 Upwelling intensity depends on wind strength and seasonal variability, as well as the vertical structure of the water, variations in the bottom bathymetry, and instabilities in the currents.In some areas, upwelling is a seasonal event leading to periodic bursts of productivity similar to spring blooms in coastal waters.Wind-induced upwelling is generated by temperature differences between the warm, light air above the land and the cooler denser air over the sea.