Once considered stable, East Antarctic ice sheet may have begun to lose ice

November 23, 2009

The East Antarctic ice sheet, the Earth’s largest repository of solid fresh water and previously considered stable, now appears to be losing ice at an estimated rate of 57 gigatonnes per year, according to scientists at The University of Texas at Austin.

Using gravity measurement data from the Gravity Recovery and Climate Experiment (GRACE) mission, researchers found that ice loss in East Antarctica may have begun as early as 2006. They also confirmed earlier estimates of ice loss in West Antarctica. The research was published in the Nov. 22 online edition of Nature Geosciences.

The GRACE mission consists of two satellites flying in formation making detailed measurements of Earth’s gravity field. Earth’s mass, and its gravity, varies from place to place. The GRACE mission is funded by NASA and the German Aerospace Center, and led by University of Texas Aerospace Engineering Professor Byron Tapley.

“One of the objectives of the GRACE mission is to look at mass flux globally, and one significant signal we see is ice loss in the polar regions,” said Tapley, director of the university’s Center for Space Research (CSR) and holder of the Clare Cockrell Williams Centennial Chair in Engineering. “Significantly, there appears to be a measurable signal that GRACE is picking up in the East Antarctic. Most previous research has assumed the East Antarctic ice sheet was stable. This is the first time we have been able to observe mass loss in this region from space, and this finding suggests that perhaps it is not stable after all.”

Lead author Jianli Chen, a Senior Research Scientist at CSR and colleagues used GRACE data to estimate Antarctica’s ice mass between 2002 and 2009. In addition to new findings about the East Antarctic ice sheet, their recent work confirms previous results showing that West Antarctica loses 132 gigatonnes of ice per year.

“East Antarctica is the biggest chunk of ice on Earth,” said Chen. “As a whole, Antarctica holds around 90 percent of the Earth’s solid fresh water, and the majority is in East Antarctica. East Antarctica is so cold that it was generally believed that its mass was in balance, with not much net change. Data from GRACE shows that some coastal regions are losing ice, in particular the Wilkes Land and Victoria Land regions.”

Unlike in the Northern Hemisphere, where ice melt could be a major effect, most of this ice loss seems to be occurring through ice dynamics.

“While we are seeing a trend of accelerating ice loss in Antarctica, we had considered East Antarctica to be inviolate,” Chen said. “But if it is losing mass, as our data indicates, it may be an indication the state of East Antarctica has changed. Since it’s the biggest ice sheet on Earth, ice loss there can have a large impact on global sea level rise in the future.”

Researchers want to confirm their results using a longer record of GRACE data as well as other remote sensing data.

GRACE is managed for NASA by the Jet Propulsion Laboratory, and is in its eighth year of a 10-year mission. The University of Texas Center for Space Research in the College of Engineering has overall mission responsibility, and GeoForschungsZentrum Potsdam (GFZ) in Potsdam, Germany, handles German mission elements. Science data processing, distribution, archiving and product verification are managed jointly by JPL, The University of Texas at Austin and GFZ.

For more information about research at the Jackson School, contact J.B. Bird at jbird@jsg.utexas.edu, 512-232-9623.