Marine Geophysics and Hydroacoustics

BOPCATS

Summary

Beaufort Offshore Permafrost and gas hydrates – Climate change impact on Arctic Transgressed continental Shelves (BOPCATS)

Arctic continental shelf regions with water depths of less than 100 m comprise ~30% of the total area of the Arctic Ocean. Throughout the Quaternary, the Arctic shelf experienced a varied climatic and thus dynamic geologic history. During periods of low sea level many of these marine shelf areas were not covered with water but were exposed to mean annual air temperatures of -20ºC or less. These cold temperatures caused the formation of significant permafrost accumulations and also established favourable pressure and temperature conditions for gas hydrates. In contrast, sea level rise during interglacial periods resulted in marine transgression, yielding degradation of offshore permafrost and associated gas hydrates. The repeated changes have had substantial impacts on the geology of Arctic shelves and slope regions in form of e.g. fast-changing styles of sedimentation pattern and sediment types, erosion and re-deposition, mass-transport deposits, changes to fluid-flow patterns, and changes in sediment compaction. These geologic processes can result in the occurrence of significant and still poorly understood geohazards (e.g. land-slides).
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This project is set to investigate the processes described above associated with permafrost degradation, gas hydrate dissociation, and gas migration from transgression and anthropogenic climate change along the southern Canadian Beaufort Sea. Furthermore, methane release at the seabed shall be quantified by hydroacoustic methods for the first time. Our working group was invited to participate in an expedition with the research icebreaker ARAON of the Korean Polar Research Institute (KOPRI). This expedition is supported and partially financed by KOPRI and the Geological Survey of Canada (GSC). The expedition and the participation with ocean bottom seismometer (OBS) provided by GEOMAR allows us to investigate three critical questions about marine permafrost and gas hydrates in the Arctic Ocean at the southern Canadian Beaufort Sea: (1) How much is the extent of the marine permafrost, especially at the shelf edge, and what concentration of ice-bonded sediments prevails? (2) Where are gas hydrate occurrences at the shelf and at deep-water, and what concentrations exist? (3) How big is the methane gas release at the seabed, to what extent does it change laterally and how much methane arrives at the atmosphere? For delineating permafrost and gas hydrate occurrences and estimating their concentrations, new multichannel reflection seismic and refraction seismic data shall be acquired by the use of the OBSs. In addition, high-resolution sediment echo imagery will complement the data. Hydroacoustic data is used to quantify methane gas flow and additional measurements on board (e.g. properties and composition of sea water and atmosphere) complete the estimations.

Project participants:  Michael Riedel (GEOMAR), Sebastian Krastel, Henrik Grob

Partnerinstitutionen:

  • GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
  • Geological Survey of Canada
  • Korea Polar Research Institute