A huge iceberg just broke off West Antarctica’s most endangered glacier
Nature News

A huge iceberg just broke off West Antarctica’s most endangered glacier

On the ice-covered edge of a remote West Antarctic bay, the continent’s most imperiled glaciers threaten to redraw Earth’s coastlines. Pine Island Glacier and its neighbor Thwaites Glacier are the gateway to a massive cache of frozen water, one that would raise global sea levels by four feet if it were all to spill into the sea. And that gateway is shattering before our eyes.

Over the weekend, the European Space Agency’s Sentinel satellites spotted a significant breakup, or calving event, underway on Pine Island Glacier’s floating ice shelf. A series of rifts that satellites have been monitoring since early 2019 grew rapidly last week. By Sunday, a 120 square-mile chunk of ice—a little under three San Franciscos in size—had broken off the glacier’s front. It quickly shattered into a constellation of smaller icebergs, the largest of which was big enough to earn itself a name: B-49. (Find out why it’s our fault that West Antarctica is melting.)

For Pine Island, it’s the latest in a string of dramatic calving events that scientists fear may be the prelude to an even larger disintegration as climate change thaws the frozen continent. With temperatures on the Antarctic Peninsula spiking to a record 65 degrees Fahrenheit last week, the signs of rapid transformation are becoming difficult to ignore.

“What is unsettling is that the daily data stream [from satellites] reveals the dramatic pace at which climate is redefining the face of Antarctica,” said Mark Drinkwater, senior scientist and cryosphere specialist at the European Space Agency, in a press release.

Glaciers are frozen rivers that channel larger, land-bound ice sheets into the ocean. Pine Island is Antarctica’s most vulnerable. Since 2012, the glacier has been shedding 58 billion tons of ice a year, making the biggest single contribution to global sea level rise of any ice stream on the planet.

The latest calving event is the seventh of the past century for Pine Island, with prior calvings occurring in 2001, 2007, 2013, 2015, 2017, and 2018, according to Copernicus. The intervals between the events seem to be getting shorter, another symptom of the glacier’s unhealthy state.

“The events of the past five to 10 years seem to be exceptional for the area compared to the retreat in the past 70 years,” Bert Wouters, a satellite remote sensing expert at TU Delft in the Netherlands who has been monitoring Pine Island Glacier closely, writes in an email.

“Although iceberg ‘calving’ from floating Antarctic ice shelves is a natural, ongoing process, the recent calving event of Pine Island Glacier was particularly large and such calving events from this glacier appear to be becoming more frequent,” says Alison Banwell, a glaciologist at CIRES, University of Colorado, Boulder.

The recent breakup, which was bigger than those in 2017 and 2018 but smaller than iceberg calvings in the early 2000s, according to Wouter

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