The role of basal hydrology in the surging of the Laurentide Ice Sheet

Abstract. We use the Glimmer ice sheet model to simulate periodic surges over the Laurentide Ice Sheet during the Last Glacial Maximum. In contrast to previous studies we use the depth of water at the base of the ice sheet as the switch for these surges. We find that the surges are supported within the model and are quite robust across a very wide range of parameter choices, in contrast to many previous studies where surges only occur for rather specific cases. The robustness of the surges is likely due to the use of water as the switch mechanism for sliding The statistics of the binge-purge cycles resemble observed Heinrich Events. The events have a period of between 10–15 thousand years and can produce fluxes of ice from the mouth of Hudson Strait of 0.05 Sv – a maximum flux of 0.06 Sv is possible. The events produce an ice volume of 2.50 × 106 km3 with a range of 4.30 × 106 km3–1.90 × 106 km3 possible. We undertake a suite of sensitivity tests varying the sliding parameter, the water drainage scheme, the sliding versus water depth parametrization, and the resolution all of which support the ice sheet surges. This suggests that internally triggered ice sheet surges were a robust feature of the Laurentide Ice Sheet and are a possible explanation for the observed Heinrich Events.

The role of basal hydrology in the surging of the Laurentide Ice Sheet

Climate of the Past ◽

10.5194/cp-12-1601-2016 ◽

2016 ◽

Vol 12 (8) ◽

pp. 1601-1617 ◽

Cited By ~ 4

Author(s):

William H. G. Roberts ◽

Antony J. Payne ◽

Paul J. Valdes

Keyword(s):

Ice Sheet ◽

Laurentide Ice Sheet ◽

Water Drainage ◽

Heinrich Events ◽

Sensitivity Tests ◽

Wide Range ◽

Switch Mechanism ◽

Abstract. We use the Glimmer ice sheet model to simulate periodic surges over the Laurentide Ice Sheet during the Last Glacial Maximum. In contrast to previous studies we use the depth of water at the base of the ice sheet as the switch for these surges. We find that the surges are supported within the model and are quite robust across a very wide range of parameter choices, in contrast to many previous studies where surges only occur for rather specific cases. The robustness of the surges is likely due to the use of water as the switch mechanism for sliding. The statistics of the binge–purge cycles resemble observed Heinrich events. The events have a period of between 10 and 15 thousand years and can produce fluxes of ice from the mouth of Hudson Strait of 0.05 Sv – a maximum flux of 0.06 Sv is possible. The events produce an ice volume of 2.50  ×  106 km3, with a range of 4.30  ×  106–1.90  ×  106 km3 possible. We undertake a suite of sensitivity tests varying the sliding parameter, the water drainage scheme, the sliding versus water depth parameterisation and the resolution, all of which support the ice sheet surges. This suggests that internally triggered ice sheet surges were a robust feature of the Laurentide Ice Sheet and are a possible explanation for the observed Heinrich events.

Ice-age ice-sheet rheology: constraints from the Last Glacial Maximum form of the Laurentide ice sheet

Annals of Glaciology ◽

10.3189/172756400781820859 ◽

2000 ◽

Vol 30 ◽

pp. 163-176 ◽

Cited By ~ 26

Author(s):

W. Richard Peltier ◽

David L. Goldsby ◽

David L. Kohlstedt ◽

Lev Tarasov

Keyword(s):

Last Glacial Maximum ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Glacial Maximum ◽

Ice Age ◽

Laurentide Ice Sheet ◽

Last Glacial ◽

Flow Law ◽

AbstractState-of-the-art thermomechanical models of the modern Greenland ice sheet and the ancient Laurentide ice sheet that covered Canada at the Last Glacial Maximum (LGM) are not able to explain simultaneously the observed forms of these cryospheric structures when the same, anisotropy-enhanced, version of the conventional Glen flow law is employed to describe their rheology. The LGM Laurentide ice sheet, predicted to develop in response to orbital climate forcing, is such that the ratio of its thickness to its horizontal extent is extremely large compared to the aspect ratio inferred on the basis of surface-geomorphological and solid-earth-geophysical constraints. We show that if the Glen flow law representation of the rheology is replaced with a new rheology based upon very high quality laboratory measurements of the stress-strain-rate relation then the aspect ratios of both the modern Greenland ice sheet and the Laurentide ice sheet, that existed at the LGM, are simultaneously explained with little or no retuning of the flow law.

