest.
... Generally, the low-lying valley mouths required a lower shear stress (50 kPa) to yield realistic ice-thicknesses, which is compatible with the glacier overriding thicker sediment fills with low yield strength at these locations (Thorp, 1991;Iverson et al., 2003). For the steep glacial troughs of the Basson and Bassa valleys, an additional F-factor adjustment, which is a function of the glacier width and thickness, was applied to account for lateral drag exerted by the valley walls (Nye, 1952;Benn & Hulton, 2010;Pellitero et al., 2016). ...
Small, peripheral mountain glaciers that remained independent from the large ice-streams throughout the Pleisto-cene glaciations represent an important source of paleoclimatic information in the European Alps. Here, we present new evidence on the evolution of the Silisia Valley and paleoglaciers on the northern side of Mount Raut (Carnic Prealps, NE Italy). The area is characterized by the presence of a variety of sediments and landforms, among them two generations of conglomerates and several deposits of glacigenic origin. The conglomerates are related to the infill and subsequent incision of the Silisia Valley during Plio (?)-Pleistocene times, whereas most of the glacigenic deposits can be ascribed to glacier advances during the Last Glacial Maximum (LGM) and following Late Glacial stadials. During the LGM, the glacial system extended from the headwalls of Mount Raut (2026 m a.s.l.) down to an elevation of 440 m, and had an equilibrium line altitude (ELA) of 1260 m (Accumulation-Area-Balance Ratio method-AABR). Assuming present-day amounts of precipitation, this corresponds to a mean summer air temperature (MSAT) depression of 8.5 or 9.4°C (V =±2.2°C), when compared to two recent (1960-1990) climatic records in the area. Two phases of glacier stabilization during the Late Glacial were inferred from frontal moraine systems at higher elevations. During the first one, the glaciers had an ELA of 1590 m (corresponding to an MSAT lowering of 6.2 or 7.1°C), whereas at the second one the ELA was at 1740 m (MSAT lowering of 5.3 or 6.1°C). Our results allow to better understand the long-term Pleistocene evolution of this sector of the southeastern Alps, probably driven by the interplay between climatic fluctuations and phases of tectonic uplift. We further provide new insights on paleoglaciers of the last glacial cycle that may help in the validation of regional climatic models.
... As the geomorphological evidence (terminal moraine and cirque walls) define sufficiently the limits of this palaeoglacier it was possible to use a geographical information systems approach (GIS) to calculate its palaeo-ELA at 2090 m above modern sea level. In particular, the surface, thickness and ELA of the former glaciers were reconstructed using the semi-automated GIS tools based on the numerical technique of Benn and Hulton (2010) and developed by Pellitero et al. (2015;2016). The ELA was calculated with the adaptation of the classic area-altitude balance ratio (AABR) method (Osmaston, 2005) using a balance ratio (BR) of 1.6, which is the average obtained on present-day glaciers in other Mediterranean mountains (Rea, 2009). ...
... The reconstructed glaciers were created using the GlaRe (Glacier Reconstruction) ArcGIS toolbox (Pellitero et al., 2015) which represent a semiautomated method of glacier reconstruction. Ice thickness was assessed along the flowline using a glacier profile model (Benn and Hulton, 2010) using basal shear stress values 50 to 100 kPa (Cuffey and Paterson, 2010) and a calculated valley shape factor. Ice thickness was adjusted to the mapped glacial landforms by fine-tuning their thickness using the basal shear stress values. ...
The Polonyna Rivna (1480 m asl) and Borzhava (1682 m asl) ranges represent medium-high mountain massifs located in the north-western part of the Ukrainian Carpathians, where the legacy of the Pleistocene glaciation has long been unexplored. Based on the first detailed mapping of glacial landforms and sedimentological analysis, we document the presence of freshly-shaped outer moraines and glacial cirques and reconstruct the extent and ice-surface geometry of the six very small (0.09–0.78 km² area) palaeoglaciers. The specific feature of the area is the presence of extensive mountain-top plateaus that play an important role as additional areas for snowblow accumulation. The equilibrium line altitudes (ELAs) calculated from hypsometry of reconstructed local Last Glacial Maximum (LLGM) using the area x altitude balance ratio (AABR) 1.6 method is exceptionally low at 1138 m asl in the Polonyna Rivna and 1230 m asl in the Borzhava range. Excluding the topographic effect produced by additional snow accumulation the ELA shift upwards between 120 and 180 m which corresponds to 25–53% of the glacier elevation range. The resulted climatic ELA (1282–1352 m asl) together with the mean cirque floor altitude (1194 m asl) and mean elevation of the glacier fronts (994 m asl) represent the lowest values in the entire Carpathian arc. Our data indicate glacier-friendly conditions in the mountain massifs exceeding 1400 m asl in the windward NW part of the Ukrainian Carpathians where due to relatively cold air temperatures and orographic induced precipitation local topolimatic factors dictated the development of marginal glaciation.
... Glacier reconstruction was performed in the GIS environment based on the mapped distribution of moraines and scattered erratic boulders . Ice thickness was assessed along the flowline using a glacier profile model (Benn and Hulton, 2010) provided in the Pellitero et al. (2015) toolbox with the use of basal shear stress values 50 to 100 kPa (Cuffey and Paterson, 2010) and a calculated valley shape factor. Ice thickness was adjusted to the mapped glacial landforms by fine-tuning their thickness using the basal shear stress values. ...
In the Northern Romanian Carpathians (NRC) small Pleistocene cirque glaciers have formed in several isolated mountain massifs exceeding 1800 m asl. This paper brings forward new geomorphological evidence of marginal glaciation in the Călimani, Suhard, and Gurghiu Mountains which are the southernmost glaciated areas of the NRC.
