First evidence of widespread active methane seepage in the Southern Ocean, off the sub-Antarctic island of South Georgia
Earth and Planetary Science Letters
An extensive submarine cold-seep area was discovered on the northern shelf of South Georgia during R/V Polarstern cruise ANT-XXIX/4 in spring 2013. Hydroacoustic surveys documented the presence of 133 gas bubble emissions, which were restricted to glacially-formed fjords and troughs. Video-based sea floor observations confirmed the sea floor origin of the gas emissions and spatially related microbial mats. Effective methane transport from these emissions into the hydrosphere was proven by relative enrichments of dissolved methane in near-bottom waters. Stable carbon isotopic signatures pointed to a predominant microbial methane formation, presumably based on high organic matter sedimentation in this region. Although known from many continental margins in the world's oceans, this is the first report of an active area of methane seepage in the Southern Ocean. Our finding of substantial methane emission related to a trough and fjord system, a topographical setting that exists commonly in glacially-affected areas, opens up the possibility that methane seepage is a more widespread phenomenon in polar and sub-polar regions than previously thought.
We greatly appreciate the shipboard support from the master and crew of the research vessel Polarstern during cruise ANT-XXIX/4. This work was supported by the Deutsche Forschungsgemeinschaft (DFG) in the framework of the priority program ‘Antarctic Research with comparative investigations in Arctic ice areas’ by a grant to BO 1049/19 and through the DFG-Research Center/Cluster of Excellence “The Ocean in the Earth System”. AGCG was supported by Natural Environment Research Council (NERC) New Investigator Grant, NEK0005271, and by a fieldwork grant from the UK Quaternary Research Association (QRA) Research Fund. KL was supported by the ChEsSo programme (Consortium Grant NE/DO1249X/1) funded by NERC. CTSL acknowledges travel funds from the Earth Surface Sciences Institute, University of Leeds.
This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.epsl.2014.06.036
Earth and Planetary Science Letters, 2014, Vol. 403, pp. 166 - 177