Degrading Offshore Permafrost and Arctic Hydrates as a Current and Potential Source of Methane on the Siberian Arctic Shelf

The Arctic region contains a huge amount of organic carbon, referred to commonly as the "Arctic Carbon Hyper Pool", within the Arctic Ocean sedimentary basin. The Russian Arctic shelf acts as an estuary of the Great Siberian Rivers. This area has the highest documented rates of coastal sedimentation with annual accumulation rates of about 10x106 t C org year-, which approximately equals the amount of sediment accumulated over the entire pelagic zone of the World Ocean. Due to the specific features of sedimentation and lithogenesis in this area, much of this organic carbon survives decomposition, and is buried within seabed sediments. These sediments are annually ("offshore" permafrost) or seasonally frozen, representing a substantial reservoir of potentially labile organic carbon. Global warming in the Arctic region is predicted to be substantial, and possibly rapid, in next few decades. Upon permafrost melting, the old carbon stored therein will be reintroduced into the modern carbon biogeochemical cycle, possibly acting as a strong source of methane to the overlying water and potentially the atmosphere. Additionally, extremely large amounts of more ancient (Pleistocene) methane are trapped as gas hydrates within and beneath the permafrost. This project to elucidate the present and future methane flux potential of sediments and permafrost in regions of the East Siberian Arctic Shelf. As a result of global warming, seafloor permafrost along the East Siberian Arctic Shelf may experience a pronounced change in thermal regime. Increased temperature may affect permafrost in several ways, ultimately leading to its degradation and enhanced CH4 release. This international, interdisciplinary research team determined the distribution and stability of permafrost on the East Siberian Arctic Shelf and evaluated this area as a methane source to the Arctic region. Cores from ten locations were obtained using dry drilling techniques.
Thermal and biogeochemical data obtained from the boreholes/sediment cores were used as input to numerical models, which were developed to describe the thermodynamic and biogeochemical aspects of permafrost methane dynamics.

NSF-OPP ARC-0909546: Colloborative research: "Degrading Offshore Permafrost and Arctic Hydrates as a Current and Potential Source of Methane on the Siberian Arctic Shelf"
List of project papers:

Shakhova, N., Semiletov, I., Leifer, I., , Sergienko, V., Salyuk, A., Kosmach, D., Chernikh D., Stubbs, Ch., Nicolsky D., Tumskoy V., and Ö. Gustafsson (2013). Ebullition and storm-induced methane release from the East Siberian Arctic Shelf, Nature Geosciences, DOI:10.1038/ NGEO2007.

