Picture: Out in the ocean. Credit: Emiliano Arano (Pexels)

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. Standard oceanographic theory suggests these gyres are driven by wind stress.

However, the simple theory based on wind stress that predicts the strength of these gyres fails in many parts of the ocean.

CLEX researchers using a direct numerical simulation and an eddy permitting ocean model have now demonstrated that ocean gyres (complete with a rich eddy field and strong western boundary current) occur even in the absence of wind forcing.

They 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.