Growth rate of the Laurentide Ice Sheet and sea Level Lowering (with Emphasis on the 115,000 BP Sea Level Low)

1976 ◽  
Vol 6 (2) ◽  
pp. 167-183 ◽  
Author(s):  
J.T. Andrews ◽  
M.A.W. Mahaffy
Keyword(s):  
Sea Level ◽  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Baffin Island ◽  
Optimum Conditions ◽  
Ice Flow ◽  
Rapid Fall ◽  
Level Lowering

A physically plausible three-dimensional numerical ice flow model is used to examine the rate at which the Laurentide Ice Sheet could spread and thicken using as input likely values for the rate of fall of snowline and the amount of net mass balance over the growing ice sheet. This provides then both a test of the hypothesis of “instantaneous glacierization” and of the suggested rapid fall of world sea level to between −20 and −70 m below present at 115,000 BP. Two experiments are described: The first terminated after 10,050 years of model run with ice sheets centered over Labrador-Ungava and Baffin Island with a total volume of 3.0 × 106 km3 of ice, whereas the second was completed after 10,000 years and resulted in a significantly larger ice sheet (still with two main centers) with a volume of 7.78 × 106 km3 of ice. This latter figure is equivalent to the mass required to lower world sea level by 19.4 m. Our results indicate that large ice sheets can develop in about 10,000 years under optimum conditions.

scholarly journals Late Pleistocene and Holocene glaciation and deglaciation of Melville Peninsula, Northern Laurentide Ice Sheet

2004 ◽  
Vol 55 (2) ◽  
pp. 159-170 ◽  
Author(s):  
Lynda A. Dredge
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
North Coast ◽  
Baffin Island ◽  
Ice Flow ◽  
Ice Caps ◽  
The North ◽  
Northern Areas ◽  
Controlled Flow

Abstract Melville Peninsula lies within the Foxe/Baffin Sector of the Laurentide Ice Sheet. Pre-Foxe/Pre-Wisconsin ice may have covered the entire peninsula. Preserved regolith in uplands indicates a subsequent weathering interval. Striations and till types indicate that, during the last (Foxe) glaciation, a local ice sheet (Melville Ice) initially developed on plateaus, but was later subsumed by the regional Foxe ice sheet. Ice from the central Foxe dome flowed across northern areas and Rae Isthmus, while ice from a subsidiary divide controlled flow on southern uplands. Ice remained cold-based and non-erosive on some plateaus, but changed from cold- to warm-based under other parts of the subsidiary ice divide, and was warm-based elsewhere. Ice streaming, generating carbonate till plumes, was prevalent during deglaciation. A late, quartzite-bearing southwestward ice flow from Baffin Island crossed onto the north coast. A marine incursion began in Committee Bay about 14 ka and advanced southwards to Wales Island by 8.6 ka. The marine-based ice centre in Foxe Basin broke up about 6.9 ka. Northern Melville Peninsula and Rae Isthmus were deglaciated rapidly, but remnant ice caps remained active and advanced into some areas. The ice caps began to retreat from coastal areas ~6.4 to 6.1 ka, by which time sea level had fallen from 150-180 m to 100 m.

scholarly journals Objective Reconstructions of the Late Wisconsinan Laurentide Ice Sheet and the Significance of Deformable Beds

2007 ◽  
Vol 39 (3) ◽  
pp. 229-238 ◽  
Author(s):  
D. A. Fisher ◽  
N. Reeh ◽  
K. Langley
Keyword(s):  
Yield Stress ◽  
Flow Direction ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Hudson Bay ◽  
Ice Streams ◽  
Ice Flow ◽  
Surface Slopes ◽  
Late Wisconsinan

ABSTRACT A three dimensional steady state plastic ice model; the present surface topography (on a 50 km grid); a recent concensus of the Late Wisconsinan maximum margin (PREST, 1984); and a simple map of ice yield stress are used to model the Laurentide Ice Sheet. A multi-domed, asymmetric reconstruction is computed without prior assumptions about flow lines. The effects of possible deforming beds are modelled by using the very low yield stress values suggested by MATHEWS (1974). Because of low yield stress (deforming beds) the model generates thin ice on the Prairies, Great Lakes area and, in one case, over Hudson Bay. Introduction of low yield stress (deformabie) regions also produces low surface slopes and abrupt ice flow direction changes. In certain circumstances large ice streams are generated along the boundaries between normal yield stress (non-deformable beds) and low yield stress ice (deformabie beds). Computer models are discussed in reference to the geologically-based reconstructions of SHILTS (1980) and DYKE ef al. (1982).