We reconstructed the extent and ice-surface geometry for 12 palaeo-glaciers in the study area during the Maximal Ice Extent (MIE) which is attributed to LGM. The equilibrium line altitudes (ELAs) calculated using the area-altitude-balance-ratio (AABR) 1.6. were between 1740 m and 1870 m which is the highest value in the Eastern Carpathians and one of the highest in the entire Carpathians. The specific features of the Călimani and Gurghiu Mountains are the extensive, gentle outer slopes of volcanic calderas that play an important role as additional areas for snowblow accumulation. Inclusion of the potential snow contribution area (snowblow and avalanche accumulation) in the ELA calculation resulted in an additional upward ELA shift up to 66 m (up to 40% of the glacier elevation range).
Our data indicate that small cirque glaciation in the NRC could develop when mountain ranges are at least 100 m above the extrapolated regional ELA. The general ELA pattern in the NRC shows a positive trend (∼3 m/km) which could reflect both the general rise in temperature and the starvation of precipitation toward the southeast. However, the observed eastward ELA rise on W-E transects in the Eastern Carpathians shows a pure precipitation effect and indicates the influence of zonal atmospheric circulation in the far interior of Europe during the LGM.
... A three-dimensional palaeoglacier reconstruction was carried out for the different glacial phases using the 'GLaRe' ArcGIS toolbox developed by Pellitero et al. (2016) and a 10-m resolution DEM, which implements a perfect-plasticity physical-based numerical model (Van der Veen 1999; Benn and Hulton 2010) that reconstructs past ice thickness assuming an average shear stress of 100 kPa along a set of flowlines (Paterson 1994;Benn and Hulton 2010). And finally, equilibrium-line altitudes (ELAs) were calculated using the automatic toolbox developed by Pellitero et al. (2015) through the methods Accumulation Area Ratio (Porter 1975; AARs: 0.6 ± 0.05) and the Area Altitude Balance Ratio (AABR; Osmaston 2005). ...
The Upper Garonne Basin included the longest glacier in the Pyrenees during the Late Pleistocene. During major glacial advances, the Garonne palaeoglacier flowed northwards along ~ 80 km from peaks of the axial Pyrenees exceeding 2800–3000 m until the foreland of this mountain range at the Loures–Barousse–Barbazan basin (LBBb), at 420–440 m. Here, the palaeoglacier formed a terminal moraine complex that is examined in this work. Based on geomorphological observations and a 12-sample data set of ¹⁰Be Cosmic-Ray Exposure (CRE) ages, the timing of the maximum glacial extent was constrained as well as the onset of the deglaciation from the end of the Last Glacial Cycle (LGC). Chronological data shows evidence that the external moraines in this basin were abandoned by the ice at the end of the Penultimate Glacial Cycle (PGC) and the onset of the Eemian Interglacial, at ~ 129 ka. No evidence of subsequent glacial advances or standstills occurred during the LGC in this basin were found, as the few existing datable boulders provided in the internal moraine showed inconsistent ages, thus probably being affected by post-glacial processes. The terminal basin was already deglaciated during the global Last Glacial Maximum at 24–21 ka, as revealed by exposure ages of polished surfaces at the confluence of the Garonne-La Pique valleys, 13 km south of the entrance of the LBBb. This study introduces the first CRE ages in the Pyrenees for the glacial advance occurred during the PGC and provides also new evidence that glaciers had already significantly shrunk during the LGM.
... The reconstructed glaciers were created using the GlaRe (Glacier Reconstruction) ArcGIS toolbox (Pellitero et al., 2015) which represent a semiautomated method of glacier reconstruction. Ice thickness was assessed along the flowline using a glacier profile model (Benn and Hulton, 2010) using basal shear stress values 50 to 100 kPa (Cuffey and Paterson, 2010) and a calculated valley shape factor. Ice thickness was adjusted to the mapped glacial landforms by fine-tuning their thickness using the basal shear stress values. ...
... The estimated ice thicknesses, together with the elevation of contemporary glacier-adjacent terrain (LINZ, 2011) were combined using the MATLAB RegulariseData3D function to generate an ice-free topography in the (currently) glacierised catchment at 100 m resolution. The ArcGIS Glacier Reconstruction (GlaRe) toolset (Pellitero et al., 2016) was then used to generate an approximated bare-ice glacier surface from a central flowline using a 2D perfect-plasticity central difference model (Benn and Hulton, 2010). The model initialisation point at the glacier terminus was defined from historical imagery from 1904, when the terminus was~100 m from the LIA moraine (Fig. 3). ...
Flood reconstruction is essential for establishing magnitude-frequency relationships and assessments of contemporary geohazards and risks. Traditionally, flood reconstructions rely upon the analysis of evidence acquired from a single discipline. This lack of integration limits the insights into a flood's source, pathway, and receptors (i.e. impacts). Here, our aim is to test the integration of qualitative historical documentary material with quantitative geomorphological and sedimentological evidence to reconstruct glacial lake outburst floods (GLOFs) in 1913 at Kea Point, Mount Cook National Park, Aotearoa New Zealand. Written documentary records show that, following heavy rainfall, GLOF events occurred in January and March, after the temporary impoundment of water between the glacier surface and lateral moraine. Peak flood discharge was estimated from slope-area and exposed boulder measurements as 316–1077 m³s⁻¹ and 496–1622 m³s⁻¹ respectively. Sedimentological information, combined with geomorphic mapping, a DEM derived from Structure from Motion (SfM) photogrammetry, and satellite imagery was used to describe the overall physical impact of the GLOF. Information from written documentary records, however, enabled a more detailed reconstruction of the timeline of the two floods and their impacts proximate to the original ‘Hermitage Hotel’, which was subsequently relocated. Our integrated approach exemplifies the informative level of multi-faceted detail that can be retrieved for historical flood events. We propose a framework for future studies that seek to reconstruct flood events and their source, pathway and receptors through combining evidence from historical documents/artefacts, sedimentological/geomorphological data, and integration with environmental monitoring/modelling outputs.