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

Journal of Glaciology ◽

10.3189/172756500781832800 ◽

2000 ◽

Vol 46 (153) ◽

pp. 311-325 ◽

Cited By ~ 82

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 ◽

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.

STRUCTURE OF THE LAST GLACIAL MAXIMUM AT THE SOUTHERN MARGIN OF THE LAURENTIDE ICE SHEET

10.1130/abs/2020am-359057 ◽

2020 ◽

Author(s):

Thomas V. Lowell ◽

◽

Henry Loope ◽

B. Brandon Curry ◽

Stephanie L. Heath ◽

...

Keyword(s):

Last Glacial Maximum ◽

Ice Sheet ◽

Glacial Maximum ◽

Laurentide Ice Sheet ◽

Last Glacial ◽

Southern Margin ◽

Individual and combined effects of ice sheets and precession on MIS-13 climate

Climate of the Past ◽

10.5194/cp-5-229-2009 ◽

2009 ◽

Vol 5 (2) ◽

pp. 229-243 ◽

Cited By ~ 41

Author(s):

Q. Z. Yin ◽

A. Berger ◽

M. Crucifix

Keyword(s):

Global Climate ◽

Wave Train ◽

Ice Sheets ◽

Ice Sheet ◽

Summer Precipitation ◽

East China ◽

Thermal Contrast ◽

Abstract. An Earth System Model of Intermediate Complexity is used to investigate the role of insolation and of the size of ice sheets on the regional and global climate of marine isotope stage (MIS) 13. The astronomical forcing is selected at two dates with opposite precession, one when northern hemisphere (NH) summer occurs at perihelion (at 506 ka (1 ka=1000 years) BP), and the other when it occurs at aphelion (at 495 ka BP). Five different volumes of the Eurasian ice sheet (EA) and North American ice sheet (NA), ranging from 0 to the Last Glacial Maximum (LGM) one, are used. The global cooling due to the ice sheets is mainly related to their area, little to their height. The regional cooling and warming anomalies caused by the ice sheets intensify with increasing size. Precipitation over different monsoon regions responds differently to the size of the ice sheets. Over North Africa and India, precipitation decreases with increasing ice sheet size due to the southward shift of the Intertropical Convergence Zone (ITCZ), whatever the astronomical configuration is. However, the situation is more complicated over East Asia. The ice sheets play a role through both reducing the land/ocean thermal contrast and generating a wave train which is topographically induced by the EA ice sheet. This wave train contributes to amplify the Asian land/ocean pressure gradient in summer and finally reinforces the precipitation. The presence of this wave train depends on the combined effect of the ice sheet size and insolation. When NH summer occurs at perihelion, the EA is able to induce this wave train whatever its size is, and this wave train plays a more important role than the reduction of the land/ocean thermal contrast. Therefore, the ice sheets reinforce the summer precipitation over East China whatever their sizes are. However, when NH summer occurs at aphelion, there is a threshold in the ice volume beyond which the wave train is not induced anymore. Therefore, below this threshold, the wave train effect is dominant and the ice sheets reinforce precipitation over East China. Beyond this threshold, the ice sheets reduce the precipitation mainly through reducing the land/ocean thermal contrast.

