scholarly journals The Last Glacial Maximum and deglaciation in central Patagonia, 44°S–49°S

2017 ◽  
Vol 43 (2) ◽  
pp. 719 ◽  
Author(s):  
M. Mendelova ◽  
A.S. Hein ◽  
R. McCulloch ◽  
B. Davies
Keyword(s):  
Southern Hemisphere ◽  
Last Glacial Maximum ◽  
Environmental Changes ◽  
Convincing Evidence ◽  
Glacial Maximum ◽  
Future Research ◽  
Last Glacial ◽  
The Antarctic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

This paper reviews published geochronological data on glacier fluctuations and environmental changes in central Patagonia (44° S - 49° S) from the Last Glacial Maximum (LGM) through to the Holocene. Well-dated glacial chronologies from the southern mid-latitudes can inform on the synchronicity of glacial advances worldwide and provide insight on the drivers of southern hemisphere glaciations. In central Patagonia, two large outlet lobes of the former Patagonian Ice Sheet advanced in broad synchrony with the global LGM. In contrast to other parts of Patagonia, there is no convincing evidence for a more extensive local LGM advance during Marine Isotope Stage 3. Deglaciation initiated at ca. 19 ka, earlier than in other parts of Patagonia and regionally in the Southern Hemisphere, and rapid deglaciation saw ice margins retreat in places by at least 80-120 km within a few millennia. The Lateglacial glacier margins are poorly constrained, but an ice mass substantial enough to maintain a large regional proglacial lake must have persisted at this time. The timing of lake drainage and opening of the Río Baker drainage route to the Pacific Ocean is debated; the only directly dated shoreline suggests this occurred at the end of the Antarctic Cold Reversal at 12.7 ka. Palaeoecological evidence for cooling during the Antarctic Cold Reversal or Younger Dryas remains equivocal, which may reflect both the eurythermic nature of Patagonian vegetation and shifting Southern Westerly Winds. Eastern outlet glaciers appear to have advanced or stabilised at the Lateglacial/Holocene transition when palaeoenvironmental records indicate warmer and drier conditions, but the reason for this is unclear. Our review reveals both spatial and temporal gaps in available data that provide avenues for future research.

scholarly journals Reconstruction of ice-sheet changes in the Antarctic Peninsula since the Last Glacial Maximum

2014 ◽  
Vol 100 ◽  
pp. 87-110 ◽  
Author(s):  
Colm Ó Cofaigh ◽  
Bethan J. Davies ◽  
Stephen J. Livingstone ◽  
James A. Smith ◽  
Joanne S. Johnson ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Antarctic Peninsula ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Antarctic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Southern Hemisphere westerly wind changes during the Last Glacial Maximum: paleo-data synthesis

2013 ◽  
Vol 68 ◽  
pp. 76-95 ◽  
Author(s):  
K.E. Kohfeld ◽  
R.M. Graham ◽  
A.M. de Boer ◽  
L.C. Sime ◽  
E.W. Wolff ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Westerly Wind ◽  
Data Synthesis ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals Were the Larsemann Hills ice-free through the Last Glacial Maximum?

2001 ◽  
Vol 13 (4) ◽  
pp. 440-454 ◽  
Author(s):  
D.A. Hodgson ◽  
P.E. Noon ◽  
W. Vyverman ◽  
C.L. Bryant ◽  
D.B. Gore ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Climate Changes ◽  
Environmental Changes ◽  
Glacial Maximum ◽  
Radiometric Dating ◽  
Supporting Evidence ◽  
Last Glacial ◽  
Larsemann Hills ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Lake sediments in the Larsemann Hills contain a great diversity of biological and physical markers from which past environments can be inferred. In order to determine the timing of environmental changes it is essential to have accurate dating of sediments. We used radiometric (210Pb and 137Cs), radiocarbon (AMS 14C) and uranium series (238U) methods to date cores from eleven lakes. These were sampled on coastal to inland transects across the two main peninsulas, Broknes and Stornes, together with a single sample from the Bolingen Islands. Radiometric dating of recent sediments yielded 210Pb levels below acceptable detection limits. However, a relatively well-defined peak in 137Cs gave a date marker which corresponds to the fallout maximum from the atmospheric testing of atomic weapons in 1964/65. Radiocarbon (AMS 14C) measurements showed stratigraphical consistency in the age-depth sequences and undisturbed laminae in some cores provides evidence that the sediments have remained undisturbed by glacial action. In addition, freshwater surface sediments were found to be in near-equilibrium with modern 14CO2 and not influenced by radiocarbon contamination processes. This dating program, together with geomorphological records of ice flow directions and glacial sediments, indicates that parts of Broknes were ice-free throughout the Last Glacial Maximum and that some lakes have existed continuously since at least 44 ka bp. Attempts to date sediments older than 44 ka bp using 128U dating were inconclusive. However, supporting evidence for Broknes being ice-free is provided by an Optically Stimulated Luminescence date from a glaciofluvial deposit. In contrast, Stornes only became ice-free in the mid to late Holocene. This contrasting glacial history results from the Dålk Glacier which diverts ice around Broknes. Lakes on Broknes and some offshore islands therefore contain the oldest known lacustrine sediment records from eastern Antarctica, with the area providing an ice-free oasis and refuge for plants and animals throughout the Last Glacial Maximum. These sediments are therefore well placed to unravel a unique limnological sequence of environmental and climate changes in East Antarctica from the late Pleistocene to the present. This information may help better constrain models of current climate changes and ensure the adequate protection of these lakes and their catchments from the impacts of recent human occupation.

