scholarly journals Modelling last glacial cycle ice dynamics in the Alps

2018 ◽  
Vol 12 (10) ◽  
pp. 3265-3285 ◽  
Author(s):  
Julien Seguinot ◽  
Susan Ivy-Ochs ◽  
Guillaume Jouvet ◽  
Matthias Huss ◽  
Martin Funk ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Climate Forcing ◽  
European Alps ◽  
Glacial Cycle ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Last Glacial ◽  
The Alps

Abstract. The European Alps, the cradle of pioneering glacial studies, are one of the regions where geological markers of past glaciations are most abundant and well-studied. Such conditions make the region ideal for testing numerical glacier models based on simplified ice flow physics against field-based reconstructions and vice versa. Here, we use the Parallel Ice Sheet Model (PISM) to model the entire last glacial cycle (120–0 ka) in the Alps, using horizontal resolutions of 2 and 1 km. Climate forcing is derived using two sources: present-day climate data from WorldClim and the ERA-Interim reanalysis; time-dependent temperature offsets from multiple palaeo-climate proxies. Among the latter, only the European Project for Ice Coring in Antarctica (EPICA) ice core record yields glaciation during marine oxygen isotope stages 4 (69–62 ka) and 2 (34–18 ka). This is spatially and temporally consistent with the geological reconstructions, while the other records used result in excessive early glacial cycle ice cover and a late Last Glacial Maximum. Despite the low variability of this Antarctic-based climate forcing, our simulation depicts a highly dynamic ice sheet, showing that Alpine glaciers may have advanced many times over the foreland during the last glacial cycle. Ice flow patterns during peak glaciation are largely governed by subglacial topography but include occasional transfluences through the mountain passes. Modelled maximum ice surface is on average 861 m higher than observed trimline elevations in the upper Rhône Valley, yet our simulation predicts little erosion at high elevation due to cold-based ice. Finally, despite the uniform climate forcing, differencesin glacier catchment hypsometry produce a time-transgressive Last Glacial Maximum advance, with some glaciers reaching their modelled maximum extent as early as 27 ka and others as late as 21 ka.

scholarly journals Modelling last glacial cycle ice dynamics in the Alps

2018 ◽  
Author(s):  
Julien Seguinot ◽  
Guillaume Jouvet ◽  
Matthias Huss ◽  
Martin Funk ◽  
Susan Ivy-Ochs ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Climate Forcing ◽  
European Alps ◽  
Glacial Cycle ◽  
Ice Flow ◽  
Last Glacial ◽  
The Alps ◽  
The Last Glacial

Abstract. The European Alps, cradle of pioneer glacial studies, are one of the regions where geological markers of past glaciations are most abundant and well-studied. Such conditions make the region ideal for testing numerical glacier models based on simplified ice flow physics against field-based reconstructions, and vice-versa. Here, we use the Parallel Ice Sheet Model (PISM) to model the entire last glacial cycle (120–0 ka) in the Alps, using horizontal resolutions of 2 and 1 km and up to 576 processors. Climate forcing is derived using present-day climate data from WorldClim and the ERA-Interim reanalysis, and time-dependent temperature offsets from multiple palaeo-climate proxies, among which only the EPICA ice core record yields glaciation during marine oxygen isotope stages 4 (69–62 ka) and 2 (34–18 ka) spatially and temporally consistent with the geological reconstructions, while the other records used result in excessive early glacial cycle ice cover and a late Last Glacial Maximum. Despite the low variability of this Antarctic-based climate forcing, our simulation depicts a highly dynamic ice sheet, showing that Alpine glaciers may have advanced many times over the foreland during the last glacial cycle. Ice flow patterns during peak glaciation are largely governed by subglacial topography but include occasional transfluences and self-sustained ice domes. Modelled maximum ice surface is 861 m higher than observed trimline elevations in the upper Rhone Valley, yet our simulation predicts little erosion at high elevation due to cold-based ice. Finally, the Last Glacial Maximum advance, often considered synchronous, is here modelled as a time-transgressive event, with some glacier lobes reaching their maximum as early as 27 ka, and some as late as 21 ka.

