How did subsea permafrost form beneath the Arctic Ocean?

Subsea permafrost in the Arctic Ocean originated during the glacial epoch, particularly around 20,000 years ago. During this period, much of the continental shelf was exposed to harsh polar climates for thousands of years, allowing cold permafrost to form to depths exceeding 700 metres.1

Over the past 10,000 years, rising sea levels caused the Arctic Ocean to advance over this previously frozen landscape. This process transformed the terrain into what is now considered degrading relict subsea permafrost. Because this ground is no longer exposed to the cold atmosphere and is instead covered by salt water, the ice-rich permafrost has lost structural strength and is undergoing melting. Currently, this permafrost is sensitive to warming from geothermal heat and human activity, as its temperatures are no longer as low as they were during glacial times.1