In recent decades, most glaciers have been melting, thinning and retreating globally in response to continuously increasing temperatures. We simulated ice thicknesses and volumes on the east and west slopes of Mt Noijin Kang‐Sang, Southern Tibetan Plateau (TP), since the Last Glacial Maximum (LGM), using a glacial flowline model. The simulated average ice thicknesses during the LGM and Lateglacial (LG), Early Holocene, Neoglacial and the Little Ice Age (LIA) periods were 1.4, 1.3, 1.1 and 1.2 times greater than those of modern glaciers in the Gangbu (eastern slope) and western valleys, respectively. In the Gangbu Valley, areas from the LGM‐LG to LIA periods were 1.7, 1.5, 1.4 and 1.2 times greater than the modern glacier area, and the volume expansion indexes were 2.2, 1.9, 1.5 and 1.4. In the western valleys, the area expansion indexes were 2.2, 1.9, 1.5 and 1.4 times greater than the modern glacier, and volumes were 5.4, 4.4, 3.4 and 2.9 times greater, respectively. Glaciers in the western valleys retreated more extensively than those on the eastern slopes of Gangbu Valley after the LGM‐LG, probably due to the smaller glaciers on the leeward western slopes with lower elevations. Equilibrium‐line altitudes dropped ~425 m in Gangbu Valley and ~385 m in the western valleys during the LGM‐LG, corresponding to a 3.8–4.1 °C temperature decrease in this region, which was consistent with cooling on the central Tibetan Plateau, but lower than cooling at the south‐eastern edge of the Tibetan Plateau.
The paper aims to reconstruct the fluctuations of Dobrowolski Glacier, a tidewater glacier located in the inner position of the Admiralty Bay (King George Island, Antarctica), from the Little Ice Age (1400-1700) until the present. Measurements of the glacier’s area and length were based on multitemporal satellite imagery and submarine glacial landforms. The glacier surface area variations between the Little Ice Age and 2014 A.D were estimated. Morainic banks and paleoglacial reconstructions provided evidence of fluctuations in the surface area of the glacier between PIG and 2014 AD. Therefore, four stages of analysis were established: Stage I (Part I) (1400 to 1700), Stage I (Part II) (1700 until the mid-20th century), Stage II (mid-20th century until the 1980s), Stage III (1980 to 2000), and Stage IV (2000 to 2020). The climate during the Little Ice Age triggered the last major glacial advance, and their grounding line position was recorded by an external and prominent morainic bank. After the major glacial advance position of the grounding line, the ice-margin has undergone higher retreat rates (stage I) as response to the warming trend and the loss of anchoring point. The stage II (Unit B) is recorded by distal and discontinuous morainal ridges and glacial lineations formed in the context of an active ice flow at a deeper point in the fjord. During stage III (Unit C) glacial lineations and steep slopes occur, while landforms are less preserved, revealing a fast shrinkage phase. Stage IV is characterized by discontinuous morainic ridges (Unit D), when the glacier presents the highest annual glacial area loss. Currently, the accelerated shrinkage may be linked to the loss of anchorage on seamounts (serving as pinning points) and increased warming. The U-shaped valley geometry has also influenced the glacier shrinkage processes and the redirection of glacial paleoflow during the last 300 years. The retreat rate to mid-20th century-2020 period is higher than Little Ice Age- mid-20th century period.
Assessing the effects of ongoing anthropogenic climatic change requires a thorough understanding of past climatic fluctuations. The reconstruction of changes in the extent of small glaciers provides valuable information on climatic changes, as smaller ice masses react sensitively to changes in precipitation and temperature. Despite a large number of studies in recent years, the configuration of the atmospheric
circulation over Europe during the Late Pleistocene [129-11.7 ka (kiloyears before present)] is still controversially discussed. One key aspect of this debate is the question whether the Mediterranean Sea and not the Atlantic Ocean (as today) served as the main moisture source for glaciers in the Alps during the last glaciation maximum in the Alps (at around 26-24 ka). If this assumption is correct, the Black
Forest (southern Germany) and the about 1000 km²-large ice caps in its southern part would have probably been in a leeward position with respect to the Alps. The location in a leeward position conceivably limited the growth of the ice caps. Therefore, it is likely that the ice caps of the Southern Black Forest reached their last maximum extent asynchronously with the Alps. Since the determination
of the age of the last glaciation maximum in the southern Black Forest is still pending, this assumption cannot yet be verified. Dating this glacial phase would allow for obtaining valuable climatic information, as the Southern Black Forest lies in a key position with respect to the Alps and in proximity to key sites
for climate reconstructions.
The general trend towards warmer climatic conditions after the last glacial maximum (27.5-23.3 ka) was punctuated by rapid decreases in temperature. Chronological data from moraines in formerly glaciated mountains of Central Europe outside the Alps, i.e., in the Vosges, Bavarian Forest, Bohemian Forest, and in the Giant Mountains, indicate several periods of ice-marginal stability and glacier re-advances
during deglaciation. Summer temperatures in ice-free areas of Central Europe during the last glacial termination have been successfully reconstructed, but precipitation patterns remain largely elusive. It has been shown that precipitation reconstructions with data from former glaciers can fill this gap, but reconstructions for other parts of the last glacial termination require additional data on the temporal and
spatial evolution of glaciers in the mountains of Central Europe. Particularly the chronology of glacier variations in the Southern Black Forest remains largely unknown, as age determinations of glacial landforms and deposits that document former ice-marginal positions are lacking.
This study addresses aims to fill these gaps by reconstructing the chronology of the last (Late Pleistocene) glaciation of the Southern Black Forest with the ultimate aim to contribute to a better understanding of the climate during the Late Pleistocene.
