Abstract The ECHAM4-T42 atmospheric general cir-culation model was applied to study the change in at-mospheric variability in the North Atlantic region over the 14.7 kyr cal BP climatic transition from Green-land Stadial 2a (GS-2a, end of Pleniglacial) to Green-land Interstadial 1e (GI-1e, start Lat...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.519.5730 http://webdocs.dow.wur.nl/internet/hwm/pdf/renssen2003_cd.pdf |
| Summary: | Abstract The ECHAM4-T42 atmospheric general cir-culation model was applied to study the change in at-mospheric variability in the North Atlantic region over the 14.7 kyr cal BP climatic transition from Green-land Stadial 2a (GS-2a, end of Pleniglacial) to Green-land Interstadial 1e (GI-1e, start Late Glacial). The following three climates are simulated: (1) present-day, (2) GS-2a and (3) GI-1e. We focus on climatic param-eters near the Earth’s surface (temperature, precipitation and sea level pressure). Results on two different tem-poral scales are analysed: seasonal and daily. The sea-sonal fields show that the main change over the 14.7 kyr BP transition occurred in winter. We calculated daily standard deviations of temperature and pressure about the seasonal means and the high-pass filtered (less than six days) variability of pressure. The largest change in atmospheric variability occurred in north-west Europe. Here, the daily temperature variability decreased by 50%, whereas storm activity also decreased substantially. These changes are related to a northward shift of the Atlantic sea-ice margin at 14.7 kyr BP, leading to a northward relocation of the Atlantic storm track. In the GS-2a experiment, a strong storm track was located over northwest Europe, where frequent de-pressions produced alternations of northerly air flow (below –30 C) and southerly air flow (close to 0 C). This strong daily atmospheric variability decreased in GI-1e because the storm track had a SW-NE orientation over the Atlantic towards Iceland. The decrease in atmospheric variability at 14.7 kyr BP probably con-tributed to landscape stabilization, for instance, through decreasing eolian transport. 1 |
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