Otago theory on sea ice breakup backed
AUSTRALIAN scientists have found evidence supporting an earlier University of Otago hypothesis over the way stormdriven ocean swells have triggered the ‘‘catastrophic’’ breakup of Antarctic ice shelves in recent decades.
This study, recently published in Nature, supports ideas arising from modelling work done by Prof Vernon Squire of Otago University and Dr Timothy Williams, then an Otago PhD student, and published in 2007.
The latest research provided ‘‘evidence to support that hypothesis’’, Prof Squire said.
He is Otago University deputy vicechancellor, academic and international, and also studies modelling processes involving polar sea ice, in the University of Otago department of mathematics and statistics.
The earlier Otago modelling work and the latest research findings highlighted the need for sea ice and ocean waves to be included in overall sea ice modelling, he said in an interview.
‘‘The more we get the model right, the more accurate our predictions are going to be.
‘‘They used the same model I developed back in 2007,’’ he said.
Lead author Dr Rob Massom, of the Australian Antarctic Division and the Antarctic Climate and Ecosystems Cooperative Research Centre, said reduced sea ice coverage since the late 1980s led to increased exposure of ice shelves on the Antarctic Peninsula to ocean swells, causing them to flex and break.
Sea ice acted as a protective buffer to ice shelves, by ‘‘dampening destructive ocean swells before they reach the ice shelf edge’’, Dr Massom said.
But where sea ice had been lost, ocean swells could easily reach the exposed ice shelf, ‘‘causing the first few kilometres of its outer margin to flex’’, and long, thin icebergs later broke away from the ice shelf, he said.
Prof Squire said the flexingrelated modelling work helped to explain the loss of ice from several ice shelves at the Antarctic Peninsula, and the outcome was ‘‘pretty common sense’’.
Some ‘‘absolutely massive’’ waves from the North Pacific—some at least 25m high— were ‘‘hitting the coast’’ at the Antarctic Peninsula, and this had a powerful effect, when there was reduced sea ice, he said.