Published on April 19th, 2010 | by Joshua S Hill
Increased Ocean Salinity Shows Intensified Water Cycle
A new study to be published in an upcoming edition of the American Journal of Climate showcases evidence that the world’s water cycle has intensified.
[social_buttons]The new study, co-authored by CSIRO scientists Paul Durack and Dr Susan Wijffels, looks at over 50 years of data and finds increases in ocean surface salinity levels across the planet. The study shows that surface ocean rainfall-dominated regions have freshened while regions dominated by evaporation are saltier.
“This is further confirmation from the global ocean that the Earth’s water cycle has accelerated,” says Paul Durack.
The water cycle refers to the continuous movement of water on, above and below the surface of the Earth. This includes water in all it’s various forms including ice, gas and liquid. Intensification of the water cycle does not intrisically mean increased rainfall, as the water cycle is responsible for rainfall as well as drought.
The 2007 Intergovernmental Panel on Climate Change predicted that the water cycle would intensify thruoghout the 21st century, and it appears that this CSIRO study is adding credance to that claim.
However, the changes occurring are not simply surface driven. The study also confirms that the warming we have seen in the surface temperatures has also seeped into the oceans’ interior, subsequently changing salinity patterns.
“While such changes in salinity would be expected at the ocean surface (where about 80 per cent of surface water exchange occurs), subsurface measurements indicate much broader, warming-driven changes are extending into the deep ocean,” Mr Durack said.
These subsurface changes have been tracked as originating from salinity changes at the surface thanks to trajectories that surface water traditionally travels into the interior.
“Observations of rainfall and evaporation over the oceans in the 20th century are very scarce,” said Mr Durack, a PhD student at the joint CSIRO/University of Tasmania, Quantitative Marine Science program. “These new estimates of ocean salinity changes provide a rigorous benchmark to better validate global climate models and start to narrow the wide uncertainties associated with water cycle changes and oceanic processes both in the past and the future – we can use ocean salinity changes as a rain-gauge.”
Information for the study included over 1.6 million salinity profiles and data from the internatinoal Argo Program, an observation program that provides real-time data for use in multiple industries and research projects. Argo is made up of a massive fleet of small oceanic robotic probes and is a collaboration between 50 research and operational agencies from 26 countries.
Image Source: CSIRO