A reconstruction of the last glacial maximum (LGM) ice-surface geometry in the western Swiss Alps and contiguous Alpine regions in Italy and France

2004 ◽  
Vol 97 (1) ◽  
pp. 57-75 ◽  
Author(s):  
Meredith A. Kelly ◽  
Jean-Fran�ois Buoncristiani ◽  
Christian Schl�chter
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Swiss Alps ◽  
Surface Geometry ◽  
Last Glacial ◽  
Alpine Regions ◽  
Ice Surface ◽  
Western Swiss Alps ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals Surface geometry of the Last Glacial Maximum (LGM) in the southeastern Swiss Alps (Graubünden) and its paleoclimatological significance

1998 ◽  
Vol 48 (1) ◽  
pp. 23-37 ◽  
Author(s):  
Duri Florineth
Keyword(s):  
Last Glacial Maximum ◽  
Storm Track ◽  
Glacial Maximum ◽  
Swiss Alps ◽  
Geographical Information ◽  
Ice Age ◽  
Surface Geometry ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Using detailed field evidence provided by trimlines on former nunataks, erratic boulders and the orientations of glacial striae, the surface geometry in the accumulation area during the Last Glacial Maximum was reconstructed for the area of SE Switzerland and adjacent Italy. Collectively, the trends of trimline elevations, flowlines deduced from glacial striae and bedrock morphology along the longitudinal valleys and their tributaries indicate that the former accumulation area consisted of an ice dome with the ice divide located over the area enclosed by Schlarignia, Cinuos-chel, Livigno and Piz Bernina. It attained a minimum altitude of approximately 3000 m. Modelling the topography of the ice surface using a Geographical Information System (GIS) is consistent with these results. The paleoclimatological signal included in this surface geometry was used to draw conclusions about the main atmospheric paleocireulation patterns and to outline the principal precipitation areas for the Alps during the last glaciation. It followed from this that ice build-up was principally related to dominating precipitation by southerly circulation (foehn). The prevaleance of foehn circulation most likely reflects a southward shift of the North Atlantic polar atmospheric front and of the accompanied storm track due to the advancing margin of sea ice. There exists good agreement between these assumptions and (a) results of global circulation models for the time of the LGM; (b) estimations of basal shear stress values and flow velocities for Ice Age glaciers; and (c) interpretations of paleowind indicators.

Ice surface lowering of Skelton Glacier, Transantarctic Mountains, since the Last Glacial Maximum: Implications for retreat of grounded ice in the western Ross Sea

2020 ◽  
Vol 237 ◽  
pp. 106305
Author(s):  
Jacob T.H. Anderson ◽  
Gary S. Wilson ◽  
R. Selwyn Jones ◽  
David Fink ◽  
Toshiyuki Fujioka
Keyword(s):  
Last Glacial Maximum ◽  
Ross Sea ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Ice Surface ◽  
Transantarctic Mountains ◽  
The Last Glacial Maximum ◽  
Western Ross Sea ◽  
The Last Glacial

scholarly journals Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum

2018 ◽  
Vol 12 (8) ◽  
pp. 2515-2544 ◽  
Author(s):  
Denis Cohen ◽  
Fabien Gillet-Chaulet ◽  
Wilfried Haeberli ◽  
Horst Machguth ◽  
Urs H. Fischer
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Swiss Alps ◽  
Shear Stresses ◽  
Last Glacial ◽  
Glacier Terminus ◽  
Basal Shear ◽  
The Last Glacial Maximum ◽  
Alpine Valleys ◽  
The Last Glacial

