A three-dimensional climate—ice-sheet model applied to the Last Glacial Maximum

A quasi-three-dimensional (3-D) climate model (Sellers, 1983) was used to simulate the climate of the Last Glacial Maximum (LGM) in order to provide climatic input for the modelling of the Northern Hemisphere ice sheets. The climate model is basically a coarse-gridded general circulation (GCM) with simplified dynamics, and was subject to appropriate boundary conditions for ice-sheet elevation, atmospheric CO2concentration and orbital parameters. When compared with the present-daysimulation, the simulated climate at the Last Glacial Maximum is characterized by a global annual cooling of 3.5°C and a reduction in global annualprecipitation of 7.5%, which agrees well with results from other, more complex GCMs. Also the patterns of temperature change compare fairly with mostother GCM results, except for a smaller cooling over the North Atlantic and the larger cooling predicted for the summer rather than for the winter over Eurasia.The climate model is able to simulate changes in Northern Hemisphere tropospheric circulation, yielding enhanced westerlies in the vicinity of the Laurentide and Eurasian ice sheets. However, the simulated precipitation patterns are less convincing, and show a distinct mean precipitation increase over the Laurentide ice sheet. Nevertheless, when using the mean-monthly fields of LGM minus present-day anomalies of temperature and precipitation rate to drive a three-dimensional thermomechanical ice-sheet model, it was demonstrated that within realistic bounds of the ice-flow and mass-balance parameters, veryreasonable reconstructions of the Last Glacial Maximum ice sheets could be obtained.

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A three-dimensional climate—ice-sheet model applied to the Last Glacial Maximum

Annals of Glaciology ◽

10.3189/s0260305500014245 ◽

1997 ◽

Vol 25 ◽

pp. 333-339 ◽

Cited By ~ 12

Author(s):

Philippe Huybrechts ◽

Stephen T’siobbel

Keyword(s):

Last Glacial Maximum ◽

Northern Hemisphere ◽

Climate Model ◽

Three Dimensional ◽

Ice Sheets ◽

Ice Sheet ◽

Glacial Maximum ◽

Last Glacial ◽

The Last Glacial Maximum ◽

The Last Glacial

A quasi-three-dimensional (3-D) climate model (Sellers, 1983) was used to simulate the climate of the Last Glacial Maximum (LGM) in order to provide climatic input for the modelling of the Northern Hemisphere ice sheets. The climate model is basically a coarse-gridded general circulation (GCM) with simplified dynamics, and was subject to appropriate boundary conditions for ice-sheet elevation, atmospheric CO2 concentration and orbital parameters. When compared with the present-daysimulation, the simulated climate at the Last Glacial Maximum is characterized by a global annual cooling of 3.5°C and a reduction in global annualprecipitation of 7.5%, which agrees well with results from other, more complex GCMs. Also the patterns of temperature change compare fairly with mostother GCM results, except for a smaller cooling over the North Atlantic and the larger cooling predicted for the summer rather than for the winter over Eurasia.The climate model is able to simulate changes in Northern Hemisphere tropospheric circulation, yielding enhanced westerlies in the vicinity of the Laurentide and Eurasian ice sheets. However, the simulated precipitation patterns are less convincing, and show a distinct mean precipitation increase over the Laurentide ice sheet. Nevertheless, when using the mean-monthly fields of LGM minus present-day anomalies of temperature and precipitation rate to drive a three-dimensional thermomechanical ice-sheet model, it was demonstrated that within realistic bounds of the ice-flow and mass-balance parameters, veryreasonable reconstructions of the Last Glacial Maximum ice sheets could be obtained.

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

10.5194/egusphere-egu21-6693 ◽

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&#8211;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. &#160;</p>

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Ice-sheet mass balance during the last glacial maximum

Annals of Glaciology ◽

10.3189/s026030550001394x ◽

1997 ◽

Vol 25 ◽

pp. 145-152 ◽

Cited By ~ 2

Author(s):

Gilles Ramstein ◽

Adeline Fabre ◽

Sophie Pinot ◽

Catherine Ritz ◽

Sylvie Joussaume

Keyword(s):

Last Glacial Maximum ◽

General Circulation ◽

Ice Sheets ◽

Ice Sheet ◽

General Circulation Models ◽

Glacial Maximum ◽

Last Glacial ◽

Intercomparison Project ◽

The Last Glacial Maximum ◽

The Last Glacial

In the framework of the Paleoclimate Modelling Intercomparison Project (PMIP), simulations of the Last Glacial Maximum (LGM) have- been performed. More than 10 different atmospheric general circulation models (AGCMs) have been used with the same boundary conditions: sea-surface temperatures prescribed by CLIMAP (1981), ice-sheet reconstruction provided by Peltier (1994), change in insolation, and reduced CO2 content. One of the major questions is to investigate whether the simulations of the LGM are in equilibrium with the prescribed ice-sheet reconstruction. To answer this question, we have used two different approaches. First, we analyze the results of a sel of LGM simulations performed with different versions of the Laboratoire de Meteorolo-gie Dynamique (LMD) AGCM and study the hydrologic and snow- budgets over the Laurcntide and Fennoscandian ice sheets. Second, we use the AGCM outputs to force an ice-sheet model in order to investigate its ability to maintain the ice sheets as reconstructed by CLIMAP (1981) or Peltier (1994).

