What is the term for the process whereby nutrients are brought to the ocean's surface?

Upwelling is the process that occurs when nutrient-rich waters from the deep ocean rise to the surface. This phenomenon typically happens in regions where winds blow across the ocean surface, pushing water away from the shore and allowing deeper water to rise and replace it. The nutrients brought to the surface are crucial for supporting marine life, particularly phytoplankton, which forms the foundation of the oceanic food web.

In contrast, downwelling refers to the process where surface waters sink into the ocean, often occurring in areas of convergence where water is pushed together. This does not promote nutrient circulation to the surface like upwelling does. Tides, driven primarily by the gravitational pull of the moon and the sun, influence water levels but do not directly facilitate the movement of nutrient-rich waters. Ocean currents do move water across large distances, but they are not specifically defined by the upward movement of nutrients from the ocean depths. Thus, upwelling is specifically recognized as the process that brings those essential nutrients to the ocean's surface.