Abstract. At the Last Glacial Maximum (LGM), the Rhine glacier in the Swiss Alps covered an area of about 16 000 km2. As part of an integrative study about the safety of repositories for radioactive waste under ice age conditions in Switzerland, we modeled the Rhine glacier using a thermodynamically coupled three-dimensional, transient Stokes flow and heat transport model down to a horizontal resolution of about 500 m. The accumulation and ablation gradients that roughly reproduced the geomorphic reconstructions of glacial extent and ice thickness suggested extremely cold (TJuly∼0∘C at the glacier terminus) and dry (∼10 % to 20 % of today's precipitation) climatic conditions. Forcing the numerical simulations with warmer and wetter conditions that better matched LGM climate proxy records yielded a glacier on average 500 to 700 m thicker than geomorphic reconstructions. Mass balance gradients also controlled ice velocities, fluxes, and sliding speeds. These gradients, however, had only a small effect on basal conditions. All simulations indicated that basal ice reached the pressure melting point over much of the Rhine and Linth piedmont lobes, and also in the glacial valleys that fed these lobes. Only the outer margin of the lobes, bedrock highs beneath the lobes, and Alpine valleys at high elevations in the accumulation zone remained cold based. The Rhine glacier was thus polythermal. Sliding speed estimated with a linear sliding rule ranged from 20 to 100 m a−1 in the lobes and 50 to 250 m a−1 in Alpine valleys. Velocity ratios (sliding to surface speeds) were >80 % in lobes and ∼60 % in valleys. Basal shear stress was very low in the lobes (0.03–0.1 MPa) and much higher in Alpine valleys (>0.2 MPa). In these valleys, viscous strain heating was a dominant source of heat, particularly when shear rates in the ice increased due to flow constrictions, confluences, or flow past large bedrock obstacles, contributing locally up to several watts per square meter but on average 0.03 to 0.2 W m−2. Basal friction acted as a heat source at the bed of about 0.02 W m−2, 4 to 6 times less than the geothermal heat flow which is locally high (up to 0.12 W m−2). In the lobes, despite low surface slopes and low basal shear stresses, sliding dictated main fluxes of ice, which closely followed bedrock topography: ice was channeled in between bedrock highs along troughs, some of which coincided with glacially eroded overdeepenings. These sliding conditions may have favored glacial erosion by abrasion and quarrying. Our results confirmed general earlier findings but provided more insights into the detailed flow and basal conditions of the Rhine glacier at the LGM. Our model results suggested that the trimline could have been buried by a significant thickness of cold ice. These findings have significant implications for interpreting trimlines in the Alps and for our understanding of ice–climate interactions.

scholarly journals Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum

2017 ◽  
Author(s):  
Denis Cohen ◽  
Fabien Gillet-Chaulet ◽  
Wilfried Haeberli ◽  
Horst Machguth ◽  
Urs H. Fischer
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Swiss Alps ◽  
Shear Stresses ◽  
Last Glacial ◽  
Glacier Terminus ◽  
Basal Shear ◽  
The Last Glacial Maximum ◽  
Alpine Valleys ◽  
The Last Glacial

Abstract. At the Last Glacial Maximum (LGM), the Rhine glacier in the Swiss Alps covered an area of about 16,000 km2. As part of an integrative study about the safety of repositories for radioactive waste under ice age conditions in Switzerland, we modeled the Rhine glacier using a fully-coupled, three-dimensional, transient, thermo-mechanical Stokes flow model down to a horizontal resolution of about 500 m. The accumulation and ablation gradients that roughly reproduced the geomorphic reconstructions of glacial extent and ice thickness suggested extremely cold (TJuly ~ 0 °C at the glacier terminus) and dry (~ 10 to 20 % of today's precipitation) climatic conditions. Forcing the numerical simulations with warmer and wetter conditions that better matched LGM climate proxy records yielded a glacier on average 500 to 700 m thicker than geomorphic reconstructions. Mass balance gradients also controlled ice velocities, fluxes, and sliding speeds. These gradients, however, had only a small effect on basal conditions. All simulations indicated that basal ice reached the pressure melting point over much of the Rhine and Linth piedmont lobes, and also in the glacial valleys that fed these lobes. Only the outer margin of the lobes, bedrock highs beneath the lobes, and Alpine valleys at high elevations in the accumulation zone remained cold based. The Rhine glacier was thus polythermal. Sliding speed estimated with a linear sliding rule ranged from 20 to 100 m a−1 in the lobes, and 50 to 250 m a−1 in Alpine valleys. Velocity ratios (sliding to surface speeds) were > 80 % (lobes) and ~ 60 % (valleys). Basal shear stress was very low in the lobes (0.03–0.1 MPa), much higher in Alpine valleys (> 0.2 MPa). In these valleys, viscous strain heating was a dominant source of heat, particularly when shear rates in the ice increased due to flow constrictions, confluences, or flow past large bedrock obstacles, contributing locally up to several W m−2 but on average 0.03 to 0.2 W m−2. Basal friction acted as a heat source at the bed of about 0.02 W m−2, 4 to 6 times less than the geothermal heat flow which is locally high (up to 0.12 W m−2). In the lobes, despite low surface slopes and low basal shear stresses, sliding dictated main fluxes of ice which closely followed bedrock topography: ice was channeled in between bedrock highs along troughs, some of which coincided with glacially eroded overdeepenings. These sliding conditions may have favored glacial erosion by abrasion and quarrying. Our results confirmed general earlier findings but provided more insights into the detailed flow and basal conditions of the Rhine glacier at the LGM. Our model results suggested that the trimline could have been buried by a significant thickness of cold ice. These findings have significant implications for interpreting trimlines in the Alps and for our understanding of ice-climate interactions.

