scholarly journals Laurentide Ice Sheet basal temperatures during the last glacial cycle as inferred from borehole data

2016 ◽  
Vol 12 (1) ◽  
pp. 115-127 ◽  
Author(s):  
C. Pickler ◽  
H. Beltrami ◽  
J.-C. Mareschal
Keyword(s):  
Ice Sheet ◽  
Internal Heat ◽  
Ground Surface ◽  
Laurentide Ice Sheet ◽  
Glacial Cycle ◽  
Ice Streams ◽  
Borehole Data ◽  
Last Glacial ◽  
Central Canada ◽  
The Last Glacial

Abstract. Thirteen temperature–depth profiles ( ≥  1500 m) measured in boreholes in eastern and central Canada were inverted to determine the ground surface temperature histories during and after the last glacial cycle. The sites are located in the southern part of the region that was covered by the Laurentide Ice Sheet. The inversions yield ground surface temperatures ranging from −1.4 to 3.0 °C throughout the last glacial cycle. These temperatures, near the pressure melting point of ice, allowed basal flow and fast flowing ice streams at the base of the Laurentide Ice Sheet. Despite such conditions, which have been inferred from geomorphological data, the ice sheet persisted throughout the last glacial cycle. Our results suggest some regional trends in basal temperatures with possible control by internal heat flow.

scholarly journals Laurentide Ice Sheet basal temperatures at the Last Glacial Cycle as inferred from borehole data

2015 ◽  
Vol 11 (4) ◽  
pp. 3937-3971
Author(s):  
C. Pickler ◽  
H. Beltrami ◽  
J.-C. Mareschal
Keyword(s):  
Ice Sheet ◽  
Internal Heat ◽  
Ground Surface ◽  
Laurentide Ice Sheet ◽  
Glacial Cycle ◽  
Ice Streams ◽  
Borehole Data ◽  
Last Glacial ◽  
Central Canada ◽  
The Last Glacial

Abstract. Thirteen temperature-depth profiles (≥ 1500 m) measured in boreholes in eastern and central Canada were inverted to determine the ground surface temperature histories during and after the last glacial cycle. The sites are located in the southern part of the region covered by the Laurentide Ice Sheet. The inversions yield ground surface temperatures ranging from −1.4 to 3.0 °C throughout the last glacial cycle. These temperatures, near the pressure melting point of ice, allowed basal flow and fast flowing ice streams at the base of the Laurentide Ice Sheet. Despite such conditions, which have been inferred from geomorphological data, the ice sheet persisted throughout the last glacial cycle. Our results suggest some regional trends in basal temperatures with possible control by internal heat flow.

Asynchronous instability of NE ice streams of the Laurentide Ice Sheet recorded in the marine sediments of Labrador Sea during the last glacial cycle

2020 ◽  
Author(s):  
Harunur Rashid ◽  
Mary Smith ◽  
Min Zeng ◽  
Yang Wang ◽  
Julie Drapeau ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Labrador Sea ◽  
Glacial Cycle ◽  
Ice Streams ◽  
Last Glacial ◽  
Ice Stream ◽  
Cumberland Sound ◽  
Detrital Carbonate ◽  
The Last Glacial

