The Atlantic–Pacific Seesaw

Abstract

A global, oceanic teleconnection of salinity, meridional overturning circulation (MOC), and climate of the North Atlantic and North Pacific is proposed. Simulations with a global climate model show that an extraction of freshwater from the Pacific results not only in an increase of salinity there, but also in a decrease of salinity in the Atlantic. As a result, a Pacific MOC develops while the Atlantic MOC collapses without freshwater perturbation in the Atlantic. Similarly, an input of freshwater to the Atlantic leads not only to a decrease of salinity there, but also to an increase of salinity in the Pacific. The Atlantic MOC collapses, whereas the Pacific MOC develops without freshwater perturbation in the Pacific. The mechanism behind this antiphase Atlantic? Pacific relationship is the positive feedback between ocean circulation and salinity contrasts, originally proposed by Stommel to operate between low and high latitudes. Here the authors show that the same mechanism operates on the Atlantic?Pacific interbasin scale, with the Southern Ocean acting as a pivot point for the interbasin seesaw. The proposed Atlantic?Pacific seesaw effect helps to explain some major out-of-phase oscillations of the climate states between the North Atlantic and North Pacific during the last deglaciation.