Thickness of sea ice in Arctic and Antarctic is poles apart

THE FLOATING sea ice surrounding the South Pole may be thicker than previous estimates have suggested, according to a study based on a submersible robot that has mapped the sea ice in three key regions of the Antarctic.

Past estimates of Antarctic sea ice were based on satellite measurements from space, which can measure its overall surface area, and ice cores drilled through the sea ice from ice-breaking ships to measure its thickness.

However, unlike the Arctic sea ice where ice thickness has been monitored for decades by nuclear submarines, there are no military submarines allowed under the Antarctic Treat.

This means that large regions of the sea ice have effectively remained unexplored from below, scientists said.

With the help of a 2m-long, twin-hulled autonomous underwater vehicle (AUV), scientists from the US, Australia and the British Antarctic Survey (BAS) have drawn up the first detailed, high-resolution 3D map of Antarctic sea ice in areas that were in the past considered too difficult to study from ice breakers.

“The AUV missions have given us a real insight into the nature of Antarctic sea ice, like looking through a microscope,” said Jeremy Wilkinson of the British Antarctic Survey. “We can now measure ice in far greater detail and were excited to measure ice up to 17m thick.

“It gave us a really good basis for what the ice thickness is at present. Over time we hope to make repeat measurements and build up a time series to see how the sea ice thickness is changing,” he said.

The robotic submersible used upward-looking sonar to map the thickness of the sea ice over an area of 1 294 994km2 in three locations – the Weddell, Bellinghausen and Wilkes Land sectors of Antarctica.

While the sea ice in the Arctic has decreased in surface area by about 40 percent over the past 40 years, the sea ice in the Antarctic has increased for reasons that are still under debate.

Wilkinson said that one cause could be a change in wind patterns that is blowing sea ice further out to sea. – The Independent