Seasonal salt budget in the northeast Pacific Ocean

The mixed layer salinity budget in the northeastern subarctic Pacific is evaluated using 5 years (2003–2007) of Argo profiling float data, precipitation and evaporation, geostrophic velocity data, and wind stress observations. In this region the mixed layer salinity has a strong seasonal cycle, driven by seasonality in precipitation, evaporation, Ekman advection, and entrainment. Geostrophic advection effects show relatively little seasonal variability. Precipitation and Ekman effects in this area generally result in net decreases in salinity, while the evaporation, geostrophic advection, and entrainment terms yield increases. Within an annual cycle, the salinity tendency is positive during winter and fall, balanced by surface fluxes (evaporation and precipitation), entrainment, and geostrophic advection. The salinity tendency is negative during spring and summer. During these two seasons, it appears that salinity is controlled by precipitation, evaporation, and geostrophic advection. Overall, the precipitation term makes the largest contribution to the seasonal salinity budget, and the entrainment is especially important in autumn and winter.