Giant spinning eddies have profound influence on marine life and world's climate

Washington, September 10 : New studies of the Southern Ocean are revealing previously unknown features of giant spinning eddies that have a profound influence on marine life and on the world's climate.

These massive swirling structures - the largest are known as gyres - can be thousands of kilometres across and can extend down as deep as 500 metres or more, a research team led by a UNSW mathematician, Dr Gary Froyland, has shown.

"The water in the gyres does not mix well with the rest of the ocean, so for long periods these gyres can trap pollutants, nutrients, drifting plants and animals, and become physical barriers that divert even major ocean currents," said Dr Froyland.

"In effect, they provide a kind of skeleton for global ocean flows. We're only just beginning to get a grip on understanding their size, scale and functions, but we are sure that they have a major effect on marine biology and on the way that heat and carbon are distributed around the planet by the oceans," he added.

One of the best known large-scale gyres in the world's oceans is that associated with the Gulf Stream in the North Atlantic, noted fellow researcher Professor Matthew England, co-director of the UNSW Climate Change Research Centre.

"This current pumps massive amounts of heat towards Europe, warming the atmosphere and giving the region a relatively mild climate: to see how important that is, you only have to compare Portugal's climate to that of Nova Scotia, in Canada, which as roughly the same latitude," he said.

After releasing heat to the atmosphere the waters re-circulate toward the equator, where they regain heat and rejoin the flow into the Gulf Stream.

In this way, the ocean's gyres play a fundamental role in pumping heat poleward, and cooler waters back to the tropics.

"This moderates the planet's extremes in climate in a profound way, reducing the equator-to-pole temperature gradients that would otherwise persist on an ocean-free planet," said Professor England.

The East Australia Current has a similar, although more modest, impact on local climate on the Australia's east coast.

Eddies also regulate biologically important properties such as nutrient upwelling to the surface. They are also fundamental in mixing heat across the Antarctic Circumpolar Current.

ANI