Hydroacoustic Characteristics of Marine Gas Seep on The West Svalbard Shelf


Dienstag, 17. Dezember 2013 - 16:00 Uhr
GEO-Gebäude, Raum 1550 (Hörsaal)
Michal Tomczyk

Abstract

Marine gas seeps on the continental shelf of the Arctic seas can play an important role in methane transport from the seabed to the atmosphere. The lack of quantitative data represents an obstacle for a better understanding of the influence of gas seepage on the carbon cycle and the global climate. This study provides the flux estimation of gas emissions from a recently discovered natural methane seepage area at the shelf west of Svalbard using hydroacoustic techniques. Quantitative assessment of the gas emissions from the seafloor is based on a novel approach combining data from single- and multi-beam echosounders and a high-frequency, horizontally-looking sonar mounted on a remotely operated vehicle (ROV). In total, over 2300 gas flares were identified spatially related to a morphological ridge system. The recordings of the ship-mounted echosounders provide the evidence that large part of the emanating gas bubbles rise through the entire water column up to the sea surface, suggesting that the released methane may enter the atmosphere. The quantification method based on the ROV-mounted high-resolution sonar echograms resulted flux values of individual bubble streams in the range of 5 to 137 mL min-1, which is in good agreement with corresponding direct measurements conducted with a reversely mounted funnel. The fluxes obtained with our method at specific locations were extrapolated for the entire study area, which resulted in a total flux of ~13 x 103 ±1.5 x 103 L h-1 in area of ~9 km2.




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