Open AccessA sian monsoon climate during the L ast G lacial M aximum: palaeo‐data–model comparisons
Author(s) -
Chabangborn Akkaneewut,
Brandefelt Jenny,
Wohlfarth Barbara
Publication year - 2014
Publication title -
boreas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.95
H-Index - 74
eISSN - 1502-3885
pISSN - 0300-9483
DOI - 10.1111/bor.12032
Subject(s) - climatology , monsoon , precipitation , proxy (statistics) , geology , intertropical convergence zone , last glacial maximum , climate model , atmospheric sciences , climate change , oceanography , geography , meteorology , holocene , machine learning , computer science
The L ast G lacial M aximum ( LGM ) (23–19 ka BP ) in the A sian monsoon region is generally described as cool and dry, due to a strong winter monsoon. More recently, however, palaeo‐data and climate model simulations have argued for a more variable LGM A sian monsoon climate with distinct regional differences. We compiled, evaluated, and partly re‐assessed proxy records for the A sian monsoon region in terms of wet/dry climatic conditions based on precipitation and effective moisture, and of sea surface temperatures. The comparison of the palaeo‐data set to LGM simulations by the C limate C ommunity S ystem M odel version 3 ( CCSM3 ) shows fairly good agreement: a dry LGM climate in the western and northern part due to a strengthened winter monsoon and/or strengthened westerly winds and wetter conditions in equatorial areas, due to a stronger summer monsoon. Data–model discrepancies are seen in some areas and are ascribed to the fairly coarse resolution of CCSM3 and/or to uncertainties in the reconstructions. Differences are also observed between the reconstructed and simulated northern boundaries of the I ntertropical C onvergence Z one ( ITCZ ). The reconstructions estimate a more southern position over southern I ndia and the B ay of B engal, whereas CCSM3 simulates a more northern position. In Indochina, the opposite is the case. The palaeo‐data indicate that climatic conditions changed around 20–19 ka BP, with some regions receiving higher precipitation and some experiencing drier conditions, which would imply a distinct shift in summer monsoon intensity. This shift was probably triggered by the late LGM sea‐level rise, which led to changes in atmosphere–ocean interactions in the I ndian O cean. The overall good correspondence between reconstructions and CCSM3 suggests that CCSM3 simulates LGM climate conditions over subtropical and tropical areas fairly well. The few high‐resolution qualitative and quantitative palaeo‐records available for the large A sian monsoon region make reconstructions however still uncertain.