A digital elevation model (DEM) with a xy-resolution of 1 m and its derivates (e.g., contour lines) were first systematically used to map glacial landforms in the Southern Black Forest with particular emphasis on terminal moraines, as these landforms document former ice-marginal positions. The results were subsequently confirmed during extensive field surveys. Geomorphological mapping revealed that some previously described moraines have to be rejected, whereas other moraines were mapped for the first time. The number of inferred ice-marginal positions turned out to be higher than in previous studies. These findings suggest highly dynamic former glaciers in the Southern Black Forest and underline that thorough geomorphological investigations with an up-to-date approach are always needed prior to the application of numerical dating methods. 10Be cosmic-ray exposure dating was applied (for the first time in the Black Forest) to boulders on
moraines in two formerly glaciated valleys north-west of the highest summit of the Black Forest, Feldberg [1493 m above sea-level (a.s.l.)] to reconstruct the chronology of the last glaciation. In the field, the determination of topographic shielding factors for age calculations was not possible at all sampling sites. To correct the ages for topographic shielding, a previously published toolbox for the
ESRI® ArcGIS software was applied that allows for calculating shielding factors with DEMs. As the performance of the toolbox has hitherto not been evaluated with an extensive set of field data, a validation study was undertaken. Boulders in three settings, i.e., the Southern Black Forest, the forefield of Steingletscher, and the Écrins massif were chosen. Shielding factors derived with the toolbox were
consistent with field data-based shielding factors and the spatial resolution of the tested DEMs did not influence the fit between the shielding factors. Replacing shielding factors with those derived with the toolbox led, in most cases, to minor shifts in ages. These findings underline that the toolbox provides precise shielding factors for age calculations. Dating the Late Pleistocene glaciation maximum was not possible in the two studied valleys, since suitable boulders for age determinations were missing in the first valley and traces of this phase of glaciation have not been preserved in the second valley. Preliminary ages of erratic boulders and boulders on moraines for an area south-east of Feldberg indicate that glacier retreat from the Late Pleistocene maximum position may have been underway by 21 ka at the latest, but this working hypothesis needs to be confirmed with additional data. Ages of moraines of the last deglaciation in the valleys north-west of Feldberg cluster around 17-16 ka, 15-14 ka, and 13 ka, thus indicating three distinct periods of repeated phases of ice-marginal stability. In most studied glacial cirques, final glacier retreat was underway by 14 ka at the latest. As this age for final glacier retreat roughly corresponds to the rapid rise in summer temperatures at around 14.7 ka, it is likely that this climatic event led to deglaciation.
DEMs of glaciers were established to reconstruct equilibrium line altitudes (ELAs) of glaciers, i.e. the zones where ablation equals accumulation on an annual timescale.
By 17-16 ka at the latest, ELAs of valley glaciers varied between about 1140 and 1160 m a.s.l. During the period of cirque glaciation at the end of the last deglaciation (no later than 15-14 ka), ELAs of the reconstructed glaciers lay between about 1150 and 1210 m a.s.l. with no clear across the studied valleys. The ELA of the last cirque glacier in one of the studied valleys was situated at around 1400 m a.s.l. by
13 ka at the latest. Annual precipitation at the ELA apparently amounted to about 3100 mm per year at around 13 ka. This unrealistically high estimate conflicts with the few available precipitation records and is probably explained by a strong effect of snow blow and avalanching on the mass balance of the glacier. Spatial
discrepancies in ELAs at around 15-14 ka are explained best by the size of the snow blow and avalanche catchment of former glaciers. Due to the strong influence of snow blow and avalanching on ELAs, reliable estimates of annual precipitation at ELAs could not be provided. Additional work is needed for realistic estimates of annual precipitation, including a detailed assessment of the effect of topographic
shading on the position of ELAs.
Mapping glacial landforms and 10Be cosmic-ray exposure dating allowed for reconstructing the chronology of the Late Pleistocene glaciation of the Southern Black Forest in unprecedented detail. 10Be cosmic-ray exposure dating of moraines made it possible, for the first time, for proposing an independent regional glacier chronology. The high potential for climate reconstructions warrants further studies on Late Pleistocene glacier fluctuations. Further efforts should particularly concentrate on dating the Late Pleistocene glaciation maximum and on extracting a climatic signal from glacier fluctuations during the last glacial termination.
The lack of continental ice sheets in Alaska during the Last Glacial Maximum (LGM; 26–19 ka) has long been attributed to arid and relatively warm summer conditions. Records of this aridity across Alaska are relatively abundant, yet quantitative temperature reconstructions have been comparatively lacking until recently. Climate model outputs, a few isolated paleoclimate studies, and global paleoclimate synthesis products show mild summer temperature depressions in Alaska compared to much of the high northern latitudes. This suggests the importance of summer temperature in controlling the relatively limited glacier growth during the LGM. We present a new statewide map of LGM alpine glacier equilibrium line altitudes (ELAs), LGM ∆ELAs (LGM ELA anomalies relative to the Little Ice Age [LIA]), and ∆ELA-based estimates of temperature depressions across Alaska to assess paleo-precipitation and -temperature conditions. We mapped glacier extents and reconstructed paleoglacier surfaces in ArcGIS to calculate ELAs using an accumulation area ratio (AAR) of 0.58 and an area-altitude balance ratio (AABR) of 1.56. We calculated LGM ELAs (n = 480) across every glaciated massif in the state, excluding areas in southern Alaska that were covered by the Cordilleran Ice Sheet. We see a similar trend of increasing ELAs from the southwest to the northeast during both the LGM and the LIA indicating a consistent southern Bering Sea and northernmost Pacific Ocean precipitation source. Our ∆ELAs from the Alaska and Brooks ranges, and the Kigluaik Mountains, average to −355 ± 176 m, well above the global LGM average of ca. −1000 m. Using atmospheric lapse rates, we calculate minimum summer cooling of −3.5 ± 1.7 ºC and maximum summer temperature depressions of −1.9 ± 0.9 ºC. Our results are consistent with a growing number of local proxy reconstructions and global data assimilation syntheses that indicate mild summer temperature across Beringia. Limited summer temperature depressions could be explained by increased incoming solar radiation across Alaska during the LGM. Limited summer temperature depressions – and general aridity – in Alaska during the LGM have been previously hypothesized as resulting from the complex influence of North American ice sheets on atmospheric circulation.
