Clarifying the relationship between sea-surface salinity and air-sea freshwater fluxes on climate scales

Author: Nadya Vinogradova and Rui M. Ponte
Date: 
December 7, 2011
Type: 
Presentation
Venue: 
AGU Fall Meeting 2011
Citation: 

Nadya Vinogradova, Rui M. Ponte (2011) Clarifying the relationship between sea-surface salinity and air-sea freshwater fluxes on climate scales. AGU Fall Meeting 2011.

A key variable in determining and understanding the global hydrological cycle is the amount of freshwater entering the ocean at the land and atmospheric boundaries. Such freshwater fluxes (FWF) are very difficult to measure directly. As most FWF into the ocean occur near the surface, variations in sea-surface salinity (SSS) can depend on FWF and are a potentially important indicator of their strength. This study aims to examine the relationship between SSS and air-sea FWF over a range of space and time scales and the potential of SSS measurements from Aquarius and SMOS to constrain FWF fields. Consistent "best" estimates of SSS and FWF are obtained from solutions produced by the ECCO consortium, which synthesize all the information available in the surface fluxes, altimetric sea level fields, GRACE mean geoid, satellite-based SST, scatterometer winds, hydrographic climatologies, etc., as well as in the physical constraints, dynamics and conservation statements that are embedded in the equations of the MIT general circulation model. Regional and global mean quantities related to the Earth's water budget are estimated on a variety of climate scales from months to years. We perform a full budget analysis of the ECCO fields in order to determine how different terms (advection, diffusion, forcing) can affect SSS tendencies. Preliminary results indicate that, depending on ocean region and time scales, SSS is tightly related to FWF and can be used as their proxy. However, over most regions, evolution of SSS is greatly affected by advective and diffusive ocean fluxes. Implications for the role of global SSS measurements from Aquarius and SMOS missions in constraining surface FWF estimates are discussed.