Return of 'ocean chimney' the size of Tasmania puzzles Antarctic scientists

A rare hole the size of Tasmania has opened up in the sea ice off Antarctica, enthralling scientists keen to understand its cause and the possible role of climate change in its formation.

Water vapour rises off the Antarctic ice sheet as a
 rare hole opens in the Antarctic winter sea ice. 

Known as the Weddell Sea or Maud Rise Polynya, the ice-free zone appeared in September and has grown to as large as 80,000 square kilometres, according to the University of Toronto.

Polynyas, defined as a stretch of open water surrounded by ice, are frequently found in the Arctic and Antarctica, usually near the coast. They rarely reach the extent now seen in middle of the pack ice.

"Something has changed" to bring the polynya back, Kent Moore, a professor of physics at the University of Toronto, said. "But we not quite sure what that trigger was," he said.

Read Peter Hannam’s story in today’s Melbourne Age - “Return of 'ocean chimney' the size of Tasmania puzzles Antarctic scientists.”