[A-CG50] Biogeochemical linkages between the surface ocean and atmosphere

[ACG50-P01] Observational activities for estimation on methane flux from the coastal area in Vietnam

*Sohiko Kameyama¹, Phuoc Hong Vo-Luong², Oanh Thi Ngoc Bui², Dung Xuan Tran², To Thi Hien², Duy Ha Phuc Cao² (1.Hokkaido University, 2.University of Science, Viet Nam National University-Ho Chi Minh Ciry)

Keywords:methane, flux, oceanic observation, coastal ocean

The ocean is known to be one of the sources of methane, the second most potent greenhouse gas after carbon dioxide. It has been pointed out that coastal areas in the ocean contribute to the release of methane to the atmosphere, especially because of the abundance of organic matter, the precursor of methane. In recent years, an international database has been constructed for a comprehensive understanding of the distribution of methane concentrations in the ocean, from which methane fluxes have been estimated (Weber et al., 2019). However, the database has a large variation in spatial data coverage, and many coastal areas, even those considered to be important emission areas, have very little data. Among them, the South China Sea/East Sea has high estimates of methane fluxes, but the data used is limited to only one research cruise, and there is definitely a lack of data for flux estimation. In particular, the southern coastal area of Vietnam is dominated by mangrove swamps, which are likely to be active in methane production due to the accumulation of abundant organic matter. This study aims to conduct observations in August 2024 and January 2025 in the coastal area around Ganh Rai Bay in southern Vietnam to characterize the distribution of methane concentration including the difference between wet and dry seasons and to estimate the methane flux from the coastal area. In this presentation, we will introduce the two oceanic observations and the preliminary data obtained up to the time of the presentation, and discuss potential future collaborations.