Acoustic and Geomorphological Signatures of Gas Seeps on the East Siberian Margin

TitleAcoustic and Geomorphological Signatures of Gas Seeps on the East Siberian Margin
Publication TypeConference Abstract
AuthorsWeidner, E, Mayer, LA, Jerram, K, Weber, TC, Jakobsson, M, Chernykh, D, Ananiev, R, Mohammad, R, Semiltov, I
Conference Name2016 Graduate Research Conference
Conference DatesApril 11-12
Keywordsacoustic, east siberian margin, gas seeps, geomorphological signatures

Rising hydrocarbon gas concentrations in the atmosphere are strongly linked to global warming. In the next century, significant amounts of hydrocarbons will be transport from the ocean to the atmosphere via thawing of flooded permafrost. The East Siberian Arctic Shelf (ESAS) holds 80% of the world’s flooded permafrost and is at risk of massive release due to bottom water warming. Gas released from permafrost is transported by gas seeps through the ocean; however, the magnitude of this gas flux has historically been difficult to quantify.

This research aims to estimate the total gas flux from a region of the ESAS, Herald Canyon, via acoustic and geomorphological characterization of gas seeps in the area. Data was collected with three acoustic systems (EM122 multibeam echosounder, SBP120 subbottom profiler, and EK80 split-beam sonar) onboard the Oden during the Swedish-Russian-US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions (SWERUS-C3) program.

53 seeps have been identified in the vicinity of Herald Canyon. Together, the EM122 high-resolution multibeam bathymetry and SBP120 chirp subbottom profiling data, provide the spatial and geologic context of the gas seeps. The EK80, which makes acoustic measurements over a broad range of frequencies, can identify individual bubble scatters. This enables estimates of bubble size distribution and rise velocity measurements in certain seeps; ultimately providing gas flux estimates. The combination of three data sets offers the opportunity to link seep flux estimates to geomorphological setting. The geomorphological setting can further be linked to local and regional geologic processes determined from seafloor morphology and subsurface structure. These links will help define our knowledge of the transport of hydrocarbon gas from flooded permafrost to the atmosphere.