The erosion is evident when you stand on the coast at Utqiańvik, the former Barrow, the northernmost city of Alaska, where the Arctic Ocean meets the edge of the continent and the permafrost is so deep that structures must be built around it. not as a graph’s abstract trend. as a moving edge. The land beneath their original foundations is melting into the Beaufort Sea in pieces of frozen earth that break away from the coastline and melt into the ocean; houses that were fifty meters from the shore ten years ago are now closer, some of which have already moved or been abandoned.
This is the surface narrative that has been observed and recorded for many years. It has now been directly connected by scientists to an event occurring on the ocean floor below, combining two distinct environmental issues into a single compounding system that is far more difficult to resolve than either would be on its own.
As warming ocean water approaches the submarine permafrost off Alaska’s Arctic coast, it thaws. Submarine permafrost is ancient frozen organic material that has been stored for thousands of years on the shallow continental shelf under temperatures cold enough to prevent microbial decomposition. Theoretically, the mechanism was known. Recent studies have more precisely demonstrated that the thawing of the seafloor below and the coastal erosion above are not separate phenomena. They are linked by a feedback loop in which previously frozen organic material and silt rich in carbon are dumped into the ocean when coasts recede and collapse.
Further offshore, the thawing of submerged permafrost is accelerated by the thermal and chemical environment created by the silt and organic material suspended in warming water. Methane, a greenhouse gas that is about 80 times more potent than carbon dioxide over a 20-year period, is released by the seafloor thaw, which is fueled by the surface collapse and contributes to the warming that drives the entire process.
Geological processes often operate on durations measured in centuries rather than years, hence the erosion rates on some parts of Alaska’s Arctic coastline have been reported to reach more than 10 to 15 meters per year. The acceleration is linked to both direct warming and sea ice loss: as the amount of Arctic sea ice decreases, coastlines that were formerly protected by frozen sea surface are now subject to open-ocean wave action for an increasing amount of the year.
Waves now reach a cliff of frozen dirt instead of a wall of ice. Alaska Native towns that have remained in the same spot for generations have had to relocate as a result of the land surrounding and beneath them disappearing into the ocean. The communities confronting that reality are dealing with climate change as an immediate logistical challenge with specific addresses and dates rather than as a future forecast.
It is most difficult to model the ramifications with confidence when it comes to the methane question. An estimated 1.5 trillion tons of organic carbon have been stored during millennia of frozen conditions in Arctic permafrost, both on land and underwater. One of the most important uncertainties in climate research is how much of that carbon gets emitted, in what form, and over what time period. Methane emitted from thawing undersea permafrost may disintegrate in the water column instead of immediately entering the atmosphere, changing the greenhouse accounting in intricate ways that are still being figured out.
Whether the seafloor thaw signifies a near-term tipping point for methane release or a slower, more dispersed process that takes decades to complete is yet unknown. It is not encouraging to conclude that both are occurring concurrently in various regions of the Arctic based on the available data.
The relationship between the surface and the seafloor isn’t theoretical, which sets this narrative apart from many climate discoveries as the feedback loop has grown more evident in the study literature over the past few years. It’s already moving and quantifiable. The thawing of the ocean floor beneath Utqiańvik is being accelerated by the eroding coastline.
Greenhouse gasses produced by the melting ocean floor warm the atmosphere, further eroding the coastline. Stopping the two processes is not made easier by realizing that they are part of the same system. It does make it more difficult to act as though they can be handled independently.
