Boffins say hot air makes Antarctica colder

The Antarctic anomaly – that it's warming slower than the rest of the world – could actually be driven by climate change, according to new modelling from the Australian National University (ANU). The research also suggests that southern Australia, particularly in the west, will get less rain as a result.

Climate change denier sites have long seized upon Antarctica's slower warming as evidence against planetary warming, but paradoxically, what's happening to the globe as a whole is what's keeping warmer air away from the southern continent.

According to the ANU research team, led by Nerilie Abram in the university's School of Earth Sciences, the wind vortex now surrounding Antarctica is the strongest in the last thousand years. Those Southern Ocean winds are blocking warmer air from reaching the continent, the researchers say – but at the same time, they're thieving rainfall from Western Australia.

The work is based on atmospheric carbon that's been trapped in the ice, with ice core samples allowing the group to test wind models stretching back 1,000 years.

Their paper, published in Nature Climate Change, (abstract here), looked at how the climatic phenomenon known as the Southern Annular Mode (SAM) has changed, based on the ice core samples, measurements from tree rings and lakes in South America, and more recent data collected since the blossoming of Antarctic science 70 years ago.

Abram's team ran simulations of the last millennium in eight different climate models, with all the models agreeing that SAM winds would increase as of 1940. As New Scientist explains, the winds could be boosted by a strong temperature gradient between the northern hemisphere and the southern, because the former has more continents and is warming faster.

That's bad news for Western Australia. The strengthening SAM had been attributed to the hole in the ozone layer. If that were the sole cause, then there would be hope that as the ozone hole shrinks, Western Australia (which has lost 20 per cent of its rainfall since the 1960s) might see fewer droughts.

However, if greenhouse gases – which are on the rise – are also a driver of the stronger SAM, then the west of the continent will stay dry.

“As the westerly winds are getting tighter they’re actually trapping more of the cold air over Antarctica,” Abram says in the ANU's release.

“As greenhouse gases continue to rise we’ll get fewer storms chased up into Australia”.

Meanwhile, western Antarctican peninsulas that are outside the vortex are warming right on cue. ®