The Arctic is melting. We know that already. But now we’re in worse trouble, because the Antarctic is disappearing too.
By studying 36 years of satellite images, researchers have spotted the worrying trend. Until now, they thought that the Antarctic ice sheet was actually growing, but that has changed.
The Arctic consists of a sea surrounded by land, and this stops its ice from drifting away every summer. The Antarctic is the opposite–land surrounded by water–so most of it melts every year. But every winter it refreezes, covering almost 7 million square miles with sea ice. And until now, the annual freeze has been laying in more ice every year. Against expectations, the ice sheet has been growing.
Until this year. After reaching a peak of 7.1 million square miles in August, the ice started disappearing a month ahead of schedule, and faster than ever. Throughout September, every day set a new record for low ice levels. This comes just two years after a record high level of sea ice in the Antarctic. What’s going on?
While the average Antarctic temperatures haven’t changed much recently, with the surface water actually cooling, deep under the ocean things are heating up.
“This cooling masks a much more ominous change deeper down in the ocean, particularly near the West Antarctic Ice Sheet and the Totten glacier in East Antarctica,” write the authors in The Conversation. “In these regions, worrying rates of subsurface ocean warming have been detected up against the base of ice sheets. There are real fears that subsurface melting could destabilize ice sheets, accelerating future global sea level rise.”
The causes for these contradictions are hard for them to pin down. It could be winds, with their patterns changed by greenhouse gasses and ozone depletion, that are pushing colder surface water north, increasing the size of the ice sheets in that direction, even as the subsurface ice melts.
Working out what’s happening Antarctic is even harder, thanks to the area’s notoriously fickle climate and the lack of historical data. “The problem we face in Antarctica is that the climate varies hugely from year to year,” say the researchers. “This means 37 years of Antarctic surface measurements are simply not enough to detect the signal of human-caused climate change.”
To be able to predict the long-term future of the Antarctic ice sheets, we may need to observe them until 2100 before we have enough data to make accurate guesses. And by then, Australia and the rest of the area’s countries may already have succumbed to drought, sea-level rises, and heat-waves.