|Variations in sea surface salinity influence the movement of seawater and heat around the globe. Credit: NASA.
After less than a month in operation, a new NASA satellite has produced the first map showing how saltiness varies across the surface of the world’s oceans. Salt influences how seawater and heat move around the globe and also tells oceanographers how much rain and evaporation is happening at the surface. Until now, salt measurements came only from ships, moorings and buoys floating at sea; NASA says its Aquarius satellite will capture in three years as much data as those earlier methods did in 125 years.
|NASA’s new map shows how salt is distributed in the surface layer of earth’s oceans. The saltiest places are in red; the least salty, in purple. Credit: NASA. [CLICK TO ENLARGE].
From space, orbiting satellites currently track sea surface temperatures, wind speed and direction, biological productivity, sea ice extent and sea surface height. Aquarius fills in the last major gap: salt. The saltiness of seawater plus its temperature, determines whether surface seawater sinks or floats, which in turn drives ocean circulation, bringing warmer waters and a milder climate to some parts of the globe and colder water and a harsher climate to others.
|Ocean salinity has traditionally been measured by dropping sensors below the sea surface. Credit: Arnold Gordon, Lamont-Doherty.|
NASA produced the salinity map using Aquarius’s first month of data, checked against older, shipboard measurements. The map confirms what oceanographers already knew; the saltiest stretch of sea is in the subtropical North Atlantic Ocean, at the same latitude as Africa’s Sahara Desert. The seas are least salty along the equator and at the poles, where more water falls as rain or snow than returns to the air through evaporation
The satellite was launched in June from Vandenberg Air Force Base in California and became operational on Aug. 25. The project is funded by NASA and Argentina’s space agency, Comisión Nacional de Actividades Espaciales.