Ekman driven upwelling describes the upwelling driven by Ekman transport (wind-driven surface currents) for Spring, Summer, Fall, and Winter in units of meters per second. Upwelling brings nutrient-rich deep water to the nutrient-deprived surface which stimulates primary production. Downwelling is where surface water is forced downwards, delivering oxygen to deeper water. Downwelling typically leads to reduced productivity, as the depth of the nutrient-limited layer is extended. In these maps, upwelling is represented by positive values, and downwelling is represented by negative values.

Upwelling occurs where surface currents are diverging, or moving away from each other. As the surface waters diverge, deeper water must be brought to the surface to replace it, creating upwelling zones. The upwelled water is cold and rich in nutrients, leading to high productivity. Many of the most productive regions on Earth are found in upwelling zones. In the equatorial Pacific, the trade winds blow the North and South Equatorial Currents towards the west, while Ekman transport causes the upper layers to move to the north and south in their respective hemispheres. This creates a divergence zone, and a region of upwelling and high productivity.

These data were derived from the NOAA CoastWatch (dataset: erdQSstress1day; 1999-2009).