The local Last Glacial Maximum in McMurdo Sound, Antarctica: Implications for ice-sheet behavior in the Ross Sea Embayment

2019 ◽  
Vol 132 (1-2) ◽  
pp. 31-47 ◽  
Author(s):  
Andrew J. Christ ◽  
Paul R. Bierman
Keyword(s):  
Last Glacial Maximum ◽  
Ross Sea ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Significant Advance ◽  
Ice Flow ◽  
Mcmurdo Sound ◽  
Last Glacial ◽  
Transantarctic Mountains ◽  
Western Ross Sea

AbstractDuring the Last Glacial Maximum (LGM), a grounded ice sheet filled the Ross Sea Embayment in Antarctica and deposited glacial sediments on volcanic islands and peninsulas in McMurdo Sound and coastal regions of the Transantarctic Mountains. The flow geometry and retreat history of this ice are debated, with contrasting views yielding divergent implications for the interaction between and stability of the East and West Antarctic ice sheets during late Quaternary time. Here, we present terrestrial geomorphologic evidence and reconstruct former ice-marginal environments, ice sheet elevations, and ice-flow directions in McMurdo Sound. Fossil algae in ice-marginal sediments provide a coherent radiocarbon chronology of maximum ice extent and deglaciation. We integrate these data with marine records to reconstruct grounded ice dynamics in McMurdo Sound and the western Ross Sea. The combined data set suggests ice flow toward the Transantarctic Mountains in McMurdo Sound during peak glaciation, with thick, grounded ice at or near its maximum position between 19.6 and 12.3 ka. Persistent grounded ice in McMurdo Sound and across the western Ross Sea after Meltwater Pulse 1a (14.0–14.5 ka) suggests that this sector of Antarctica did not significantly contribute to this rapid sea-level rise event. Our data show no significant advance of locally derived ice from the Transantarctic Mountains into McMurdo Sound during the local LGM.

scholarly journals A numerical investigation of ice-lobe–permafrost interaction around the southern Laurentide ice sheet

2000 ◽  
Vol 46 (153) ◽  
pp. 311-325 ◽  
Author(s):  
Paul M. Cutler ◽  
Douglas R. MacAyeal ◽  
David M. Mickelson ◽  
Byron R. Parizek ◽  
Patrick M. Colgan
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Surface Profile ◽  
Glacial Maximum ◽  
Laurentide Ice Sheet ◽  
Ice Dynamics ◽  
Last Glacial ◽  
Glacier Ice ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractPermafrost existed around and under marginal parts of the southern Laurentide ice sheet during the Last Glacial Maximum. The presence of permafrost was important in determining the extent, form and dynamics of ice lobes and the landforms they produced because of influences on resistance to basal motion and subglacial hydrology. We develop a two-dimensional time-dependent model of permafrost and glacier-ice dynamics along a flowline to examine: (i) the extent to which permafrost survives under an advancing ice lobe and how it influences landform development and hydrology, and (ii) the influence of permafrost on ice motion and surface profile. The model is applied to the Green Bay lobe, which terminated near Madison, Wisconsin, during the Last Glacial Maximum. Simulations of ice advance over permafrost indicate that the bed upstream of the ice-sheet margin was frozen for 60–200 km at the glacial maximum. Permafrost remained for centuries to a few thousand years under advancing ice, and penetrated sufficiently deep (tens of meters) into the underlying aquifer that drainage of basal meltwater became inefficient, likely resulting in water storage beneath the glacier. Our results highlight the influence of permafrost on subglacial conditions, even though uncertainties in boundary conditions such as climate exist.

scholarly journals The effect of climate forcing on numerical simulations of the Cordilleran ice sheet at the Last Glacial Maximum

2013 ◽  
Vol 7 (6) ◽  
pp. 6171-6212 ◽  
Author(s):  
J. Seguinot ◽  
C. Khroulev ◽  
I. Rogozhina ◽  
A. P. Stroeven ◽  
Q. Zhang
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Climate Forcing ◽  
Last Glacial ◽  
North American Regional Reanalysis ◽  
Regional Reanalysis ◽  
Cordilleran Ice Sheet ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. We present an ensemble of numerical simulations of the Cordilleran ice sheet during the Last Glacial Maximum performed with the Parallel Ice Sheet Model (PISM), applying temperature offsets to the present-day climatologies from five different datasets. Monthly mean surface air temperature and precipitation from WorldClim, the NCEP/NCAR reanalysis, the ERA-Interim reanalysis, the Climate Forecast System Reanalysis and the North American Regional Reanalysis are used to compute surface mass balance in a positive degree-day model. Modelled ice sheet outlines and volumes appear highly sensitive to the choice of climate forcing. For three of the four reanalysis datasets used, differences in precipitation are the major source for discrepancies between model results. We assess model performance against a geomorphological reconstruction of the ice margin at the Last Glacial Maximum, and suggest that part of the mismatch is due to unresolved orographic precipitation effects caused by the coarse resolution of reanalysis data. The best match between model output and the reconstructed ice margin is obtained using the high-resolution North American Regional Reanalysis, which we retain for simulations of the Cordilleran ice sheet in the future.

