An upward movement of cold nutrient rich water from ocean depths. Upwelling areas can be constant or seasonal and are characterized by increased productivity on all trophic levels of the marine ecosystem (productive fishing areas). Well known areas with constant upwelling are: e.g. off West Africa (Morocco, Spanish Sahara), and off Peru. Temporarily (seasonal) upwelling areas: eastern Banda Sea (Indonesia), off Somalia and Oman, off west India.