An assessment of basic processes controlling mean surface salinity over the global ocean

Abstract

A data-constrained ocean state estimate that permits closed property budget diagnostics is used to examine the balance between surface forcing ((Formula presented.)), advective ((Formula presented.)), and diffusive ((Formula presented.)) fluxes in maintaining the large-scale time-mean surface salinity (Formula presented.). Time-mean budgets (1993–2010) are considered for the 10 m thick top layer. In general, (Formula presented.) tends to counteract (Formula presented.), but (Formula presented.) is important almost everywhere, and some regions show a main balance between (Formula presented.) and (Formula presented.) (Bay of Bengal, Arctic) or (Formula presented.) and (Formula presented.) (tropical Atlantic and Pacific). Advection tends to freshen the surface in the tropics and high latitudes, with opposite tendencies in midlatitudes. For various (Formula presented.) tropical extrema, (Formula presented.) adds to the (Formula presented.) tendencies in precipitation regions and opposes (Formula presented.) in evaporation regions. Long-term (Formula presented.) conditions thus reflect more than a simple diffusive adjustment to (Formula presented.), likely involving close interaction between wind- and buoyancy-driven circulation and mixing processes.