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Ice-sheet mass balance during the last glacial maximum

Annals of Glaciology ◽

10.1017/s026030550001394x ◽

1997 ◽

Vol 25 ◽

pp. 145-152 ◽

Cited By ~ 4

Author(s):

Gilles Ramstein ◽

Adeline Fabre ◽

Sophie Pinot ◽

Catherine Ritz ◽

Sylvie Joussaume

Keyword(s):

Last Glacial Maximum ◽

General Circulation ◽

Ice Sheets ◽

Ice Sheet ◽

General Circulation Models ◽

Glacial Maximum ◽

Last Glacial ◽

Intercomparison Project ◽

The Last Glacial Maximum ◽

The Last Glacial

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Drainage pathways beneath ice sheets and their implications for ice sheet form and flow: the example of the British Ice Sheet during the Last Glacial Maximum

Journal of Quaternary Science ◽

10.1002/jqs.1407 ◽

2010 ◽

Vol 25 (4) ◽

pp. 483-500 ◽

Cited By ~ 11

Author(s):

Geoffrey Boulton

Keyword(s):

Last Glacial Maximum ◽

Ice Sheets ◽

Ice Sheet ◽

Glacial Maximum ◽

Last Glacial ◽

The Last Glacial Maximum ◽

The Last Glacial

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Modeling the marine extent of Northern Hemisphere ice sheets during the last glacial cycle

Annals of Glaciology ◽

10.3189/172756403781815870 ◽

2003 ◽

Vol 37 ◽

pp. 173-180 ◽

Cited By ~ 20

Author(s):

Chris Zweck ◽

Philippe Huybrechts

Keyword(s):

Northern Hemisphere ◽

Water Depth ◽

Three Dimensional ◽

Ice Sheets ◽

Ice Sheet ◽

Glacial Cycle ◽

Last Glacial ◽

History Of ◽

The Last Glacial Maximum ◽

The Last Glacial

AbstractMechanisms that determine time-dependent changes of the marine ice margin in dynamic ice-sheet models are important but poorly understood. Here we derive an empirical formulation for changes in the marine extent when modelling the Northern Hemisphere ice sheets over the last glacial cycle in a three-dimensional thermomechanically coupled ice-sheet model. We assume that the strongest control on changes in marine extent is ice calving, and that the variable most crucial to calving is water depth. The empirical marine-extent relationship is tuned so that the major marine-retreat history of the Laurentide and Eurasian ice sheets is modelled accurately in time and space. We find that this empirical treatment relating marine extent to water depth is sufficient to reproduce the observations, and discuss the implications for the physics of marine margin changes and the dynamics of the Northern Hemisphere ice sheets since the Last Glacial Maximum.

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The origin and flux of icebergs released into the Last Glacial Maximum Northern Hemisphere oceans: the impact of ice-sheet topography

Journal of Quaternary Science ◽

10.1002/jqs.628 ◽

2001 ◽

Vol 16 (6) ◽

pp. 565-573 ◽

Cited By ~ 26

Author(s):

Grant R. Bigg ◽

Martin R. Wadley

Keyword(s):

Last Glacial Maximum ◽

Northern Hemisphere ◽

Ice Sheet ◽

Glacial Maximum ◽

Last Glacial ◽

The Impact ◽

The Last Glacial Maximum ◽

Ice Sheet Topography ◽

The Last Glacial

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Impact of the North American ice-sheet orography on the Last Glacial Maximum eddies and snowfall

Geophysical Research Letters ◽

10.1029/1999gl011274 ◽

2000 ◽

Vol 27 (10) ◽

pp. 1515-1518 ◽

Cited By ~ 69

Author(s):

Masa Kageyama ◽

Paul J. Valdes

Keyword(s):

Last Glacial Maximum ◽

North American ◽

Ice Sheet ◽

Glacial Maximum ◽

Last Glacial ◽

The North ◽

The Last Glacial Maximum ◽

The Last Glacial

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Investigating the evolution of major Northern Hemisphere ice sheets during the last glacial-interglacial cycle

Climate of the Past ◽

10.5194/cp-5-329-2009 ◽

2009 ◽

Vol 5 (3) ◽

pp. 329-345 ◽

Cited By ~ 62

Author(s):

S. Bonelli ◽

S. Charbit ◽

M. Kageyama ◽

M.-N. Woillez ◽

G. Ramstein ◽

...

Keyword(s):

Northern Hemisphere ◽

Climate Model ◽

Ice Sheets ◽

Ice Sheet ◽

Co2 Concentration ◽

Atmospheric Co2 ◽

Glacial Cycle ◽

Last Glacial ◽

Atmospheric Co2 Concentration ◽

The Last Glacial

Abstract. A 2.5-dimensional climate model of intermediate complexity, CLIMBER-2, fully coupled with the GREMLINS 3-D thermo-mechanical ice sheet model is used to simulate the evolution of major Northern Hemisphere ice sheets during the last glacial-interglacial cycle and to investigate the ice sheets responses to both insolation and atmospheric CO2 concentration. This model reproduces the main phases of advance and retreat of Northern Hemisphere ice sheets during the last glacial cycle, although the amplitude of these variations is less pronounced than those based on sea level reconstructions. At the last glacial maximum, the simulated ice volume is 52.5×1015 m3 and the spatial distribution of both the American and Eurasian ice complexes is in reasonable agreement with observations, with the exception of the marine parts of these former ice sheets. A set of sensitivity studies has also been performed to assess the sensitivity of the Northern Hemisphere ice sheets to both insolation and atmospheric CO2. Our results suggest that the decrease of summer insolation is the main factor responsible for the early build up of the North American ice sheet around 120 kyr BP, in agreement with benthic foraminifera δ18O signals. In contrast, low insolation and low atmospheric CO2 concentration are both necessary to trigger a long-lasting glaciation over Eurasia.

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