Upwelling Index

An upwelling index quantifies the intensity of wind-driven coastal upwelling, most commonly the Bakun index, the offshore Ekman transport per unit length of coastline computed from the alongshore component of wind stress. Bakun’s index is given in cubic meters per second per 100 meters of coastline; positive values mean equatorward winds drive surface water offshore, forcing cold, nutrient-rich water up to replace it. It is computed operationally for eastern boundary systems such as the California, Humboldt, Canary, and Benguela Currents, where it predicts the timing and strength of the productive upwelling season. Newer indices (CUTI, BEUTI) refine it with full Ekman dynamics and stratification.