Warming water under Antarctica’s ice shelves risks ice melting that could lead to a “worrying” rise in global sea levels, research has shown.
Loss of the Antarctic ice shelves, which extend from the southern polar land mass over the underwater continental shelf, are likely to result in the glaciers behind them flowing more rapidly into the sea.
That would feed more melting ice into the oceans, pushing up sea levels.
Total melting of the West Antarctic ice sheet, which is close to the regions known to be warming, would raise global sea levels by 4.8 metres (15.7ft) – enough to have a severe impact on coastal populations.
Professor Karen Heywood, from the University of East Anglia’s Centre for Ocean and Atmospheric Sciences, said: “Although many of the large ice shelves buttressing the Antarctic ice sheet are not yet melting, the source of warm water seems to be getting closer, so these ice shelves could begin to melt in future which is worrying in terms of global sea level rise.”
The scientists looked at data from oceanographic records dating back to 1960 and found that temperatures in the West Antarctic Amundsen Sea and the Bellingshausen Sea have risen significantly.
For example, the temperatures of the warmest waters near the sea bed in the Bellingshausen Sea have risen from about 0.8C in the 1970s to 1.2C in 2010.
“This might not sound like much, but it is a large amount of extra heat available to melt the ice,” said co-author Dr Sunke Schmidtko, from the Geomar Helmholtz Centre for Ocean Research in Kiel, Germany.
The water around Antarctica was also getting less salty, which was a sign that freshwater ice was melting. Accelerated melting made it easier for big glaciers to slide towards the sea.
Higher temperatures around Antarctica could also affect ocean biodiversity, said the researchers whose findings are reported in the journal Science.
The Intergovernmental Panel on Climate Change (IPCC) current highest estimate for sea level rises is (0.91 meters, or 3ft) by 2100.
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