<p>Hughes et al. (1977) hypothesized of a pan-Arctic Ice Sheet that behaved as a single dynamic system during the Last Glacial Maximum. Moreover, the authors suggested a nearly grounded ice shelf in Davis Strait implying that little or no exchange between Baffin Island and the Labrador Sea. Here we present data at 1-cm (<100 years) resolution between ~12 ka and 45 ka that shed light on the discharge from Hudson Strait and Lancaster Sound ice streams of the Late Pleistocene Laurentide Ice Sheet. A reference sediment core at 938 m water depth on the SE Baffin Slope was investigated with new oxygen isotope stratigraphy, X-ray fluorescence geochemistry, and 18 14C-AMS dates and correlated to 14 regional deep-water cores. Detrital carbonate-rich sediment layers H0-H4 were derived principally from Hudson Strait. Shortly after H2 and H3, the shelf-crossing Cumberland Sound ice stream supplied dark brown ice-proximal stratified sediments but no glacigenic debris-flow deposits. The counterparts of H3, H4, and (?)H5 events in the deep Labrador basin are 4–10 m thick units of thin-bedded carbonate-rich mud turbidites from glacigenic debris flows on the Hudson Strait slope. The behavior of the Hudson Strait ice stream changed through the last glacial cycle. The Hudson Strait ice stream remained at the shelf break in H3-H5 but retreated rapidly across the shelf in H0-H2 and did not deglaciate Hudson Bay. During this time, Cumberland Sound ice twice reached the shelf edge. In H3–H5, it remained at the shelf break long enough to supply thick turbidites. Minor supply of carbonate-rich sediment from Baffin Bay allows chronologic integration of the Baffin Bay and Labrador Sea detrital carbonate records, which is diachronous with respect to Heinrich events. The asynchrony of the carbonate events implies an open seaway through Davis Strait. Our data suggest that the maximum extent of ice streams in Hudson Strait, Cumberland Sound, and Lancaster Sound was neither synchronous.</p>

scholarly journals Evolution of the large-scale atmospheric circulation in response to changing ice sheets over the last glacial cycle

2014 ◽  
Vol 10 (4) ◽  
pp. 1453-1471 ◽  
Author(s):  
M. Löfverström ◽  
R. Caballero ◽  
J. Nilsson ◽  
J. Kleman
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Glacial Cycle ◽  
Mean Flow ◽  
Geological Evidence ◽  
Last Glacial ◽  
The Last Glacial

Abstract. We present modelling results of the atmospheric circulation at the cold periods of marine isotope stage 5b (MIS 5b), MIS 4 and the Last Glacial Maximum (LGM), as well as the interglacial. The palaeosimulations are forced by ice-sheet reconstructions consistent with geological evidence and by appropriate insolation and greenhouse gas concentrations. The results suggest that the large-scale atmospheric winter circulation remained largely similar to the interglacial for a significant part of the glacial cycle. The proposed explanation is that the ice sheets were located in areas where their interaction with the mean flow is limited. However, the LGM Laurentide Ice Sheet induces a much larger planetary wave that leads to a zonalisation of the Atlantic jet. In summer, the ice-sheet topography dynamically induces warm temperatures in Alaska and central Asia that inhibits the expansion of the ice sheets into these regions. The warm temperatures may also serve as an explanation for westward propagation of the Eurasian Ice Sheet from MIS 4 to the LGM.

Streaming flow in an ice sheet through a glacial cycle

2003 ◽  
Vol 36 ◽  
pp. 117-128 ◽  
Author(s):  
Geoffrey S. Boulton ◽  
Magnus Hagdorn ◽  
Nicholas R.J. Hulton
Keyword(s):  
Three Dimensional ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Ice Streams ◽  
Geological Evidence ◽  
Last Glacial ◽  
Bed Topography ◽  
Basal Melting ◽  
Realistic Topography ◽  
The Last Glacial

AbstractGeological evidence indicates that the flow of the last European ice sheet was dominated by numerous large ice streams. Although some were ephemeral, most were sustained along well-defined axes at least during the period of retreat after the Last Glacial Maximum. A thermomechanically coupled three-dimensional numerical ice-sheet model has been used to simulate the ice sheet through the whole of the last glacial cycle, but with a spatial resolution that is high enough to capture streaming behaviour. An experiment with a smoothed bed is used to explore the self-organizing behaviour of streams when they are not forced by bed topography. On such a bed, streams typically have a width of 1–10 km, much narrower than the inferred European ice streams. An experiment using a realistic topography suggests that widths of ice streams are strongly influenced by topography, and tend to be of order 100 km. Moreover, even where the topography is muted, it stabilizes the locations of ice streams which, once formed, tend to be sustained along pre-existing axes. The model creates patterns of streaming that are similar to inferred patterns, suggesting strong topographic forcing. In a simulation using a realistic bed in which the ice was very cold and basal melting rarely occurred, streams were again very narrow. Widespread streaming under low driving stresses tends to reduce ice-sheet thicknesses compared with weak streaming or models that do not produce streaming. Consequently, ice thicknesses are smaller and tend to be consistent with the results of sea-level inversions based on geophysical Earth models.

