Once thought to be relatively stable, the Southern Antarctic Peninsula is experiencing a sudden onset of massive and ongoing ice loss. Glaciers in the area became destabilized in 2009, and they’ve been melting faster and faster ever since. According to new findings published in Science this week, about 56 gigatons of water are unloaded into the ocean every year.
Floating ice shelves in this rapidly warming region have lost nearly a fifth of their thickness within the last two decades alone. Just last week, researchers revealed how Larsen C, one of Antarctica’s largest ice shelves, has been thinning from warm air above and warm water below. It’ll likely collapse within a century. On the Southern Antarctic Peninsula, glacier masses help buttress inland ice shelves, slowing down their impending flow into the ocean. But thinning ice reduces this resisting force. Not to mention, these glaciers are grounded on bedrock that’s submerged just below sea level, with a slope that deepens toward the interior of the continent. That means as the glaciers retreat, the warming waters will track them inland to melt them more.
An international team led by Bert Wouters from the University of Bristol measured the elevation of the Antarctic ice sheet using satellites, including the European Space Agency’s CryoSat-2 satellite. From about 700 kilometers (435 miles) above, the satellite sends down a radar pulse that’s reflected by the ice and then received back at the satellite. By measuring the amount of time the pulse takes to travel back, researchers can estimate the elevation of the ice sheet. After analyzing five years’ worth of data, the team found that the ice surface of glaciers have dropped by as much as four meters (13 feet) a year.
This ice loss was so massive that it even caused small yet noticeable changes in Earth’s gravity field. These were detected by NASA’s Gravity Recovery and Climate Experiment (GRACE), which maps the gravity field by measuring the distance between a pair of satellites flying 500 kilometers (370 miles) above. "The fact that so many glaciers in such a large region suddenly started to lose ice came as a surprise to us," Wouters says in a news release. "It shows a very fast response of the ice sheet: In just a few years the dynamic regime completely shifted."
For several years, there were no signs of change, but by about 2009, the glaciers began losing mass at accelerating rates—adding 55 trillion liters of water to the ocean each year, or 300 trillion liters of water to date. “That's the equivalent of the volume of nearly 350,000 Empire State Buildings combined,” Wouters adds.
The team thinks that warming ocean currents are to blame. As a response to climate change and ozone depletion, vigorous wind circulation brought warmer waters to the coast, wearing away the ice from below.
“Compared to other regions in Antarctica, the Southern Peninsula is rather understudied,” Wouters says, “exactly because it did not show any changes in the past, ironically.”
Images: Jonathan L. Bamber (top), Alba Martin-Español (middle)