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Salinity

Salinity is the dissolved-salt content of seawater. Open-ocean surface values are typically about 32-37 grams of salt per kilogram of water: practical salinity, numerically close to the PSU scale.

Saltier water is denser. Together with temperature, salinity sets the density that drives thermohaline circulation: the slow overturning that links surface currents to the deep ocean. Rivers, rain, and melting ice freshen the surface; evaporation and sea-ice formation make it saltier.

The figures are NASA Aquarius observations of sea-surface salinity from the 2011-2015 mission.

Mollweide map of ocean surface salinity from Aquarius, 2011, purple fresh to red salty, gray land
NASA / JPL-Caltech, Aquarius mission first global salinity map. Vintage: 25 Aug-11 Sep 2011.

NASA Aquarius, 2011-2015. Observed surface salinity in g/kg. Later satellite months: SMAP, in NASA Worldview.

Satellite · Aquarius SSS 2011 NASA Aquarius 2011

Aquarius first global salinity map

NASA Aquarius, 25 August-11 September 2011: the mission’s first global sea-surface salinity map. Microwave SSS, in g/kg. Fresher plumes at the Amazon and Ganges; saltier subtropical Atlantic.

On the 2011 global map, purple and blue mark fresher water (Amazon and Ganges plumes, high latitudes); yellow and red mark saltier subtropical seas, especially the North Atlantic and the Arabian Sea. Units are g/kg. The second figure is a 3-D Atlantic view from the same mission.

The SMAP mission continues microwave sea-surface salinity after Aquarius. World Ocean Atlas 2023 is a separate in-situ climatology: bottles, CTDs, and floats, averaged over many years.

NASA / JPL-Caltech, Aquarius mission first global salinity map
Vintage: 25 Aug-11 Sep 2011
https://www.jpl.nasa.gov/images/pia14786-aquarius-unveils-the-salty-sea/
License: Public domain (NASA)

Open NASA Worldview SMAP salinity → World Ocean Atlas 2023 →