Methane in the Rhone River Delta

Quantification, controls, and fate of methane ebullition in the Rhone River Delta, Lake Geneva

We are investigating the importance of methane production in and emission from the Rhone River delta of Lake Geneva. As part of the éLemo project, several submersible dives with the Russian MIR submarines took place in Summer 2011 using in situ mass spectrometry and taking sediment cores in exact locations for carbon and methane information. Intensive surface studies using an echosounder were also conducted to measure methane bubble flux, which is one of the most efficient methane release pathways.
We hypothesize that the Rhone River delta is a disproportionately large source of atmospheric methane and that emissions vary seasonally. Methane bubble release seems to be structurally controlled in deeper areas of the delta and is strongest in the active canyon made by the Rhone River. Older canyons formed during past locations of the Rhone River still emit methane but significantly less than the active canyon. It is most likely the current input of organic substance from the Rhone River making the active canyon such an intense methane emitter. 

Collaboration

• éLEMO project EPFL
• Dr. David Senn
• Richard Camilli, Woods Hole Oceanographic Institute, USA