Ocean Salinity, a Key Parameter to Study the Linkages of the Oceans with the Terrestrial Water Cycle
[14-Dec-2018] Fournier, S.
Presented at the 2018 AGU Fall Meeting
Salinity is a key parameter reflecting the global water cycle changes, including impacts of precipitation, evaporation, and runoff. The water cycle is dominated by ocean-atmosphere exchanges, with 86% (76%) of the evaporation (precipitation) occurring over the ocean. The net evaporation-precipitation ends up on land, and returns to the ocean via runoff. Although runoff only accounts for about 10% of the total oceanic freshwater input, it is critical to the coastal oceans through its effects on marine biogeochemistry and physical processes. Terrigenous matters carried by rivers can have a profound impact on marine ecology, and river discharge affects the surface layer buoyancy, ocean currents, and air-sea interactions.
The water cycle is expected to intensify in a warmer climate with more extreme droughts and floods and stronger storms. Salinity data in the last 50 years revealed salinifying subtropical gyres and freshening tropical and high-latitude oceans, consistent with the expected impacts of an intensified water cycle. Understanding related changes in coastal oceans, if any, requires a new capability beyond that provided by in situ
Since 2010, ESA's SMOS, NASA's Aquarius and NASA's SMAP missions provide unprecedented capability to monitor sea surface salinity (SSS) over the global ocean at several temporal and spatial scales, complementing the in situ
salinity observing system. In coastal oceans and marginal seas, measurements are sparse, thus satellite SSS provide a unique advantage to study the linkages of the ocean with terrestrial water cycle and the associated oceanic impacts.
In this presentation, examples of satellite SSS applications to study land-sea linkages will be presented, including studies of river plume variability in the tropics (tropical Atlantic and Bay of Bengal), mid-latitude regions (Gulf of Mexico), and high-latitude oceans (Arctic Ocean). The capability of satellite SSS in characterizing seasonal and interannual variability of river plumes and monitoring the impact of flooding on coastal oceans will be illustrated, as well as, examples of using satellite SSS to study cross-shelf exchanges. The examples also underline the importance of using satellite SSS to constrain global models that often use climatological discharges and relax model SSS to climatology.