A group of scientists has claimed that some regions of Antarctica are gaining ice as a result of snowfall 10,000 years ago – but the rate is decreasing such that in mere decades, it may shift to an annual net loss of ice.
In the study, published in the Journal of Glaciology and led by Jay Zwally of the NASA Goddard Space Flight Center, it's explained that the rate of increase inland compared to decrease at the coastal regions is resulting in a net gain. This is in contrast to the Intergovernmental Panel on Climate Change’s (IPCC) 2013 report, which says the loss is already happening.
"We're essentially in agreement with other studies that show an increase in ice discharge in the Antarctic Peninsula and the Thwaites and Pine Island region of west Antarctica," Zwally said in a statement. “Our main disagreement is for east Antarctica and the interior of west Antarctica – there, we see an ice gain that exceeds the losses in the other areas.”
Zwally and his co-authors compared satellite observations of the height of the Antarctic ice sheets from 1992 to 2001 and 2003 to 2008. During the earlier period the continent put on a net 112 billion tons of ice a year, plus or minus 61 billion tons. After 2003, however, the paper reports gains of 136 billion tons per year in eastern Antarctica and 72 billion tons in four drainage systems in western Antarctic that exceed losses of 97 billion tons a year from three coastal drainage systems and 29 billion tons from the Antarctic Peninsula.
The net effect is an extra 82 billion tons of ice a year from 2003 to 2008, with an uncertainty of 25 billion tons, significantly less than the annual gain between 1992 and 2001.
Previous studies attributed rises in Antarctica’s central plateaus to recent snowfalls yet to condense to solid ice. However, Zwally found evidence these areas have been building up for a millennia, and the recent seasons have not been particularly snowy.
“At the end of the last Ice Age, the air became warmer and carried more moisture across the continent, doubling the amount of snow dropped on the ice sheet,” Zwally said.
The IPCC's 2013 report, summarising numerous studies, concluded that overall Antarctica is losing ice to the oceans. This latest study, however, suggests that something else has caused the well established rise in ocean height over the last two decades, and that when the reversal of ice growth does eventually happen, the rise could be accelerated.
“If the 0.27 millimeters [0.01 inches] per year of sea level rise attributed to Antarctica in the IPCC report is not really coming from Antarctica, there must be some other contribution to sea level rise that is not accounted for,” said Zwally.
Indeed, the 30 billion ton reduction in annual ice accumulation between the two periods is unlikely to be a fluke. Instead, the authors expect the loss of ice from coastal areas to accelerate until, in roughly 20 years' time, it overtakes the build-up inland.
“The new study highlights the difficulties of measuring the small changes in ice height happening in East Antarctica,” Ben Smith, a glaciologist with the University of Washington in Seattle who was not involved in Zwally’s study, added in the statement.