Subsurface salt flow is driven by differential loading, which is typically caused by tectonics or sedimentation. During glaciations, the weight of an ice sheet represents another source of differential loading. In salt-bearing basins affected by Pleistocene glaciations, such as the Central European Basin System, ice loading has been postulated as a trigger of young deformation at salt structures. Here, we present finite-element simulations (ABAQUS) with models based on a simplified 50-km-long and 10-km-deep two-dimensional geological cross-section of a salt diapir subject to the load of a 300-m-thick ice sheet. The focus of our study is to evaluate the sensitivity of the model to material parameters, including linear and non-linear viscosity of the salt rocks and different elasticities. A spatially and temporarily variable pressure was applied to simulate ice loading. An ice advance towards the diapir causes lateral salt flow into the diapir and diapiric rise. Complete ice coverage leads to downward displacement of the diapir. After unloading, displacements are largely restored. The modelled displacements do not exceed few metres and are always larger in models with linear viscosity than in those with non-linear viscosity. Considering the low stresses caused by ice-sheet loading and the long time-scale, the application of linear viscosity seems appropriate. The elastic parameters also have a strong impact, with lower Young's moduli leading to larger deformation. The impact of both the viscosity and the elasticity highlight the importance of a careful parameter choice in numerical modelling, especially when aiming to replicate any real-world observations.
Most mid-latitude mountain glaciers reached their maximum extent around the global Last Glacial Maximum (gLGM). However, some also strongly responded to the regional climate change or local non-climatic factors such as topography, leading to asynchronous maximum advances. This study documents the maximum extent and chronology of two paleoglaciers in the Ih Bogd massif of Mongolia: one facing north into the Jargalant Valley and the other facing south into the Ih Artsan valley. 10Be surface exposure age dating revealed that the Ih Artsan short valley glacier reached its maximum position (MIh1) around 20.1 ± 0.7 ka, coinciding with the gLGM. In contrast, the Jargalant paleoglacier (MJ1) reached its maximum extent around 17.2 ± 1.5 ka, around Heinrich 1 stadial and during the post-gLGM northern hemisphere warming. Our 2D ice surface model, which includes the temperature-index melt model, suggests that an aspect can result in a melt difference between north and south-facing slopes. Glaciers retreated from their maximum modeled extent asynchronously when we assign a 0.5 ℃ lower temperature for Jargalant valley (northern slope), based on the observation that present-day mean annual Jargalant temperatures are lower than in the south-facing Ih Arstan. Modelled timing of the maximum extents (20.23 ka in Ih Artsan, 17.13 ka in Jargalant) are consistent with 10Be exposure age results (20.1 ka in Ih Artsan, 17.2 ka in Jargalant). We also observed several sequences of post LGM or/and Holocene moraines in both cirques. Extremely old ages ranging from 636.2 ka to 35.9 ka were measured for the inner moraines in the Jargalant cirque (MJ2–MJ4), suggesting a problem with inheritance from boulders eroded from the summit plateau.
Reconstructing three-dimensional palaeoglacier surface, thickness, and volume provides useful information for quantifying palaeo-climate conditions during glacial stages and assessing the impact of glacier change on water resources. A glacial flowline model has been implemented in Excel and ArcGIS to reconstruct palaeoglaciers based on digital elevation models and geomorphic constraints, such as moraines and trimlines that represent the margins and local heights of palaeoglaciers, respectively. However, significant efforts are still needed in using these tools for palaeoglacier reconstruction, such as digitizing flowlines, adjusting shear stress, and deriving shape factors. This paper presents an automated method, PalaeoIce, to reconstruct palaeoglaciers using geomorphic constraints. Coded in python, PalaeoIce is an ArcGIS toolbox with a set of tools to generate glacial flowlines, optimize shear stress, derive shape factors, calculate ice thickness values along flowlines, and interpolate palaeo ice surfaces based on geomorphic constraints. The use of PalaeoIce is demonstrated using extant glaciers with measured thickness values and moraines/trimlines of the Little Ice Age (LIA) and Marine Isotope Stage (MIS) 2 in the eastern Tian Shan, China. The reconstructed ice thickness values of Glacier No. 1 in this area show a reasonable agreement with field measurements with 1.4 % and 5.4 % differences between measured and reconstructed mean ice thickness values using the two methods included in PalaeoIce: a revised ice thickness model for extant glaciers and a palaeoglacier reconstruction method based on glacier outlines, respectively. Two approaches are then illustrated for palaeoglacier reconstructions using two sets of geomorphic constraints: one with the fully reconstructed glacier outlines during the LIA, and the other with just the terminal moraine and limited trimlines during MIS 2. PalaeoIce can significantly improve the efficiency of palaeoglacier reconstructions and the understanding of the impact of glacier change on water resources.
The maximum extent and elevation of the Greenland Ice Sheet in southwestern Greenland during the Last Glacial Maximum (LGM, 26–19.5 ka) is poorly constrained. Yet, the size of the Greenland Ice Sheet during the LGM helps to inform estimates of past ice-sheet sensitivity to climate change and provides benchmarks for ice-sheet modeling. Reconstructions of LGM ice extents vary between an inner continental shelf minimum, a mid-shelf position, and a maximum extent at the shelf break. We use three approaches to resolve LGM ice extent in the Sisimiut sector of southwestern Greenland. First, we explore the likelihood of minimum versus maximum Greenland Ice Sheet reconstructions using existing relative sea-level data. We use an empirical relationship between marine limit elevation and distance to LGM terminus established from other Northern Hemisphere Pleistocene ice sheets as context for interpreting marine limit data in southwestern Greenland. Our analysis supports a maximum regional Greenland Ice Sheet extent to the shelf break during the LGM. Second, we apply a simple 1-D crustal rebound model to simulate relative sea-level curves for contrasting ice-sheet sizes and compare these simulated curves with existing relative sea-level data. The only realistic ice-sheet configuration resulting in relative sea-level model-data fit suggests that the Greenland Ice Sheet terminated at the shelf break during the LGM. Lastly, we constrain the LGM ice-sheet thickness using cosmogenic 10Be, 26Al, and 14C exposure dating from two summit areas, one at 381 m above sea level at the coast, and another at 798 m asl 32 km inland. Twenty-four cosmogenic radionuclide measurements, combined with results of our first two approaches, reveal that our targeted summits were likely ice-covered during the LGM and became deglaciated at ca. 11.6 ka. Inventories of in situ 14C in bedrock at one summit point to a small degree of inherited 14C and suggest that the Greenland Ice Sheet advanced to its maximum late Pleistocene extent at 17.1 ± 2.5 ka. Our results point to a configuration where the southwestern part of the Greenland Ice Sheet reached its maximum LGM extent at the continental shelf break.
