Coastal upwelling occurs when winds blowing parallel to the coast displace surface water offshore (via Coriolis effect), and deep, cold (8–14 °C), nutrient-rich water rises to replace it.
On the Iberian Peninsula
The Atlantic coast of Portugal and Galicia experiences strong summer upwelling driven by the nortada. This explains the cold summer waters of Galicia and the extraordinary fishing richness of the area (sardines, mussels). Upwelling also lowers coastal temperatures and generates advection fog when warm air passes over cold water.