Meetings: Documents

Subtropical Surface Salinity Maximum Inferred from Aquarius, SMAP, and SMOS
[28-Aug-2018] Yu, L.
Presented at the 2018 Ocean Salinity Science Team and Salinity Continuity Processing Meeting
The subtropical surface salinity maximum (SSS-max), the net evaporation maximum, and the subtropical underwater (STUW) are intertwined with each other and with the wind-driven gyre circulation of the upper ocean. The evaporation-minus-precipitation (E-P) flux is a forcing for SSS-max, and the SSS-max is the source water in the subduction process that forms the STUW. Since neither the E-P flux nor the subduction process can be observed directly, satellite observations of the SSS-max provide not only a useful additional gauge on the change of ocean water cycle but also a window into the water mass exchange between the ocean surface and the permanent pycnocline. However, the SSS-max pattern and magnitude derived from the satellite Aquarius, SMAP, and SMOS differ considerably from each other and from the Argo-based depiction. The differences give rise to a large uncertainty when the products are used to determine the formation rate of STUW. In the North Atlantic, the estimates of the annual STUW volume differ by a factor of two among products. The STUW formation is highly sensitive to the SSS-max position, as the latter determines the outcrop area bounded by isohalines that define the STUW properties. This study calls attention to the SSS-max differences between products and to the importance of having a consistent pattern to help tracking the change of E-P maximum. Attempts are being made to develop a physical check from Argo salinity and temperature profiles to evaluate the fidelity of the SSS-max pattern derived from Aquarius, SMAP and SMOS.

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