Upwelling occurs in any location where the continuous action of wind against the ocean surface pushes the top layer of water away, causing deeper water to rise to the surface. Coastal upwelling is common, and most coastal regions with rich fisheries are locations with frequent upwelling.
Although upwelling also occurs in the middle of the ocean, much of the upwelling research has focused on coastal regions. Coastal upwelling is associated with winds blowing parallel to the shore. These winds cause upwelling currents in which deep water flows toward the shore, rises and flows back out to sea along the surface. Equatorial upwelling is associated with the Intertropical Convergence Zone, which results in a large band of higher phytoplankton concentration in the Pacific Ocean along the equator.