Satellite‐based Sea Surface Salinity designed for Ocean and Climate Studies

Type Article
Date 2021-11
Language English
Author(s) Boutin J.ORCID1, Reul NicolasORCID2, Koehler J.3, Martin A4, Catany R.5, Guimbard Sebastien6, Rouffi F.7, Vergely J.L.7, Arias M.ORCID5, Chakroun M.7, Corato G.8, Estella‐perez V.ORCID1, Hasson A.ORCID1, Josey S.ORCID4, Khvorostyanov D.1, Kolodziejczyk NicolasORCID12, Mignot J.1, Olivier L.ORCID1, Reverdin G.ORCID1, Stammer D.ORCID3, Supply Alexandre1, 13, Thouvenin‐masson C.1, Turiel A.ORCID9, Vialard J.ORCID1, Cipollini P.10, Donlon C.10, Sabia R.11, Mecklenburg S.10
Affiliation(s) 1 : Sorbonne University LOCEAN/IPSL Laboratory CNRS–IRD–MNHN Paris ,France
2 : University of Brest LOPS Laboratory IUEM UBO–CNRS–IRD–Ifremer Plouzané ,France
3 : Institut für Meereskunde Centrum für Erdsystemwissenschaften und Nachhaltigkeit Universität Hamburg ,Germany
4 : National Oceanography Centre Southampton,UK
5 : ARGANS Ltd, UK
6 : OceanScope, Brest, France
7 : ACRI‐st, Biot, France
8 : Adwaiseo ,Luxemburg
9 : Barcelona Expert Center (BEC) and Institute of Marine Sciences (ICM) CSIC ,Spain
10 : European Space Agency ECSAT Harwell ,United Kingdom
11 : Telespazio‐UK for ESA ESRIN Frascati, Italy
12 : University of Brest LOPS Laboratory IUEM UBO–CNRS–IRD–Ifremer, Plouzané, France
13 : University of Brest LOPS Laboratory IUEM UBO–CNRS–IRD–Ifremer, Plouzané, France
Source Journal Of Geophysical Research-oceans (2169-9275) (American Geophysical Union (AGU)), 2021-11 , Vol. 126 , N. 11 , P. e2021JC017676 (28p.)
DOI 10.1029/2021JC017676
WOS© Times Cited 18
Keyword(s) climate, ocean, salinity, satellite

Sea Surface Salinity (SSS) is an increasingly-used Essential Ocean and Climate Variable. The SMOS, Aquarius, and SMAP satellite missions all provide SSS measurements, with very different instrumental features leading to specific measurement characteristics. The Climate Change Initiative Salinity project (CCI+SSS) aims to produce a SSS Climate Data Record (CDR) that addresses well-established user needs based on those satellite measurements. To generate a homogeneous CDR, instrumental differences are carefully adjusted based on in-depth analysis of the measurements themselves, together with some limited use of independent reference data. An optimal interpolation in the time domain without temporal relaxation to reference data or spatial smoothing is applied. This allows preserving the original datasets variability. SSS CCI fields are well-suited for monitoring weekly to interannual signals, at spatial scales ranging from 50 km to the basin scale. They display large year-to-year seasonal variations over the 2010-2019 decade, sometimes by more than +/-0.4 over large regions. The robust standard deviation of the monthly CCI SSS minus in situ Argo salinities is 0.15 globally, while it is at least 0.20 with individual satellite SSS fields. r2 is 0.97, similar or better than with original datasets. The correlation with independent ship thermosalinographs SSS further highlights the CCI dataset excellent performance, especially near land areas. During the SMOS-Aquarius period, when the representativity uncertainties are the largest, r2 is 0.84 with CCI while it is 0.48 with the Aquarius original dataset. SSS CCI data are freely available and will be updated and extended as more satellite data become available.

Plain Language Summary

Salinity measures the mass of dissolved salts in seawater. Together with temperature and pressure, it determines the seawater density, which is crucial in driving oceanic motions. Low sea surface salinity (SSS) can be the result of freshwater inputs such as rain, river runoffs, and ice melt. In contrast, high SSS often characterize regions of strong evaporation. The salinity imprint of these processes is then carried by ocean currents over long distances and long periods of time. SSS also impacts ocean circulation through its effect on density, and modulates ocean-atmosphere exchanges of heat and gases. SSS is a hence key variable for ocean and climate studies, both as a passive tracer and as an important actor of oceanic processes.

Since 2010, three satellite missions have monitored SSS with an unprecedented spatial and temporal resolution. For the first time, data from these satellites are combined, taking each instrument specific features into account. The resulting dataset enables global SSS to be monitored and studied with unprecedented accuracy over the 2010-2019 period, at a 50km, weekly or monthly resolution. It reveals large SSS signals related to phenomena affecting climate in various parts of the world ocean.

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Boutin J., Reul Nicolas, Koehler J., Martin A, Catany R., Guimbard Sebastien, Rouffi F., Vergely J.L., Arias M., Chakroun M., Corato G., Estella‐perez V., Hasson A., Josey S., Khvorostyanov D., Kolodziejczyk Nicolas, Mignot J., Olivier L., Reverdin G., Stammer D., Supply Alexandre, Thouvenin‐masson C., Turiel A., Vialard J., Cipollini P., Donlon C., Sabia R., Mecklenburg S. (2021). Satellite‐based Sea Surface Salinity designed for Ocean and Climate Studies. Journal Of Geophysical Research-oceans, 126(11), e2021JC017676 (28p.). Publisher's official version : , Open Access version :