It’s not just the ice caps that are melting; underwater permafrost is, too. Giant sinkholes -- one larger and deeper than a city block of six-story buildings -- have started cropping up across the floor of Canada’s Beaufort Sea, an isolated part of the Arctic. A new study found that in one 10-square-mile area, 41 steeply-sided holes appeared between 2010 and 2019.

"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," said marine geologist Charlie Paull, a senior scientist at Monterey Bay Aquarium Research Institute and one of the lead authors of the study.

Why This Matters

Much of the Arctic and Antarctic’s permafrost has continued to melt due to human-caused climate change, and it’s only getting worse. When iceberg A68 broke off an Antarctic island, 152 billion tons of fresh water were dumped into the ocean. An ice shelf in Antarctica ominously named the "Doomsday Glacier” could collapse in the next few years, raising the global sea level by up to 25%. This sea level rise could have catastrophic consequences. Melting ice caps could devastate coastlines globally, damage sewage systems, flood low-lying islands in the South Pacific, and even speed up climate change by releasing greenhouse gases.

Why Sinkholes?

It’s unclear why so many Arctic sinkholes appeared in the last decade, especially since deep waters haven’t warmed as much as water near the surface. What is clear is that the sinkholes developed over the course of thousands of years, ever since the ice age ended. Water-filled cavities emerged within permafrost over time, and when these cavities caved in, they became sinkholes. Unlike permafrost on land, subsea permafrost responds much more slowly to climate change.

Sue Natali, Arctic program director and senior scientist at the Woodwell Climate Research Center in Massachusetts, told CNN: "Changes described in this study are responding to events that occurred over the centennial to millennial time frame. That said, these changes can still impact climate if they are resulting in emissions of greenhouse gases as the subsea permafrost thaws."