Ice-sheet mass balance at the Last Glacial Maximum from the GENESIS version 2 global climate model

S. L. Thompson, David Pollard

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

At the Last Glacial Maximum (LGM) about 21 000 years ago (21 ka BP), the overall mass balance of the Laurentide and Eurasian ice sheets should have been close to zero, since their rate of change of total ice volume was approximately zero at that time. The surface mass balance should have been zero or positive to balance any iceberg/iceshelf discharge and basal melting, but could not have been strongly negative. In principle this can be tested by global climate model (GCM) simulations with prescribed ice-sheet extents and topography. We describe results from a suite of 21 ka BP simulations using a new GCM (GENESIS version 2.0a), with sea-surface temperatures (SSTs) prescribed from CLIMAP (1981) and predicted by a mixed-layer ocean models, and with ice sheets prescribed from both the ICE-4G (Peltier, 1994) and CLIMAP (1981) reconstructions. This GCM is well suited for ice-sheet mass-balance studies because (i) the surface can be represented at a finer resolution than the atmospheric GCM, (ii) an elevation correction accounts for spectral distortions of the atmospheric GCM topography, (iii) a simple post-processing correction for the refreezing of meltwater is applied, and (iv) the model's precipitation and mass balances for present-day Greenland and Antarctica are realistic. However, for all reasonable combinations of SSTs and ice-sheet configurations, the predicted annual surface mass balances of the LGM Laurentide and Eurasian ice sheets are implausibly negative. Possible reasons for this discrepancy are discussed, including increased ice-age aerosols, higher CLIMAP-like ice-sheet profiles in the few thousand years preceding the LGM, and a surface of the southern Laurentide just before the LGM to produce fleetingly the ICE-4G profile at 21 ka BP.

Original languageEnglish (US)
Pages (from-to)250-258
Number of pages9
JournalAnnals of Glaciology
Volume25
StatePublished - 1997

Fingerprint

Last Glacial Maximum
ice sheet
global climate
mass balance
climate modeling
sea surface temperature
topography
basal melting
iceberg
meltwater
mixed layer
simulation
Pleistocene
aerosol
ice
ocean

All Science Journal Classification (ASJC) codes

  • Earth-Surface Processes

Cite this

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abstract = "At the Last Glacial Maximum (LGM) about 21 000 years ago (21 ka BP), the overall mass balance of the Laurentide and Eurasian ice sheets should have been close to zero, since their rate of change of total ice volume was approximately zero at that time. The surface mass balance should have been zero or positive to balance any iceberg/iceshelf discharge and basal melting, but could not have been strongly negative. In principle this can be tested by global climate model (GCM) simulations with prescribed ice-sheet extents and topography. We describe results from a suite of 21 ka BP simulations using a new GCM (GENESIS version 2.0a), with sea-surface temperatures (SSTs) prescribed from CLIMAP (1981) and predicted by a mixed-layer ocean models, and with ice sheets prescribed from both the ICE-4G (Peltier, 1994) and CLIMAP (1981) reconstructions. This GCM is well suited for ice-sheet mass-balance studies because (i) the surface can be represented at a finer resolution than the atmospheric GCM, (ii) an elevation correction accounts for spectral distortions of the atmospheric GCM topography, (iii) a simple post-processing correction for the refreezing of meltwater is applied, and (iv) the model's precipitation and mass balances for present-day Greenland and Antarctica are realistic. However, for all reasonable combinations of SSTs and ice-sheet configurations, the predicted annual surface mass balances of the LGM Laurentide and Eurasian ice sheets are implausibly negative. Possible reasons for this discrepancy are discussed, including increased ice-age aerosols, higher CLIMAP-like ice-sheet profiles in the few thousand years preceding the LGM, and a surface of the southern Laurentide just before the LGM to produce fleetingly the ICE-4G profile at 21 ka BP.",
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Ice-sheet mass balance at the Last Glacial Maximum from the GENESIS version 2 global climate model. / Thompson, S. L.; Pollard, David.

In: Annals of Glaciology, Vol. 25, 1997, p. 250-258.

Research output: Contribution to journalArticle

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AU - Thompson, S. L.

AU - Pollard, David

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N2 - At the Last Glacial Maximum (LGM) about 21 000 years ago (21 ka BP), the overall mass balance of the Laurentide and Eurasian ice sheets should have been close to zero, since their rate of change of total ice volume was approximately zero at that time. The surface mass balance should have been zero or positive to balance any iceberg/iceshelf discharge and basal melting, but could not have been strongly negative. In principle this can be tested by global climate model (GCM) simulations with prescribed ice-sheet extents and topography. We describe results from a suite of 21 ka BP simulations using a new GCM (GENESIS version 2.0a), with sea-surface temperatures (SSTs) prescribed from CLIMAP (1981) and predicted by a mixed-layer ocean models, and with ice sheets prescribed from both the ICE-4G (Peltier, 1994) and CLIMAP (1981) reconstructions. This GCM is well suited for ice-sheet mass-balance studies because (i) the surface can be represented at a finer resolution than the atmospheric GCM, (ii) an elevation correction accounts for spectral distortions of the atmospheric GCM topography, (iii) a simple post-processing correction for the refreezing of meltwater is applied, and (iv) the model's precipitation and mass balances for present-day Greenland and Antarctica are realistic. However, for all reasonable combinations of SSTs and ice-sheet configurations, the predicted annual surface mass balances of the LGM Laurentide and Eurasian ice sheets are implausibly negative. Possible reasons for this discrepancy are discussed, including increased ice-age aerosols, higher CLIMAP-like ice-sheet profiles in the few thousand years preceding the LGM, and a surface of the southern Laurentide just before the LGM to produce fleetingly the ICE-4G profile at 21 ka BP.

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