Thermohaline Circulation

Thermohaline circulation describes the large-scale global pattern of ocean water movement driven by density differences that arise from variation in temperature (thermo) and salinity (haline), the two properties that together determine the density of seawater. In the theory, cold, salty and therefore dense water sinks at a small number of specific high-latitude locations, most notably in the North Atlantic near Greenland and around parts of Antarctica, and then flows slowly through the deep ocean basins over centuries before eventually mixing upward and returning to the surface elsewhere, where warmer, less dense surface currents carry it back toward the sinking regions to complete the circuit. Oceanographer Wallace Broecker helped popularize the now-common description of this slow, interconnected global circulation pattern as a conveyor belt in research published in the late 1980s, emphasizing its role in redistributing heat between ocean basins over long timescales. Because thermohaline circulation moves an enormous volume of heat, disruption to its sinking regions, for example through an influx of fresh meltwater reducing surface salinity, is a subject of ongoing research into how the pattern might change under a warming climate and what regional climate effects such a change could produce.