Late Wisconsinan buildup and wastage of the Innuitian Ice Sheet across southern Ellesmere Island, Nunavut

Canadian Journal of Earth Sciences ◽

10.1139/e03-082 ◽

2004 ◽

Vol 41 (1) ◽

pp. 39-61 ◽

Cited By ~ 34

Author(s):

John H England ◽

Nigel Atkinson ◽

Arthur S Dyke ◽

David JA Evans ◽

Marek Zreda

Keyword(s):

Ice Sheet ◽

Greenland Ice Sheet ◽

Ellesmere Island ◽

Laurentide Ice Sheet ◽

Subsequent Removal ◽

Baffin Bay ◽

Late Wisconsinan ◽

Global Sea Level ◽

During the Late Wisconsinan, a precursor of the Prince of Wales Icefield, southern Ellesmere Island, formed a prodigious ice divide of the Innuitian Ice Sheet. Initial buildup occurred after 19 ka BP, when the icefield advanced west (inland) across Makinson Inlet from margins similar to present. Subsequent reversal of flow to the east required ice divide migration to the west onto a plateau that is largely ice-free today. From this divide, a trunk glacier flowed eastward through Makinson Inlet to join the Smith Sound Ice Stream en route to nothern Baffin Bay. Westward flow from this divide filled Baumann Fiord, depositing a granite dispersal train that extends a further 600 km across the archipelago to the polar continental shelf. Deglaciation of most of Makinson Inlet occurred catastrophically at ~9.3 ka BP, forming a calving bay that thinned the Innuitian divide, thereby triggering deglaciation of most of Baumann Fiord by 8.5 ka BP. Ninety 14C dates on Holocene shells and driftwood constrain deglacial isochrones and postglacial emergence curves on opposite sides of the former Innuitian divide. Isobases drawn on the 8 ka BP shoreline rise northwest towards Eureka Sound, the axis of maximum former ice thickness. Ice margins on Ellesmere Island were similar to present from ~5019 ka BP (spanning marine isotope stages 3 and 2). However, significant regional variation in ice extent during this interval is recorded by ice rafting from the Laurentide Ice Sheet into Baffin Bay. Later buildup of the Innuitian Ice Sheet occurred during the low global sea level that defines the last glacial maximum (18 ka BP). We also suggest that the Innuitian Ice Sheet was influenced by the buttressing and subsequent removal of the Greenland Ice Sheet along eastern Ellesmere Island.

The deglaciation of the northwestern Laurentide Ice Sheet in the Mackenzie Mountains

10.5194/egusphere-egu2020-570 ◽

2020 ◽

Author(s):

Benjamin J. Stoker ◽

Martin Margold ◽

Duane G. Froese ◽

John C. Gosse

Keyword(s):

Numerical Modelling ◽

Last Glacial Maximum ◽

Ice Sheet ◽

Glacial Maximum ◽

Laurentide Ice Sheet ◽

Last Glacial ◽

Modelling Studies ◽

Mackenzie Mountains ◽

The northwestern sector of the Laurentide Ice Sheet coalesced with the Cordilleran Ice Sheet over the southern Mackenzie Mountains, and with local montane glaciers along the eastern slopes of the Mackenzie Mountains. Recent numerical modelling studies have identified rapid ice sheet thinning in this region as a major contributor to Meltwater Pulse 1A. Despite advances in remote sensing and numerical dating methods, the configuration and chronology of the northwestern sector of the Laurentide Ice Sheet has not been reconstructed in detail. The last available studies date back to the 1990s, where field surveys and mapping from aerial imagery were used to reconstruct the Last Glacial Maximum glacier extents in the Mackenzie Mountains. Cross-cutting relationships between glacial landforms and a series of 36Cl cosmogenic nuclide dates were used to propose a deglacial model involving a significant ice readvance in the region. However, the chronological evidence supporting the readvance is uncertain because the individual ages are few and poorly clustered. Here we present an updated map of the Last Glacial Maximum glacial limits and the recessional record in the Mackenzie Mountains, based on glacial geomorphological mapping from the ArcticDEM. Sixteen new 10Be dates from four sites that were previously glaciated by the Laurentide Ice Sheet constrain the deglacial sequence across the region. These dates indicate ice sheet detachment from the eastern Mackenzie Mountains at ~16 ka as summits became ice-free. The Mackenzie Valley at ~ 65 &#176;N became ice free at ~ 13 &#8211; 14 ka, towards the end of the B&#248;lling-Aller&#248;d warm period. These chronological constraints on the deglaciation of the Laurentide Ice Sheet allow us to reinterpret landform relationships in the Mackenzie Mountains to reconstruct the ice sheet retreat pattern. Our updated model of the LGM extent and timing of deglaciation in the Mackenzie Mountains provides important constraints for quantifying past sea level contributions and numerical modelling studies.

