Fluctuations in Ocean Salinity Could Forewarn of Climate Change

Significant increase or decrease in ocean salinity could forewarn of climate change in 10 to 20 years time, researchers say.

The results, presented at a recent European Science Foundation (ESF) conference states that a build up of salty water stimulates deep-water circulation, while a diluting of the waters results in sluggish flow.

“Salt plays a far more important role that we first thought,” said Prof. Rainer Zahn, a palaeoclimatologist at the Autonomous University of Barcelona in Spain.

Salt increases the density of water. Once a pocket of water becomes salty enough, it sinks, drawing in additional water from surrounding areas, and initiating an ocean circulation loop called thermohaline overturning.

Using a combination of modern observations, numerical models and palaeoclimate data, scientists have now discovered that a build up of salt in the waters off the coast of South Africa could help speed up ocean circulation in the North Atlantic, despite the two areas being thousands of kilometres apart.

“A salt surge is enough to kick start circulation. Meanwhile, a decrease in saltiness in South African waters could be linked to a slowing down of the North Atlantic circulation,” said Prof. Zahn.

Prof. Zahn said though models and data both indicate that these changes in ocean circulation over on a very short time-scale, usually in less than a decade or two (It takes nearly a century for a parcel of water to move from the South Atlantic to the North Atlantic), the energy is transferred through the ocean along a deep pressure wave.

“The surge of salt generates a pressure gradient in the ocean that sends energy to the north without water actually being transported,” said Prof. Zahn.

“Currently there is no large-scale salt monitoring system in place in the southern hemisphere oceans. Regular measurements taken in the waters around South Africa and New Zealand could be useful. It could act as an early warning system for climate changes 10-20 years down the road,” he said.

The work was presented at the ‘Ocean Controls in Abrupt Climate Change’ conference, held at the University of Innsbruck Conference Centre in Obergurgl, Ötz Valley, Austria, May 19-24, 2007.

Source-ANI
MED/L