The status of the Indo-Pacific Warm Pool and adjacent land at the Last Glacial Maximum

Since the Climate: Long Range Investigation, Mapping and Prediction (CLIMAP) reconstructions for the Earth at the Last Glacial Maximum (LGM), there have been conflicting views on the extent of cooling of the oceans of tropical Australasia—here, referred to as the Indo-Pacific Warm Pool—in contrast with those temperatures registered on land. Based on sea-surface temperature (=SST) reconstructions for the Indo-Pacific Warm Pool, and on vegetation reconstruction for SE Asia as well as by considering the increase of land mass area engendered during low sea levels, we identify for the LGM a significant drop in precipitation in the Warm Pool region that would explain an increase in salinity while SST decreased by about 2 °C at the most. The latter would have caused a substantial decrease of large-scale atmospheric convection over the Indo-Pacific Warm Pool and suppressed deep atmospheric convection that would help maintain somewhat elevated SSTs. The drier atmosphere and diminished level of cloud cover would also have reduced nocturnal temperatures at elevation in the region and produced a steeper mean atmospheric lapse rate, forcing the tree line to drop and glaciers to be maintained down to much lower altitudes than today.