Methane flows at the water–atmosphere interface in the South China Sea according to the results of expeditionary research

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Abstract

The article presents the results of studies of the spatiotemporal distribution of calculated methane flows at the water-atmosphere interface in the waters of the Vietnam continental shelf, slope and open part of the sea according to flight № 88 of the SRV Academician M.A. Lavrentiev (LV88) in the period from November 1 to November 29, 2019. As a result of the research, high variability was established from equilibrium and weak emission of 0–1 mole/(km²×day) to a very high intensity flux of 29 mole/(km²×day). The activity of gas exchange at the bottom–water–atmosphere boundary is due to the active release of CH4 from bottom sediments and is controlled by a complex of geological and hydrological factors.

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About the authors

Alexey A. Legkodimov

V.I. Il’ichev Pacific Oceanological Institute, FEB RAS

Email: legkodimov.aa@poi.dvo.ru
ORCID iD: 0000-0002-1768-8222

Junior Researcher

Russian Federation, Vladivostok

Galina I. Mishukova

V.I. Il’ichev Pacific Oceanological Institute, FEB RAS

Email: gmishukova@poi.dvo.ru
ORCID iD: 0000-0002-2806-3834

Candidate of Sciences in Geography, Senior Researcher

Russian Federation, Vladivostok

Duc Anh Le

Vietnam Academy of Science and Technology

Email: leducanh010282@gmail.com
ORCID iD: 0000-0003-2995-9752

Candidate of Sciences in Computer

Viet Nam, Hanoi

Maria A. Bovsun

V.I. Il’ichev Pacific Oceanological Institute, FEB RAS

Email: bovsun.ma@poi.dvo.ru
ORCID iD: 0000-0003-1916-3566

Junior Researcher

Russian Federation, Vladivostok

Pavel D. Zherdev

V.I. Il’ichev Pacific Oceanological Institute, FEB RAS

Author for correspondence.
Email: zherdev.pd@poi.dvo.ru

Senior Engineer

Russian Federation, Vladivostok

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Supplementary files

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2. Fig. 1. Distribution of methane flows at the water-atmosphere interface for cruise No. 88 of the R/V Akademik M.A. Lavrentyev

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3. Fig. 2. Distribution of methane flux into the atmosphere along the regional gas geochemical profile on the tectonic map of the South China Sea. Legend: 1 – gas deposits, 2 – oil deposits, 3 – faults (1) first order; 2) second order; 3) third order), 4 - main sedimentary basins (Paleogene, synrift sedimentary strata with high carbon content) (I - deltas of the Zhemchuzhnaya River, II - Son Hong, III - Kyongdongnan, IV - Fu Khan, V - Ku Long, VI - Nam Kon Son, VII - Natunsky, VIII - Malayan), 5 - schematic outline of the boundaries of the oceanic crust block, 6 - direction of surface currents in winter, 7 - areas of oil and gas exploration drilling in China, 8 - gas hydrate-bearing area, 9 - inset, 10 - area with active hydrocarbon gas emissions on the bottom of the shelf of Hainan Island [9], 11 - anomalous methane field in the bottom layer (100-250 nl/l), discovered in 1983, 12 - designations and serial numbers of methane emission zones into the atmosphere. Gas fields: DT – Dan Tai, LD – Lan Do. CH₄F – methane flux (mol/km²×day). Projection WGS 84

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4. Fig. 3. Change in the maximum methane flux at the water-atmosphere interface depending on the wind speed and the difference in methane concentration in seawater and its equilibrium value with the atmosphere

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5. Fig. 4. Spatial variability of CO₂ and CH₄ concentrations during cruise LV88 along the course of the R/V Akademik M.A. Lavrentyev, 2019.

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