scholarly journals Modeling the oxygen-isotopic composition of the North American Ice Sheet and its effect on the isotopic composition of the ocean during the last glacial cycle

2006 ◽  
Vol 33 (15) ◽  
Author(s):  
Adriana Sima ◽  
André Paul ◽  
Michael Schulz ◽  
Johannes Oerlemans
Keyword(s):  
Isotopic Composition ◽  
North American ◽  
Ice Sheet ◽  
Oxygen Isotopic Composition ◽  
Glacial Cycle ◽  
Last Glacial ◽  
The North ◽  
Oxygen Isotopic ◽  
The Last Glacial

scholarly journals The impact of the North American glacial topography on the evolution of the Eurasian ice sheet over the last glacial cycle

2016 ◽  
Vol 12 (5) ◽  
pp. 1225-1241 ◽  
Author(s):  
Johan Liakka ◽  
Marcus Löfverström ◽  
Florence Colleoni
Keyword(s):  
North American ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Stationary Wave ◽  
Ocean Heat Transport ◽  
Glacial Cycle ◽  
Last Glacial ◽  
The North ◽  
The Impact ◽  
The Last Glacial

Abstract. Modeling studies have shown that the continental-scale ice sheets in North America and Eurasia in the last glacial cycle had a large influence on the atmospheric circulation and thus yielded a climate distinctly different from the present. However, to what extent the two ice sheets influenced each others' growth trajectories remains largely unexplored. In this study we investigate how an ice sheet in North America influences the downstream evolution of the Eurasian ice sheet, using a thermomechanical ice-sheet model forced by climate data from atmospheric snapshot experiments of three distinctly different phases of the last glacial cycle: the Marine Isotope Stages 5b, 4, and 2 (Last Glacial Maximum – LGM). Owing to the large uncertainty associated with glacial changes in the Atlantic meridional overturning circulation, each atmospheric snapshot experiment was conducted using two distinctly different ocean heat transport representations. Our results suggest that changes in the North American paleo-topography may have largely controlled the zonal distribution of the Eurasian ice sheet. In the MIS4 and LGM experiments, the Eurasian ice sheet migrates westward towards the Atlantic sector – largely consistent with geological data and contemporary ice-sheet reconstructions – due to a low wave number stationary wave response, which yields a cooling in Europe and a warming in northeastern Siberia. The expansion of the North American ice sheet between MIS4 and the LGM amplifies the Siberian warm anomaly, which limits the glaciation there and may therefore help explain the progressive westward migration of the Eurasian ice sheet in this time period. The ocean heat transport only has a small influence on the stationary wave response to the North American glacial topography; however, because temperature anomalies have a smaller influence on an ice sheet's ablation in a colder climate than in a warmer one, the impact of the North American glacial topography on the Eurasian ice-sheet evolution is reduced for colder surface conditions in the North Atlantic. While the Eurasian ice sheet in the MIS4 and the LGM experiments appears to be in equilibrium with the simulated climate conditions, the MIS5b climate forcing is too warm to grow an ice sheet in Eurasia. First-order sensitivity experiments suggest that the MIS5b ice sheet was established during preceding colder stages.

scholarly journals Tracking the History of the North American Ice Sheet during the Last Glacial Cycle

2020 ◽  
Author(s):  
Rebecca Parker ◽  
Gavin Foster ◽  
Marcus Gutjahr ◽  
Paul Wilson ◽  
Kate Littler ◽  
...  
Keyword(s):  
North American ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Last Glacial ◽  
The North ◽  
History Of ◽  
The Last Glacial

scholarly journals The impact of the North American ice sheet on the evolution of the Eurasian ice sheet during the last glacial cycle

2015 ◽  
Vol 11 (6) ◽  
pp. 5203-5241 ◽  
Author(s):  
J. Liakka ◽  
M. Löfverström ◽  
F. Colleoni
Keyword(s):  
North American ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Climate Data ◽  
Glacial Cycle ◽  
Atlantic Sector ◽  
Last Glacial ◽  
The North ◽  
The Impact ◽  
The Last Glacial

Abstract. Modeling studies show that the massive ice sheet expanding over the North American and Eurasian continents in the last glacial cycle has a large impact on the atmospheric stationary waves and thus yielded a glacial climate distinctly different from the present. However, to what extent the two ice sheets influenced each others growth trajectories remains largely unexplored. In this study we investigate how ice sheets in North America influence the downstream evolution of the Eurasian ice sheet, using a thermomechanical ice-sheet model forced by climate data from snapshot simulations of three distinctly different phases of the last glacial cycle: the Marine Isotope Stages 5b, 4 and 2 (LGM). Our results suggest that changes in the North American paleo-topography may have had a large influence on evolution of the Eurasian ice sheet. In the MIS4 and LGM experiments, the Eurasian ice sheet migrates westward towards the Atlantic sector – largely consistent with geological data and contemporary ice-sheet reconstructions – due to a low wavenumber stationary wave response, which yields a cooling in Europe and a warming in northeastern Siberia. The expansion of the North American ice sheet between MIS4 and LGM amplifies the Siberian warm anomaly, which limits the glaciation there and may therefore help to explain the progressive westward migration of the Eurasian ice sheet over this time period. While the Eurasian ice sheet in the MIS4 and LGM experiments appears to be in equilibrium with the simulated climate conditions, the MIS5b climate forcing is too warm to grow an ice sheet. First-order sensitivity experiments suggest that most of the MIS5b ice sheet was established during preceding colder stages.

