scholarly journals Deglaciation of the Laurentide Ice Sheet from the Last Glacial Maximum

2017 ◽  
Vol 43 (2) ◽  
pp. 377 ◽  
Author(s):  
Ch.R. Stokes
Keyword(s):  
Sea Level ◽  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Laurentide Ice Sheet ◽  
Boreal Summer ◽  
Last Deglaciation ◽  
Ice Streams ◽  
Surface Mass ◽  
Last Glacial

The last deglaciation of the Laurentide Ice Sheet (LIS) was associated with major reorganisations in the ocean-climate system and its retreat also represents a valuable analogue for understanding the rates and mechanisms of ice sheet collapse. This paper reviews the characteristics of the LIS at its Last Glacial Maximum (LGM) and its subsequent deglaciation, with particular emphasis on the pattern and timing of ice margin recession and the driving mechanisms of retreat. The LIS initiated over the eastern Canadian Arctic ~116-110 ka (MIS 5d), but its growth towards the LGM was highly non-linear and punctuated by several episodes of expansion (~65 ka: MIS 4) and retreat (~50-40 ka: MIS 3). It attained its maximum position around 26-25 ka (MIS 2) and existed for several thousand years as an extensive ice sheet with major domes over Keewatin, Foxe Basin and northern Quebec/Labrador. It extended to the edge of the continental shelf at its marine margins and likely stored a sea-level equivalent of around 50 m and with a maximum ice surface ~3,000 m above present sea-level. Retreat from its maximum was triggered by an increase in boreal summer insolation, but areal shrinkage was initially slow and the net surface mass balance was positive, indicating that ice streams likely played an important role in reducing the ice sheet volume, if not its extent, via calving at marine margins. Between ~16 and ~13 ka, the ice sheet margin retreated more rapidly, particularly in the south and west, whereas the north and east underwent only minimal recession. The overall rate of retreat decreased during the Younger Dryas (YD), when several localised readvances occurred. Following the YD, the ice sheet retreated two to five times faster than previously, and this was primarily driven by enhanced surface melting while ice streams reduced in effectiveness. Final deglaciation of the Keewatin and Foxe Domes, left a remnant Labrador Dome that disappeared ~6.7 ka.

Exploring the complex uncertainties in coupled climate-ice simulations of the Last Glacial Maximum

2021 ◽  
Author(s):  
Lauren Gregoire ◽  
Niall Gandy ◽  
Lachlan Astfalck ◽  
Robin Smith ◽  
Ruza Ivanovic ◽  
...  
Keyword(s):  
Mass Balance ◽  
Last Glacial Maximum ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Sea Surface ◽  
Surface Mass ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Simulating the co-evolution of climate and ice-sheets during the Quaternary is key to understanding some of the major abrupt changes in climate, ice and sea level. Indeed, events such as the Meltwater pulse 1a rapid sea level rise and Heinrich, Dansgaard–Oeschger and the 8.2 kyr climatic events all involve the interplay between ice sheets, the atmosphere and the ocean. Unfortunately, it is challenging to simulate the coupled Climate-Ice sheet system because small biases, errors or uncertainties in parts of the models are strongly amplified by the powerful interactions between the atmosphere and ice (e.g. ice-albedo and height-mass balance feedbacks). This leads to inaccurate or even unrealistic simulations of ice sheet extent and surface climate. To overcome this issue we need some methods to effectively explore the uncertainty in the complex Climate-Ice sheet system and reduce model biases. Here we present our approach to produce ensemble of coupled Climate-Ice sheet simulations of the Last Glacial maximum that explore the uncertainties in climate and ice sheet processes.</p><p>We use the FAMOUS-ICE earth system model, which comprises a coarse-resolution and fast general circulation model coupled to the Glimmer-CISM ice sheet model. We prescribe sea surface temperature and sea ice concentrations in order to control and reduce biases in polar climate, which strongly affect the surface mass balance and simulated extent of the northern hemisphere ice sheets. We develop and apply a method to reconstruct and sample a range of realistic sea surface temperature and sea-ice concentration spatio-temporal field. These are created by merging information from PMIP3/4 climate simulations and proxy-data for sea surface temperatures at the Last Glacial Maximum with Bayes linear analysis. We then use these to generate ensembles of FAMOUS-ice simulations of the Last Glacial maximum following the PMIP4 protocol, with the Greenland and North American ice sheets interactively simulated. In addition to exploring a range of sea surface conditions, we also vary key parameters that control the surface mass balance and flow of ice sheets. We thus produce ensembles of simulations that will later be used to emulate ice sheet surface mass balance.  </p>

