Early deglaciation and paleolake history of Río Cisnes Glacier, Patagonian Ice Sheet (44°S)

2018 ◽  
Vol 91 (1) ◽  
pp. 194-217 ◽  
Author(s):  
Juan-Luis García ◽  
Antonio Maldonado ◽  
María Eugenia de Porras ◽  
Amalia Nuevo Delaunay ◽  
Omar Reyes ◽  
...  
Keyword(s):  
Landscape Change ◽  
Ice Sheet ◽  
Optically Stimulated Luminescence ◽  
Orbital Forcing ◽  
West Antarctica ◽  
West Antarctic ◽  
Chilean Patagonia ◽  
History Of ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractThe timing, structure, and landscape change during the Patagonian Ice Sheet deglaciation remains unresolved. In this article, we provide a geomorphic, stratigraphic, and geochronological deglacial record of Río Cisnes Glacier at 44°S and also from the nearby Río Ñirehuao and Río El Toqui valleys (45°S) in Chilean Patagonia. Our 14C, 10Be, and optically stimulated luminescence data indicate that after the last glacial maximum, Río Cisnes Glacier experienced ~100 km deglaciation between >19.0 and 12.3 ka, accompanied by the formation of large glacial paleolakes. Deglaciation was interrupted by several ice readvances, and by 16.9±0.3 ka, Río Cisnes Glacier extended only ~40% of its full glacial extent. The deglaciation of Río Cisnes Glacier and other sensitive Patagonian glaciers occurred at least 1 ka earlier than the ca. 17.8 ka normally assumed for the local termination, coincident with West Antarctic isotope records. This early deglaciation can be linked to an orbital forcing–driven decline of Southern Ocean sea ice associated with a distinct atmospheric warming that is apparent for West Antarctica through Patagonia.

scholarly journals Morphology and late Cenozoic (<5 Ma) glacial history of the area between David and Mawson Glaciers, Victoria Land, Antarctica

1994 ◽  
Vol 20 ◽  
pp. 55-60
Author(s):  
Anja L.L.M. Verbers ◽  
Volkmar Damm
Keyword(s):  
Ice Sheet ◽  
Field Work ◽  
Topographic Map ◽  
Glacial History ◽  
Ice Surface ◽  
Victoria Land ◽  
Radio Echo Sounding ◽  
History Of ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Glacio-geological field work and radar ice-thickness sounding were carried out in the area between David and Mawson Glaciers. A subglacial topographic map has been compiled from radio-echo-sounding data. The northern part of this map shows that the trench of David Glacier reaches a depth of more than 1000 m below sea level. The area south of David Glacier comprises a landscape of nunatak clusters dissected by glaciated valleys with ice thicknesses as much as 800 m. Subglacial cirques occur at the outer margins of the nunatak clusters. A model for the regional glacial history is proposed. It starts with a major deglaciation in the Pliocene, which results in marine transgression in basins west of the Transantarctic Mountains. During the late Pliocene, the ice advanced towards the northeast, depositing a thin layer of (Sirius Group) till containing reworked mid-Pliocene marine diatoms. Due to accelerated mountain uplift, the ice cut iIlto the pre-Pliocene peneplain, eroding broad valleys. A period of ice-sheet retreat followed to expose a landscape of large nunataks separated by wide valleys. During this period, local cirque glaciation occurred. When the ice sheet advanced again, another phase of uplift forced the glaciers to cut deeper into the valleys. Probably since the Last Glacial Maximum the ice surface has lowered by about 100 m.

scholarly journals Morphology and late Cenozoic (<5 Ma) glacial history of the area between David and Mawson Glaciers, Victoria Land, Antarctica

