Physical Processes and wind-driven circulation in the Northern Indian Ocean. In: Winter School on Impact of Climate Change on Indian Marine Fisheries held at CMFRI, Cochin 18.1.2008 to 7.2.2008

The vast expanses of oceanic waters are continuously in motion and one wonders what makes ocean waters in a state of perpetual restlessness. Ocean currents are important as they redistribute heat, salt, nutrients, and biological organisms. As they transport heat from tropics to poles they are capable of influencing the climate. There are two physical processes that drive the ocean circulation and they are (1) transfer of momentum from wind to the ocean (tangential stress) and (2) convection driven by buoyancy changes due to heating and cooling or addition or removal of salt. The motion of the ocean due to the first process is known as the wind-driven circulation in which winds impart momentum to the ocean. The motion due to the second process is known as the thermohaline circulation in which the cooling in the Polar Regions result in loss of buoyancy and causes water to sink to deep ocean. The above separation of circulation into two components, though provides a conceptual simplification of circulation, is somewhat artificial in the real world