Methan oxidation in the water column and its role in the carbon budget of the coastal ocean

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The release of large amounts of the greenhouse gas methane from marine gas reservoirs is believed to have advanced warming episodes in Earth¿s history. However, methane emitted at the seafloor is consumed partly in the ocean by microorganisms, reducing the portion reaching the atmosphere. The main purpose of this project is to quantify the fraction of CH4 oxidized in the water column in relation to the amount discharging, dispersed in the water column and escaping into the atmosphere at different seep settings. For that purpose, the proposer will learn the 14C/3H-tracer technique including the synthesis of the tracers at the University of California, Santa Barbara (UCSB), USA, and apply this technique to measure oxidation rates of CH4 in the water column. The acquired technique will be ideally complemented by CH4 concentration analyses in the water column, ocean current measurements, mapping of bubble plumes, and gas analyses at the sea surface. These investigations will be performed at several vent sites situated in the Santa Barbara Basin/Channel of California in close cooperation with the SEEPS project at the UCSB. The area is ideally suited as it is one of the most active areas of natural marine hydrocarbon seepage in the world. The comparison of results from distinct vent sites will provide new insight to the buffer system of the ocean with regard to hydrocarbon seepage. This is of great value for the assessment of the climatological response of a sudden release of CH4 from marine gas resources.