Disappearing: The melting Thwaites Glacier in west Antarctica is projected to raise global sea levels by nearly 60 centimetres over coming centuries.
Key glaciers in Antarctica haemorrhage ice as temperatures rise
Glaciers in west Antarctica are melting so quickly they are losing the equivalent of a Mount Everest of ice every two years, a peer reviewed study has found.
The increasing pace of melting means the glaciers have haemorrhaged an average 83 billion tonnes into the Amundsen Sea annually over the past 21 years.
Accepted for publication in the journal Geophysical Research Letters, the study used four sets of satellite measurements to determine ice loss in the Amundsen Sea embayment from 1992 to 2013.
"The mass loss of these glaciers is increasing at an amazing rate," said study co-author Isabella Velicogna, a scientists with the University of California and NASA.
This remote and uninhabited region is now under a scientific spotlight similar to that which previously fell on the Antarctic Peninsula, where floating sea ice shelves broke up dramatically more than a decade ago. The floating Larsen B ice shelf - which was bigger than the Australian Capital Territory - fell apart in a month in 2002. A study published in the journal Science this year found that collapse was due to rising air temperatures and rainfall.
While the loss of the Larsen B floating peninsula made no difference to sea level - it was the equivalent to an ice cube melting in a glass of water - the loss of the Amundsen Sea glaciers will raise it.
A separate Science study this year found the west Antarctic ice sheet had gone into an irreversible retreat.
Glaciologist Eric Rignot, of the University of California, said melting of the sheet would raise the sea level by 1.2 metres over the next two centuries.
"This retreat will have major consequences for sea level rise worldwide," Professor Rignot said.
The latest study came as the World Meteorological Organisation last week told the United Nations' climate talks in Peru that 2014 was on track to be hottest year on record.
Scientists say the most concerning melting glacier in west Antarctica is the giant Pine Island glacier, which has an enormous drainage area not held back from the sea by a floating shelf. It has been thinning and retreating for 40 years and, according to a study published in Nature Climate Change, is projected to add 3.5 to 10 millimetres of sea level rise over 20 years.
The nearby Thwaites Glacier also appears to be in the early stages of a collapse due to warmer water melting its underside. Scientists say it could add up to 60 centimetres to global sea level over centuries.
While west Antarctic ice is rapidly retreating, the larger east Antarctic ice sheet - mostly grounded on rock above sea level - may be gaining mass through increased snowfall. The recent fifth assessment report by the UN's Intergovernmental Panel on Climate Change found the loss of ice in the west was outpacing the growth in the east.
Scientists say that predicting glacier and ice sheet behaviour is the least certain component when making projections about future sea level rise.
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