Huge Sinkholes Are Forming on Arctic Seafloor

Melting permafrost has been wreaking havoc on the Arctic landscape, triggering ground collapses that leave deep holes in the earth. Now we have evidence that the same thing is happening under the ocean. Large sections of permafrost, or permanently frozen ground, were submerged as glaciers melted around the end of the last ice age. Now, at least one large section of subsea permafrost, nearly 500 feet deep at the edge of the continental slope of Canada's Beaufort Sea, is melting, triggering "extraordinarily rapid morphologic changes," according to new research. The speed is surprising, particularly because the new features aren't attributed to methane gas explosions or human-driven climate change more broadly.

Researchers who mapped a 10-square-mile area of the seafloor in 2010 and 2019 say they saw the emergence of 41 holes, at an average of 22 feet deep. One was so large—95 feet deep, 738 feet long, and 312 feet wide—that it could hold "a city block made up of six-story buildings," CNN reports. Elsewhere, ice-filled hills—33 feet high and 164 feet wide on average—similar to pingos on land rose from the seafloor. "We know that big changes are happening across the Arctic landscape, but this is the first time we've been able to deploy technology to see that changes are happening offshore too," Monterey Bay Aquarium Research Institute marine geologist Charlie Paull, co-author of a study published Monday in PNAS, says in a release.

Limited data for seafloor temperature don't show a warming trend. Rather, "the evidence suggests that the submarine features we observed forming are essentially sinkholes and retreating scarps, collapsing into void space left behind by the thawing of ice-rich permafrost," due to heat carried in slowly moving groundwater systems, Paull tells Newsweek. Such changes "derive from much older, slower climatic shifts related to Earth's emergence from the last ice age, and appear to have been happening along the edge of the permafrost for thousands of years," Paull adds. "Whether anthropogenic climate change will accelerate the process remains unknown." Researchers plan to continue their survey this summer. (More Arctic Ocean stories.)