Distribution characteristics of methane in the water column and sea-to-air flux in “Haima” cold seep, South China Sea

Abstract

Methane (CH4) is a powerful greenhouse gas with a stronger greenhouse effect than carbon dioxide. The ocean is the largest CH4 reservoir in the world and plays an important role in adjusting climate change. Water column CH4 distribution and sea-to-air in the marine CH4 seeping areas are crucial to finger the ultimate fate of marine CH4. In this research, we investigated the distribution of dissolved CH4 and environmental factors in the water column, and calculated the sea-to-air flux in the "Haima" cold seep area. The results showed that the surface dissolved CH4 concentration ranged from 0.50 to 53.20 nM, and the sea-to-air flux was 38.56 μmol/m 2 /d. Compared with previous studies, it was higher than that on the general ocean surface but lower than that in the estuary area. In addition, the vertical distribution showed that the CH4 concentration in the surface layer was lower than that in the bottom layer, and the maximum value appeared at about 150 m. By PCA analysis, it can be found that SO4 2and TOC were important factors affecting the dissolved CH4 concentration. In conclusion, understanding the CH4 emissions in cold seep areas is of great significance for coping with global warming.