Morphology reveals deglaciation patterns of the Laurentide Ice Sheet in the Clyde Inlet fjord-cross-shelf trough system, eastern Baffin Island (Arctic Canada)

2020 ◽  
Author(s):  
Pierre-Olivier Couette ◽  
Patrick Lajeunesse ◽  
Boris Dorschel ◽  
Catalina Gebhardt ◽  
Dierk Hebbeln ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Spatial And Temporal Variability ◽  
Baffin Island ◽  
Glacial Cycle ◽  
Arctic Canada ◽  
Ice Dynamics ◽  
Last Glacial ◽  
Climatic Cooling ◽  
The Last Glacial

<p>The maximal extent and subsequent deglaciation of the Laurentide Ice Sheet (LIS) across eastern Baffin Island during the last glacial cycle (MIS-2) has been widely debated during the last decades as different palaeo-glaciological models have been proposed. Spatial and temporal variability of ice sheets extension during Quaternary glaciations complicate the establishment of a reliable reconstruction of the ice dynamics in the area. Furthermore, the lack of geophysical data in most of the fjords, and seaward, makes it difficult to reconcile the proposed terrestrial and marine glacial margins. High-resolution swath-bathymetric data, collected between 2003 and 2017, display a diversity of glacial bedforms in the Clyde Inlet fjord-cross-shelf-trough system (Eastern Baffin Island, Arctic Canada). These bedforms reveal a potential position of the LIS margin during the Last Glacial Maximum (LGM) near the shelf break. Early deglaciation of the Clyde Trough was marked by an initial break up of the ice sheet. This rapid retreat of the ice margin was punctuated by episodic stabilizations forming GZWs. This retreat was followed by a readvance and subsequent slow retreat of the LIS, as indicated by the presence of recessional moraines. Long-term stabilizations within the trough possibly coincided with major climatic cooling episodes, such as the end of Heinrich event 1 (H1) and the Younger Dryas. However, these stabilizations appear to have been influenced by topography, as GZWs can be found at pinning points in the trough. Deglaciation of the fjord occurred during the early Holocene and was faster, probably due to increased water depths. The presence of multiple moraine systems however indicate that deglaciation of Clyde Inlet was marked by stages of ice margin stabilization.</p>

scholarly journals An Ice Sheet’s Footprint on Ancient Shorelines

Eos ◽  
2020 ◽  
Vol 101 ◽  
Author(s):  
Kate Wheeling
Keyword(s):  
Ice Sheet ◽  
Earth’S Crust ◽  
Laurentide Ice Sheet ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Earth's Crust ◽  
The Last Glacial

Researchers combine observations of ancient shorelines and properties of Earth’s crust to infer the size of the Laurentide Ice Sheet during the last glacial cycle.

scholarly journals Evolution of the large-scale atmospheric circulation in response to changing ice sheets over the last glacial cycle

2014 ◽  
Vol 10 (2) ◽  
pp. 1381-1420 ◽  
Author(s):  
M. Löfverström ◽  
R. Caballero ◽  
J. Nilsson ◽  
J. Kleman
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Glacial Cycle ◽  
Mean Flow ◽  
Geological Evidence ◽  
Last Glacial ◽  
The Last Glacial

Abstract. We present modelling results of the atmospheric circulation at the cold periods of marine isotope stage 5b (MIS 5b), MIS 4 and the Last Glacial Maximum (LGM), as well as the interglacial. The paleo-simulations are forced by ice sheet reconstructions consistent with geological evidence and by appropriate insolation and greenhouse gas concentrations. The results suggest that the large-scale atmospheric winter circulation remained largely similar to the interglacial for a significant part of the glacial cycle. The proposed explanation is that the ice sheets were located in areas where their interaction with the mean flow is limited. However, the LGM Laurentide Ice Sheet induces a much larger planetary wave that leads to a zonalisation of the Atlantic jet. In summer, the ice sheet topography dynamically induces warm temperatures in Alaska and central Asia that inhibits the expansion of the ice sheets into these regions. The warm temperatures may also serve as an explanation for westward propagation of the Eurasian Ice Sheet from MIS 4 to the LGM.

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