Dynamical and observational constraints on tropical Pacific sea surface temperatures at the last glacial maximum

Asynchronously coupled atmosphere and ocean general circulation model simul ations are used to examine the consequences of changes in the west/east sea -surface temperature (SST) gradient across the equatorial Pacific at the la st glacial maximum (LGM). Simulations forced by the CLIMAP SST for the LGM, where the west/east SST gradient across the Pacific is reduced compared to present, produce a reduction in the strength of the trade: winds and a dec rease in the west/east slope of the equatorial thermocline that is incompat ible with thermocline depths newly inferred from foraminiferal assemblages. Stronger- than-present trade winds, and a more realistic simulation of the thermocline slope, are produced when eastern Pacific SSTs are 2 degrees C cooler than western Pacific SSTs. Our study highlights the importance of sp atial heterogeneity in tropical SSTs in determining key features of the gla cial climate.