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Variability of the South Pacific SSS Maximum
[12-Feb-2018] Bingham, F., Busecke, J.J.M., Gordon, A.L., Giulivi, C.F., and Li, Z.
Presented at the 2018 Ocean Sciences Meeting
The sea surface salinity (SSS) maximum area of the South Pacific subtropical gyre was examined using satellite and in situ data. The mean center of the feature is at 21°S,120°W. It tilts northwest-southeast and has a size of about 30 degrees in longitude and 8 degrees in latitude as measured by the area of a given surface isohaline (36.258). The area enclosed by this isohaline has nearly doubled between 2012 and 2017 from 2 to 4X106 km2. The mean SSS within the feature has been increasing as well as maintaining a robust seasonal cycle with maximum SSS in winter (June-July). We tracked the east-west and north-south movement of the feature's centroid. Most significantly, it has been moving northward steadily since 2011. The different datasets generally agree, but SMAP and binned Aquarius ('SCI') tend to be outliers.
We also examined variability in freshwater forcing, subtropical gyre strength and position and Ekman transport. The cumulative freshwater forcing does have interannual variability, but it seems unrelated to changes in the position of the SSS-max. The subtropical gyre, as measured by dynamic height, is strongly seasonal, but has little interannaul variability. Southward Ekman transport is largest in 2012 and 2017, again not seeming related to the position of the SSS-max.

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