scholarly journals Glacial and Sea Level History of Lowther and Griffith Islands, Northwest Territories: A Hint of Tectonics

2007 ◽  
Vol 47 (2) ◽  
pp. 133-145 ◽  
Author(s):  
Arthur S. Dyke
Keyword(s):  
Northwest Territories ◽  
Sea Level ◽  
Ice Sheet ◽  
Canadian Arctic ◽  
Laurentide Ice Sheet ◽  
Structural Elements ◽  
Ice Flow ◽  
Ice Load ◽  
Last Glaciation ◽  
History Of

ABSTRACT Lowther and Griffith islands, in the centre of Parry Channel, were overrun by the Laurentide Ice Sheet early in the last glaciation. Northeastward Laurentide ice flow persisted across at least Lowther Island until early Holocene déglaciation. Well constrained postglacial emergence curves for the islands confirm a southward dip of raised shorelines, contrary to the dip expected from the ice load configuration. This and previously reported incongruities may indicate regionally extensive tectonic complications of postglacial rebound aligned with major structural elements in the central Canadian Arctic Islands.

scholarly journals The Antarctic Ice Sheet response to glacial millennial scale variability

2018 ◽  
Author(s):  
Javier Blasco ◽  
Ilaria Tabone ◽  
Jorge Alvarez-Solas ◽  
Alexander Robinson ◽  
Marisa Montoya
Keyword(s):  
Sea Level ◽  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Climate Impacts ◽  
Strong Impact ◽  
Appreciable Effect ◽  
Antarctic Ice Sheet ◽  
The Antarctic ◽  
Millennial Scale

Abstract. The Antarctic Ice Sheet (AIS) is the largest ice sheet on Earth and hence a major potential contributor to future global sea-level rise. A wealth of studies suggest that increasing oceanic temperatures could cause a collapse of its marine-based western sector, the West Antarctic Ice Sheet, through the mechanism of marine ice-sheet instability, leading to a sea-level increase of 3–5 m. Thus, it is crucial to constrain the sensitivity of the AIS to rapid climate changes. The Last Glacial Period is an ideal benchmark period for this purpose as it was punctuated by abrupt Dansgaard-Oeschger events at millennial timescales. Because their centre of action was in the North Atlantic, where their climate impacts were largest, modelling studies have mainly focused on the millennial-scale evolution of Northern Hemisphere (NH) paleo ice sheets. Sea-level reconstructions attribute the origin of millennial-scale sea-level variations mainly to NH paleo ice sheets, with a minor but not negligible role to the AIS. Here we investigate the AIS response to millennial-scale climate variability for the first time. To this end we use a three-dimensional, thermomechanical hybrid, ice-sheet-shelf model. Different oceanic sensitivities are tested and the sea-level equivalent (SLE) contributions computed. We find that whereas atmospheric variability has no appreciable effect on the AIS, changes in submarine melting rates can have a strong impact on it. We show that in contrast to the widespread assumption that the AIS is a slow reactive and static ice sheet that responds at orbital timescales only, it can lead to ice discharges of almost 15 m of SLE involving substantial grounding line migrations at millennial timescales.

scholarly journals Surficial geology, northeastern Cameron Hills, Northwest Territories, NTS 85-C/3, 4, 5, and 6

2021 ◽  
Author(s):  
I R Smith ◽  
R C Paulen ◽  
G W Hagedorn
Keyword(s):  
Northwest Territories ◽  
Sea Level ◽  
Ice Sheet ◽  
Alluvial Fan ◽  
Laurentide Ice Sheet ◽  
Ice Flow ◽  
Boreal Plains ◽  
Surficial Geology ◽  
Sediment Cover

The northeastern Cameron Hills comprise a Cretaceous bedrock upland, rising >550 m above the regional boreal plains. It was inundated by the Laurentide Ice Sheet and includes much of a prominent 60 by 20 km southwest-oriented mega-scale glacial lineation field, formed in thick till. Subsequent ice flow on northeast Cameron Hills occurred north to south, and a series of lobate and ice-thrust moraines suggest glacial surging. Rotational bedrock slumps cover the eastern and northern flanks of Cameron Hills, and extensive alluvial fan deposits draining from these slopes blanket the surrounding topography. The Cameron River formed as a glacial spillway, draining southwest across the upland before turning north and draining into Tathlina Lake. An expansive raised delta and glaciolacustrine sediment cover extending up to ~295 m above sea level, south of Tathlina Lake, records impoundment of an ice-marginal lake between the northeastward-retreating Laurentide Ice Sheet and Cameron Hills.

