DISTRIBUTION OF METHANE FLUXES AT THE WATER-ATMOSPHERE BOUNDARY AND SIMULATION OF TRANSPORT PROCESSES WITHIN PETER THE GREAT BAY WATER AREA AND THE ADJACENT SLOPE IN AUTUMN SEASON
G. Mishukova, A. Yatsuk, V. Mishukov
1V.I. Il’ichev Pacific Oceanological Institute, Far Eastern Branch of the Russian Academy of Sciences, Vladivostok, Russia
2Sirius University of Science and Technology: Krasnodar Region, federal territory "Sirius", urban-type settlement Sirius, Olympic Avenue, 1, Russia
Keywords: methane, fluxes, concentrations, distribution, impurity transport, Tumannaya River, Peter the Great Bay, Sea of Japan
Abstract
The paper presents the research results based on experimental data received in the expedition of the R/V “Akademik Oparin” in the water area of Peter the Great Bay (cruise No. 54, October 2017). Methane fluxes on the water-atmosphere boundary were calculated for each sampling point on the basis of measured concentrations of dissolved methane in the surface layer of seawater, methane in the surface layer of atmosphere, temperature, salinity, and wind speed. In all cases, surface water was supersaturated with methane. Methane fluxes from the sea surface varied from 1 to 981 mol/km2·day with an average value of 7.1±4.5 mol/km2·day. The most intense emission was observed near the estuary of the Tumannaya River. Gas-saturated sediments with inclusions of subaqueous authigenic minerals have been discovered on the slope of the continental shelf. After analysis of geological and hydrochemical information, areas where methane from bottom sediments enters the marine environment were identified. During the expedition to the water area under study, the use of current field and advective impurity transport models made it possible to discover the prospective zones of elevated dissolved methane concentrations and also to identify for the first time an underwater source of methane discharge (a potential element of the paleochannel of the Tumannaya River), which affects the dissolved methane concentrations and salinity distribution in the subsurface waters of the bay. Comparison of the calculated methane transport with experimental results showed good spatial agreement, especially within the Tumannaya River estuary zone. The calculations showed that tidal currents cause not only the local maxima of methane concentrations and its fluxes from the sea surface in certain areas of the bay, but also its transport to the pelagic waters in the western part of the Central Basin of the Sea of Japan.
|
