Global climate change and ocean upwelling



The influence of global greenhouse warming on the ocean's biological productivity may be more complicated and weaker than that proposed by Bakun (1990). A doubled carbon dioxide simulation made with the Canadian Climate Centre atmospheric general circulation model coupled to a simplified mixed layer ocean model suggests that the midlatitude continents do not all follow the Bakun scenario in developing anomalous low pressure in summer and enhancing coastal winds favorable to upwelling. In the open ocean the equatorial and subpolar zonal upwelling bands and the subtropical downwelling bands generally weaken as winds diminish owing to the weakening of the equator-to-pole temperature gradient in the lower troposphere under global warming. With a weakening of open ocean upwelling and an absence of enhanced coastal upwelling, the overall effect of global warming could be to decrease the global biological productivity.