Last updated June 14, 2018 at 9:47 am
Storm swells causing ‘catastrophic disintegration’.
© Esmee van Wijk/Australian Antarctic Division
Storm-driven ocean swells have triggered the catastrophic disintegration of Antarctic ice shelves, according to Australian researchers.
They say reduced sea ice coverage since the late 1980s has left ice shelves more exposed, causing them to flex and break. And they have called for sea ice and ocean waves to be included in future ice sheet modelling.
“Sea ice acts as a protective buffer to ice shelves by dampening destructive ocean swells before they reach the ice shelf edge,” said lead author Dr Rob Massom, from the Australian Antarctic Division and the Antarctic Climate and Ecosystems Cooperative Research Centre.
“But where there is loss of sea ice, storm-generated ocean swells can easily reach the exposed ice shelf, causing the first few kilometres of its outer margin to flex. Over time, this flexing enlarges pre-existing fractures until long thin sliver icebergs break away or calve from the shelf front.
“This is like the straw that broke the camel’s back, triggering the runaway collapse of large areas of ice shelves weakened by pre-existing fracturing and decades of surface flooding.”
Five major disintegrations analysed
The research team, including scientists from Australia, the US and New Zealand, combined satellite images and surface and ocean wave data with modelling to analyse five major ice shelf disintegrations between 1995 and 2009.
These included the abrupt and rapid losses of 1600 square kilometres of ice from the Larsen A Ice Shelf in 1995, 3320 square kilometres from the Larsen B Ice Shelf in 2002, and 1450 square kilometres from the Wilkins Ice Shelf in 2009.
Each disintegration event occurred during periods when sea ice was significantly reduced or absent, and when ocean waves were large.
According to Dr Luke Bennetts, from the University of Adelaide, the contribution of the Antarctic Ice Sheet is the greatest source of uncertainty in projections of global mean sea level rise.
“Ice shelves fringe about three quarters of the Antarctic coast and they play a crucially important role in moderating sea level rise by buttressing and slowing the movement of glacial ice from the interior of the continent to the ocean,” he said.
“While ice shelf disintegration doesn’t directly raise sea level because they are already floating, the resulting acceleration of the tributary glaciers behind the ice shelf, into the Southern Ocean, does.”
The paper published in Nature.
