Ice lost from bottom up

Antarctica loses more ice from submerged ice melting—as much as 90 per cent in some areas—than iceberg calving (when chunks of ice break from a glacier’s edge), according to recent research published by the University of Bristol in September, 2013.

For many decades, scientists believed iceberg production and melting was the primary cause for the loss of 2,800 cubic kilometers (approximately 672 cubic miles) from Antarctic’s ice sheet every year. New research, led by the University of Bristol and in collaboration with Utrecht University and the University of California, used satellite and climate model data to prove that sub-shelf melting equally impacts Antarctica’s ice sheet, and in some areas, poses a greater impact.

“Understanding how the largest ice mass on the planet loses ice to the oceans is one of the most fundamental things we need to know for Antarctica,” said Jonathan Bamber, professor at the University of Bristol’s School of Geographical Sciences. “Until recently, we assumed that most of the ice was lost through icebergs.”

Recent reports show the annual turnover of ice equals up to 700 times the four cubic kilometers per year—equivalent to the entire domestic water supply for the UK.

The scientists used data from a suite of satellite and airborne missions to measure the flow of the ice, its elevation and its thickness. These observations were combined with the output of a climate model for snowfall over the ice sheet.

They compared how much snow fell and accumulated on a surface against how much ice that left the continent, entering the ocean and calving. By comparing these estimates, they were able to determine the proportion that was lost by each process.

“Now we realize that melting underneath the ice shelves by the ocean is equally important and for some places, far more important. This knowledge is crucial for understanding how the ice sheets interact now, and in the future, to changes in climate.”

The research was funded by an EU program called ice2sea and a Natural Environment Research Council (NERC) funded project called Resolving Antarctic mass TrEnds (RATES).