Antarctica is warmer than it should be
Eyal Bartov / Alamy
Since the beginning of September, temperatures in the atmosphere above Antarctica have soared by over 35°C (63°F), while wind speeds have halved and ozone depletion has suddenly stalled.
This kind of upheaval should happen only once every 20 years or so, says Martin Jucker at the University of New South Wales in Sydney, Australia. Instead, these events seem to be becoming more frequent, with short-lived disruption occurring last year, and more serious events in both 2019 and 2002.
Jucker says to have four of these events in less than a quarter of a century indicates alarming changes are under way in the global climate system.
Antarctic atmospheric temperatures should normally be -55°C (-67°F), but since 5 September, they have risen inexorably to -20°C (-4°F). While this is still frigid, it means that wind speeds in the stratosphere – the polar vortex – have dropped by half to a comparatively calm 100 kilometres per hour.
The warming doesn’t yet constitute the formal definition of a sudden stratospheric warming event, says Jucker. To hit that threshold, the winds would need to cease altogether during a warming spike lasting days, not a few weeks. However, he says, the implications for the southern hemisphere in the coming months could be significant.
Meteorologists in Australia, who initially predicted a wetter-than-normal spring, are now warning of potential strong westerlies over the Australian continent, leading to warmer, drier conditions.
The strange weather is also not yet over. A couple of scenarios may unfold in the coming weeks, says Jucker. The first is that the polar vortex re-establishes itself and atmospheric temperatures return to the average trendline.
Alternatively, the anomaly could continue, with some suggestions that the atmospheric temperature rise could increase another 20°C (36°F). As a result, northern latitudes of the southern hemisphere could be in for some wild weather.
While the cause of the anomaly hasn’t yet been scientifically established, Jucker says he is almost certain that increasing sea surface temperatures due to climate change, by between 1°C (1.8°F) and 2°C (3.6°F) in the Pacific, is driving the current slowdown in the polar vortex.
“We’ve also had these three massive typhoons in the Pacific, which are also due to sea surface temperatures,” Jucker says. “We have just generally had very weird weather for the last two years and that all coincides with this very big jump in ocean temperature.”
Edward Doddridge at the University of Tasmania, Hobart, Australia, says the list of extreme changes at the bottom of the world keeps getting longer. In the last few years, there’s been sea ice loss, heatwaves, widespread breeding failures at emperor penguin colonies, and a dramatic slowdown in the Antarctic overturning circulation.
“Antarctica keeps surprising us,” he says. “While each of these changes is concerning in its own right, my biggest worry is that we are starting to see changes that not only reinforce themselves, but also cascade through different parts of the Antarctic environment.
“Sea ice loss in the summer enhances the breakup of ice shelves and causes ocean warming. These warmer ocean waters melt the remaining ice shelves faster, and this fresh water slows down the Antarctic overturning circulation,” says Doddrige.
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