Timing of advance and basal condition of the Laurentide Ice Sheet during the last glacial maximum in the Richardson Mountains, NWT

2013 ◽  
Vol 80 (2) ◽  
pp. 274-283 ◽  
Author(s):  
Denis Lacelle ◽  
Bernard Lauriol ◽  
Grant Zazula ◽  
Bassam Ghaleb ◽  
Nicholas Utting ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Laurentide Ice Sheet ◽  
Last Glacial ◽  
Glacial Chronology ◽  
Northwestern Margin ◽  
Richardson Mountains ◽  
The Last Glacial ◽  
Peel Plateau

This study presents new ages for the northwest section of the Laurentide Ice Sheet (LIS) glacial chronology from material recovered from two retrogressive thaw slumps exposed in the Richardson Mountains, Northwest Territories, Canada. One study site, located at the maximum glacial limit of the LIS in the Richardson Mountains, had calcite concretions recovered from aufeis buried by glacial till that were dated by U/Th disequilibrium to 18,500 cal yr BP. The second site, located on the Peel Plateau to the east yielded a fossil horse (Equus) mandible that was radiocarbon dated to ca. 19,700 cal yr BP. These ages indicate that the Peel Plateau on the eastern flanks of the Richardson Mountains was glaciated only after 18,500 cal yr BP, which is later than previous models for the global last glacial maximum (LGM). As the LIS retreated the Peel Plateau around 15,000 cal yr BP, following the age of the Tutsieta phase, we conclude that the presence of the northwestern margin of the LIS at its maximum limit was a very short event in the western Canadian Arctic.

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

2000 ◽  
Vol 30 ◽  
pp. 163-176 ◽  
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 ◽  
The Last Glacial Maximum ◽  
The Last Glacial

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.

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

2000 ◽  
Vol 46 (153) ◽  
pp. 311-325 ◽  
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 ◽  
The Last Glacial Maximum ◽  
The Last Glacial

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.

scholarly journals The U-Pb detrital zircon signature of West Antarctic ice stream tills in the Ross embayment, with implications for Last Glacial Maximum ice flow reconstructions

2014 ◽  
Vol 26 (6) ◽  
pp. 687-697 ◽  
Author(s):  
Kathy J. Licht ◽  
Andrea J. Hennessy ◽  
Bethany M. Welke
Keyword(s):  
Last Glacial Maximum ◽  
Detrital Zircon ◽  
Ross Sea ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Ice Streams ◽  
The West ◽  
Zircon Age ◽  
Last Glacial ◽  
West Antarctic

AbstractGlacial till samples collected from beneath the Bindschadler and Kamb ice streams have a distinct U-Pb detrital zircon signature that allows them to be identified in Ross Sea tills. These two sites contain a population of Cretaceous grains 100–110 Ma that have not been found in East Antarctic tills. Additionally, Bindschadler and Kamb ice streams have an abundance of Ordovician grains (450–475 Ma) and a cluster of ages 330–370 Ma, which are much less common in the remainder of the sample set. These tracers of a West Antarctic provenance are also found east of 180° longitude in eastern Ross Sea tills deposited during the last glacial maximum (LGM). Whillans Ice Stream (WIS), considered part of the West Antarctic Ice Sheet but partially originating in East Antarctica, lacks these distinctive signatures. Its U-Pb zircon age population is dominated by grains 500–550 Ma indicating derivation from Granite Harbour Intrusive rocks common along the Transantarctic Mountains, making it indistinguishable from East Antarctic tills. The U-Pb zircon age distribution found in WIS till is most similar to tills from the west-central Ross Sea. These data provide new specific targets for ice sheet models and can be applied to pre-LGM deposits in the Ross Sea.

