Cascadia Gas Vent Distribution and Challenges to Quantify Margin-Wide Methane Fluxes
Abstract
Gas venting along the Cascadia Margin has been mapped over decades with ship sonar and in recent years with permanent seafloor installations utilizing the seafloor observatories NEPTUNE of Ocean Networks Canada and the Cabled Array of the Ocean Observatories Initiative. We show the distribution of over 1000 vents, most on the shallow shelf. For a third of the vents we have estimated methane flow rates, ranging from 0.05 to 69 L/min, and extrapolate these results to a margin-wide methane flow estaimate of around 4 Mt/yr (at surface pressure and temperature) and a flux estimate of 0.05 kg yr-1 m-2. However, these estimates are based on several assumptions, e.g. bubble sizes or data coverage, providing large uncertainties. With continued research expeditions and potential seafloor calibration experiments, these data can be refined and improved in future years.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMOS11B1132S
- Keywords:
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- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 3004 Gas and hydrate systems;
- MARINE GEOLOGY AND GEOPHYSICS;
- 4302 Geological;
- NATURAL HAZARDS