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A research team co-led by a geologist at the Monterey Bay Aquarium Research Institute conducted a first-of-its-kind study of underwater permafrost and changes to the Arctic seafloor. (Photo: Charlie Paull/MBARI)

Scientists Find Craters—Including One Bigger Than a City Block—in Arctic Seafloor

"We know that big changes are happening across the Arctic landscape," said the lead researcher, "but this is the first time we've been able to deploy technology to see that changes are happening offshore too."

Jessica Corbett

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.

The underwater research was released the same day as multiple studies on terrestrial permafrost. One paper, published in the journal Nature Communications, found that alpine permafrost is expected to melt at a faster rate than Arctic permafrost under current conditions.

"Our findings were very surprising and highlight the fact that we need to put more effort into monitoring the stability of the permafrost in the alpine region," said lead author Feng Cheng of China's Peking University.

Paper co-author Carmala Garzione, dean of the University of Arizona College of Science, agreed. As she put it:

We need better and broader studies of the vulnerability of alpine regions under global warming scenarios. There's been a lot of focus on the stability of Arctic permafrost, because it covers more land area and contains a huge reservoir of organic carbon trapped in permafrost, but we also need to be aware that alpine regions stand to lose more permafrost proportionally and are important in understanding of potential carbon release under global warming scenarios.

Another study, published in the journal Nature Climate Change, warned that peatlands in Europe and Western Siberia—which store up to 39 billion tons of carbon—are closer to a climatic tipping point than previously thought.

"Our modeling shows that these fragile ecosystems are on a precipice and even moderate mitigation leads to the widespread loss of suitable climates for peat permafrost by the end of the century," said lead author Richard Fewster of the University of Leeds in the United Kingdom.

"But that doesn't mean we should throw in the towel," he said. "The rate and extent to which suitable climate are lost could be limited, and even partially reversed, by strong climate change mitigation policies."

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