ENVIRON 222 Lecture 9: 9. Deep Ocean Circulation
Document Summary
Wind-driven currents - to be covered later - dominate ocean circulation in the near surface. Density contrasts, along with pressure gradients, drive circulation in the deep ocean. Once density of surface water is greater than water below, sinking occurs. Water will reach a density equilibrium level and spread horizontally, in response to gradients in pressure. Density-driven circulation also known as thermohaline circulation (thermo - heat, haline - salt), or meridional overturning circulation. Density increases if salinity increases or temperature decreases. Density decreases if salinity decreases or temperature increases. Sea surface temperature is generally warm in low latitudes, cold in high latitudes. In the vertical direction, temperatures change most rapidly in the. thermocline, the upper 500-1000m of the water column. Below about the 1000m, temperatures change slowly and are near freezing, even near the equator, meaning that deep waters source from high latitude regions. At low latitudes there is a well-developed pycnocline (zone of rapid change in density with water depth)
