<P> Some models of the ocean circulation suggest that broad - scale upwelling occurs in the tropics, as pressure driven flows converge water toward the low latitudes where it is diffusively warmed from above . The required diffusion coefficients, however, appear to be larger than are observed in the real ocean . Nonetheless, some diffusive upwelling does probably occur . </P> <Ul> <Li> Local and intermittent upwellings may occur when offshore islands, ridges, or seamounts cause a deflection of deep currents, providing a nutrient rich area in otherwise low productivity ocean areas . Examples include upwellings around the Galapagos Islands and the Seychelles Islands, which have major pelagic fisheries . </Li> <Li> Upwelling can also occur when a tropical cyclone transits an area, usually when moving at speeds of less than 5 mph (8 km / h). The churning of a cyclone eventually draws up cooler water from lower layers of the ocean . This causes the cyclone to weaken . </Li> <Li> Artificial upwelling is produced by devices that use ocean wave energy or ocean thermal energy conversion to pump water to the surface . Ocean wind turbines are also known to produce upwellings . Ocean wave devices have been shown to produce plankton blooms . </Li> </Ul> <Li> Local and intermittent upwellings may occur when offshore islands, ridges, or seamounts cause a deflection of deep currents, providing a nutrient rich area in otherwise low productivity ocean areas . Examples include upwellings around the Galapagos Islands and the Seychelles Islands, which have major pelagic fisheries . </Li> <Li> Upwelling can also occur when a tropical cyclone transits an area, usually when moving at speeds of less than 5 mph (8 km / h). The churning of a cyclone eventually draws up cooler water from lower layers of the ocean . This causes the cyclone to weaken . </Li>

Why is there upwelling off the coast of peru