Ice sheets breaking off Antarctica isn’t anything particularly new. But when one defies previous methods, things start to get worrisome.
That’s what appears to have happened with the Pine Island Glacier. Researchers from Ohio State University studied a 583-square-kilometer (225 square miles) iceberg, which broke off from the glacier in 2015.
Using satellite images from ESA’s Sentinel-1A and NASA’s Landsat 8 satellite, they found that the ice sheet was formed by a rift that formed at the base of the ice shelf 32 kilometers (20 miles) inland in 2013. This rift gradually moved upwards until it broke through, causing the sheet – 10 times the size of Manhattan – to break off in mid-2015. The findings are published in the journal Geophysical Research Letters.
Ice sheets like this normally break when the shelf sticks out and snaps off from the bedrock. “It’s kinda like a diving board sticking out over a pool,” lead author Ian Howat told Gizmodo.
So the fact this sheet was broken by an inland crack is particularly unusual, and rather worrying. It’s another example of how rapidly some glaciers are retreating and, explained Howat in a statement, it adds to the probability “that we may see significant collapse of West Antarctica in our lifetimes."
This series of Sentinel-1A images shows the break-up
This is the first such break-up seen in the Antarctic, although similar rifts have been seen in Greenland. It suggests that ocean water is melting ice far below the surface and drifting inland.
And that’s bad news for, well, a lot of people. More than half of the world’s fresh water is frozen in Antarctica, and if the entire West Antarctic Ice Sheet collapses, it would result in a sea-level rise of about 3 meters (10 feet), which would engulf cities including New York and Miami.
"It's generally accepted that it's no longer a question of whether the West Antarctic Ice Sheet will melt, it's a question of when," Howat said in the statement.
Good thing we’re taking climate change seriously then, eh? Oh, wait.