The climate of the Last Glacial Maximum: Results from a coupled atmosphere-ocean general circulation model

Results from a coupled atmosphere-ocean general circulation model simulatio n of the Last Glacial Maximum reveal annual mean continental cooling betwee n 4 degrees and 7 degrees C over tropical landmasses, up to 26 degrees of c ooling over the Laurentide ice sheet, and a global mean temperature depress ion of 4.3 degrees C. The simulation incorporates glacial ice sheets, glaci al land surface, reduced sea level, 21 ka orbital parameters, and decreased atmospheric CO2. Glacial winds, in addition to exhibiting anticyclonic cir culations over the ice sheets themselves, show a strong cyclonic circulatio n over the northwest Atlantic basin, enhanced easterly flow over the tropic al Pacific, and enhanced westerly flow over the Indian Ocean. Changes in eq uatorial winds are congruous with a westward shift in tropical convection, which leaves the western Pacific much drier than today but the Indonesian a rchipelago much wetter. Global mean specific humidity in the glacial climat e is 10% less than today. Stronger Pacific easterlies increase the tilt of the tropical thermocline, increase the speed of the Equatorial Undercurrent , and increase the westward extent of the cold tongue, thereby depressing g lacial sea surface temperatures in the western tropical Pacific by similar to 5 degrees-6 degrees C.