An iceberg breaks off the Knox Coast in Antarctica. Reuters

By Ben Cubby, Environment Editor
23 October 2012 ANTARCTICA is shedding an average of 190 million tonnes of ice daily – and causing sea levels to rise about a millimetre a year. Although parts of East Antarctica are growing, glaciers in West Antarctica are melting faster, leading to a net loss of ice across the continent, according to a study published in the journal Nature. ”We’re confident that the ice cover is shrinking, and the rate along the Amundsen Sea coast is accelerating,” said Professor Matt King, of the University of Tasmania. Rapid melting in some parts of the continent is partially offset by some heavy snowfalls elsewhere, meaning that the net loss of ice per year is about 69 billion tonnes. Previous studies struggled to accurately map the land mass under most of Antarctica’s huge ice shelves, and this knowledge is crucial to measuring the thickness of the ice. As ice melts, the land mass gradually rises at a rate of about two millimetres a year, like a cake baking in an oven. ”It’s like if you’re standing on a beach with some wet sand, and you move your foot and the print disappears pretty quickly, it just flows back into place,” Professor King said. The answer was a new analytical model that was able to make satellite data match the ground-based observations about ice-melt and land-rise, and revised down the speed that the land was coming up. One result of the findings is that melting ice in Antarctica is not contributing as much to global sea level rise as some other studies assumed. While the continent contains enough frozen water to raise global sea levels by 59 metres should it ever all melt, the findings show it is currently contributing less than a millimetre a year. Professor King said the findings showed sea levels had risen faster than they had for centuries without extra water from the Antarctic ice sheet. ”The melt in some key areas is sped up between 2006 and 2010, when the study ended,” he said. ”So it shows that sea level rise can be expected to change quite sharply if the melt rate continues to increase, on top of what’s already happening.”

190m tonnes of ice a day has sea rising 1mm a year