Definition - What does Upwelling mean?
Upwelling is the process by which deep, cold water at the bottom the ocean rises to the top. This cold water is filled with nutrients. The process of upwelling takes place along coastlines as well as in the open ocean. The nutrients in the upwelled water fertilize surface water, providing them with a higher biological value. As a result, upwelling areas are usually productive fishing grounds.
Safeopedia explains Upwelling
The opposite process to upwelling is downwelling. Downwelling occurs when winds cause surface water to build up along coastlines, forcing the water to sink to the bottom of the ocean. The nutrient rich waters that rise to the surface through upwelling promote the growth of phytoplankton, which blooms to form an excellent energy source for fish, marine life, mammals and seabirds.