The Laurentide ice sheet through the last glacial cycle: the topology of drift lineations as a key to the dynamic behaviour of former ice sheets

1990 ◽  
Vol 81 (4) ◽  
pp. 327-347 ◽  
Author(s):  
G. S. Boulton ◽  
C. D. Clark
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Aerial Photographs ◽  
Laurentide Ice Sheet ◽  
Glacial Cycle ◽  
Sheet Flow ◽  
Integrative Framework

ABSTRACTStudy of satellite images from most of the area of the Canadian mainland once covered by the Laurentide ice sheet reveals a complex pattern of superimposed drift lineations. They are believed to have formed subglacially and parallel to ice flow. Aerial photographs reveal patterns of superimposition which permit the sequence of lineation patterns to be identified. The sequential lineation patterns are interpreted as evidence of shifting patterns of flow in an evolving ice sheet. Flow stages are recognised which reflect roughly synchronous integrated patterns of ice sheet flow. Comparison with stratigraphic sections in the Hudson Bay Lowlands suggests that all the principal stages may have formed during the last, Wisconsinan, glacial cycle. Analogy between Flow stage lineation patterns and the form and flow patterns of modern ice sheets permits reconstruction of patterns of ice divides and centres of mass which moved by 1000–2000 km during the glacial period. There is evidence that during the early Wisconsinan, ice sheet formation in Keewatin may have been independent of that in Labrador–Quebec, and that these two ice masses joined to form a major early Wisconsinan ice sheet. Subsequently the western dome decayed whilst the eastern dome remained relatively stable. A western dome then re-formed, and fused with the eastern dome to form the late Wisconsinan ice sheet before final decay.Because of strong coupling between three-dimensional ice sheet geometry and atmospheric circulation, it is suggested that the major changes of geometry must have been associated with large scale atmospheric circulation changes.Lineation patterns suggest very little erosional/depositional activity in ice divide regions, and can be used to reconstruct large scale patterns of erosion/deposition.The sequence of flow stages through time provides an integrative framework allowing sparse stratigraphic data to be used most efficiently in reconstructing ice sheet history in time and space.

Deglaciation of the Greenland and Laurentide ice sheets interrupted by glacier advance during abrupt coolings

2020 ◽  
Author(s):  
Nicolas Young ◽  
Jason Briner ◽  
Gifford Miller ◽  
Alia Lesnek ◽  
Sarah Crump ◽  
...  
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Holocene ◽  
Laurentide Ice Sheet ◽  
Baffin Island ◽  
Alpine Glacier ◽  
Baffin Bay ◽  
Warming World ◽  
Exposure Ages

<p>The early Holocene (11.7 ka to 8.2 ka) represents the most recent period when the Laurentide and Greenland ice sheets underwent large-scale recession. Moreover, this ice-sheet recession occurred under the backdrop of regional temperatures that were similar to or warmer than today, and comparable to those projected for the upcoming centuries. Reconstructing Laurentide and Greenland ice sheet behavior during the early Holocene, and elucidating the mechanisms dictating this behavior may serve as a partial analog for future Greenland ice-sheet change in a warming world. Here, we use 123 new <sup>10</sup>Be surface exposure ages from two sites on Baffin Island and southwestern Greenland that constrain the behavior of the Laurentide and Greenland ice sheets, and an independent alpine glacier during the early Holocene. On Baffin Island, sixty-one <sup>10</sup>Be ages reveal that advances and/or stillstands of the Laurentide Ice Sheet and an alpine glacier occurred in unison around 11.8 ka, 10.3 ka, and 9.2 ka. Sixty-two <sup>10</sup>Be ages from southwestern Greenland indicate that the GrIS margin experienced re-advances or stillstands around 11.6 ka, 10.4 ka, 9.1 ka, 8.1 ka, and 7.3 ka. Our results reveal that alpine glaciers and the Laurentide and Greenland ice sheets responded in unison to abrupt early Holocene climate perturbations in the Baffin Bay region. We suggest that during the warming climate of the early Holocene, freshening of the North Atlantic Ocean induced by a melting Laurentide Ice Sheet resulted in regional abrupt cooling and brief periods of ice-sheet stabilization superimposed on net glacier recession. These observations point to a negative feedback mechanism inherent to melting ice sheets in the Baffin Bay region that slows ice-sheet recession during intervals of otherwise rapid deglaciation.</p>

scholarly journals The Speed of Glacier Ization of Canada During the Wisconsin Ice Age

