Trouble ahead for Antarctic ice

Researchers have long recognized that the glaciers of West Antarctica are losing mass: Ice is oozing off the continent and into the sea faster than it’s being replaced from above. But the long-term implications have been uncertain. Is the mass loss a short-lived response to the thermal forcing of warmer-than-usual ocean waters? Or will the collapse continue unchecked even if the forcing is removed? Two papers widely reported last week conclude that the West Antarctic’s unstoppable collapse has probably begun. Eric Rignot and colleagues (University of California, Irvine, and NASA’s Jet Propulsion Laboratory) document the accelerating glacial retreat in the region shaded in purple in the figure, and they note the lack of any geological features that could restabilize the ice. Ian Joughin and colleagues (University of Washington) used a computer model to simulate the dynamics of the same region; they found that for a wide range of forcing conditions, full-scale collapse of the glaciers is likely to occur over the next several centuries. Meanwhile, Matthias Mengel and Anders Levermann (Potsdam Institute for Climate Impact Research in Germany) have shown that the larger, thicker, and less dynamic ice sheet of East Antarctica may not be as stable as previously thought. Using new topographic data in conjunction with simulations, they show that the Wilkes Basin, shaded in blue, is held in place by a small volume of coastal ice that could eventually melt. Loss of the East Antarctic ice sheet would have catastrophic consequences for global sea levels over the coming millennia. (E. Rignot et al., Geophys. Res. Lett., in press , doi:10.1002/2014GL060140; I. Joughin, B. E. Smith, B. Medley, Science 344, 735, 2014 ; M. Mengel, A. Levermann, Nat. Climate Change, in press, doi:10.1038/nclimate2226 .)