&main=Winds that blow to the south along a westward facing coast cause coastal waters to move offshore or to “diverge” from the coast. That in turn causes water to move up or “upwell” from below, because no water can be replaced from the landward side on a coast. Upwelling occurs along the equator and some coasts when the wind blows in an ideal direction. Winds acting on the sea surface cause the underlying water to move unexpectedly – not in the same direction as the wind, but ~45° to the right of the wind direction, no matter the direction of wind in the northern hemisphere. In the southern hemisphere, the water moves ~45 to the left of the wind direction. The concept of Ekman transport explains how this happens in more detail. This concept is useful because it allows us to predict how surface waters will move in response to particular winds. It allows us to predict situations that maintain or stop upwelling. Upwelling is important because upwelling supplies nutrients that support biological productivity in surface waters – less nutrients, less biota. Wind causes water to move and in a coastal setting it can also lead to upwelling.