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

A data‐constrained ocean state estimate that permits closed property budget diagnostics is used to examine the balance between surface forcing ( F ¯ ), advective ( A ¯ ), and diffusive ( D ¯ ) fluxes in maintaining the large‐scale time‐mean surface salinityS s¯ . Time‐mean budgets (1993–2010) are considered for the 10 m thick top layer. In general,D ¯ tends to counteractF ¯ , butA ¯ is important almost everywhere, and some regions show a main balance betweenA ¯ andD ¯ (Bay of Bengal, Arctic) orA ¯ andF ¯ (tropical Atlantic and Pacific). Advection tends to freshen the surface in the tropics and high latitudes, with opposite tendencies in midlatitudes. For variousS s¯ tropical extrema,A ¯ adds to theF ¯ tendencies in precipitation regions and opposesF ¯ in evaporation regions. Long‐termS s¯ conditions thus reflect more than a simple diffusive adjustment toF ¯ , likely involving close interaction between wind‐ and buoyancy‐driven circulation and mixing processes.