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Geological features of methane vents in the East Siberian Sea, the Arctic Ocean

Authors :
Jong Kuk Hong
Yeonjin Choi
Tae Siek Rhee
Sookwan Kim
Young-Gyun Kim
Seung-Goo Kang
Young Keun Jin
Publication Year :
2023
Publisher :
Copernicus GmbH, 2023.

Abstract

The East Siberian Sea is known for its high methane emissions, and the extent of massive methane emissions in remote areas from the coast is considered an important factor in estimating total methane emissions in the Arctic Ocean. In 2021, a multidisciplinary survey was conducted on the continental shelf of the East Siberian Sea aboard the Korean icebreaker Araon. The area is in international waters and is located more than 500 km from the coast. We conducted high-resolution sparker seismic survey and sub-bottom profiling to find detailed geological structure for gas expulsion and high-frequency echo sounding using EK80 to detect gas bubbles in water column EK80. We also measured underway CH4 concentration and sampled water and sediment with CTD and a multi corer. A high methane-concentration zone was found on the very shallow continental shelf at depths of 50–70 m by the underway CH4 measurements. It is developed in a northwest-southeast direction and has a width of several kilometers in the northwest and about 50 kilometers in the southeast. Because thick sea ice remained in the southeast zone, we have to surveye in the northwest zone. During the survey, many gas flares in the echograms and gas bubbles on the sea surface were found. In the gas flare field, we conducted extensive experiments with CTDs and sediment sampling using a multi-corer. A single channel sparker seismic survey was conducted crossing the high concentration zone with a source of 3000–5000 J. The acquired data were processed to get migration section and seismic profiles show well-stratified sedimentary layers clearly. On the gas expulsion sites, the seismic profiles show many vertical faults in the shallow sedimentary layers and vertical reflections in the water column caused by the methane emission from the seafloor. Acoustic features related to gas expulsion and gas charged sediments were also observed in the SBP data. Narrow and vertical reflections are also observed in the water column above the seafloor and the location of these reflections corresponds with the edge of the high amplitude, undulated subsurface reflector at shallow depths (~5 m) below the seafloor.

Details

Database :
OpenAIRE
Accession number :
edsair.doi...........70956385c38efa7ac56d0d5fac883ac4