Was the last glaciation of the Black Forest (southern Germany) synchronous with the Alpine glaciation?

2020 ◽  
Author(s):  
Felix Martin Hofmann ◽  
William McCreary ◽  
Frank Preusser
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Black Forest ◽  
Last Glacial ◽  
The North ◽  
Alpine Glaciers ◽  
The Alps ◽  
The Last Glacial

<p>Chronological evidence from the southern part of the Alps (Monegato et al. 2017) indicates an earlier last glacial maximum of the Alpine glaciers relative to the Eurasian Ice Sheet maximum extent. This asynchronicity is probably due to the expansion of the North American Ice Sheet causing a southward shift of the North Atlantic jet stream and the establishment of a meridional atmospheric circulation over Europe (Luetscher et al. 2015). The advection of humid air masses from the Mediterranean Sea caused the Alpine glaciers to reach their maximum extent prior to the Eurasian ice sheet. Hence, the ice cap of the southern Black Forest must have been in a lee position with respect to the Alpine glaciers. This suggests that the last glacial maximum in the Black Forest was out of phase with the Alps. Since the lack of chronological data from the southern Black Forest prevents this hypothesis to be tested, a glacier chronology is crucially needed. As a first step towards such a framework, glacial landforms in the southern Black Forest are mapped based on both the analysis of highresolution LiDAR (Light detecting and ranging) data and its derivates as well as field mapping. Geomorphological mapping of a key site resulted in the identification of 18 ice-marginal positions in a single valley, whereby a significant number of moraines has been mapped for the first time. These findings reinforce the idea of a dynamic Lateglacial in the southern Black Forest interrupted by multiple periods of moraine stabilisation. Additional geomorphological and sedimentological investigations will be carried out to provide a solid base for the application of up-to-date geochronological methods (<sup>10</sup>Be exposure dating of boulders on moraines and optically stimulated luminescence dating) with particular emphasis on supposed last local glacial maximum moraines. Geomorphological, sedimentological and geochronological evidence will then be combined for palaeoglacier modelling. The determination of equilibrium line altitudes will ultimately enable the determination of palaeo-precipitation and –temperature during the last local glacial maximum and the subsequent Lateglacial. This palaeoclimatic reconstruction will be supported by data from the lake Bergsee record (southernmost Black Forest) spanning the 45-14.7 ka period (Duprat-Oualid et al. 2017).</p><p><strong>References</strong></p><p>Duprat-Oualid F., Rius D., Bégeot C., Magny M., Millet L., Wulf S., Appelt O. 2017. Vegetation response to abrupt climate changes in Western Europe from 45 to 14.7 k cal a BP: the Bergsee lacustrine record (Black Forest, Germany). J. Quaternary Sci. 32, 1008-1021.</p><p>Luetscher M., Boch R., Sodemann H., Spötl C., Cheng H., Edwards R.L., Frisia S., Hof F., Müller W. 2015. North Atlantic storm track changes during the Last Glacial Maximum recorded by Alpine speleothems. Nat. Commun. 6, 6344.</p><p>Monegato G., Scardia G., Hajdas I., Rizzini F., Piccin A. 2017. The Alpine LGM in the boreal ice-sheets game. Sci. Rep-UK 7, 2078.</p><p> </p>

scholarly journals A composite <sup>10</sup>Be, IR-50 and <sup>14</sup>C chronology of the pre-Last Glacial Maximum (LGM) full ice extent of the western Patagonian Ice Sheet on the Isla de Chiloé, south Chile (42° S)

2021 ◽  
Vol 70 (1) ◽  
pp. 105-128
Author(s):  
Juan-Luis García ◽  
Christopher Lüthgens ◽  
Rodrigo M. Vega ◽  
Ángel Rodés ◽  
Andrew S. Hein ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Luminescence Dating ◽  
Climate History ◽  
Ice Dynamics ◽  
Last Glacial ◽  
Mountain Glaciers ◽  
Mis 3 ◽  
Past Climate Change

