Methane production, consumption and its carbon isotope ratios in the Southern Ocean during the austral summer

Abstract

The distribution of dissolved CH4 in the Southern Ocean at 140 E was measured during the austral summer. Surface CH4 was supersaturated on average, and the calculated mean sea-air flux rate was 0.32 μmolm−2 d−1. The vertical distributions exhibited a CH4 5 maximum at approximately 125 m (ÉCH4, 2.94 nM) below the chlorophyll-rich layer, suggesting a relationship between CH4 production and plankton dynamics in this area. CH4 oxidation and ocean movement characteristics in the deep layer led to the enrichment and fluctuation of 13CCH4 . We estimated the influence of Southern Ocean CH4, a source of isotopically heavy CH4 to the atmosphere, on the global CH4 budget 10 to be approximately 0.19Gg d−1.