Glacier Modeling and the Climate of Patagonia during the Last Glacial Maximum

1994 ◽  
Vol 42 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Nick Hulton ◽  
David Sugden ◽  
Antony Payne ◽  
Chalmers Clapperton
Keyword(s):  
Mass Balance ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Equilibrium Line Altitude ◽  
Last Glacial ◽  
Ice Cap ◽  
The Andes ◽  
The Antarctic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractIce cap modeling constrained by empirical studies provides an effective way of reconstructing past climates. The former Patagonian ice sheet is in a climatically significant location since it lies athwart the Southern Hemisphere westerlies and responds to the latitudinal migration of climatic belts during glacial cycles. A numerical model of the Patagonian ice cap for the last glacial maximum (LGM) is developed, which is time-dependent and driven by changing the mass balance/altitude relationship. It relies on a vertically integrated continuity model of ice mass solved over a finite difference grid. The model is relatively insensitive to ice flow parameters but highly sensitive to mass balance. The climatic input is adjusted to produce the best fit with the known limits of the ice cap at the LGM. The ice cap extends 1800 km along the Andes and has a volume of 440,000 km3. During the LGM the equilibrium line altitude (ELA) was lower than at present by at least 560 m near latitude 40°S, 160 m near latitude 50°S, and 360 m near latitude 56°S. The latitudinal variation in ELA depression can be explained by an overall fall in temperature of about 3.0°C and the northward migration of precipitation belts by about 5° latitude. Annual precipitation totals may have decreased by about 0.7 m at latitude 50°S and increased by about 0.7 m at latitude 40°S. The ELA rises steeply by up to 4 m per kilometer from west to east as the westerlies cross the Andes and this prevents ice growth to the east. The limited decrease in temperature during the LGM could be related to the modest migration of the Antarctic convergence between South America and the Antarctic Peninsula.

scholarly journals Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison

2013 ◽  
Vol 64 ◽  
pp. 104-120 ◽  
Author(s):  
Louise C. Sime ◽  
Karen E. Kohfeld ◽  
Corinne Le Quéré ◽  
Eric W. Wolff ◽  
Agatha M. de Boer ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Westerly Wind ◽  
Model Data ◽  
Last Glacial ◽  
Data Comparison ◽  
The Last Glacial Maximum ◽  
The Last Glacial

The deglacial history of NW Alexander Island, Antarctica, from surface exposure dating

2012 ◽  
Vol 77 (2) ◽  
pp. 273-280 ◽  
Author(s):  
Joanne S. Johnson ◽  
Jeremy D. Everest ◽  
Philip T. Leat ◽  
Nicholas R. Golledge ◽  
Dylan H. Rood ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Antarctic Peninsula ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Ice Shelf ◽  
Last Glacial ◽  
Ice Cap ◽  
The Antarctic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Recent changes along the margins of the Antarctic Peninsula, such as the collapse of the Wilkins Ice Shelf, have highlighted the effects of climatic warming on the Antarctic Peninsula Ice Sheet (APIS). However, such changes must be viewed in a long-term (millennial-scale) context if we are to understand their significance for future stability of the Antarctic ice sheets. To address this, we present nine new cosmogenic 10Be exposure ages from sites on NW Alexander Island and Rothschild Island (adjacent to the Wilkins Ice Shelf) that provide constraints on the timing of thinning of the Alexander Island ice cap since the last glacial maximum. All but one of the 10Be ages are in the range 10.2–21.7 ka, showing a general trend of progressive ice-sheet thinning since at least 22 ka until 10 ka. The data also provide a minimum estimate (490 m) for ice-cap thickness on NW Alexander Island at the last glacial maximum. Cosmogenic 3He ages from a rare occurrence of mantle xenoliths on Rothschild Island yield variable ages up to 46 ka, probably reflecting exhumation by periglacial processes.

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