Laurentide ice sheet aspect ratio in models based on Glen’s flow law

Annals of Glaciology ◽

10.3189/172756400781820804 ◽

2000 ◽

Vol 30 ◽

pp. 177-186 ◽

Cited By ~ 10

Author(s):

Lev Tarasov ◽

W. Richard Peltier

Keyword(s):

Aspect Ratio ◽

Climate Models ◽

Three Dimensional ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Laurentide Ice Sheet ◽

Flow Enhancement ◽

Flow Law ◽

AbstractThe problem of recovering the small aspect ratio of the ICE-4G reconstruction of the Last Glacial Maximum Laurentide ice sheet has proven to be a challenge for state-of-the-art thermomechanically-coupled three-dimensional ice-sheet models coupled to reduced climate models. Flow enhancements to Glen’s flow law, 20 to 30 times those required to adequately simulate the present-day Greenland ice sheet, have been found necessary in order to reproduce both the thickness and areal extent of the geophysical reconstruction. Within the confines of the Glen flow rheology, it is unclear what mechanism might explain the magnitude of this discrepancy in required flow enhancement for the Laurentide relative to the Greenland ice sheet We present a comparative analysis of three alternative explanations of such a questionable flow-law enhancement: radical changes to mass balance; radical changes to ice-sheet history; and strongly enhanced basal flows Based on this analysis, we argue that none of these alternatives provide a fully acceptable explanation for the small ICE-4G LGM aspect ratio of the Laurentide ice sheet, that has been inferred geophysically.

The Effects of the Laurentide Ice Sheet on North American Climate during the Last Glacial Maximum

Géographie physique et Quaternaire ◽

10.7202/032684ar ◽

2008 ◽

Vol 41 (2) ◽

pp. 291-299 ◽

Cited By ~ 22

Author(s):

A. J. Broccoli ◽

S. Manabe

Keyword(s):

North America ◽

Last Glacial Maximum ◽

North American ◽

Ice Sheet ◽

Glacial Maximum ◽

Laurentide Ice Sheet ◽

Last Glacial ◽

North American Climate ◽

ABSTRACT A climate model, consisting of an atmospheric general circulation model coupled with a simple model of the oceanic mixed layer, is used to investigate the effects of the continental ice distribution of the last glacial maximum (LGM) on North American climate. This model has previously been used to simulate the LGM climate, producing temperature changes reasonably in agreement with paleoclimatic data. The LGM distribution of continental ice according to the maximum reconstruction of HUGHES et al. (1981) is used as input to the model. In response to the incorporation of the expanded continental ice of the LGM, the model produces major changes in the climate of North America. The ice sheet exerts an orographic effect on the tropospheric flow, resulting in a splitting of the midlatitude westerlies in all seasons but summer. Winter temperatures are greatly reduced over a wide region south of the Laurentide ice sheet, although summer cooling is less extensive. An area of reduced soil moisture develops in the interior of North America just south of the ice margin. At the same time, precipitation increases in a belt extending from the extreme southeastern portion of the ice sheet eastward into the North Atlantic. Some of these findings are similar to paleoclimatic inferences based on geological evidence.