Study: Antarctic glacier thinning more rapidly than thought

Paris: A large glacier in West Antarctica lost up to half a kilometre in thickness in seven years, thinning more quickly than scientists thought possible. The Smith Glacier, spilling into the Amundsen Sea, shed up to 70 m per year between 2002 and 2009, according to the study, based on Nasa data collected during aerial flyovers. “If I had been using data from only one instrument, I wouldn’t have believed what I was looking at because the thinning was so large,” said author Ala Khazendar, a researcher at Nasa’s Jet Propulsion Laboratory. Ice-penetrating radar and laser altimetry both yielded the same results. Earlier studies using less precise techniques estimated that two ice shelves buttressing the glacier lost about 12 m in thickness each year over the same period. Ocean-fronting glaciers are dense bodies of ice atop land, pushed by gravity and their own weight toward the sea. Adjoining ice shelves — up to two km thick — float on water. Ice atop West Antarctica and Greenland has the potential to lift sea levels by many metres, submerging cities and river deltas home to hundreds of millions of people. But the exact location and speed at which the ice is melting is debated. The dynamics of melting — and how it might vary from one glacier to the next — also remains poorly understood. The findings provide fresh evidence that warming sea water is eroding the underbelly of some Antarctic glaciers. But they also show that the massive ice blocks each have their own personality. During the same 2002-2009 period, for example, the Pope and Kohler glaciers — on either side of Smith — retreated more slowly, in the first case, and advanced somewhat, in the second.