Geomorphological record and equilibrium line altitude of glaciers during the last glacial maximum in the Rodna Mountains (eastern Carpathians)

2020 ◽  
pp. 1-20
Author(s):  
Piotr Kłapyta ◽  
Marcel Mîndrescu ◽  
Jerzy Zasadni
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Equilibrium Line ◽  
Surface Geometry ◽  
Equilibrium Line Altitude ◽  
Last Glacial ◽  
Eastern Carpathians ◽  
Glacial Stage ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract In the eastern Carpathians the legacy of glaciation is preserved in several isolated mountain massifs. This paper presents new mapping results of glaciated valley land systems in the Rodna Mountains, the highest part of the eastern Carpathians (2303 m above seal level). In most of the glacial valleys, the maximal Pleistocene extent is marked by freshly shaped moraines, which are referred in this study as the Pietroasa glacial stage and regarded as the last glacial maximum (LGM) advance. Only in three valleys do older Şesura glacial stage moraines (pre-LGM, likely Marine Oxygen Isotope Stage 6) occur. On the basis of the geomorphological record, we reconstruct the extent, surface geometry, and equilibrium line altitude (ELA) of Pietroasa-stage glaciers. The local ELA pattern of north-exposed glaciers in the Rodna Mountains shows a rising trend towards the southeast, which suggests dominant snow-bearing winds and orographically induced precipitation from the west. This finding fits well with the dominant palaeo-wind direction inferred from other Carpathian proxies and confirms the dominance of zonal circulation pattern during the global LGM in central eastern Europe.

New constraints on Plio-Pleistocene East Antarctic Ice Sheet thickness: cosmogenic exposure data from western Dronning Maud Land

2020 ◽  
Author(s):  
Jane L. Andersen ◽  
Jennifer C. Newall ◽  
Robin Blomdin ◽  
Sarah E. Sams ◽  
Derek G. Fabel ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Glacial Cycle ◽  
Antarctic Ice Sheet ◽  
Last Glacial ◽  
Ice Surface ◽  
Dronning Maud Land ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p><span>Reconstructing past ice surface changes is key to test and improve ice-sheet models. Yet, data constraining the past behaviour of the East Antarctic Ice Sheet are sparse, limiting our understanding of its response to past and future climate changes. Here, we attempt to test whether the ice-sheet margin in western Dronning Maud Land has thinned since the last glacial maximum or whether it perhaps thickened in places due to increased precipitation associated with warmer climates. We report cosmogenic multi-nuclide (<sup>10</sup>Be, <sup>26</sup>Al, <sup>36</sup>Cl,<sup> 21</sup>Ne) data from bedrock and erratics on nunataks along Jutulstraumen ice stream and the Penck Trough in western Dronning Maud Land, East Antarctica. Spanning elevations between 751-2387 m above sea level, and between 5 and 450 m above the contemporaneous local ice sheet surface, the samples record apparent exposure ages between 2 ka and 5 Ma. The highest bedrock sample indicates (near-) continuous exposure since at least the Pliocene, with a very low apparent erosion rate of 15</span><span>±</span><span>3 cm Ma<sup>-1</sup>. However, there are also clear indications of a thicker-than-present ice sheet within the last glacial cycle, thinning ~35-120 m at several nunataks during the Holocene (~2-11 ka). Owing to difficulties in retrieving suitable sample material from the often rugged and quartz-poor mountain summits, and due to the presence of inherited nuclides in many of our samples, we are unable to present robust thinning estimates from elevational profiles. Nevertheless, the results clearly indicate ice-surface fluctuations of several hundred meters within the last glacial cycle in this sector of the EAIS, between the current grounding line and the edge of the polar plateau. </span><span>Finally, inverse modelling of the cosmogenic multi-nuclide inventories in bedrock yields estimates of total erosion and ice cover across multiple glacial cycles. Our results show that the EAIS in western Dronning Maud Land was thicker than present during most of the Quaternary, covering sample sites up to 200 m above the present-day ice sheet for ~80 % of this period. Thinning of the ice since the last glacial maximum, combined with a long-term record of thicker-than-present ice, indicate that the ice sheet below the polar plateau in western Dronning Maud Land generally expands and thickens during climate cooling, despite decreasing precipitation associated with a cooler Southern Ocean.</span></p>

