Simulation of the Greenland Ice Sheet over two glacial–interglacial cycles: investigating a sub-ice-shelf melt parameterization and relative sea level forcing in an ice-sheet–ice-shelf model
Observational evidence, including offshore moraines and sediment cores, confirm that at the Last Glacial Maximum (LGM) the Greenland ice sheet (GrIS) expanded to a significantly larger spatial extent than seen at present, grounding into Baffin Bay and out onto the continental shelf break. Given...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-05-01
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| Series: | Climate of the Past |
| Online Access: | https://www.clim-past.net/14/619/2018/cp-14-619-2018.pdf |
| Summary: | Observational evidence, including offshore moraines and sediment cores,
confirm that at the Last Glacial Maximum (LGM) the Greenland ice sheet (GrIS)
expanded to a significantly larger spatial extent than seen at present,
grounding into Baffin Bay and out onto the continental shelf break. Given
this larger spatial extent and its close proximity to the neighbouring
Laurentide Ice Sheet (LIS) and Innuitian Ice Sheet (IIS), it is likely these
ice sheets will have had a strong non-local influence on the spatial and
temporal behaviour of the GrIS. Most previous paleo ice-sheet modelling
simulations recreated an ice sheet that either did not extend out onto the
continental shelf or utilized a simplified marine ice parameterization which
did not fully include the effect of ice shelves or neglected the sensitivity
of the GrIS to this non-local bedrock signal from the surrounding ice sheets.
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In this paper, we investigated the evolution of the GrIS over the two most
recent glacial–interglacial cycles (240 ka BP to the present day) using the
ice-sheet–ice-shelf model IMAU-ICE. We investigated the solid earth
influence of the LIS and IIS via an offline relative sea level (RSL) forcing
generated by a glacial isostatic adjustment (GIA) model. The RSL forcing governed the spatial and temporal pattern of sub-ice-shelf melting via changes in the water depth below the ice shelves.
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In the ensemble of simulations, at the glacial maximums, the GrIS coalesced
with the IIS to the north and expanded to the continental shelf break to the
southwest but remained too restricted to the northeast. In terms of the
global mean sea level contribution, at the Last Interglacial (LIG) and LGM
the ice sheet added 1.46 and −2.59 m, respectively. This LGM contribution
by the GrIS is considerably higher (∼ 1.26 m) than most previous
studies whereas the contribution to the LIG highstand is lower
(∼ 0.7 m). The spatial and temporal behaviour of the northern margin
was highly variable in all simulations, controlled by the sub-ice-shelf
melting which was dictated by the RSL forcing and the glacial history of the
IIS and LIS. In contrast, the southwestern part of the ice sheet was
insensitive to these forcings, with a uniform response in all simulations
controlled by the surface air temperature, derived from ice cores. |
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| ISSN: | 1814-9324 1814-9332 |