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Tuesday, May 5, 2009

A Reason the North Atlantic is getting Saltier

Research from the United Kingdom (U.K.) suggests that the amount of salt in seawater is varying in direct response to man-made climate change.

Working with data collected over the past 50 years, and comparing the data to climate models that correct for naturally occurring salinity variations in the ocean, Peter Stott, head of climate monitoring and attribution at the Met Office, has found that man-made global warming, over and above any possible natural sources of global warming, such as carbon dioxide given off by volcanoes or increases in the heat output of the sun, may be responsible for making parts of the North Atlantic Ocean more salty, according to the article from NASA's Jet Propulsion Laboratory.

The increase in North Atlantic salinity over the past 50 years has been less than 1%, but that is still significant, according to Stott.

Salinity levels directly affect seawater density (salty water is denser than fresh) and the circulation of ocean currents from the tropics to the poles. These currents control how heat is carried within the oceans and ultimately regulate the world's climate. Second, sea surface salinity is intimately linked to Earth's overall water cycle and to how much freshwater leaves and enters the oceans through evaporation and precipitation.

The conveyor belt of the world's ocean currents.

The low resolution graphic below shows the observed and predicted salinity changes over the top 500 meters of seawater in the Atlantic. Graphic courtesy of the JPL.

Important paragraph from the article........

Stott’s analysis suggests that global warming is changing precipitation patterns over our planet. Higher temperatures increase evaporation in subtropical zones; the moisture is then carried by the atmosphere towards higher latitudes (towards the poles), and by trade winds across Central America to the Pacific, where it provides more precipitation. This process concentrates the salt in the water left behind in the North Atlantic, causing salinity to increase.

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