Effects of extratropical solar penetration on North Atlantic Ocean circulation and climate

Abstract

Effects of extratropical solar penetration on the North Atlantic Ocean circulation and climate are investigated using a coupled ocean-atmosphere model. In this model, solar penetration generates basinwide cooling and warming in summer and winter, respectively. Associated with SST changes, annual mean surface wind stress is intensified in both the subtropical and subpolar North Atlantic, which leads to acceleration of both subtropical and subpolar gyres. Owing to warming in the subtropics and significant saltiness in the subpolar region, potential density decreases (increases) in the subtropical (subpolar) North Atlantic. The north-south meridional density gradient is thereby enlarged, accelerating the Atlantic meridional overturning circulation (AMOC). In addition, solar penetration reduces stratification in the upper ocean and favors stronger vertical convection, which also contributes to acceleration of the AMOC.