loading page

Seasonal Phase Relationships between Sea Surface Salinity, Surface Freshwater Forcing and Ocean Surface Processes
  • Frederick M Bingham,
  • Susannah Brodnitz
Frederick M Bingham
University of North Carolina Wilmington

Corresponding Author:[email protected]

Author Profile
Susannah Brodnitz
University of North Carolina Wilmington
Author Profile

Abstract

Sea Surface Salinity (SSS) can change as a result of surface freshwater forcing (FWF), or internal ocean processes such as upwelling or advection. At the seasonal scale, SSS should follow FWF by ¼ cycle, or 3 months, if FWF is the primary process controlling it at the seasonal scale. In this paper we compare the phase relationship between SSS and FWF (i.e. evaporation minus precipitation over mixed layer depth) over the global (non-Arctic) ocean using in situ SSS and satellite evaporation and precipitation. We find that instead of the expected 3 month delay between SSS and FWF, the delay is mostly closer to 1-2 months, with SSS peaking too soon relative to FWF. We then compute monthly vertical entrainment and horizontal advection terms of the upper ocean salinity balance equation and add their contributions to the phase of the FWF. The addition of these processes to the seasonal upper ocean salinity balance brings the phase difference between SSS and the forcing processes closer to the expected value. We do a similar computation with the amplitude of the seasonal SSS and the forcing terms, with less definitive results. The results of this study highlight the important role that ocean processes play in the global freshwater cycle at the seasonal scale.