1994 ◽  
Vol 20 ◽  
pp. 55-60
Author(s):  
Anja L.L.M. Verbers ◽  
Volkmar Damm
Keyword(s):  
Ice Sheet ◽  
Field Work ◽  
Topographic Map ◽  
Glacial History ◽  
Ice Surface ◽  
Victoria Land ◽  
Radio Echo Sounding ◽  
History Of ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Glacio-geological field work and radar ice-thickness sounding were carried out in the area between David and Mawson Glaciers. A subglacial topographic map has been compiled from radio-echo-sounding data. The northern part of this map shows that the trench of David Glacier reaches a depth of more than 1000 m below sea level. The area south of David Glacier comprises a landscape of nunatak clusters dissected by glaciated valleys with ice thicknesses as much as 800 m. Subglacial cirques occur at the outer margins of the nunatak clusters. A model for the regional glacial history is proposed. It starts with a major deglaciation in the Pliocene, which results in marine transgression in basins west of the Transantarctic Mountains. During the late Pliocene, the ice advanced towards the northeast, depositing a thin layer of (Sirius Group) till containing reworked mid-Pliocene marine diatoms. Due to accelerated mountain uplift, the ice cut iIlto the pre-Pliocene peneplain, eroding broad valleys. A period of ice-sheet retreat followed to expose a landscape of large nunataks separated by wide valleys. During this period, local cirque glaciation occurred. When the ice sheet advanced again, another phase of uplift forced the glaciers to cut deeper into the valleys. Probably since the Last Glacial Maximum the ice surface has lowered by about 100 m.

scholarly journals Retreat history of the East Antarctic Ice Sheet since the Last Glacial Maximum

2014 ◽  
Vol 100 ◽  
pp. 10-30 ◽  
Author(s):  
Andrew N. Mackintosh ◽  
Elie Verleyen ◽  
Philip E. O'Brien ◽  
Duanne A. White ◽  
R. Selwyn Jones ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Antarctic Ice Sheet ◽  
Last Glacial ◽  
History Of ◽  
The Last Glacial Maximum ◽  
The Last Glacial ◽  
East Antarctic Ice Sheet

scholarly journals Thickness of the divide and flank of the West Antarctic Ice Sheet through the last deglaciation

2019 ◽  
Author(s):  
Perry Spector ◽  
John Stone ◽  
Brent Goehring
Keyword(s):  
Ice Sheet ◽  
Weddell Sea ◽  
Last Deglaciation ◽  
West Antarctica ◽  
Last Glacial Period ◽  
West Antarctic Ice Sheet ◽  
The Past ◽  
West Antarctic ◽  
Grounding Line ◽  
The Last Glacial

Abstract. We report cosmogenic-nuclide measurements from two isolated groups of nunataks in West Antarctica: the Pirrit Hills, located midway between the grounding line and the divide in the Weddell Sea sector, and the Whitmore Mountains, located along the Ross-Weddell divide. At the Pirrit Hills, ice reached a highstand ~ 320 m above present during the last glacial period. Subsequent thinning mostly occurred after ~ 14 kyr B.P., and modern ice levels were established some time after ~ 4 kyr B.P. We infer that, like at other flank sites, these changes were primarily controlled by the position of the grounding-line downstream. At the Whitmore Mountains, cosmogenic 14C concentrations in bedrock surfaces demonstrate that ice there was no more than ~ 190 m thicker than present during the past ~ 30 kyr. Combined with other constraints from West Antarctica, the 14C data imply that the divide was thicker than present for a period of less than ~ 8 kyr within the past ~ 15 kyr. These results are consistent with the hypothesis that the divide initially thickened due to the deglacial rise in snowfall, and subsequently thinned in response to retreat of the ice-sheet margin. We use these data to evaluate several recently-published ice-sheet models at the Pirrit Hills and Whitmore Mountains.

scholarly journals Deglacial ice sheet meltdown: orbital pacemaking and CO<sub>2</sub> effects

2014 ◽  
Vol 10 (4) ◽  
pp. 1567-1579 ◽  
Author(s):  
M. Heinemann ◽  
A. Timmermann ◽  
O. Elison Timm ◽  
F. Saito ◽  
A. Abe-Ouchi
Keyword(s):  
Three Dimensional ◽  
Ice Sheet ◽  
Orbital Forcing ◽  
Orbital Parameters ◽  
Ice Volume ◽  
Milankovitch Theory ◽  
The Last Glacial Maximum ◽  
Global Mean ◽  
Good Agreement ◽  
The Last Glacial

