A combination of wind blowing parallel to a coastline combined with the rotation of the Earth pushes surface waters away from the coast and causes upwelling. Upwelling is the flow of water from deep in the ocean to the surface, adding cold and nutrient-rich water to the coastal waters.
Upwelling is a very important process for ocean currents and marine ecosystems. The nutrient-rich waters carried up support the growth of seaweeds and plankton. This, in turn, supports organisms higher on the food chain, such as birds, marine mammals and fish. Upwelling also has a strong effect on animal distributions due to the movement of animal larvae. The young of many marine animals are very tiny and drift with the currents, and the currents caused by upwelling can be hundreds of miles long. This can be a negative effect for marine animals, moving their young out of their native environments and decreasing their chances of survival.
Upwelling varies between different coastlines and regions of the same coastline. In some places, upwelling is regular, while in others, it is only seasonal. Coastlines with rift valleys on the nearby seafloor can have upwelling from deeper parts of the ocean than shallower coastlines, which changes the quality of the water received.