Ocean currents and circulation

Latitude alone does not determine a coast's climate or its fisheries. Heat and nutrient transport do both, which is what ocean circulation supplies. Surface circulation is driven by prevailing winds and deflected by the Coriolis force into subtropical gyres, intensified into narrow warm western boundary currents such as the Gulf Stream and Kuroshio and broad cold eastern boundary currents such as the Peru and Benguela. Offshore Ekman transport along eastern margins drives upwelling of nutrient-rich water. Beneath this, thermohaline circulation moves water by density, with deep water forming where surface water is cold and saline. The North Indian Ocean circulation reverses seasonally with the monsoon.