Abstract. Unanswered questions about the glacier and climate history preceding the global Last Glacial Maximum (LGM) in the southern temperate latitudes remain. The Marine Isotope Stage (MIS) 3 is normally understood as a global interstadial period; nonetheless its climate was punctuated by conspicuous variability, and its signature has not been resolved beyond the polar realms. In this paper, we compile a 10Be depth profile, single grain infrared (IR) stimulated luminescence dating and 14C samples to derive a new glacier record for the principal outwash plain complex, deposited by the western Patagonian Ice Sheet (PIS) during the last glacial period (Llanquihue Glaciation) on the Isla de Chiloé, southern Chile (42∘ S). In this region, the Golfo de Corcovado Ice Lobe left a distinct geomorphic and stratigraphic imprint, suitable for reconstructing former ice dynamics and timing of past climate change. Our data indicate that maximum glaciation occurred by 57.8±4.7 ka without reaching the Pacific Ocean coast. Ice readavanced and buttressed against the eastern side of the Cordillera de la Costa again by 26.0±2.9 ka. Our data further support the notion of a large ice extent during parts of the MIS 3 in Patagonia and New Zealand but appear to contradict near contemporaneous interstadial evidence in the southern midlatitudes, including Chiloé. We propose that the PIS expanded to its full-glacial Llanquihue moraines, recording a rapid response of southern mountain glaciers to the millennial-scale climate stadials that punctuated the MIS 3 at the poles and elsewhere.

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

&lt;p&gt;&lt;span&gt;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 (&lt;sup&gt;10&lt;/sup&gt;Be, &lt;sup&gt;26&lt;/sup&gt;Al, &lt;sup&gt;36&lt;/sup&gt;Cl,&lt;sup&gt; 21&lt;/sup&gt;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&lt;/span&gt;&lt;span&gt;&amp;#177;&lt;/span&gt;&lt;span&gt;3 cm Ma&lt;sup&gt;-1&lt;/sup&gt;. 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. &lt;/span&gt;&lt;span&gt;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.&lt;/span&gt;&lt;/p&gt;

Extent and age of the Last Glacial Maximum in the southeastern sector of the Scandinavian Ice Sheet

2001 ◽  
Vol 31 (1-4) ◽  
pp. 407-425 ◽  
Author(s):  
Juha Pekka Lunkka ◽  
Matti Saarnisto ◽  
Valeri Gey ◽  
Igor Demidov ◽  
Vera Kiselova
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Scandinavian Ice Sheet ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals Last Glacial Maximum-Holocene Glacial and Depositional History From Sediment Cores at Coulman High Beneath the Ross Ice Shelf, Antarctica

2021 ◽  
Author(s):  
◽  
Sanne M Maas
Keyword(s):  
Last Glacial Maximum ◽  
Ross Sea ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Open Water ◽  
Glacial Maximum ◽  
Ice Shelf ◽  
Last Glacial ◽  
Ross Ice Shelf ◽  
Grounding Line

<p>Sediment Cores collected from the shallow sub-sea floor beneath the Ross Ice Shelf at Coulman High have been analysed using sedimentological techniques to constrain the retreat history of the Last Glacial Maximum (LGM) ice sheet in the Ross Embayment, and to determine when the modern-day calving line location of the Ross Ice Shelf was established. A characteristic vertical succession of facies was identified in these cores, that can be linked to ice sheet and ice shelf extent in the Ross Embayment. The base of this succession consists of unconsolidated, clast rich muddy diamicts, and is interpreted to be deposited subglacially or in a grounding line proximal environment on account of a distinct provenance in the clast content which can only be attributed to subglacial transport from the Byrd Glacier 400 km to the south of the drill site. This is overlain by a mud with abundant clasts, similar in character to a granulated facies that has been documented previously in the Ross Sea, and is interpreted as being a characteristic grounding line lift-o facies in a sub-ice shelf setting. These glacial proximal facies pass upward into a mud, which comprises three distinctive units. i) Muds with sub-mm scale laminae resulting from traction currents occurring near the grounding line in a sub-ice shelf environment overlain by, ii) muds with sub-mm scale laminae and elevated biogenic content (diatoms and foraminifera) and sand/gravel clasts, interpreted as being deposited in open water conditions, passing up into a iii) bioturbated mud, interpreted as being deposited in sub-ice shelf environment, proximal to the calving line. The uppermost facies consists of a 20 cm thick diatom ooze with abundant clasts and pervasive bioturbation, indicative of a condensed section deposited during periodically open marine conditions. During post-LGM retreat of the ice sheet margin in western Ross Sea, and prior to the first open marine conditions at Coulman High, it is hypothesized that the grounding and calving line were in relative close proximity to each other. As the calving line became "pinned" in the Ross Island region, the grounding line likely continued its retreat toward its present day location. New corrected radiocarbon ages on the foraminifera shells in the interval of laminated muds with clasts, provide some of the first inorganic ages from the Ross Sea, and strengthen inferences from previous studies, that the first open marine conditions in the vicinity of Ross Island were 7,600 14C yr BP. While retreat of the calving line south of its present day position is implied during this period of mid-Holocene warmth prior to its re-advance, at present it is not possible to constrain the magnitude of retreat or attribute this to climate change rather than normal calving dynamics.</p>

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