PHYSICAL PROCESSES AND THE MAINTENANCE OF NUTRIENT-RICH EUPHOTIC ZONES

Oceanic euphotic zones characterized by high macronutrients but low primary productivity are found in the upwelling gyres of the world ocean. This paper reviews the physical processes which interact to maintain high nutrient concentrations in the near-surface ocean in such regions, illustrating the range of relevant forcing functions with regional examples. Predictions of the direction of change of the physical systems in these areas under increasing greenhouse gas concentrations can be based on the present generation of coupled ocean-atmosphere global circulation models, but these results have significant uncertainty.