scholarly journals The origin of till sequences by subglacial sediment deformation beneath mid-latitude ice sheets

1996 ◽  
Vol 22 ◽  
pp. 75-84 ◽  
Author(s):  
G. S. Boulton
Keyword(s):  
North American ◽  
Large Scale ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Erosion And Deposition ◽  
The North ◽  
Sediment Deformation ◽  
Source Materials ◽  
The Last Glacial

A theory of erosion and deposition as a consequence of subglacial sediment deformation over beds of unlithified sediment is reviewed and applied to large-scale till sequences formed on the southern flanks of the North American and British and European ice sheets during the last glacial cycle. The distribution of till thickness, till lithology in relation to source materials and intra-till erosion surfaces along a flowline in the Michigan lobe of the North American ice sheet are shown to be compatible with the deformational theory but not with other modes of till genesis. It is then demonstrated, in the case of the British ice sheet, how the assumption of a deformational origin for tills can be used to infer time-dependent patterns of ice-sheet dynamic behaviour. By reference to an example from the Netherlands, it is argued that many till sequences interpreted as melt-out tills are more likely to have formed by subglacial sediment deformation.

scholarly journals The deglaciation of coastal areas of southeast Greenland

The Holocene ◽  
2018 ◽  
Vol 28 (9) ◽  
pp. 1535-1544 ◽  
Author(s):  
Laurence M Dyke ◽  
Anna LC Hughes ◽  
Camilla S Andresen ◽  
Tavi Murray ◽  
John F Hiemstra ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Younger Dryas ◽  
Greenland Ice Sheet ◽  
Coastal Areas ◽  
Glacial Cycle ◽  
Last Glacial ◽  
The North ◽  
Exposure Ages ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Large marine-terminating glaciers around the margins of the Greenland Ice Sheet have retreated, accelerated and thinned over the last two decades. Relatively little is known about the longer term behaviour of the Greenland Ice Sheet, yet this information is valuable for assessing the significance of modern changes. We address this by reporting 11 new beryllium-10 (10Be) exposure ages from previously uninvestigated coastal areas across southeast Greenland. The new ages are combined with existing data from the region to assess the timing of glacier retreat after the Last Glacial Maximum. The results show that deglaciation occurred first in the north of the region (~68°N) and progressed southwards. This north–south progression is attributed to the influence of the warm Irminger Current on the ice margin. Areas in the south of the region were isolated from the warm waters by the shallow bathymetry of the continental shelf. This demonstrates that oceanographic forcing paced the deglaciation of southeast Greenland through the Younger Dryas and early Holocene. In most areas of southeast Greenland bedrock ages are systematically older than their counterpart boulder samples; this offset is likely the result of inherited 10Be content in bedrock surfaces. This suggests that subglacial erosion during the last glacial cycle was insufficient to completely remove pre-existing 10Be content. Alternatively, this pattern may be the signature of a substantial retreat and advance cycle prior to final Holocene deglaciation.

scholarly journals The origin of till sequences by subglacial sediment deformation beneath mid-latitude ice sheets

1996 ◽  
Vol 22 ◽  
pp. 75-84 ◽  
Author(s):  
G. S. Boulton
Keyword(s):  
North American ◽  
Large Scale ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Erosion And Deposition ◽  
The North ◽  
Sediment Deformation ◽  
Source Materials ◽  
The Last Glacial

A theory of erosion and deposition as a consequence of subglacial sediment deformation over beds of unlithified sediment is reviewed and applied to large-scale till sequences formed on the southern flanks of the North American and British and European ice sheets during the last glacial cycle. The distribution of till thickness, till lithology in relation to source materials and intra-till erosion surfaces along a flowline in the Michigan lobe of the North American ice sheet are shown to be compatible with the deformational theory but not with other modes of till genesis. It is then demonstrated, in the case of the British ice sheet, how the assumption of a deformational origin for tills can be used to infer time-dependent patterns of ice-sheet dynamic behaviour. By reference to an example from the Netherlands, it is argued that many till sequences interpreted as melt-out tills are more likely to have formed by subglacial sediment deformation.

North American Ice Sheet build-up during the last glacial cycle, 115–21kyr

2010 ◽  
Vol 29 (17-18) ◽  
pp. 2036-2051 ◽  
Author(s):  
Johan Kleman ◽  
Krister Jansson ◽  
Hernán De Angelis ◽  
Arjen P. Stroeven ◽  
Clas Hättestrand ◽  
...  
Keyword(s):  
North American ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Last Glacial ◽  
The Last Glacial
Sign in / Sign up

Export Citation Format

Share Document