1976 ◽  
Vol 16 (74) ◽  
pp. 300-301
Author(s):  
M.W. Mahaffy ◽  
J.T. Andrews
Keyword(s):  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Time Dependent ◽  
Ice Age ◽  
Water Volume ◽  
Baffin Island ◽  
Areal Extent ◽  
Equilibrium Line Altitude ◽  
High Plateau

AbstractA three-dimensional, time-dependent numerical model of ice sheets, developed by Mahaffy (unpublished), has been applied to the general problem of the speed of ice-sheet inception and development over Canada during the last major glaciation. Ice sheet development is assumed to begin due to a lowering of the equilibrium-line altitude with a resulting increase in the accumulation over Baffin Island and Laborador in Canada. This leads to the development of large snow fields over the high plateau areas of this region. Preliminary results are given for the areal extent and the water volume of the ice sheets possible after a period of 10000 years from the initiation of glaciation.

scholarly journals The Antarctic Ice Sheet response to glacial millennial-scale variability

2019 ◽  
Vol 15 (1) ◽  
pp. 121-133 ◽  
Author(s):  
Javier Blasco ◽  
Ilaria Tabone ◽  
Jorge Alvarez-Solas ◽  
Alexander Robinson ◽  
Marisa Montoya
Keyword(s):  
Sea Level ◽  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Climate Impacts ◽  
Strong Impact ◽  
Appreciable Effect ◽  
Antarctic Ice Sheet ◽  
The Antarctic ◽  
Millennial Scale

Abstract. The Antarctic Ice Sheet (AIS) is the largest ice sheet on Earth and hence a major potential contributor to future global sea-level rise. A wealth of studies suggest that increasing oceanic temperatures could cause a collapse of its marine-based western sector, the West Antarctic Ice Sheet, through the mechanism of marine ice-sheet instability, leading to a sea-level increase of 3–5 m. Thus, it is crucial to constrain the sensitivity of the AIS to rapid climate changes. The last glacial period is an ideal benchmark period for this purpose as it was punctuated by abrupt Dansgaard–Oeschger events at millennial timescales. Because their center of action was in the North Atlantic, where their climate impacts were largest, modeling studies have mainly focused on the millennial-scale evolution of Northern Hemisphere (NH) paleo ice sheets. Sea-level reconstructions attribute the origin of millennial-scale sea-level variations mainly to NH paleo ice sheets, with a minor but not negligible role of the AIS. Here we investigate the AIS response to millennial-scale climate variability for the first time. To this end we use a three-dimensional, thermomechanical hybrid, ice sheet–shelf model. Different oceanic sensitivities are tested and the sea-level equivalent (SLE) contributions computed. We find that whereas atmospheric variability has no appreciable effect on the AIS, changes in submarine melting rates can have a strong impact on it. We show that in contrast to the widespread assumption that the AIS is a slow reactive and static ice sheet that responds at orbital timescales only, it can lead to ice discharges of around 6 m SLE, involving substantial grounding line migrations at millennial timescales.

scholarly journals The Speed of Glacier Ization of Canada During the Wisconsin Ice Age

1976 ◽  
Vol 16 (74) ◽  
pp. 300-301
Author(s):  
M.W. Mahaffy ◽  
J.T. Andrews
Keyword(s):  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Time Dependent ◽  
Ice Age ◽  
Water Volume ◽  
Baffin Island ◽  
Areal Extent ◽  
Equilibrium Line Altitude ◽  
High Plateau

Abstract A three-dimensional, time-dependent numerical model of ice sheets, developed by Mahaffy (unpublished), has been applied to the general problem of the speed of ice-sheet inception and development over Canada during the last major glaciation. Ice sheet development is assumed to begin due to a lowering of the equilibrium-line altitude with a resulting increase in the accumulation over Baffin Island and Laborador in Canada. This leads to the development of large snow fields over the high plateau areas of this region. Preliminary results are given for the areal extent and the water volume of the ice sheets possible after a period of 10000 years from the initiation of glaciation.

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