what causes the process called upwelling
Upwelling occurs when winds blowing across the ocean surface push water away from an area and subsurface water rises up to replace the diverging surface water. Upwelling occurs in the open ocean and along coastlines. The reverse process, called downwelling, also occurs when wind causes surface water to build up along a coastline. The surface water eventually sinks toward the bottom. Subsurface water that rises to the surface as a result of upwelling is typically colder, rich in nutrients, and biologically productive.