Ocean gyres driven by surface buoyancy forcing

Ocean gyres are persistent, large-scale circulation features that give rise to important ocean currents such as the Gulf Stream in the North Atlantic and the Kuroshio current off the east coast of Japan.  These gyres are critical in transporting heat from the tropics to the poles. For the last 70 years, oceanographers have assumed that these gyres are driven by wind stress, however, the simple theory that predicts the strength of these gyres fails in many parts of the ocean. In this talk, I will demonstrate that ocean gyres (complete with a rich eddy field and strong western boundary current) occur even in the absence of wind forcing. Thus, I contend that a significant component of gyre circulation, particularly in the subpolar regions, is due to temperature-driven buoyancy fluxes. This result represents a profound change to our understanding of one of the most fundamental aspects of the ocean’s large-scale circulation. 

Snapshot of Sea Surface Temperature in the North Atlantic Ocean from a high resolution global ocean-sea ice model. The Gulf Stream is shown by the tongue of warm water (violet colours) extending up the eastern seaboard of the USA, before it separates from the coast and transports heat into the interior North Atlantic against a background of strong turbulence.