Scientists find link between Southern Ocean winds and drying Australia

Updated

Researchers have established a new explanation for why southern Australia has dried out over the past few decades - and it is all to do with Antarctica.

A painstaking reconstruction of the past 1,000 years of Southern Ocean winds has found they are strengthening and moving closer to Antarctica.

The report in the journal Nature Climate Change has found the winds keep Antarctica cool and effectively pull storm clouds away from Australia.

Australian National University researcher Dr Nerilie Abram said those winds, known as the Southern Annular Mode, posed significant problems for farmers, particularly the nation's south-west.

"As we see those westerly winds pull in tighter towards Antarctica, it means that the farmers in [southern Australia] are actually getting less of those storms bringing them that vital rain," the lead author said.

The report shows that between 1300 and 1400AD there was a significant weakening of the winds, but Dr Abram said this recent strengthening was more than natural variability.

"That's why having these long records [is so important]," she said.

"We can see that what's happening now steps outside that envelope of natural variability and is something that's unusual.

"We can then relate that quite clearly to the increases in greenhouse gases in the atmosphere."

Sceptics have pointed to the fact that Antarctica is not warming as fast as the rest of the world, as an example of the climate change threat being overblown.

Dr Abram said her work questioned some of those theories.

"We can explain Antarctica not getting warmer as quickly as the other continents by the strengthening of the westerly winds," she said.

"Because as those westerly winds tighten around Antarctica, they actually trap air and they stop those warm winds from being able to come in over the continent."

Warming Antarctic ice contributing to sea level

Since the 1970s, Antarctic sea ice has on the whole actually been increasing - adding 285,000 square kilometres every decade according to the Antarctic Climate and Ecosystems Cooperative Research Centre.

Sceptics say that is another reason why warming is not as bad as first thought, but University of New South Wales Professor Matthew England does not agree with that argument.

"I wish they were right because it would leave one part of the climate system relatively untouched from global warming, but unfortunately they're wrong," he said.

Sorry, this video has expired Video: Dr Nerilie Abram describes her research (ABC News)

"They're avoiding looking at the data of the West Antarctic Ice Sheet which shows rapid warming, a loss of ice and a contribution to sea level that is accelerating.

"Of course, even if the whole of Antarctica was staying resilient and cold and there was no ice lost from that part of the world, the fact is the Greenland ice sheet is melting rapidly and that doesn't just leave sea levels rising in the north Atlantic.

"That sea level rise from Greenland alone spreads globally and makes an impact."

Professor England and Dr Abram, who both worked on the paper, said the solution was clear.

"The model clearly tells us those westerly winds are going to continue contracting towards Antarctica and Australia will continue to miss out on rainfall," Dr Abram said.

"So really it's a very simple story - if we can get on board and do things that are going to reduce our emissions then this system should respond very quickly to that."

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Topics: climate-change, environment, antarctica, australia

First posted