Mean Salt Balance of the North Atlantic Salinity Maximum
[27-Feb-2014] Schmitt, R.W., Blair, A., St Laurent, L., and Schanze, J.
Presented at the 2014 Ocean Sciences Meeting
The North Atlantic Salinity Maximum is the world's saltiest open ocean S-max and was the focus of the recent SPURS process study. It is formed by an excess of evaporation over precipitation and the wind-driven convergence of the subtropical gyre. Such salty areas are getting saltier with global warming (a record high SSS was observed in SPURS) and it is imperative to determine the relative roles of surface fluxes and oceanic processes in such trends. One approach to understanding the mean salinity balance in the ocean is to define a control volume by the 37.0 isohaline, across which all mean advective terms cancel. This is a "sock-shaped" closed surface around the S-max, with the "toe" trending to the southwest at depth. Using estimates of the net surface water flux (E-P) at the surface, it is possible to apportion the salt flux between lateral and vertical mixing processes. Direct measurements of the vertical mixing rate in the thermocline from the SPURS field program allow us to constrain the lateral mixing rate at the 1 degree scale of the water mass climatology.