An evaluation of the simulated water balance of Eurasia and northern Africa at 6000?y BP using lake status data |
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Authors: | G Yu S P Harrison |
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Institution: | (1) Dynamic Palaeoclimatology, Lund University, Box 117, S-221 00 Lund, Sweden, SE |
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Abstract: | Changes in the water balance of Eurasia and northern Africa in response to insolation forcing at 6000 y BP simulated by five
atmospheric general circulation models have been compared with observations of changes in lake status. All of the simulations
show enhancement of the Asian summer monsoon and of the high pressure cells over the Pacific and Central Asia and the Middle
East, causing wetter conditions in northern India and southern China and drier conditions along the Chinese coast and west
of the monsoon core. All of the models show enhancement of the African monsoon, causing wetter conditions in the zone between
ca 10–20 °N. Four of the models show conditions wetter than present in southern Europe and drier than present in northern
Europe. Three of the models show conditions similar to present in the mid-latitude continental interior, while the remaining
models show conditions somewhat drier than present. The extent and location of each of the simulated changes varies between
the models, as does the mechanism producing these changes. The lake data confirm some features of the simulations, but indicate
discrepancies between observed and simulated climates. For example, the data show: (1) conditions wetter than present in central
Asia, from India to northern China and Mongolia, indicating that the simulated Asian monsoon expansion is too small; (2) conditions
wetter than present between ca. 10–30 °N in Africa, indicating that the simulated African monsoon expansion is too small;
(3) that northern Europe was drier, but the area of significantly drier conditions was more localized (around the Baltic)
than shown in the simulations; (4) that southern Europe was wetter than present, apparently consistent with the simulations,
but pollen data suggest that this reflects an increase in summer rainfall whereas the models show winter precipitation, and
(5) that the mid-latitude continental interior was generally wetter than present.
Received: 29 March 1996 / Accepted: 31 May 1996 |
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