Thermohaline Circulation

Abstract The thermohaline circulation transports heat, salt and chemical elements through the deep ocean. At high latitudes, cooling and salting of surface water produce dense waters that sink in the deep ocean. North Atlantic Deep Water is formed in the Arctic Seas and Antarctic Bottom water is produced around Antarctica. It triggers the thermohaline circulation that flushes the deep ocean on a time scale of ∼900 y as indicated by the radioactive decay of 14C. Anthropogenic tracers mark the inflow of newly (< 60 y) formed deep waters. 14C-transient tracer comparison highlights water recirculation in the deep basins. The closure of the thermohaline circulation requires the upwelling of deep waters to the ocean surface. In the deep basins upwelling is enhanced by current flowing over rough topographies. The bottleneck of the thermocline is passed in the Southern Ocean where steep isopycnal surfaces connect the deep and the surface ocean.