Abstract. One hundred thousand years of ice sheet buildup came to a rapid end ∼25–10 thousand years before present (ka BP), when ice sheets receded quickly and multi-proxy reconstructed global mean surface temperatures rose by ∼3–5 °C. It still remains unresolved whether insolation changes due to variations of earth's tilt and orbit were sufficient to terminate glacial conditions. Using a coupled three-dimensional climate–ice sheet model, we simulate the climate and Northern Hemisphere ice sheet evolution from 78 ka BP to 0 ka BP in good agreement with sea level and ice topography reconstructions. Based on this simulation and a series of deglacial sensitivity experiments with individually varying orbital parameters and prescribed CO2, we find that enhanced calving led to a slowdown of ice sheet growth as early as ∼8 ka prior to the Last Glacial Maximum (LGM). The glacial termination was then initiated by enhanced ablation due to increasing obliquity and precession, in agreement with the Milankovitch theory. However, our results also support the notion that the ∼100 ppmv rise of atmospheric CO2 after ∼18 ka BP was a key contributor to the deglaciation. Without it, the present-day ice volume would be comparable to that of the LGM and global mean temperatures would be about 3 °C lower than today. We further demonstrate that neither orbital forcing nor rising CO2 concentrations alone were sufficient to complete the deglaciation.

Pleistocene raised marine deposits on Wrangel Island, northeast Siberia and implications for the presence of an East Siberian ice sheet

2003 ◽  
Vol 59 (3) ◽  
pp. 399-410 ◽  
Author(s):  
Lyn Gualtieri ◽  
Sergey Vartanyan ◽  
Julie Brigham-Grette ◽  
Patricia M. Anderson
Keyword(s):  
Electron Spin Resonance ◽  
Ice Sheet ◽  
Optically Stimulated Luminescence ◽  
Marine Deposits ◽  
Grain Sizes ◽  
Wrangel Island ◽  
Northeastern Siberia ◽  
Spin Resonance ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractTwo previously undocumented Pleistocene marine transgressions on Wrangel Island, northeastern Siberia, question the presence of an East Siberian or Beringian ice sheet during the last glacial maximum (LGM). The Tundrovayan Transgression (459,000–780,000 yr B.P.) is represented by raised marine deposits and landforms 15–41 m asl located up to 18 km inland. The presence of high sea level 64,000–73,000 yr ago (the Krasny Flagian Transgression) is preserved in deposits and landforms 4–7 m asl in the Krasny Flag valley. These deposits and landforms were mapped, dated, and described using amino acid geochronology, radiocarbon, optically stimulated luminescence, electron spin resonance, oxygen isotopes, micropaleontology, paleomagnetism, and grain sizes. The marine deposits are eustatic and not isostatic in origin. All marine deposits on Wrangel Island predate the LGM, indicating that neither Wrangel Island nor the East Siberian or Chukchi Seas experienced extensive glaciation over the last 64,000 yr.

scholarly journals Modeling the marine extent of Northern Hemisphere ice sheets during the last glacial cycle

2003 ◽  
Vol 37 ◽  
pp. 173-180 ◽  
Author(s):  
Chris Zweck ◽  
Philippe Huybrechts
Keyword(s):  
Northern Hemisphere ◽  
Water Depth ◽  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Last Glacial ◽  
History Of ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractMechanisms that determine time-dependent changes of the marine ice margin in dynamic ice-sheet models are important but poorly understood. Here we derive an empirical formulation for changes in the marine extent when modelling the Northern Hemisphere ice sheets over the last glacial cycle in a three-dimensional thermomechanically coupled ice-sheet model. We assume that the strongest control on changes in marine extent is ice calving, and that the variable most crucial to calving is water depth. The empirical marine-extent relationship is tuned so that the major marine-retreat history of the Laurentide and Eurasian ice sheets is modelled accurately in time and space. We find that this empirical treatment relating marine extent to water depth is sufficient to reproduce the observations, and discuss the implications for the physics of marine margin changes and the dynamics of the Northern Hemisphere ice sheets since the Last Glacial Maximum.

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