The long-term cyclicity and temporal succession of glacial-periglacial (or deglacial) periods or epochs are keynotes of Quaternary geology on Earth. Relatively recent work has begun to explore the histories of the mid- to higher-latitudinal terrain of Mars, especially in the northern hemisphere, for evidence of similar cyclicity and succession in the Mid to Late Amazonian Epoch.
Here, we carry on with this work by focusing on Protonilus Mensae [PM] (43–49⁰ N, 37–59⁰ E). More specifically, we discuss, describe and evaluate an area within PM that straddles a geological contact between two ancient units: [HNt], a Noachian-Hesperian Epoch transition unit; and [eHT] an early Hesperian Epoch transition unit. Dark-toned terrain within the eHt unit (HiRISE image ESP_028457_2255) shows continuous coverage by structures akin to clastically-sorted circles [CSCs]. The latter are observed in permafrost regions on Earth where the freeze-thaw cycling of surface and/or near-surface water is commonplace and cryoturbation is not exceptional.
The crater-size frequency distribution of the dark-toned terrain suggests a minimum age of ~100 Ma and a maximum age of ~1 Ga. The age estimates of the candidate CSCs fall within this dispersion. Geochronologically, this places the candidate CSCs among the oldest periglacial landforms identified on Mars so far, by at least one and possibly two orders of magnitude.
Unit HNt is adjacent to unit eHt and shows surface material that is relatively light in tone. The coverage is topographically irregular and, at some locations, discontinuous. Amidst the light-toned surface, structures are observed that are akin to clastically non-sorted polygons [NSPs] and polygonised thermokarst-depressions on Earth. Terrestrial polygon/thermokarst assemblages occur in permafrost regions where the freeze thaw cycling of surface and/or near-surface water is commonplace and the permafrost is ice-rich. The crater-size frequency distribution of the light-toned terrain suggests a minimum age of ~10 Ma and a maximum age of ~100 Ma. The age estimates of the candidate ice-rich assemblages fall within this dispersion. Geochronologically, this places them well beyond the million-year ages associated with most of the other candidate ice-rich assemblages reported in the literature.
Stratigraphically intertwined with the two possible periglacial terrains are landforms and landscape features (observed or unobserved but modelled) that are indicative of relatively recent glaciation (~10 Ma - 100 Ma) and glaciation long past (≥ ~ 1 Ga) to decametres of depth: glacier-(cirque) like features; viscous-flow features, lobate-debris aprons; moraine-like ridges at the fore, sides and midst of the aprons; and, patches of irregularly shaped (and possibly volatile-depleted) small-sized ridge/trough assemblages. Collectively, this deeply-seated intertwining of glacial and periglacial cycles suggests that the Mid to Late Amazonian Epochs might be more Earth-like in their cold-climate geology than has been thought hitherto.
Although numerous global Last Glacial Maximum (gLGM) dating-based paleoclimatic and paleoglacial reconstructions exist for the Tibetan Plateau, no such study is available for the mountains to the Tibetan Plateau's east. Mount Taibai lies east of the Tibetan Plateau, and is known to have experienced glaciation during the Quaternary. In this study, optically stimulated luminescence (OSL) dating was employed to determine the ages of two lateral moraines in the Eryehai Valley on Mount Taibai. The ages obtained were 22.1 ± 1.7–18.7 ± 1.1 ka and 25.8 ± 1.8–24.3 ± 1.5 ka, constrain the timing of the gLGM glaciation in the study area. Using GlaRe and equilibrium-line altitude (ELA) calculations, these two toolboxes, based on a Geographic Information System (GIS), were used to reconstructed the extent of the study area's paleoglacial surface and the ∆ELA. The glacial coverage and ELA for the gLGM in the Eryehai Valley on Mount Taibai were 0.17 km³ and 3351.5 ± 5 m above sea level (asl), respectively. This gLGM ELA is lower than the modern theoretical ELA (4816.5 m asl) by 1465 ± 5 m. From the sporopollen records of the Zoigê Basin in the northwestern Mount Taibai, the precipitation during the gLGM period was equivalent to 60–80% of the present, combined with this record, ∆ELA-based models of the precipitation–temperature relationship (P-T) and the temperature lapse rate (LR) model at the ELA indicate that this area was 7.0–9.4 °C colder during the gLGM. Combined with other paleoclimatic proxies, a decrease in temperature emerges as the primary driver of glaciation during the gLGM on Mount Taibai. Paleoclimatic reconstructions of paleoglaciers on the Tibetan Plateau and its adjacent mountains also indicate that a drop in temperatures was the principal driver of glacial advances in these regions during the gLGM. Regions affected by the East Asian Monsoon, the Indian Monsoon and the Westerlies would have experienced a greater cooling during the gLGM, while regions blocked by high mountains, and therefore less affected by monsoons and westerly winds, would have seen less cooling.
