An international team of researchers led by the University of Otago studied a form of sea ice known as platelet ice and constructed a century-long record of the condition of Antarctica's Ross Ice Shelf.
The pioneering dataset indicated that over the past century the Ross shelf had remained largely stable in contrast with shelves in other parts of Antarctica, which had been thinning from below and collapsing in recent years, likely helped by warmer water temperatures.
They had also been able to establish a continent-wide baseline for melt-refreeze processes at the bases of Antarctic ice shelves so that future change could be measured, study leader Associate Professor Pat Langhorne said in a statement.
Instead of directly measuring the ice shelves, they studied a signature in sea ice cores taken from the frozen ocean that surrounded the continent in winter.
The signature revolved around the presence or absence of platelet ice, which grew at the base of sea ice when super-cooled seawater flowed out from under the shelves and into the surrounding ocean.
"In many places, this very cold seawater, which is on the point of refreezing, flows out from under the ice shelf to the bottom of coastal sea ice. The platelet ice this forms reflects lower temperatures at the base of the shelf which prevent its thinning," said Langhorne.
Being able to monitor the health of the bases of Antarctic ice shelves was vital because the shelves acted as "corks" that kept the ice on continental Antarctica from flowing into the ocean and catastrophically raising global sea levels, she said.
"Once ice shelves collapse, there can be a dramatic increase in the rate at which ice flows into the ocean. The need for better understanding and monitoring of ice shelf basal processes is urgent and our work is helping to provide this."
Xinhua - china.org.cn
22/7/15
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