The serendipitous decision of a pod of elephant seals to winter near one of Antarctica’s largest ice shelves has helped researchers build the most complete picture to date of how, and how fast, ice shelves fringing East Antarctica are melting.
Nearly 90 percent of all ice lost from the Antarctic continent passes through the ice shelves at its edges before entering the Southern Ocean. If those ice shelves melt, continental ice loss most likely will increase, and that will, in turn, raise the sea level. But little is known about how oceanic heat melts ice shelves. In 2009, oceanographer Ole Anders Nøst of the Norwegian Polar Institute in Tromsø, Norway, and colleagues drilled three holes averaging nearly a quarter of a mile deep through the Fimbul Ice Shelf, which lies at the prime meridian. Through sensors moored beneath the 15,800-squaremile shelf, the team collected data on water currents, salinity, temperature, and dissolved oxygen from 2010 to 2012.
The researchers also took advantage of a wealth of continuous measurements gathered from nine male elephant seals, which had been outfitted with state-of-theart instruments to retrieve data for unrelated studies of marine mammals. Capable of diving more than a mile deep and remaining submerged for up to two hours, the seals had conveniently spent the entire winter of 2008 along the ice shelf.
The study provides the first direct measurements of the Fimbul Ice Shelf’s melting underside, proving a twenty-year-old theory of how changes in water circulation patterns melt the ice. But most important, it reports that present melting rates are significantly lower than those predicted by ice-shelf computer models that had been built without direct data. The research instead supports previous satellite observations that contradicted the computer models, demonstrating that the processes contributing to Antarctic melting are far more complex than previously understood. (Geophysical Research Letters)