Density Driven Circulation

Density-driven circulation is flow forced by horizontal density gradients in seawater, where pressure differences from variations in temperature and salinity drive motion, in contrast to wind-driven circulation. It is the dynamical core of thermohaline and overturning circulation: dense water formed by cooling and brine rejection at high latitudes sinks and spreads at depth, while lighter water flows in to replace it. The density field links to the velocity field through the geostrophic and thermal-wind relations, so the slope of isopycnals sets the vertical shear of the current. It governs deep-water renewal and the global conveyor.