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 ( falsescriptF¯), advective ( falsescriptA¯), and diffusive ( falsescriptD¯) fluxes in maintaining the large‐scale time‐mean surface salinity falseSs¯. Time‐mean budgets (1993–2010) are considered for the 10 m thick top layer. In general, falsescriptD¯ tends to counteract falsescriptF¯, but falsescriptA¯ is important almost everywhere, and some regions show a main balance between falsescriptA¯ and falsescriptD¯ (Bay of Bengal, Arctic) or falsescriptA¯ and falsescriptF¯ (tropical Atlantic and Pacific). Advection tends to freshen the surface in the tropics and high latitudes, with opposite tendencies in midlatitudes. For various falseSs¯ tropical extrema, falsescriptA¯ adds to the falsescriptF¯ tendencies in precipitation regions and opposes falsescriptF¯ in evaporation regions. Long‐term falseSs¯ conditions thus reflect more than a simple diffusive adjustment to falsescriptF¯, likely involving close interaction between wind‐ and buoyancy‐driven circulation and mixing processes.

Halosteric Sea Level Changes during the Argo Era

“…Therefore, decadal and long-term salinity analyses still require more comprehensive studies in the future, once longer salinity time series are available. Since the underlying mechanisms of salinity changes are still not fully understood, it is urgent to examine the salinity change, via both reanalysis data and ocean models, and a simple budget analysis, such as [15][16][17][18] etc., is highly preferred to separate ocean dynamics with surface flux changes. It is also recommended to better reconstruct the historical ocean subsurface salinity field, given the importance of the halosteric sea level to the total sea level.…”

“…and fresh water flux forcing [15][16][17][18]. The long-term ocean salinity change is dominated by the freshwater flux over the sea surface [9,15].…”

El Niño–Southern Oscillation‐time scale covariation of sea surface salinity and freshwater flux in the western tropical and northern subtropical Pacific

“…Spatiotemporal changes of SSS are caused by the variations in sea surface freshwater flux (evaporation minus precipitation rates), horizontal advection, and vertical mixing [e.g., Ponte and Vinogradova, 2016;Gordon, 2016]. Spatiotemporal changes of SSS are caused by the variations in sea surface freshwater flux (evaporation minus precipitation rates), horizontal advection, and vertical mixing [e.g., Ponte and Vinogradova, 2016;Gordon, 2016].…”

Regime Changes in Global Sea Surface Salinity Trend

“…The consequences of the SSS changes being associated with mean or trend changes have repercussions beyond the SSS evolution and affect the global water cycle [5,6,15]. Our goal is to isolate different regimes to provide understanding of potential future global cycle changes.…”

“…The intensification of the global water cycle is expected to be occurring at a rate of 8% •−1 of surface warming [4] or around 20% considering the projected 2-3 • of temperature increase over the next century. The mechanisms controlling the intensification of the water cycle have recently been evaluated [5,6].…”