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| Titel |
Modelling large-scale ice-sheet-climate interactions at the last glacial inception |
| VerfasserIn |
O. J. H. Browne, J. M. Gregory, A. J. Payne, J. K. Ridley, I. C. Rutt |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250033955
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| Zusammenfassung |
| In order to investigate the interactions between coevolving climate and ice-sheets on
multimillenial timescales, a low-resolution atmosphere-ocean general circulation model
(AOGCM) has been coupled to a three-dimensional thermomechanical ice-sheet model. We
use the FAMOUS AOGCM, which is almost identical in formulation to the widely used
HadCM3 AOGCM, but on account of its lower resolution (7.5- longitude à 5- latitude in the
atmosphere, 3.75-Ã 2.5- in the ocean) it runs about ten times faster. We use the community
ice-sheet model Glimmer at 20Â km resolution, with the shallow ice approximation and an
annual degree-day scheme for surface mass balance. With the FAMOUS-Glimmer coupled
model, we have simulated the growth of the Laurentide and Fennoscandian ice sheets at the
last glacial inception, under constant orbital forcing and atmospheric composition for
116Â ka BP. Ice grows in both regions, totalling 5.8Â m of sea-level equivalent in
10Â ka, slower than proxy records suggest. Positive climate feedbacks reinforce this
growth at local scales (order hundreds of kilometres), where changes are an order of
magnitude larger than on the global average. The albedo feedback (higher local albedo
means a cooler climate) is important in the initial expansion of the ice-sheet area.
The topography feedback (higher surface means a cooler climate) affects ice-sheet
thickness and is not noticeable for the first 1Â ka. These two feedbacks reinforce
each other. Without them, the ice volume is ~90% less after 10Â ka. In Laurentia,
ice expands initially on the Canadian Arctic islands. The glaciation of the islands
eventually cools the nearby mainland climate sufficiently to produce a positive
mass balance there. Adjacent to the ice-sheets, cloud feedbacks tend to reduce the
surface mass balance and restrain ice growth; this is an example of a local feedback
whose simulation requires a model that includes detailed atmospheric physics. |
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