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| Titel |
LGM ice sheets simulated with a complex fully coupled ice sheet - climate model |
| VerfasserIn |
F. Ziemen, C. Rodehacke, U. Mikolajewicz |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064159
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| Zusammenfassung |
| One major challenge in predicting future climate change is the validation of the
numerical models. A particular good time period for testing ice sheet – climate
interactions is the last glacial maximum (LGM). It combines large ice sheets with
good proxy data cover. We use a coarse resolution complex climate model coupled
with an ice sheet model to study the ice sheets and the climate of the last glacial
maximum and validate our setup by comparing glacial as well as pre-industrial
equilibrium experiments with reconstructions and the present state. Since the last glacial
maximum climate is largely different from the pre-industrial climate, we can test our
model under large perturbations that go beyond the linear range by running both
setups.
Our model comprises of the atmosphere-ocean-vegetation general circulation model
ECHAM5/MPIOM/LPJ interactively coupled with the ice sheet model mPISM.
mPISM is a modified version of the Parallel Ice Sheet Model from the University of
Alaska, Fairbanks. We run ECHAM5 in T31 resolution (~ 3.75°), and mPISM
on a 20 km grid covering most of the northern hemisphere. We do not use flux
correction or anomaly maps in our models. For the surface mass balance, we use a
positive degree day scheme with lapse rate correction and height desertification
effect.
We show results from steady state experiments under last glacial maximum as well as
pre-industrial boundary conditions. In both cases, we are able to maintain reasonable ice
sheet distributions. In the pre-industrial setup, the Greenland ice sheet looks realistic, and the
only major deviation is an ice sheet forming in the Rocky Mountains due to a cold bias in
ECHAM5 in this region. The last glacial maximum ice sheets largely agree with the
reconstructions except for an ice sheet that forms in eastern Siberia and extends to the
Alaskan end of the Laurentide ice sheet. The ice sheets never reach a perfectly
steady state because parts show repeated surges resembling Heinrich events. Most of
Siberia stays ice free during the multi-millennial runs. We present the mass balances
of the ice sheets and discuss deviations from observations and reconstructions. |
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