Global warming is making some parts of the oceans saltier, a new study has claimed.
A research led by Australian scientists showed a clear link between salinity changes at the surface and changes in the deeper waters over the last six decades caused by the warming seen over the same period.
“The saltiness or salinity of the oceans is controlled by evaporation and rainfall at earth’s surface,” said senior researcher Paul Durack of CSIRO, the Australian government’s research agency.
“The supercharging of weather patterns by global warming is making some parts of earth’s oceans much saltier while others parts are getting fresher,” Durack wrote in the Journal of Climate.
He said, the more evaporation there is at a given patch of ocean, the more concentrated the salts get in the seawater and the higher the salinity, however in places where lots of rain is falling, the water gets more diluted, becoming fresher.
The team analysed more than 460,000 oceanic readings collected by an army of 3,200 autonomous ARGO buoys and after subtracting out such things as cyclical seasonal salinity changes and other extreme events, they found a strong signal of more evaporation and rainfall over the oceans — an enhancement to the average surface salinity.
What they found is that the subtropical, evaporation-dominated waters of the Indian, Atlantic and Pacific oceans are getting saltier while the tropical and higher latitude waters are getting fresher — these later areas being where there is more rainfall than evaporation over the year.
But the matter goes deeper than just the ocean surface water, Durack said, adding “the ARGO buoys don’t just float around on the surface, they can sink down to two kilometres below the surface and rise again, gathering data the whole way to create three dimensional ocean profiles”.
These show that the salinity changes are actually moving, following the paths that ocean water circulates from the surface into the depths, Discovery Channel reported.
“While such changes in salinity would be expected at the ocean surface (where about 80 per cent of surface water exchange occurs), sub-surface measurements indicate much broader, warming-driven changes are extending into the deep ocean,” said Durack.
“This is probably one of the most significant papers we’ve seen yet in this area,” said Dean Roemmich, part of the ARGO leadership team.