The flow of valley glaciers is examined in the light of recent laboratory experiments on the behaviour of ice under load. Simple expressions are given for the velocity distributions in some cases of laminar flow, and the modification of a pure laminar flow theory necessary to explain the formation of transverse crevasses and thrust planes is considered. The paper ends with some remarks about the formation of crevasse patterns on the surfaces of glaciers. The statical equilibrium of a circular ice cap is discussed in an appendix.
At Hardangerjøkulen, central southern Norway, detailed knowledge of the number, age and magnitude of Holocene glacier fluctuations is used to reconstruct variations in equilibrium-line altitude (ELA) for the last 10 000 years. Present and past ELAs are based on an accumulation-area ratio (AAR) of 0.7 and are adjusted for land uplift. A synchronous relationship between advanced glacier positions and the highest pine-tree limits (Pinus sylvestris L.) is demonstrated for the early to mid-Holocene in southern Scandinavia, which indicates that warm summers were compensated for by high winter precipitation. Based on pine-tree limit fluctuations as a measure of mean ablation-season temperature, Holocene variations in winter precipitation at Hardangerjøkulen have been calculated by substitution in the close exponential relationship between mean ablation-season temperature and winter precipitation at the ELA of Norwegian glaciers. Setting the winter precipitation during the period AD 1961-1990 at 100%, mean values varied from about 65 to c. 175%. The wettest phase, at c. 8500-8300 cal. BP, experienced a mean summer temperature of c. 1.35°C warmer than at present, and may be regarded as a climatic analogue for the increase in precipitation which may accompany greenhouse warming of the atmosphere during the next century. These early-Holocene 'greenhouse centuries' ended abruptly within 30-50 years, and changed into a climatic regime dominated by dry winters and by summers only a little warmer than at present. The transition is synchronous with the most notable δ 18O minimum recorded in Greenland ice cores at 8210 ± 30 years ago (before AD 1990), and is tentatively suggested as a Holocene analogue for the climatic instability (which may have been) recorded in the GRIP ice core during the last interglacial period (the Eemian).
The flow of valley glaciers is examined in the light of recent laboratory experiments on the behaviour of ice under load. Simple expressions are given for the velocity distributions in some cases of laminar flow, and the modification of a pure laminar flow theory necessary to explain the formation of transverse crevasses and thrust planes is considered. The paper ends with some remarks about the formation of crevasse patterns on the surfaces of glaciers. The statical equilibrium of a circular ice cap is discussed in an appendix.
This book, first published in 2005, provides students and practising glaciologists with the tools they need to understand modern glaciology. Relatively simple concepts are introduced first, followed by mathematically more sophisticated chapters. A knowledge of basic calculus is assumed, but important concepts of physical processes are developed from elementary principles. Emphasis is placed on connections between modern research in glaciology and the origin of features of glacial landscapes. Student exercises are included. This new edition builds on the successful first edition: it has been completely updated, and important new sections and whole chapters have been added. Principles of Glacier Mechanics is designed to be used as a primary textbook in upper division and graduate courses in glaciology, and can be used as either a primary or supplementary text in courses in glacial geology. Practising glacial geologists and glaciologists will also find it useful as a reference book.
Fundaments of Glacier Dynamics presents an introduction to modelling the flow and dynamics of glaciers. The emphasis is more on developing and outlining procedures than on providing a complete overview of all aspects of glacier dynamics. Derivations leading to frequently-used equations are presented step-by-step to allow the reader to grasp the mathematical details and approximations involved and gain the understanding needed to apply similar concepts to different applications. The first four chapters discuss the background and theory needed for glacier modelling. The central part of the book discusses simple analytical solutions and time-evolving numerical models that are used to study general aspects of glacier dynamics and important feedback mechanisms. The final three chapters discuss applications specific to smaller mountain glaciers, the Greenland Ice Sheet, and the Antarctic Ice Sheet, respectively. This book will be suitable for graduate courses in geophysics and will also serve as a reference volume for scientists active in all aspects of glaciology and related research. Standard undergraduate mathematics and physics are sufficient background for studying the text.
This new edition of a successful textbook will supply advanced
undergraduate and graduate students with the tools they need to
understand modern glaciology. Practicing glacial geologists and
glaciologists will also find the volume useful as a reference book.
Relatively simple concepts are followed by more mathematically advanced
chapters. Student exercises are included.
Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies
Geomorphological mapping in the West Drumochter Hills provides evidence of a readvance of locally nourished glaciers during the Loch Lomond (Younger Dryas) Stade, in the form of an icefield 67.7 km2 in area drained by outlet glaciers. The icefield limits accord broadly with those proposed by Sissons (1980) but all geomorphic, stratigraphic and sedimentological evidence conflicts with a recent proposal that the landforms in the area reflect southwestwards retreat of the last ice sheet. Up-valley continuity of recessional moraines indicates that the ice remained active and close to climatic equilibrium during the earlier stages of glacier retreat, consistent with slow warming following the coldest part of the stade. The pattern of equilibrium line altitudes (ELAs) across the icefield is consistent with transfer of snow by westerly and southerly winds. The ELA of the reconstructed icefield as a whole is 622–629 m, although this figure is likely to be lower than the regional (climatic) ELA because the icefield probably received additional snow blown from adjacent plateau surfaces and slopes. Inclusion of potential snow-blow areas in the ELA calculation yields a value of 648–656 m; the climatic ELA is therefore likely to have lain between 622 and 656 m. Mean June to August temperature at the ELA, based on chironomid assemblages at two sites, falls within the range 4.0 ± 0.7°C. Empirical relationships between temperature and precipitation at modern glacier ELAs indicate that mean annual precipitation (MAP) at the ELA was 1977 ± 464 mm, statistically indistinguishable from modern values. Comparison with precipitation values calculated for the Isle of Mull on the west coast suggest that the precipitation gradient across the Central Highlands of Scotland was steeper during the Loch Lomond Stade than at present, probably as the result of efficient scavenging of precipitation from westerly airflows by the West Highland Icefield. Copyright © 2005 John Wiley & Sons, Ltd.
