Description: Ocean currents are generally divided into two categories: thermohaline currents and wind driven currents. Both types of currents are forced remotely rather than locally. Wind driven currents are initially forced by the wind stress causing water to pile up in certain locations. This produces a pressure gradient, which is then balanced by the Coriolis force and geostrophic currents develop. The gyre circulations found in the Atlantic and Pacific Oceans are wind driven currents. There is a connection between the physics of these currents and the biological productivity in the ocean. For example, productivity is greatest in areas of equatorial and coastal upwelling as nutrient rich deep water is brought to the sunlit surface.