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A Comparison of Satellite-Derived Sea Surface Salinity and Salt Fluxes in the Southern Ocean

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Abstract

Sea surface salinity (SSS) derived from the multi-satellite missions, NASA’s Aquarius/SAC–D and Soil Moisture Active and Passive (SMAP), and ESA’s Soil Moisture and Ocean Salinity (SMOS) are compared and used to estimate horizontal advective salt fluxes in the Southern Ocean (SO). In comparison with an Argo product, all three satellites estimate similar SSS in the Southern Hemisphere mid-latitudes (30° S–45° S) with low variability among the products. At high latitudes, there are temporal patterns of bias (relative to Argo) in Aquarius during Austral summer and in SMOS during Austral winter. Differences in the satellite products and Argo exist along coastal boundaries, low temperatures, and strong currents. Satellite-derived salinity indicates low temporal–mean standard deviations with Aquarius (0.215) and moderate standard deviations with SMOS (0.294) and SMAP (0.325) against Argo in the SO. Differences in satellite-derived zonal and meridional SSS gradients are large; standard deviation values are 2.52 and 1.49 × 10−6 psu m−1, respectively, and similarly located within the sub-tropical salinity maxima, Antarctic Circumpolar Current, and coastal zones. Differences in the horizontal advective fluxes are on average small, but large variability greater than 275 mm month−1 indicates errors of similar magnitude to the estimated Argo flux. Based on these results, the use of satellite-derived salinity may prove to be a useful resource for observing salinity and horizontal salt fluxes, outside the inaccuracies associated with the high latitudes and coastal currents between the various remotely sensed products, and could significantly influence the results depending on the product.

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Acknowledgments

Brady S. Ferster is supported by the NASA/South Carolina Space Grant Graduate Fellowship. Aquarius version 5.0 L3 (ftp://podaac-ftp.jpl.nasa.gov/allData/aquarius/L3/mapped/V5/monthly/SCI/) and OSCAR (https://doi.org/10.1175/1520-0485(2002)032<2938:DMAAOT>2.0.CO;2) datasets are obtained from the NASA’s JPL Physical Oceanography Distributed Active Archive Center (PO.DAAC). The SMOS unbiased binned data used for this study is the L3 Operational version 2.0 provided by the ESA obtained from the SMOS Barcelona Expert Center Data distribution and visualization services (https://doi.org/10.1016/j.rse.2016.02.038). The SMAP data are produced by Remote Sensing Systems, Santa Rosa, CA, and version 2.0 level 3 is obtained from NASA JPL PO.DAAC (ftp://podaac-ftp.jpl.nasa.gov/allData/smap/L3/RSS/V2/monthly/SCI/). Argo data (Argo DOI: https://doi.org/10.17882/42182) is obtained from the Asia-Pacific Data Research Center (APDRC) of the International Pacific Research Centre (IPRC), the 1° gridded on standard levels product. The authors would like to thank the anonymous reviewers and the editor, whose comments significantly contributed to the improvement of this paper.

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  1. School of the Earth, Ocean and Environment, University of South Carolina, Columbia, SC, 29208, USA

    Brady S. Ferster & Bulusu Subrahmanyam

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Correspondence to Brady S. Ferster.

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Ferster, B.S., Subrahmanyam, B. A Comparison of Satellite-Derived Sea Surface Salinity and Salt Fluxes in the Southern Ocean. Remote Sens Earth Syst Sci 1, 1–13 (2018). https://doi.org/10.1007/s41976-018-0001-5

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