Linking Information from Sea Surface Salinity to Oceanic Freshwater Fluxes Using Near-Surface Salinity Budgets
[11-Nov-2014] Vinogradova, N., Ponte, R., and Buckley, M.
Presented at the 2014 Aquarius/SAC-D Science Team Meeting
Characterizing freshwater fluxes (FWF) over the oceans is a key element in advancing our understanding of climate change. One way to improve knowledge of these fluxes is to use variations in sea-surface salinity (SSS). However, the problem is challenging because the relationship between SSS and FWF can depend on complex upper-ocean dynamic processes. A common approach to describe such dependencies is to use salinity budget framework and consider the nature of oceanic fluxes in relation to forcing and salinity tendency. Once properly formulated, salinity budget allows one to explore how freshwater fluxes can be expressed as a combination of ocean variables, including SSS. Here we examine global, near-surface salinity budgets computed within dynamically-consistent, constrained estimation of the oceanic state during the last two decades. Dynamical consistency of the solution ensures physically realistic correspondence between FWF and SSS tendencies. The focus is to explore budget closure and the effect of a realistic real freshwater surface boundary condition. Preliminary results show that ocean contribution to salinity variations is particular important in the tropics, high latitudes, and many coastal regions, which may complicate the use of salinity observations as a direct proxy of FWF, at least on timescales from months to years.