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

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 ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals Geodetic measurements reveal similarities between post–Last Glacial Maximum and present-day mass loss from the Greenland ice sheet

2016 ◽  
Vol 2 (9) ◽  
pp. e1600931 ◽  
Author(s):  
Shfaqat A. Khan ◽  
Ingo Sasgen ◽  
Michael Bevis ◽  
Tonie van Dam ◽  
Jonathan L. Bamber ◽  
...  
Keyword(s):  
Mass Loss ◽  
Sea Level ◽  
Last Glacial Maximum ◽  
Hot Spot ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Glacial Maximum ◽  
Satellite Mission ◽  
Last Glacial ◽  
Modern Mass

Accurate quantification of the millennial-scale mass balance of the Greenland ice sheet (GrIS) and its contribution to global sea-level rise remain challenging because of sparse in situ observations in key regions. Glacial isostatic adjustment (GIA) is the ongoing response of the solid Earth to ice and ocean load changes occurring since the Last Glacial Maximum (LGM; ~21 thousand years ago) and may be used to constrain the GrIS deglaciation history. We use data from the Greenland Global Positioning System network to directly measure GIA and estimate basin-wide mass changes since the LGM. Unpredicted, large GIA uplift rates of +12 mm/year are found in southeast Greenland. These rates are due to low upper mantle viscosity in the region, from when Greenland passed over the Iceland hot spot about 40 million years ago. This region of concentrated soft rheology has a profound influence on reconstructing the deglaciation history of Greenland. We reevaluate the evolution of the GrIS since LGM and obtain a loss of 1.5-m sea-level equivalent from the northwest and southeast. These same sectors are dominating modern mass loss. We suggest that the present destabilization of these marine-based sectors may increase sea level for centuries to come. Our new deglaciation history and GIA uplift estimates suggest that studies that use the Gravity Recovery and Climate Experiment satellite mission to infer present-day changes in the GrIS may have erroneously corrected for GIA and underestimated the mass loss by about 20 gigatons/year.

Excess ice loads in the Indian Ocean sector of East Antarctica during the last glacial period

Geology ◽  
2021 ◽  
Author(s):  
Takeshige Ishiwa ◽  
Jun’ichi Okuno ◽  
Yusuke Suganuma
Keyword(s):  
Sea Level ◽  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Antarctic Ice Sheet ◽  
Last Glacial ◽  
Indian Ocean Sector ◽  
Ocean Sector ◽  
The Antarctic ◽  
The Last Glacial

An accurate reconstruction of the Antarctic Ice Sheet is essential in order to develop an understanding of ice-sheet responses to global climate changes. However, the erosive nature of ice-sheet expansion and the difficulty of accessing much of Antarctica make it challenging to obtain field-based evidence of ice-sheet and sea-level changes before the Last Glacial Maximum. Limited sedimentary records from Lützow-Holm and Prydz Bays in East Antarctica demonstrate that the sea level during Marine Isotope Stage 3 was close to the present level despite the global sea-level drop lower than –40 m. We demonstrate glacial isostatic adjustment modeling with refined Antarctic Ice Sheet loading histories. Our experiments reveal that the Indian Ocean sector of the Antarctic Ice Sheet would have been required to experience excess ice loads before the Last Glacial Maximum in order to explain the observed sea-level highstands during Marine Isotope Stage 3. As such, we suggest that the Antarctic Ice Sheet partly reached its maximum thickness before the global Last Glacial Maximum.

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