Abstract
Salinity is an essential proxy for estimating the global net freshwater input into the ocean. Due to the limited spatial and temporal coverage of the existing salinity measurements, previous studies of global salinity changes focused mostly on the surface and upper oceans. Here, we examine global ocean salinity changes and ocean vertical salt fluxes over the full depth in a dynamically consistent and data-constrained ocean state estimate. The changes of the horizontally averaged salinity display a vertically layered structure, consistent with the profiles of the ocean vertical salt fluxes. For salinity changes in the relatively well-observed upper ocean, the contribution of vertical exchange of salt can be on the same order of the net surface freshwater input. The vertical redistribution of salt thus should be considered in inferring changes in global ocean salinity and the hydrological cycle from the surface and upper ocean measurements.
Highlights
Salinity is an essential proxy for estimating the global net freshwater input into the ocean
In addition to estimates of salinity over the global ocean and its full-depth, ocean synthesis provides a number of unobservable quantities and can be used to quantify the various dynamical terms that contribute to ocean salinity changes
We will focus on changes of horizontally averaged salinity in different layers of the global ocean and explore the role of the vertical redistribution of salt in determining the salinity changes in the well-observed upper ocean In addition, implications for interpreting the changes in the upper ocean salinity and inferring information about the total freshwater input at the surface from existing observations will be briefly discussed
Summary
Salinity is an essential proxy for estimating the global net freshwater input into the ocean. For salinity changes in the relatively well-observed upper ocean, the contribution of vertical exchange of salt can be on the same order of the net surface freshwater input. We will focus on changes of horizontally averaged salinity in different layers of the global ocean and explore the role of the vertical redistribution of salt in determining the salinity changes in the well-observed upper ocean (hereinafter defined as the layer above 2000 m.) In addition, implications for interpreting the changes in the upper ocean salinity and inferring information about the total freshwater input at the surface from existing observations will be briefly discussed
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