Scientists have discovered massive sinkholes on the Arctic seafloor as submerged permafrost thaws. Rather than climate change, these sinkholes appear to be caused by heated, slowly moving groundwater systems.
The Arctic permafrost at the bottom of the Canadian Beaufort Sea has been submerged for about 12,000 years, since the end of the last ice age, when meltwater grom glaciers covered the region. Only recently has this remote part of the Arctic become accessible to researchers on ships as climate change causes the sea ice to retreat, said the researchers. The team used both ship-based sonar and an autonomous underwater vehicle.
Here’s how the researchers propose the circular holes are forming: as gradual warming thaws the permafrost beneath the Arctic Shelf, an area that was once filled with frozen ground becomes fluid. The surface material then collapses into the fluid-filled void; these seafloor collapses happen periodically over time, the researchers said.
In some regions, where the discharge of this warm groundwater is more limited, the seawater on the floor stays cold enough that any groundwater percolating up refreezes once it’s reached near-surface sediments. That frozen sediment expands, heaving upward to form little cone shaped mounds called pingos. These frozen mounds and sinkholes are responsible for the unusual roughness of the area.
The study also showed that the sinkholes are expanding over time. “The continued enlargement of some depressions observed over multiple surveys indicates that the development of these depressions is part of on-going processes,” the researchers wrote.
https://www.livescience.com/sinkholes-opening-arctic-seafloor