Inferring the Base of Submarine Permafrost in the Canadian Beaufort Sea From Seismic Data and the Depth of the Gas Hydrate Stability Zone

The widespread presence of submarine permafrost in the southern Canadian Beaufort Sea provides necessary stability conditions for gas hydrates on the shallow shelf. However, the submarine permafrost is still relatively underexplored. Representing mostly relict terrestrial permafrost, submarine permafrost was formed by subaerial exposure to ∼−20°C in the Pliocene and Pleistocene. With the end of the last glaciation, the former terrestrial permafrost became inundated as a result of a marine transgression that caused a significant change in thermal conditions. The submarine permafrost is still responding to this thermal change and continues to degrade. The degradation of permafrost can cause greenhouse gas emissions having an important impact on the global climate. In this study, we use marine multichannel seismic data to calculate the base of permafrost using the seismically detected base of the gas hydrate stability zone. From the depth of the base of the gas hydrate stability zone, we estimate the theoretical gas hydrate dissociation temperature, which allows us to calculate the depth of the remotely inaccessible thermal base of permafrost (0°C isotherm). This calculated base of permafrost correlates with the lower boundary of a diffuse zone of high diffraction strength in seismic data indicating the presence of ice-bearing permafrost. Our study provides a new approach to access the current depth and extent of submarine permafrost on the outermost Canadian Beaufort Shelf and indicates less thawing of permafrost than previously thought.