Rapid Coastal Bottom Water Temperature Rises

Rapid 5 to 15°F (2.8 to 8.3°C) increases of normally stable water temperature at depths of 63 to 76 ft. (19 to 23 m) in Nahant Bay, Mass., were observed during summer 1972. These rises, which occurred in a few hours and persisted for several days, were apparently caused by a temporary replacement of preexisting cooler bottom water by warm surface water which was transported into the bay by northeast winds. Weather records indicate that these events occur in Nahant Bay an average of three times per year between June and September when vertical temperature gradients occur. These rapid bottom water temperature rises are significant from an engineering standpoint because of potential deleterious effects on heated effluent diffusion and on efficiency of circulating water cooling systems. They also represent a natural means by which marine organisms are exposed to thermal stress.