ACOUSTIC INVESTIGATIONS OF THE DEEPEST METHANE SEEPS IN THE OKHOTSK SEA

• Published in: Bulletin of the Tomsk Polytechnic University Geo Assets Engineering
• Main Authors: Denis V. Chernykh, Alexander S. Salomatin, Vladimir I. Yusupov, Natalia E. Shakhova, Denis A. Kosmach, Oleg V. Dudarev, Elena V. Gershelis, Vyacheslav I. Silionov, Roman A. Ananiev, Andrey A. Grinko, Igor P. Semiletov
• Format: Article in Journal/Newspaper
• Language: Russian
• Published: Tomsk Polytechnic University 2021
• Subjects: sea of okhotsk; deep and shallow arctic hydrates; acoustic research; seeps; methane; deep-water currents; methane release from sea bottom to water column; Engineering geology. Rock mechanics. Soil mechanics. Underground construction; TA703-712; Arctic; Okhotsk; okhotsk sea
• Online Access: https://doi.org/10.18799/24131830/2021/10/3286; https://doaj.org/article/eb9fbb708fe448aa883ee1b1df4df4f3

The relevance. Seeps – areas of bubble emanation of natural gases from the seabed into the water column and the atmosphere – were found in different World Ocean locations at depths from tens meters to several kilometers. Direct measurements of gas samples carried by rising bubbles have shown that they contain more than 80 % of the second most important greenhouse gas methane. The emissions of which, due to the re-preservation of deposits of natural hydrocarbons (for example, arctic or oceanic gas hydrates), can acquire a large-scale character and cause irreversible climatic changes. Detection of seeps in the water column may be the first indication of the presence of gas hydrates in the sediment. Therefore, assessment of the methane fluxes carried by seeps into the water column, detection of their variability, and identification of new regions of seepage are in the forefront of the marine and climate-related sciences. Moreover, understanding of deep seepage mechanism from disturbed gas hydrates observed in the Sea of Okhotsk is crucially important for study of methane ebullition from the shelf slope hydrates in the East Siberian Arctic seas – source of atmospheric methane of global significance. The main aim: to assess the quantity of methane transported by methane seeps from a depth of 2220 m into the water for the period from 2012 to 2018; to identify the relationship between the flux of methane from this area and deep earthquakes that occurred in the Sea of Okhotsk; based on the available acoustic data, estimate the speed of deep-water currents in the seepage areas. Objects: seeps, which forms hot spots of anomalously high dissolved methane concentrations in the water column-atmosphere. Methods. Acoustic observations of the seeps were carried out using a complex unit installed on board of the RV «Academic M.A. Lavrentiev», which is based on modernized ship echosounders Sargan-EM, ELAC LAZ-72, Sargan-GM sonars and a multichannel system for digital recording of acoustic signals. Methane flux from the seabed ...