Dec 22, 2014

Salinity matters

(18 December 2014) Measurements of salt held in surface seawater are becoming ever-more important for us to understand ocean circulation and Earth’s water cycle. ESA’s SMOS mission is proving essential to the quest.

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The Soil Moisture and Ocean Salinity satellite, SMOS, is monitoring changes in the amount of water held in the surface layers of soil and concentrations of salt in the top layer of seawater – both of which are a consequence of the continuous exchange of water between the oceans, the atmosphere and the land.

Launched in 2009, SMOS has provided the longest continuous record of sea-surface salinity measurements from space.

The salinity of surface seawater is controlled largely by the balance between evaporation and precipitation, but fresh water from rivers and the freezing and melting of ice also changes the concentrations.

Along with temperature, salinity drives ocean circulation, which, in turn, plays a key role in the global climate.

With a wealth of salinity data from SMOS now in hand complemented by measurements from the US–Argentinian Aquarius satellite, which uses a different technique, scientists gathered recently at the UK Met Office to review the benefits this has brought to science.

Speaking at the Ocean Salinity Science and Salinity Remote-Sensing Workshop, Prof. Dame Julia Slingo, Met Office Chief Scientist, said, “We need to understand the role of salinity in the closure of the hydrology cycle – arguably the weakest point in global climate modelling.

“Salinity, and particularly sea-surface salinity, is a challenging but important topic for ocean circulation and climate variability about which we need to know more, especially given the recent climate-warming hiatus.