Upwelling
The major upwellings in the ocean are associated with the divergence of currents that bring deeper, colder, nutrient rich waters to the surface. There are at least five types of upwelling: coastal upwelling, large-scale wind-driven upwelling in the ocean interior, upwelling associated with eddies, topographically-associated upwelling, and broad-diffusive upwelling in the ocean interior.
Cold core ring
The governing forces of an eddy are very dependent on its size. Small eddies are largely governed by viscosity and direction of a water body. However larger eddies are formed from a balance between the horizontal pressure gradient force, arising from differences in densities of the meeting water masses, and the Coriolis force. Due to the turbulent nature of the earth’s oceans, eddies can be found almost everywhere. Mesoscale eddies are usually seen in areas of intense, winding currents such as the Gulf Stream and the Antarctic Circumpolar Current that feeds into the South Pacific and Indian oceans, but in general can be caused by a combination of factors such as cooling of sea surface temperature, convection, direct generation from wind, or water flow past an irregular coastline. Cycolic cold-core eddies are frequently formed at the polar front by the Gulf Stream and Labrador Current. The cold, nutrient-rich waters from the Labrador Sea flow south and get caught in the eastward meandering of the Gulf Stream, traveling east across the Atlantic Ocean.