Unlike other methods of estimating the Equilibrium Line Altitude of present or former glaciers from morphometric data (as distinct from direct observations of the glacier mass balance), the Area×Altitude, the Area×Altitude Balance Ratio and the Area×Altitude Balance Index methods take explicit account of hypsometric differences between glaciers and thus yield more reliable results. In addition they offer the means of applying various mass balance/altitude relationships of increasing complexity and examining which of these is most correct; the last of these methods is newly developed to permit the application of any desired relationship. Their general adoption has been restricted hitherto by computational problems, but this objection is removed by the easy-to-use spread sheets presented in this paper. By whatever method estimates are derived, it is essential to validate the optional variables used in the computations and methods for doing this are set out.
Past fluctuations of tropical and sub-tropical glaciers provide important palaeoclimate proxies for regions where other forms of evidence are rare. However, published equilibrium-line altitude (ELA) estimates for tropical and sub-tropical glaciers at the LGM vary widely, reflecting the diversity of methods and approaches employed by different research groups. This complicates regional and global comparisons of ELA estimates, and emphasises the need for standardised methods. The distinctive character of tropical and sub-tropical glaciers, however, means that standard methods for reconstructing former glacier limits, ELAs, and palaeoclimate need to be adapted for local conditions. Many methods of ELA reconstruction explicitly or implicitly make assumptions about glacier mass balance gradients, and care needs to be taken that the choice of accumulation area ratios (AARs), balance ratios (BRs) and terminus-to-head ratios (THARs) is appropriate, as such indices are influenced by climatic regime, debris cover and other factors. ELA reconstructions should employ multiple methods, and should be cross-checked and fully reported, to allow assessment of the accuracy of ELA estimates. Reliable glacier chronologies are equally important. Dating should be based on multiple radiometric techniques wherever possible, and method of dating, the type of material dated, and the context of the date must all be reported.
With the increasing use of digital elevation models in palaeo-glacier reconstructions and the availability of freeware spreadsheets the Area-Altitude Balance Ratio (AABR) and Balance Ratio (BR) methods are becoming increasingly used in palaeo-glacier reconstruction for estimating Equilibrium Line Altitudes (ELA) and subsequently deriving quantitative estimates of palaeo-climate. While there are many data detailing contemporary Accumulation Area Ratios, there are still only a few studies that have established, from contemporary environments, AABR/BR ratios. Publicly available glacier mass balance (World Glacier Monitoring Service, US Geological Survey, and Norwegian Water Directorate) and spatial extent datasets provided the basis for this research. From a time series of mass balance, regressing specific net balance against ELA allows the zero net balance ELA to be identified. Once the zero balance ELA is established, the glacier hypsometry above and below the ELA is defined. The AABR/BR is calculated by using (the right hand side) the following: where, bnab and bnac are the net mass balance gradients in the ablation and accumulation zones respectively, and are the area-weighted mean altitudes of the accumulation and ablation areas respectively and Aac and Aab are the areas of the accumulation and ablation areas respectively. AABRs are calculated for a suite of glaciers located across a range of climatic zones and glacier types, with Antarctica being excluded. The following “representative” AABRs are found: a global AABR = 1.75 ± 0.71; Mid-latitude maritime = 1.9 ± 0.81; High-latitude = 2.24 ± 0.85; North America – West Coast = 2.09 ± 0.93; North America – Eastern Rockies = 1.11 ± 0.1; Canadian Arctic = 2.91 ± 0.35; Svalbard = 2.13 ± 0.52; Western Norway = 1.5 ± 0.4; European Alps = 1.59 ± 0.6; Central Asia = 1.75 ± 0.56; Kamchatka = 3.18 ± 0.16. This study provides an empirically derived dataset characterising AABR ratios which may be used for ELA estimation in palaeo-glacier reconstructions and for palaeo-climate quantification.
Øksfjordjøkelen is located at ∼ 70° N on the Troms–Finnmark border in North Norway. During the Younger Dryas, it was decoupled from and sat just beyond the margin of the Scandinavian Ice Sheet. At this time the major fjords in Troms and Finnmark were ice-free with outlet glaciers from the icefield filling a number of smaller side valleys. Only one outlet from the icefield, Sörfjorddalen, is temporally well-constrained by 14C dating and association with the Main Shoreline (associated with a period of minimal crustal rebound dated to the Younger Dryas). Sörfjorddalen is reconstructed using a valley centre-line iterative model and assuming a no-slip basal boundary condition. This assumption of cold-based ice is supported by the geomorphological evidence of angular bouldery fronto-lateral moraines formed during the Younger Dryas. The equilibrium line altitude for the Sörfjorddalen is calculated using both the Balance Ratio and Accumulation Area Ratio methods, and this is used to constrain the snout positions (generally to mapped moraines) of the other outlets. This approach assumes similarity of mass balance gradients and geometries of the outlet glaciers which is supported by present-day symmetry of the icefield. This method is extremely useful in such environments where dateable material is often difficult, if not impossible, to find. Some margins terminated in deep water where bathymetry was lacking, making calving quantification problematic with subsequent impacts on equilibrium line altitudes poorly constrained. These deep-water terminating snouts were discounted from subsequent palaeo-climate reconstructions. An empirical equilibrium line altitude temperature-precipitation relationship was used to define limits of climate change required to sustain the reconstructed icefield. Palaeo-precipitation estimates were refined using a palaeo-temperature estimate for the Younger Dryas from Andøya. Calculations of ice flux through the equilibrium line altitude were used to further constrain the mass balance characteristics of the reconstructed icefield and these suggest similarities with ice masses found in the northern (Nordaustlandet) regions of Svalbard.
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Van der Veen, C.J., 1999. Fundamentals of Glacier Dynamics. Balkema, Rotterdam 462 pp. D.I. Benn, N.R.J. Hulton / Computers & Geosciences 36 (2010) 605–610