Upwelling is an oceanographic phenomenon that occurs when strong, usually seasonal, winds push water away from the coast, bringing cold, nutrient-rich deep waters up to the surface. These waters cause very high levels of productivity in phytoplankton compared to other areas of the ocean, and these effects are propagated up the food chain. Currently known regions of upwelling include coastal Peru, Arabian Sea, western South Africa, eastern New Zealand and the California coast.
Localized upwelling may be due to deflection of deep currents by a seamount providing a nutrient rich island in otherwise low productivity ocean areas. These provide islands of life in such areas and are important to migrating species and human fishing.