Investigating the sensitivity of the Atmospheric General Circulation Model ECHAM 3 to paleoclimatic boundary conditions |
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| Authors: | S Lorenz B Grieger Ph Helbig K Herterich |
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| Institution: | 1. Universit?t Bremen, Fachbereich 5, Geowissenschaften, Postfach 33 04 40, D-28334, Bremen, Germany
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| Abstract: | We present atmospheric simulations of three different time slices of the late Quaternary using the ECHAM 3 general circulation
model in T42 resolution. In this work we describe the results of model runs for the time slices 6000 years BP (last climate
optimum), 21 000 BP (last glacial maximum) and 115 000 years BP (glacial inception). Although the solar insolation is known
for all time slices, a complete data set of the other boundary conditions which are necessary for running the atmospheric
model exists only for the last glacial maximum in the form of the CLIMAP reconstruction. For the other two time slices, which
are interglacial states like the modern climate, sea surface temperatures, land albedo and ice sheet topography are kept at
modern values and only the solar insolation is changed appropriately. The response of the model to solar insolation changes
is quite reasonable. The modelled anomalies are small and roughly opposite in sign for 6000 BP and 115 000 BP, respectively.
In the case of last glacial maximum, the glacial ice sheet topography and ice albedo produce a much larger climate anomaly
in the model. However, to enable a real test of model performance under glacial boundary conditions, the CLIMAP sea surface
temperatures, which are now known to be partly inaccurate, should be replaced by an updated “state-of-the-art” reconstruction. |
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| Keywords: | Atmospheric response General circulation models Glacial maximum Milankovitch Theory Paleoclimate Climate optimum Glacial inception |
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