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Oceans

Ocean Hotspots and Strengthening Winds Driving Ocean Currents Poleward

Oceanographers from across the world have identified a series of ocean hotspots that have been generated by strengthening wind systems across the planet that are successfully pushing oceanic current polewards, well beyond their known boundaries.

The hotspots – locations where the temperature has increased outside of expected norms – have formed alongside ocean currents that wash up against the east coast of major continents, including the Agulhas off the coast of Africa, Kuroshio near Japan, the famous Gulf Stream off the coast of North America,  Brazil off the continent of South America, and the East Australian Current which evident describes it’s own location.

The research was published Monday in the journal Nature Climate Change, and paper co-author Wenju Cai, from Australia’s CSIRO lab, said that while the finding has local ecological implications in the region surrounding the hotspots, the major influence is upon the ocean’s ability to take up heat and carbon from the atmosphere.

Speaking of the impact on the East Australian Current, scientists report intensifying east-west winds at high latitudes pushing southward and speed up the gyre circulating in the South Pacific which extends from South America to the Australian Coast. As a result of this push, the East Australian current has been pushed approximately 350 kilometres south, shifting temperatures east of Tasmania by as much as 2 degrees Celsius warmer than they were 60 years ago.

“We would expect natural change in the oceans over decades or centuries but change with such elevated sea surface temperatures in a growing number of locations and in a synchronised manner was definitely not expected,” said CSIRO’s Dr Wenju Cai, a climate scientist at CSIRO’s Wealth from Oceans Research Flagship.

“Detecting these changes has been hindered by limited observations but with a combination of multi-national ocean watch systems and computer simulations we have been able to reconstruct an ocean history in which warming over the past century is 2-3 times faster than the global average ocean warming rate,” says Dr Cai.

The changes Dr. Cai refers to are characterised by currents pushing nearer to the polar regions as well as an intensification in the systematic changes of wind over both hemispheres.

Dr Cai said the increase of carbon dioxide and other greenhouse gases in the atmosphere has been the major driver of the surface warming of the Earth over the 20th century. This is projected to continue.

He said the research points to the need for a long-term monitoring network of the western boundary currents. In March next year, Australian scientists plan to deploy a series of moored ocean sensors across the East Australian Current to observe change season-to-season and year-to-year.

Source: CSIRO




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