Low-latitude forcing of meridional temperature and salinity gradients in the subpolar North Atlantic and the growth of glacial ice sheets

Sea-surface temperature (SST) and salinity (SSS) records obtained from two deep-sea cores have been used to reconstruct meridional gradients in the mi d-latitude North Atlantic over the past 40 k.y. During the buildup of ice s heets toward the last glacial maximum, SST and SSS gradients between 40 deg rees and 50 degrees N increased by 6-8 degrees C and similar to 2 parts per thousand, respectively. This trend represents a two-fold increase in surfa ce-water gradients between 40 and: 20 ka and strongly overprints the signal of high-frequency climatic oscillations, We attribute the gradual intensif ication of meridional SST and SSS gradients to a precession-driven increase in advection within the glacial North Atlantic Current resulting from chan ges in low-latitude insolation and seasonality. A strongly zonal ocean circ ulation pattern, maintained by greater advection and enhanced heat storage within the subtropical ocean at the last glacial maximum, persisted until c a. 20 ka, when a decrease in glacial SST gradients, coincident with a reduc tion in low-latitude climate forcing, marked the initiation of the last deg laciation.