A third of Antarctic ice shelves could collapse at current pace of warming

Cracked surface of Larsen b ice shelf — An image shows cracks on the surface of the Larsen b ice shelf, which covers waters off the shore of the Antarctic peninsula.

(Image credit: Shutterstock)

A third of Antarctica's vast offshore ice shelves could collapse into the ocean if the world warms by 4 degrees Celsius (7.2 degrees Fahrenheit) above pre-industrial levels. These floating platforms of solid water wouldn't directly raise sea levels if they melted; they already sit in the ocean. But they're important barriers preventing the immense bulk of the frozen continent's glaciers from rolling out to sea. If those inland glaciers reached open water, sea level could rise catastrophically.

Of the 34% of ice shelves at risk of collapse by the end of the 21st century, many are concentrated in the Antarctic Peninsula — a region of West Antarctica that juts northward toward South America. The at-risk ice makes up two-thirds of the peninsula's ice shelf extent. In total, 190,000 square miles (500,000 square kilometers) of Antarctic ice would be at risk. That's a region much bigger than California.

The good news is that this sort of ice-shelf breakdown is far from inevitable. Right now, the world has already warmed by about 1 C (1.8 F) above pre-industrial levels. If we managed to hold warming to 2 C (3.6 F) — which some scientists suspect may not be possible, as the Associated Press reported — then just half of the 34% of threatened ice shelves would be at risk. Stop the warming at 1.5 C (2.7 F) and the impacted region would be even smaller.

In the past, researchers have modeled the future behavior of ice shelves at the scale of the entire Antarctic, without fine attention to the details of individual ice shelves. This new study modeled ice melt in different scenarios with previously unheard-of resolution and complexity. The result: visions of Antarctica in a world where climate change goes further than even some pessimistic projections, and in a world where society makes substantial progress against greenhouse gas emissions.

"My personal opinion is that staying below 1.5 C (2.7 F) is pretty much out of the question unless we deploy some type of solar radiation geoengineering," Dessler told Live Science, noting that not every scientist agrees on this point. "Two C (3.6 F) will be very very difficult, but I believe that we could still limit warming to that without significant economic cost if all of the world's governments work together on climate change. I'll leave it up to you to decide how likely that is."

Rafi joined Live Science in 2017. He has a bachelor's degree in journalism from Northwestern University’s Medill School of journalism. You can find his past science reporting at Inverse, Business Insider and Popular Science, and his past photojournalism on the Flash90 wire service and in the pages of The Courier Post of southern New Jersey.