North Atlantic Ocean Circulation and Related Exchange of Heat and Salt Between Water Masses

Abstract

The meridional transport of mass, heat, and salt in the North Atlantic Ocean is often described for separate regions and parts, but rarely are all components of the circulation followed at once. Lagrangian trajectories have here been used to divide the North Atlantic Ocean circulation into four different pathways. In the boundary between the Subpolar and Subtropical Gyres, we show that the northward flowing waters exchange heat and salt with the water originating from the subpolar regions. This subsurface water mass exchange takes place in the first 1,000 m and is a key piece of the puzzle of how the Atlantic Meridional Overturning Circulation transports heat and salt. Between 30° and 60°N the northward flowing water loses 8.8 Gg/s salt to the Subpolar Gyre and an equivalent loss of only 1.7 Gg/s to the atmosphere due to the net fresh water influx.