Submarine Permafrost on the Siberian Shelf

Recent results include the publication of drilling results from the central Laptev Sea, carried out by a consortium of partners from t. Petersburg (Arctic and Antarctic Research Institute), Yakutsk (Mel’nikov Permafrost Institute), the Universities of Hamburg and Potsdam, and two Potsdam research institutes (Alfred Wegener Institute, Geoforschungszentrum). We were able to measure methane concentrations within thawing but still frozen submarine permafrost. Based on approximate duration of inundation, it was possible to estimate rates of methane release (Overduin et al. 2015). Surprisingly, however, methane from permafrost did not migrate to the sea bed, but was oxidized by bacteria within the unfrozen sediment on top of the frozen permafrost (see Nature Climate Change comment on our work: Thornton and Crill, 2015). In further work, results of the innovative passive seismic method for detection of frozen submarine permafrost were published, detailing the method and first results. Modelling demonstrated that the observed signals correlate with the depth of unfrozen sediment overlying the ice-bonded permafrost (Overduin et al. 2015). This method is promising, since it has no impact on the seabed or biota, and can be operated without disturbing marine mammals. The next steps are to develop the instruments for operation over larger regions and for a wider range of permafrost depths. Real time operation (as opposed to deployment with autonomous logging) promises to speed up measurement, an important consideration for the large area of the Siberian shelf. Part of 2015 was occupied with proposal-writing to obtain support for this instrument development and testing in Siberia; the review process is on-going. Modelling efforts continue, together with a new partner, Climate Analytics GmbH in Berlin. A functioning model of submarine permafrost has been developed and is currently being tested. The goal is to develop a circum-arctic understanding of permafrost development over glacial-interglacial cycles. The first stage of modelling is expected to be completed by the end of the year, with results to be publicized at next year’s 11th International Conference on Permafrost in Potsdam, Germany. References Overduin, P. P., C. Haberland, T. Ryberg, F. Kneier, T. Jacobi, M. N. Grigoriev, and M. Ohrnberger (2015), Submarine permafrost depth from ambient seismic noise, Geophys. Res. Lett., 42, doi:10.1002/2015GL065409. Overduin, P. P., Liebner, S. , Knoblauch, C. , Günther, F. , Wetterich, S. , Schirrmeister, L. , Hubberten, H. W. and Grigoriev, M. N. (2015), Methane oxidation following submarine permafrost degradation: Measurements from a central Laptev Sea shelf borehole, Journal of Geophysical Research: Biogeosciences, 120 (5), pp. 965-978, doi:10.1002/2014JG002862. Thornton, B. F., and Crill, P. (2015), Arctic Permafrost: Microbial lid on subsea methane, Nature Climate Change, 5: 723-724