Scientists at the Monterey Bay Aquarium Research Institute in the US spent nine years studying an area of about twenty-six square kilometers in the Beaufort Sea, Canada. During that very short period on a geological time scale, researchers saw more than half a million cubic meters of permafrost. In addition, they found “sewers” the size of a few blocks of apartments. Drains are holes in the soil created by subsidence.
The painful consequences of the disappearance of permafrost are already visible on the mainland: houses in Yakutsk, Siberia, for example, regularly collapse as the groundwater thaws. This study shows for the first time that at depths of 120 to 150 meters below sea level, thawing of permafrost leads to soil collapse.
On Earth, the human influence on thawing is great. On the other hand, the bottom of the Arctic Ocean is melting mainly due to a much older process: the transition from the previous ice age to the current warm period. The melting of many ice caps has raised sea levels and inundated large coastal areas. This relatively warm water causes the slow thawing of permafrost. The heat from the Earth’s core speeds up this process even more. Permafrost thaws from the bottom up, forming “sewage”.
The researchers used sonar from their icebreakers: sound waves that travel through water and bounce off the permafrost. The longer the sound waves return to the transmitter, the farther they are from the sea floor. Using this technology, the researchers drew a 3D map of the sea floor, with a point measuring every two metres. A submarine robot made additional measurements depicting deflections at the bottom of less than one meter.
In addition to the loss of permafrost and the creation of giant sewers, researchers have found the so-called “bingo”. These are permafrost blisters that form when melt water moves up, bumps into cold water, and freezes again. These structures further prove that water flows upward from the permafrost.
Although researchers do not directly link northern seafloor melting to human-induced climate change, the disappearance of permafrost itself will lead to increased global warming. Permafrost contains material that, after thawing, can decompose into methane, a potent greenhouse gas that ends up in the atmosphere.
These new discoveries are valuable, according to Paul Overden, a permafrost researcher at the Alfred Wegener Institute in Potsdam, who was not involved in the new study. “It’s surprising that such big changes can happen in just nine years,” he says. Overdeen is curious as to how much the sea floor is also melting in other regions of the Arctic. This will explain the role that the melting of the sea floor in the Arctic plays in global warming.
