A new NASA study
says that Antarctica is overall accumulating ice. Still, areas of the
continent,
like the Antarctic
Peninsula photographed above, have increased their mass loss in the last
decades. Credits:
NASA's Operation IceBridge
(October 31, 2015) A
new NASA study says that an increase in Antarctic snow accumulation that began
10,000 years ago is currently adding enough ice to the continent to outweigh
the increased losses from its thinning glaciers.
The research challenges the conclusions of other studies,
including the Intergovernmental Panel on Climate Change’s (IPCC) 2013 report,
which says that Antarctica is overall losing land ice.
According to the new analysis of satellite data, the
Antarctic ice sheet showed a net gain of 112 billion tons of ice a year from
1992 to 2001. That net gain slowed to
82 billion tons of ice per year between 2003 and 2008.
“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,” said Jay Zwally, a glaciologist with
NASA Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the
study, which was published on Oct. 30 in the Journal of Glaciology. “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 added that his team “measured small
height changes over large areas, as well as the large changes observed over
smaller areas.”
Map showing the
rates of mass changes from ICESat 2003-2008 over Antarctica. Sums are
for all of
Antarctica: East Antarctica (EA, 2-17); interior West Antarctica (WA2, 1, 18,
19, and 23);
coastal West Antarctica
(WA1, 20-21); and the Antarctic Peninsula (24-27).
A gigaton (Gt)
corresponds to a billion metric tons, or 1.1 billion U.S. tons.
Credits: Jay
Zwally/ Journal of Glaciology
Scientists calculate how much the ice sheet is growing or
shrinking from the changes in surface height that are measured by the satellite
altimeters. In locations where the amount of new snowfall accumulating on an
ice sheet is not equal to the ice flow downward and outward to the ocean, the
surface height changes and the ice-sheet mass grows or shrinks.
But it might only take a few decades for Antarctica’s growth
to reverse, according to Zwally. “If the losses of the Antarctic Peninsula and
parts of West Antarctica continue to increase at the same rate they’ve been
increasing for the last two decades, the losses will catch up with the
long-term gain in East Antarctica in 20 or 30 years -- I don’t think there will
be enough snowfall increase to offset these losses.”
The study analyzed changes in the surface height of the
Antarctic ice sheet measured by radar altimeters on two European Space Agency
European Remote Sensing (ERS) satellites, spanning from 1992 to 2001, and by
the laser altimeter on NASA’s Ice, Cloud, and land Elevation Satellite (ICESat)
from 2003 to 2008.