[A-OS12] Ocean Science Revealed by Global Observation System

[AOS12-03] Advancements of satellite-derived sea surface salinity

*Kaushik Sasmal¹, Xingkun Xu^1,2, Pavel Tkalich^1,2, Sumit Dandapat^1,2, Bijoy Thompson², Rajesh Kumar³, Kalli Furtado³, Hugh Zhang³ (1.Technology Centre for Offshore and Marine, Singapore (TCOMS), 2.Tropical Marine Research Institute (TMSI), National University of Singapore (NUS), 3.Centre for Climate Research Singapore (CCRS))

Keywords:Satellite observations, sea surface salinity, ARGO, river runoff

Salinity is a crucial ocean and environmental variable that impacts halosteric ocean potential and biogeochemical cycles. Salinity plays a key role in the hydrological cycle, global ocean thermohaline circulation, and climate variability. Measuring salinity is important in understanding density stratification, changes in the hydrological cycle, and the spreading of river plumes in coastal regions. Sea surface salinity (SSS) was identified as one of the essential climate variables (ECV) by the Global Climate Observing System (GCOS). A new era of satellite remote sensing of SSS began in November 2009 with the Soil Moisture and Ocean Salinity (SMOS) mission launched by the European Space Agency (ESA). SMOS has been operational for more than 15 years and provides the longest continuous SSS dataset at ~50 km spatial resolution with a repeat cycle of 2-3 days. Aquarius/SAC-D was launched in June 2011 by the National Aeronautics and Space Administration (NASA) and the Argentinean Space Agency (CONAE) and was operational until June 2015, thus completing its primary three-year mission. Aquarius mapped the SSS at ~150 km spatial resolution with a repeat cycle of 7 days. The Soil Moisture Active and Passive (SMAP) was launched by NASA in January 2015 and has been operational for more than 10 years. SMAP provides SSS at a higher spatial resolution (~40 km) than SMOS and Aquarius, with a repeat cycle of 8 days. The long-term availability of satellite SSS from SMOS and SMAP enabled researchers to examine changes in salinity at monthly, seasonal and interannual time scales. These data can provide new insights into mechanisms of moisture exchange between the land, ocean and atmosphere, as well as freshwater contribution to ocean circulation, weather, and climate. Despite many advancements in satellites measuring salinity, they still encounter challenges. Land-sea contamination near the coastal region is one of the issues in the retrieval of the remote SSS data. Efforts were made to rectify errors and improve the quality of SSS data and to reduce the systematic error caused by land-sea contamination. As such, the satellite SSS data require validation against in-situ measurements. In this presentation, we demonstrate the validation of satellite SSS against ARGO SSS for the Southeast Asian seas. This region is dominated by strong precipitation, evaporation, and a large volume of river runoff. Satellite SSS could be useful in enhancing our understanding of the hydrological cycle, ocean circulation, air-sea interaction, weather, and climate in Southeast Asia. This presentation highlights the advancements and challenges of satellite SSS.