While thawing permafrost on land tied to human-driven global temperature rise has generated worldwide alarm in recent years, a new study out this week is garnering attention for researchers' discoveries underwater.
"As climate change continues to reshape the Arctic, it's critical that we also understand changes in the submerged permafrost offshore."
An international team of researchers led by Charlie Paull, a geologist at the Monterey Bay Aquarium Research Institute in California, and Scott Dallimore of the Geological Survey of Canada published their findings in the peer-reviewed journal Proceedings of the National Academy of Sciences (PNAS).
Permafrost is a mix of ice, rocks, sand, and soil that remains frozen year-round. The thawing of terrestrial permafrost in places like Siberia has fueled concerns about not only damage to at-risk infrastructure but also the release of planet-heating gases as well as ancient bacteria and viruses.
However, Paull and Dallimore's team analyzed changes in the permafrost that lies beneath Arctic waters. Specifically, they focused on 10 square miles of the Canadian Beaufort Sea, using underwater vehicle and ship-mounted sonar for surveys of the seafloor in 2010, 2013, 2017, and 2019.
The researchers found craters—including one that was 92 feet deep, 738 feet long, and 312 feet wide, or bigger than a city block of six-story buildings—as well as ice-cored hills resembling "pingos" previously documented on land.
"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," Paull noted in a statement Monday.
Unlike terrestrial permafrost thawing, the limited data available signals that human-caused global heating is not "driving the dramatic changes in the seafloor terrain," Paull explained. "Instead, heat carried in slowly moving groundwater systems is driving these changes."
Though the team connected the seafloor changes to climatic shifts related to the planet's emergence from the last ice age nearly 12,000 ago, Paull stressed that research like his first-of-its-kind study are important in an era of rising temperatures from human activities like burning fossil fuels.
"While the underwater sinkholes we have discovered are the result of longer-term, glacial-interglacial climate cycles, we know the Arctic is warming faster than any region on Earth," he said. "As climate change continues to reshape the Arctic, it's critical that we also understand changes in the submerged permafrost offshore."
Sue Natali, Arctic Program Director and senior scientist at the Woodwell Climate Research Center in Massachusetts—who was not involved in the study—made a similar point to CNN on Monday.
"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," she explained.
