A subtropical North Atlantic regional atmospheric moisture budget

The synergistic effects of evaporation (E), precipitation (P), and Ekman transport make the Salinity Processes in the Upper Ocean Regional Study (SPURS‐1) region in the subtropical North Atlantic (15–30°N, 30–45°W) the natural location for the world's highest open ocean SSS maximum. Using the MERRA and ERA‐Interim atmospheric reanalyses, we reproduce the mean hydrologic state of the atmosphere over the SPURS‐1 region since 1979 and roughly deduce the change in salinity across the meridional domain due solely to interactions between E‐P and Ekman transport. Our findings suggest a region that is highly evaporative at a mean rate of 4.87 mm/d with a standard deviation of 1.2 mm/d and little seasonality. Precipitation is much more variable with an annual fall maximum around 3 mm/d but only a mean rate of 1.37 mm/d with a standard deviation of 1.46 mm/d. The resulting E‐P variable has a mean rate of 3.50 mm/d with a standard deviation of 1.92 mm/d and matches well with the moisture flux divergence term although the former is typically larger by a small margin. Strong prevailing easterly trade winds generate northward Ekman transports that advect water toward the salinity maximum around 25°N. A short calculation shows that atmospheric moisture dynamics could potentially account for about one third of the change in salinity between 15°N and 25°N giving an estimate of the role that surface freshwater flux plays in the maintenance of the salinity maximum. Key Points: Understanding air/sea fluxes over the SPURS‐1 region Connecting air/sea fluxes to SSS Produce quantitative analysis of how air/sea fluxes affect SSS