Three studies released in November and December 2012 addressed two facets of ice melt and its repercussions in Greenland and the Antarctic. These reveal that the rate of melt has accelerated drastically over the past 20 years, since reliable satellite-based monitoring began. In the study published in Science  “A Reconciled Estimate of Ice-Sheet Mass” by Shepherd and 47 scientists backed by the European Union, NASA, the National Science Foundation and research councils in Britain and the Netherlands, found the ice melt over the Poles is accelerating. Comparing satellite data ranging from radar and laser readings to measurements of tiny changes in gravity around the thick sheets of ice overlaying Greenland and Antarctica, the researchers found that three ice sheets—Greenland and West Antarctica and Antarctica Peninsula —have lost about 237 billion metric tons between 1992 and 2011. The ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by –142 ± 49, +14 ± 43, –65 ± 26, and –20 ± 14 gigatonnes/ year, respectively. Arctic is losing more mass today than it was in 1990 by a factor of five.  The net loss of billions of tons of ice a year added about 11 millimeters to global average sea levels between 1992 and 2011, about 20% of the increase during this period.

In a paper published in Geophysical Research Letters Australian Scientists (Simmonds and Rudeva, 2012) have documented the impact of an unprecedented storm — what is known as the Great Arctic Cyclone —that may have contributed to the ice melt in that region which hovered for days in August over the Arctic Ocean. Scientists were concerned not only about the accelerating melt and what it could mean for coastal cities worldwide in terms of sea level rise, and also about the effects the changing dynamics could have on climate change. The Australian scientists examined data from 19,625 Arctic storms and found the Great Cyclone to be the most extreme summer storm when evaluated by size, duration and other “key cyclone properties,” as the authors termed them. Ian Simmonds and Irina Rudeva, both of the School of Earth Sciences at the University of Melbourne, said it was also the 13^th most powerful storm since satellite record keeping began in 1979.The Arctic cyclone further weakened the ice, the scientists found, though they did not go deep as to say it was the cause of the acceleration.

References:

Andrew Shepherd, Erik R. Ivins, Geruo A, Valentina R. Barletta, Mike J. Bentley, Srinivas Bettadpur, Kate H. Briggs, David H. Bromwich, René Forsberg, Natalia Galin, Martin Horwath, Stan Jacobs, Ian Joughin, Matt A. King, Jan T. M. Lenaerts, Jilu Li, Stefan R. M. Ligtenberg, Adrian Luckman, Scott B. Luthcke, Malcolm McMillan, Rakia Meister, Glenn Milne, Jeremie Mouginot, Alan Muir, Julien P. Nicolas, John Paden, Antony J. Payne, Hamish Pritchard, Eric Rignot, Helmut Rott, Louise Sandberg Sørensen, Ted A. Scambos, Bernd Scheuchl, Ernst J. O. Schrama, Ben Smith, Aud V. Sundal, Jan H. van Angelen, Willem J. van de Berg, Michiel R. van den Broeke, David G. Vaughan, Isabella Velicogna, John Wahr, Pippa L. Whitehouse, Duncan J. Wingham, Donghui Yi, Duncan Young, and H. Jay Zwally (2012). A Reconciled Estimate of Ice-Sheet Mass Balance. Science, vol.338, issue 6111, pp.1117-1248.

Simmonds, I. and I. Rudeva (2012), The great Arctic cyclone of August 2012, Geophysical Research Letters, 39, L23709, doi:10.1029/2012GL054259.