Global Warming

Gaping 'sinkholes' opening up on the Arctic seafloor

Giant "sinkholes" — one of which could devour an entire city block holding six-story buildings — are appearing along the Arctic seafloor, as submerged permafrost thaws and disturbs the area, scientists have discovered.

But even though human-caused climate change is increasing the average temperatures in the Arctic, the thawing permafrost that's creating these sinkholes seems to have a different culprit — 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 from glaciers blanketed the region. Until now, the frozen seafloor had been hidden from scientists' peering eyes. This remote part of the Arctic has only recently become accessible to researchers on ships as climate change causes the sea ice to retreat, the researchers said.

As gradual warming thaws the permafrost beneath the Arctic Shelf, an area that was once filled with a solid (frozen ground) becomes fluid. The surface material then collapses into that liquid-filled void; these seafloor collapses happen intermittently over time, the researchers said.

Vanishing Arctic Ice

Fresh data from NASA’s ice-monitoring CryoSat-2 and IceSat-2 spacecraft reveal that the sea ice surrounding the North Pole is thinner and disappearing more quickly than previously thought.

Using radar and lidar, the satellites can measure the thickness of the ice with a resolution of about 1.3 cm. With that data, a new report says that the Arctic Ocean has lost about a third of its winter sea ice cover over the past 20 years.

Scientists say ice that once did not melt over the summer has lost an average of about 0.5 metres in thickness just since IceSat-2 began operating in 2019. This shrinking leaves only much thinner seasonal ice, which melts completely each summer.