Japan Geoscience Union Meeting 2018

Presentation information

[EJ] Oral

A (Atmospheric and Hydrospheric Sciences) » A-AS Atmospheric Sciences, Meteorology & Atmospheric Environment

[A-AS06] Atmospheric Chemistry

Thu. May 24, 2018 1:45 PM - 3:15 PM A05 (Tokyo Bay Makuhari Hall)

convener:Yoko Iwamoto(Graduate School of Biosphere Science, Hiroshima University), Tomoki Nakayama(Graduate School of Fisheries and Environmental Sciences, Nagasaki University), Sakae Toyoda(東京工業大学物質理工学院, 共同), Nawo Eguchi(Kyushu University), Chairperson:Minejima Chika(International Christian University), Takigawa Masayuki(Japan Agency for Marine-Earth Science and Technology)

1:45 PM - 2:15 PM

[AAS06-17] Methane exchange between atmosphere and ocean

★Invited Papers

*Kosuke Noborio1, Shinsuke Aoki1, Shujiro Komiya4, Fumiyoshi Kondo3, Yuki Ito1, Toshihiro Doi1, Mitsuo Uematsu2, Ryo Matsumoto1 (1.Meiji University, 2.The University of Tokyo, 3.Japan Coast Guard Academy, 4.Max Planck Institute for Biogeochemistry)

Keywords:gas flux, relaxed eddy accumulation, Pacific Ocean

Methane (CH4) is one of the major greenhouse gases with approximate 30 times as much greenhouse effect as carbon dioxide. Sources of CH4 would be biogenic, thermogenic, and combustion. Agricultural lands are a major contributor to CH4 emission. Although the ocean is thought to be a sink for methane, little research has been conducted to directly measure CH4 flux on the ocean. Our objective was to gain our knowledge on the CH4 exchange between the atmosphere and the ocean by direct measurement of CH4 flux on a ship. Row, pitch, and yaw were detected in real time with three-axils inclinometer and accelerometer on board, and wind speed and wind direction were corrected to compensate ship's motion to separate upward and downward eddies of air. The methane concentration of upward and downward air was measured every 30 min to estimate CH4 flux with the relaxed eddy accumulation method. Methane concentration in the atmosphere varied along the course of the ship: (1) high in Tokyo and decreased to the equator; and (2) abruptly increased in the Berling Sea after the northern Pacific Ocean. Methane flux was tended to increase where CH4 concentration was high. As reported by the previous workers, we found the direct measurement of flux was larger than the conventional bulk method.