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Ocean eddy freshwater flux convergence into the North Atlantic subtropics



For a quasi steady state condition, the water vapor flux from the ocean to atmosphere typical of the salty subtropics must be compensated by ocean processes that transfer freshwater into the evaporative regime. Observations of the North Atlantic subtropical sea surface salinity maximum region frequently reveal the presence of eddies with distinct salinity/temperature signatures of up to 0.2 psu/1°C, with horizontal scales of up to 200 km. Using the surface layer salinity and meridional velocity from the Simple Ocean Data Assimilation (SODA) reanalysis data, we find that the eddy flux can accomplish 50% to 75% of the required freshwater convergence into the subtropical regime, the rest being delivered by Ekman transport convergence, and therefore represents a significant component of the marine hydrological cycle. Interannual fluctuations of the eddy freshwater flux are reflected in sea surface salinity variability.

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