A New Paradigm for Atlantic Ocean Deep Water Formation

Abstract:

The Atlantic Meridional Overturning Circulation (AMOC), a key mechanism in the climate system, delivers warm and salty waters from the subtropical gyre to the subpolar gyre and Nordic Seas, where they are transformed into colder and fresher waters by wintertime convection. For over three decades, waters formed in the Labrador and Nordic Seas were considered the sources for the AMOC lower limb, but recent observations reveal that convection in the Labrador Sea contributes minimally to the total overturning of the subpolar gyre. In this study, we show that the AMOC is instead primarily comprised of waters formed in the Nordic Seas and in the Irminger and Iceland basins. A first direct estimate of air-sea heat and freshwater fluxes over the basins reveals that buoyancy forcing during the winter months can almost wholly account for the deep waters of the subpolar North Atlantic that are exported as part of the AMOC.