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Sea Surface Salinity

Related Missions
  • Aquarius/SAC-D
    The Aquarius/SAC-D (Satélite de Aplicaciones Científicas-D) mission, launched on June 10, 2011 and decommissioned on June 7, 2015 was a joint venture between NASA and the Argentinean Space Agency Comisión Nacional de Actividades Espaciales (CONAE).  It was the first NASA mission dedicated to measuring sea surface salinity (SSS) from space. Data from Aquarius and now from SMAP is playing a large role in understanding physical oceanographic processes and the global hydrological cycle.
  • SMAP
    The NASA Soil Moisture Active Passive (SMAP) mission was launched on January 31, 2015 to principally measure soil moisture and freeze/thaw state from space for all non-liquid water surfaces globally within the top layer of the Earth.
    The Salinity Processes in the Upper Ocean Regional Study (SPURS) project is a series of science process studies and associated oceanographic field campaigns that aim to elucidate key mechanisms responsible for near-surface salinity variations in the oceans.
What is Sea Surface Salinity?

aquarius_globe_STILL.11000_webSalinity in the ocean is defined  as the grams of salt per 1000 grams of water. One gram of salt per 1000 grams of water is defined as one practical salinity unit or one PSU.  Salinity varies due to evaporation and precipitation over the ocean as well as river runoff and ice melt. Along with temperature, it is a major factor in contributing to changes in density of seawater and therefore ocean circulation.

How is Sea Surface Salinity Measured?

The Aquarius mission, launched on June 10, 2011, is the first mission with the primary goal of measuring sea surface salinity (SSS) from space. Data from Aquarius will play a large role in understanding both climate change and the global water cycle.
data collectorsIn the open ocean the range of salinity is generally from 32 psu to 37 psu.  Along with temperature, it is a major factor in contributing to changes in the density of seawater and therefore ocean circulation. Salinity is the key to understanding the global water cycle. 97% of the Earth's free water resides in the oceans.  The water cycle is dominated by precipitation and evaporation. Precipitation over the oceans account for 12 Sverdrups (Sv = 1 million m3s-1), with an additional Sv flowing into the oceans from terrestrial runoff.  Evaporation over the ocean is equal to 13 Sv.  In contrast precipitation and evaporation over land account for 3 Sv and 2 Sv respectively. Sea surface salinity can be used to measure the difference of these two processes, with excess precipitation resulting in lower salinities and excess evaporation yielding higher sea surface salinities. SSS is a measure of ice melt at high latitudes with glacial and sea ice melt causing a freshening of the surface waters
While sea surface temperatures have been measured from space for over 3 decades, the technology to measure sea surface salinity from space has only recently emerged.  Sea surface density, a driving force in ocean circulation and a function of temperature and salinity will finally be measurable every month on a  global scale. As the oceans have 1100 times the heat capacity of the atmosphere, the  ocean circulation becomes critical for understanding the transfer of heat over the Earth and thus understanding climate change

About Data
  • Aquarius Validated Project Data
    • All Aquarius validated data (version 2.0 and above) and related documentation and reader software resources are accessible via the public PO.DAAC FTP-site.  Descriptions and metadata on all Aquarius data products are available via the PO.DAAC portal online data catalogue.
  • NASA Ocean Data Sources Page administered by Goddard
    • Includes Discovery & Exploration, Water Cycle, Ocean Circulation & Climate, Scientific Investigations, Data Sources and References sections.