Distributions and sea-to-air fluxes of methane and nitrous oxide in the North East China Sea in summer

The methane (CH₄) and nitrous oxide (N₂O) in the north East China Sea were measured during September 5 to 25 of 2003. The vertical profiles of CH₄ along four sections of the East China Sea showed high spatial variability due to the influence of complex water masses and the variable controlling factors. The vertical profiles of N₂O were less variable and were characterized by an increase from the surface to the bottom water, and were influenced mainly by the hydrographic conditions and biological production. CH₄ saturations in the surface waters ranged from 148% to 2490% with the average of 487 ± 555%, while the N₂O saturations ranged from 94% to 382% with an average of 191 ± 74%. The sea-to-air CH₄ fluxes were estimated to be 20.9 ± 54.8 μmol m^{- 2} d^{- 1} using the LM86 equations, and 36.3 ±95.7 μmol m^{- 2} d^{- 1} using the W92 equation. The sea-to-air N₂O fluxes were estimated to be 9.8 ± 16.0 μmol m^{- 2} d^{- 1} using the LM86 equations and 17.1 ± 26.4 μmol m^{- 2} d^{- 1} using the W92 equation. Both the saturations and fluxes of CH₄ and N₂O showed obvious spatial variations, which furthermore suggests that the northern region of the East China Sea is a net source of atmospheric CH₄ and N₂O.