Hydrological Cycle And

The atmospheric hydrological cycle is compared for diierent time slices of the late Quaternary. Simulations have been conducted with an atmospheric circulation model at T42 resolution, and we have performed a global evaluation of the atmospheric water vapor transport. The water export from the Atlantic catchment area, important for driving the large-scale thermohaline ocean circulation, is analyzed in detail. For the Last Glacial Maximum (LGM), we examine the model's sensitivity with respect to tropical cooling relative to the CLIMAP reconstruction which is motivated by recent data. We nd that the LGM experiment with tropical cooling is in better agreement with proxy data available. Our experiments indicate that the water vapor transport is strongly aaected by three mechanisms: continental drying, eddy moisture transport, and changes in the tropical circulation. Except for the continental drying and the blocking eeect of the Laurentide ice sheet, the hydrological cycle is substancially diierent for both LGM experiments. We nd that the hydrological system is rather sensitive to tropical temperature change which is important to understand paleoclimate and future climate changes.