In 2013, a huge iceberg broke away from the Pine Island Glacier, one of the largest in West Antarctica. Two years later, the glacier lost another hulking chunk of ice. And just a few days ago, a similarly unfortunate event happened once again. As Chris Mooney reports for the Washington Post, the Pine Island Glacier has released an iceberg more than 100 square miles in size, deepening scientists’ concerns about thinning ice shelves and rising sea levels.
Satellite images captured the break—or “calving,” as it is known among experts—between September 23 and September 24. Stef Lhermitte, a satellite observation specialist at Delft University of Technology in the Netherlands, posted photos of the calving event on Twitter this past Saturday. He explained that the iceberg spanned 580 square kilometers (approximately 103 square miles), making it roughly four times the size of Manhattan.
Scientists have been watching the Pine Island Glacier closely over the years. It is one of the fastest-melting glaciers in Antarctica, and could raise global sea levels by 1.7 feet if it melted entirely. Last fall, NASA’s Operation IceBridge mission captured a photo of a large rift in the glacier, portending the recent calving event.
The latest iceberg to break away from the Pine Island Glacier is not as big as the ones that calved in 2013 and 2015—which measured 252 square miles and 225 square miles, respectively—and it is much smaller than the mammoth iceberg that split from Antarctica’s Larsen C ice shelf in July of this year. Thus by itself, the latest chunk breaking off from the floating ice shelf isn't worrisome.
"Floating ice shelves are like ice cubes in a glass of water,” Alessandra Potenza writes for the Verge. “[W]hen the ice cubes melt, the water level in the glass doesn’t rise.” But what is concerning about this recent breakup is that the floating ice shelves form a vital barrier that stops the bulk of the glacier from drifting into the sea and contributing to rising water levels.
Lhermitte, the satellite observation specialist, tells Mooney of the Washington Post that scientists “are very worried about what might happen to Pine Island Glacier in relation to sea level rise.”
Also troubling is the fact that the rift formed at the center of the glacier’s floating ice shelf, rather than at its sides. According to Gizmodo’s George Dvorsky, the likely cause is warmer ocean temperatures, which are hitting the base of the glacier.
Unfortunately, more trouble may lie ahead for the Pine Island Glacier. Ian Howat, a glaciologist at Ohio State University, tells Mooney that in March of 2017, a “series of thin cracks was visible in the center of the ice shelf about 3 km inland of the current break”—suggesting that another calving event could be on the horizon.