May 28, 2017

Antarctica heights settle polar warming puzzle

Antarctica
by
Tim Radford
,
Climate News Network
The distant summit of Mount Vinson in Antarctica, rising to 4,892 meters, is higher than Mont Blanc (4,810 metres) in the European Alps. Photo: Torch Magazine via Flickr
The distant summit of Mount Vinson in Antarctica, rising to 4,892 meters, is higher than Mont Blanc (4,810 metres) in the European Alps. Photo: Torch Magazine via Flickr

Scientists believe they have settled one of the great polar puzzles − why Antarctica is warming at a rate so much slower than the Arctic region. And the answer is a simple one: Antarctica is so much higher.

To ram the point home, they used a computer simulation to hammer the entire southern continent until it was no more than a metre above sea level. At which point, in their simulation, warming at the South Pole became much more dramatic.

The two poles are very different: the Arctic is an ocean almost entirely surrounded by land, while Antarctica is a vast continent entirely surrounded by frozen ocean.

Landmass of ice

As the north polar ocean ice melts, dark seas begin to absorb more radiation. In the southern hemisphere, the landmass of ice reflects radiation back into space to insulate the continent and keep its temperatures far below freezing.

But the new study published in Earth System Dynamics journal shows that what makes the biggest difference is the elevation of the surface. Antarctica is not just an enormous continent: thanks to many millions of years of snowfall at very low temperatures, it is banked high with ancient ice.

Its average elevation is 2,500 metres − far higher than the highest peaks in the UK, for example − and its highest mountain, Mount Vinson, reaches 4,892 metres, which is higher than any alpine peak in Europe.

Evidence from the distant past and climate models both show that, in a warming world, the poles should warm faster than the rest of the planet. But while the Arctic is warming at twice the rate of the rest of the globe, change in Antarctica has been much more sluggish.