Current rates and mechanisms of subsea permafrost degradation in the East Siberian Arctic Shelf

The rates of subsea permafrost degradation and occurrence of gas-migration pathways are key factors controlling the East Siberian Arctic Shelf (ESAS) methane (CH4) emissions, yet these factors still require assessment. It is thought that after inundation, permafrost-degradation rates would decrease over time and submerged thaw-lake taliks would freeze; therefore, no CH4 release would occur for millennia. Here we present results of the first comprehensive scientific re-drilling to show that subsea permafrost in the near-shore zone of the ESAS has a downward movement of the ice-bonded permafrost table of ∼14 cm year−1 over the past 31–32 years. Our data reveal polygonal thermokarst patterns on the seafloor and gas-migration associated with submerged taliks, ice scouring and pockmarks. Knowing the rate and mechanisms of subsea permafrost degradation is a prerequisite to meaningful predictions of near-future CH4 release in the Arctic.
The rate of subsea permafrost degradation is a key factor controlling marine methane emissions in the Arctic. Here, using re-drilled boreholes, the authors show that the ice-bonded permafrost table in the near-shore East Siberian Arctic Shelf has deepened by ∼14 cm per year over the past 31–32 years.