scholarly journals Amplification of Elevation-Dependent Temperature Variability Since the Last Glacial Maximum

2021 ◽  
Author(s):  
Fenglin Lü ◽  
Zhe Sun ◽  
Kan Yuan ◽  
Xiaohuan Hou ◽  
Mingda Wang ◽  
...  
Keyword(s):  
Climate Change ◽  
Last Glacial Maximum ◽  
Elevation Gradient ◽  
Glacial Maximum ◽  
Lapse Rate ◽  
Last Glacial ◽  
Alpine Regions ◽  
The Future ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract The mechanisms of recent Elevation-Dependent Warming (EDW) remain debated because nearly all data sources are limited to past decades and subject to anthropogenic effects. Here, we study how temperature changed along the elevation gradient since the Last Glacial Maximum (LGM) and aim to shed lights on the mechanisms of EDW and implications for the future climate change in alpine regions. We present a unique network of 192 quantitative terrestrial temperature records along elevation gradient up to ~5000 m to study the Elevation-Dependent Temperature Amplification (EDTA) since LGM. EDTA is exemplified by stronger variability at high-elevation sites during climate transitions of millennial- to centennial-scales. The spatiotemporal patterns of EDTA indicate that the surface albedo, caused by changes in glacier and vegetation coverage, played the most important role, which resulted in steeper lapse rate during LGM and flatter in Mid-Holocene. This suggests that alpine regions experienced much colder environments in glacial and much warmer in interglacial periods. This also implies that the mountain regions would warm much faster in the context of current global change. The study emphasizes the need to reassess and reevaluate alpine climate change mechanisms, and to reconsider the mitigation and adaptation implementation strategies under the future global warming scenarios.

Fast-flowing outlet glaciers of the Last Glacial Maximum Patagonian Icefield

2005 ◽  
Vol 63 (2) ◽  
pp. 206-211 ◽  
Author(s):  
Neil F. Glasser ◽  
Krister N. Jansson
Keyword(s):  
Last Glacial Maximum ◽  
Surface Profile ◽  
Glacial Maximum ◽  
Ice Streams ◽  
Last Glacial ◽  
Ice Surface ◽  
Discharge Patterns ◽  
Induced Changes ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Glacial geomorphology around the Northern Patagonian Icefield indicates that a number of fast-flowing outlet glaciers (the continuation of ice streams further upglacier) drained the icefield during the Last Glacial Maximum. These topographically controlled fast-flowing glaciers may have dictated the overall pattern of Last Glacial Maximum ice discharge, lowered the ice-surface profile, and forced the ice-divide westward. The influence of the fast-flowing outlet glaciers on icefield behavior also helps to explain why the configuration of the Patagonian Icefield at the Last Glacial Maximum is not accurately represented in existing numerical ice-sheet models. Fast-flowing outlet glaciers would have strongly influenced ice discharge patterns and therefore partially decoupled the icefield from climatically induced changes in thickness and extent.

Continental/Cordilleran ice interactions: a dominant cause of westward super-elevation of the last glacial maximum continental ice limit in southwestern Alberta, Canada

2001 ◽  
Vol 30 (1) ◽  
pp. 43-52 ◽  
Author(s):  
Edward C. Little ◽  
Lionel E. Jackson ◽  
Thomas S. James ◽  
Stephen R. Hicock ◽  
Elizabeth R. Leboe
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial
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