What phenomenon causes upwelling in ocean waters?

Upwelling in ocean waters is primarily caused by the vertical circulation of water, which occurs when deeper, colder, and nutrient-rich water rises to the surface. This process typically happens along coastlines when prevailing winds blow surface water away from the shore, allowing deeper water to move upwards to replace it. The nutrients from this deep water support marine life and create fertile fishing areas.

While horizontal water circulation does play a role in the overall dynamics of ocean currents, it does not directly cause the upwelling phenomenon. Wind patterns are certainly influential because they initiate the process, but they don't account for the vertical movement of water. Tidal movements, which are caused by the gravitational pull of the moon and sun, have little direct impact on the vertical circulation that leads to upwelling. Thus, the vertical circulation of water is the most accurate description of the mechanism behind upwelling.