Revealing the Extent of Submarine Permafrost and Gas Hydrates in the Canadian Arctic Beaufort Sea Using Seismic Reflection Indicators

<title xmlns:mml="http://www.w3.org/1998/Math/MathML">Abstract</title><p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en">The Canadian Arctic Southern Beaufort Sea is characterized by prominent relict submarine permafrost and gas hydrate occurrences formed by subaerial exposure during extensive glaciations in Pliocene and Pleistocene. Submarine permafrost is still responding to the thermal change as a consequence of the marine transgression that followed the last glaciation. Submarine permafrost is still underexplored and is currently the focus of several research projects as its degradation releases greenhouse gases that contribute to climate change. In this study, seismic reflection indicators are used to investigate the presence of submarine permafrost and gas hydrates on the outer continental shelf where the base of permafrost is expected to cross‐cut geological layers. To address the challenges of marine seismic data collected in shallow water environments, we utilize a representative synthetic model to assess the data processing and the detection of submarine permafrost and gas hydrate by seismic data. The synthetic model allows us to minimize the misinterpretation of acquisition and processing artifacts. In the field data, we identify features along with characteristics arising from the top and base of submarine permafrost and the base of the gas hydrate stability zone. This work shows the distribution of the present submarine permafrost along the southern Canadian Beaufort Sea region and confirms its extension to the outer continental shelf. It supports the general shape suggested by previous works and previously published numerical models.</p>

Plain Language Summary: Submarine permafrost, ground beneath the seafloor that perennially remains below 0°C, is present on the continental shelf of the Canadian Beaufort Sea. During the Late Pleistocene (∼1 Million years ago), the continental shelf was subaerially exposed to the cold Arctic air causing the formation of ice in the ground. This period was followed by a sea level rise that flooded the continental shelf with warmer waters, resulting in an intensive change of the thermal regime. The relict permafrost still reacts to this thermal change and is continuously thawing. Associated with the presence of relict permafrost, extensive gas hydrates exist to &gt;1,000 m below the seafloor. Climate warming threatens both the stability of permafrost and associated gas hydrates. Their thawing and decomposition can cause a release of greenhouse gases which in turn amplifies climate warming. This study uses marine seismic reflection data to identify permafrost and gas hydrate in the southern Canadian Beaufort Sea. We find indicators of the top and base of permafrost and the base of the gas hydrate stability zone in the outer continental shelf area. Our work shows that the permafrost and gas hydrates still extend to the outer continental shelf and thereby supports previously published numerical models.</p>

Key Points: <list list-type="bullet"> <list-item> <p xml:lang="en">Seismic reflection data reveal occurrences and extent of submarine permafrost and associated gas hydrates at the Canadian Beaufort Shelf</p></list-item> <list-item> <p xml:lang="en">Synthetic modeling of permafrost and gas hydrate is required to assess seismic processing minimizing the potential for misinterpretation</p></list-item> <list-item> <p xml:lang="en">Indicators of top and base of permafrost and the base of gas hydrate stability support previously published numerical models</p></list-item> </list> </p>

Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659

Korean Ministry of Oceans and Fisheries

Environmental Geoscience Program of the Geological Survey of Canada

https://dx.doi.org/doi:10.22663/KOPRI-KPDC-00001958.3