Abstract

Northwards ocean heat transport is critical for maintaining the mild climate of Western Europe. As sun-warmed currents from the tropics reach the subpolar and polar latitudes, they lose heat to the atmosphere and whatever sea ice is present, gaining density in the process and sinking away from the surface. This deep convection feeds into south-ward returning flows as part of the Atlantic meridional overturning circulation (AMOC) in a process that redistributes heat around the globe. Climate models indicate that freshwater released from ice melt and other processes from the Arctic and Greenland will enter the North Atlantic, where it could remain at the surface because its low salt content makes it lighter than saltier seawater below. Thin layers of surface freshwater would warm up more rapidly in summer and lose heat more rapidly in winter than thicker surface mixed layers would. So the future North Atlantic may be fresher and warmer, aka more “springy”, at the surface in summer. Such springiness has the potential to limit deep convection in the subpolar North Atlantic. We combine observations with coupled models to determine if the fingerprints of springiness are already present in the North Atlantic.