Glaciers Holding Back Sea Level Rise Are Showing Signs of Collapse

There’s a new hot spot for ice loss in Antarctica, say scientists, which may add to the problems sea-level rise is causing around the world.

The Southern Antarctic Peninsula has long been stable, even as dramatic global warming–driven changes, such as the abrupt collapse of the enormous Larsen B ice shelf on the Northern Antarctic Peninsula in 2002, have hit other parts of the continent.

But starting around 2009, many of the Southern Antarctic Peninsula’s glaciers began to shed enormous amounts of ice into the ocean, according to a new analysis published Thursday in the journal Nature.

Since then, about 300 billion tons of Southern Antarctic Peninsula ice have dropped into the ocean, where it melts. It’s the equivalent of as much water as “the volume of nearly 350,000 Empire State Buildings,” according to Bert Wouters, a geologist at the University of Bristol in the United Kingdom and the lead author of the study.

This melt has accounted for roughly 0.006 inches of sea rise per year since 2009, and it shows no signs of stopping.

Why You Should Care: Although a few thousandths of an inch may not seem like much, the process contributes to a positive feedback loop: As ice melts, surrounding water warms, which accelerates the rate of ice melt, and so on. Warmer water also has more volume, so the same mass of ocean water leads to higher seas when it is of a higher temperature—and oceans' absorption of heat from the atmosphere will continue for centuries to come even if greenhouse gas emissions were to halt overnight. If the burning of fossil fuels is not sharply cut back before 2050, sea levels are likely to rise 1.74 to 3.18 feet by the turn of the century, according to the United Nations’ climate science group. With 44 percent of the world's population living near coastlines, according to the U.N., rising seas pose a threat to homes and costly infrastructure, and warming seas contribute to stronger storms battering coasts further, as with Cyclone Pam in Vanuatu in March, Typhoon Haiyan in the Philippines in 2013, and Hurricane Sandy—which had a record-setting 14-foot storm surge—in 2012. Sea level in the New York metro area has risen about one foot since 1900. 

The study “shows that the Antarctic ice sheet can react very quickly to changes in the environment, at a very high rate,” Wouters said, adding that within a matter of just a few years, the previously unchanged area transformed from being “in balance” to “being the highest contributor to sea-level rise in Antarctica.”

“It also implies that this southern ice loss could start in other regions as well, where we don’t expect it,” he said. In March, scientists reported that the ice sheets of Western Antarctica were thinning at an unexpectedly high rate.

If the melt-off were to remain steady, that would add up to about half an inch of additional water in the ocean by 2100. But a recent study showed that global sea-level rise is accelerating. 

“We know that ocean temperatures in the area have risen in the past several years and have warmed the waters around the ice shelves,” he said. “It’s still cold but above the freezing point, so it carries enough heat to melt the ice shelves.”

Wouters and his colleagues discovered the abrupt changes by mapping recent satellite data about the ice sheet’s elevation, including readings from the European Space Agency’s CryoSat-2, the “first radar altimeter dedicated to ice,” said Wouters.

“Most of the glaciers in this area end up as floating ice shelves,” which, when stable, hold back the flow of ice from land into the ocean, Wouters said. Changes in the area’s air temperatures and snowfall levels were too small to explain why the glaciers began flowing faster into the sea, he said, which left the ocean as the only reasonable explanation. 

Related stories on TakePart:

• 10 Beautiful, Sometimes Troubling Photographs of the Arctic and Antarctica

• Antarctica Is Melting, and Here’s Why We Should Be Alarmed

• We Might Avert Climate Catastrophe With This One Radical Choice

Original article from TakePart