The massive ice shelves surrounding Antarctica are melting ever faster, bringing an increased risk in rising sea levels, according to researchers.
Some ice shelves at the edges of the frozen continent have thinned by as much as 18 percent in the last 20 years — and the rate of that thaw is increasing.
The fastest-receding ice shelves could disappear entirely within a hundred years, according to a report in the journal Science.
The findings are based on an analysis of satellite radar altimetry missions that provided a high-resolution record of ice shelf thickness.
The European Space Agency conducted three separate missions from 1994 to 2012. The researchers then combined the data to develop a model revealing the changes in all of Antarctica's ice sheets over the 18-year period. The study is the first to continuously plot volume changes in the ice sheet system.
While the melting of the ice shelves doesn't directly contribute to rising sea levels, the researchers say an indirect but important effect exists, and it is one of great concern.
"The ice shelves buttress the flow from grounded ice into the ocean, and that flow impacts sea-level rise, so that's a key concern from our new study," said glaciologist Helen Amanda Fricker from the Scripps Institution of Oceanography in California.
That grounded ice sitting on the Antarctic continent holds the equivalent of almost 200 feet of increased sea level, and if the ocean ice sheets disappear, then the movement of that grounded ice into the ocean could accelerate.
The ice shelves holding back grounded glaciers in a vulnerable sector of West Antarctica could have their volume reduced by half within the next two centuries, researchers estimate.
The reduction of ice shelves in the region has already led to a 59 percent increase in ice discharge from some areas, they noted.
The accelerating loss of ice shelf area in West Antarctica is mainly being caused by warmer ocean water, which is the result of climate change. The warmer water flows in underneath the shelves, driven by winds that are also getting stronger, according to Scripps graduate student Fernando Paolo.
"We are seeing large changes over the course of decades," he said. "If the loss rates that we observed during the past two decades are sustained, some ice shelves in the Amundsen and Bellingshausen seas could disappear within this century."