Chuvilin, E.M., Bukhanov, B.A., Tumskoy, V.E., Shakhova, N.E., Dudarev, O.E., and I.P. Semiletov (2013). Thermal conductivity of bottom sediments in the region of Buor Khaya Bay (Shelf of the Laptev Sea), Earth Cryosphere, 17(2), 32-40.
Semiletov, I.P., Shakhova, N.E., Pipko, I.I., Pugach, S.P., Charkin, A.N., Dudarev, O.V., Kosmach, D.A., and S. Nishino (2013). Space-time dynamics of carbon and environmental parameters related to carbon dioxide emissions in the Buor-Khaya Bay of the Laptev Sea, Biogeosciences, 10, 5977-5996, www.biogeosciences.net/10/5997/2013/doi:10.5194/bg-10-5977-2013.
Nicolsky, D.J., Romanovsky, V.E., Romanovskii, N., Kholodov, A.L., Shakhova, N.E., and I. Semiletov (2012). Modeling sub-sea permafrost in the East Siberian Arctic Shelf: The Laptev Sea Region, Journal of Geophysical Research, doi:10.1029/2012JF002358
Nicolsky, D., and N. Shakhova (2010). Modeling sub-sea permafrost in the East-Siberian Arctic Shelf: the Dmitry Laptev Strait, Env. Res. Lett.,5, doi:10.1088/1748-9326/5/1/015006.
Semiletov, I.P., Shakhova, N. E., Sergienko, V.I., Pipko, I.I., and O. Dudarev (2012). On carbon transport and fate in the East Siberian Arctic Land-Shelf-Atmosphere System, Environment Research Letters, 7, doi:10.1088/1748-9326/7/1/015201
Semiletov, I.P., Pipko, I.I., Shakhova, N.E., Dudarev, O.V., Pugach, S.P., Charkin, A.N., McRoy, C.P., Kosmach, D., and Ö. Gustafsson (2011). Carbon transport by the Lena River from its headwaters to the Arctic Ocean, with emphasis on fluvial input of terrestrial particulate organic carbon vs. carbon transport by coastal erosion, Biogeosciences, 8, 2407-2426.
Karlsson, E.S., Charkin, A., Dudarev, O., Semiletov, I., Vonk, J.E., Sánchez-García, L., Andersson, A., and Ö. Gustafsson (2011). Carbon isotopes and lipid biomarker investigation of sources, transport and degradation of terrestrial organic matter in the Buor-Khaya Bay, SE Laptev Sea, Biogeosciences, 8, 1865-1879, doi:10.5194/bg-8-1865-2011
Shakhova, N., Nicolsky, D., and I. Semiletov (2009). Current state of sub-sea permafrost on the East-Siberian Shelf: Testing of modeling results by observational data, Doklady Earth Science 429 (2), 1518-1521.
Semiletov, I., Shakhova, N., Lobkovsky, L., Dmitrevsky, N., Dudarev, O., Tumskoy, V., Grigoriev, M., Ananiev, R., Charkin, A., Koshurnikov, A., and E. Chuvilin . Degradation offshore permafrost as a source of methane on the East Siberian Arctic shelf, Science, in preparation

北冰洋沉积盆地中蕴藏着巨量有机碳，该储库通常被称为"北极碳超聚库（Arctic Carbon Hyper Pool）"。俄罗斯北极陆架作为西伯利亚大型河流的入海口区域，拥有记录在案的最高海岸沉积速率，年沉积有机碳通量约为10×10⁶吨·年⁻¹，这一规模大致相当于全球海洋远洋带的总沉积量。由于该区域沉积作用和成岩作用的独特特征，大部分有机碳未被分解，得以埋藏于海底沉积物中。这些沉积物呈常年（"离岸"多年冻土）或季节性冻结状态，构成了一个规模可观的潜在易分解有机碳储库。

据预测，未来数十年北极地区将经历显著且可能快速的全球变暖过程。多年冻土融化后，其中封存的古老碳将重新进入现代碳生物地球化学循环，可能对上覆水体乃至大气成为强效甲烷（CH4）源。此外，巨量更古老的更新世（Pleistocene）甲烷以天然气水合物的形式封存于多年冻土内部及下方。

本项目旨在阐明东西伯利亚北极陆架区域沉积物与多年冻土当前及未来的甲烷通量潜力。受全球变暖影响，东西伯利亚北极陆架沿线的海底多年冻土的热状态可能发生显著变化。温度升高会通过多种途径影响多年冻土，最终导致其退化并加剧甲烷释放。这支国际性跨学科研究团队探明了东西伯利亚北极陆架多年冻土的分布与稳定性，并评估了该区域作为北极地区甲烷源的潜力。研究团队采用干式钻探技术，获取了10个采样点的沉积物岩芯。

从钻孔与沉积物岩芯中获取的热学与生物地球化学数据，被用作数值模型的输入参数；该模型用于刻画多年冻土甲烷动力学的热力学与生物地球化学过程。

美国国家科学基金会极地项目办公室（NSF-OPP）资助项目ARC-0909546：合作研究"Degrading Offshore Permafrost and Arctic Hydrates as a Current and Potential Source of Methane on the Siberian Arctic Shelf"

项目已发表论文列表：
1. Shakhova, N., Semiletov, I., Leifer, I., Sergienko, V., Salyuk, A., Kosmach, D., Chernikh D., Stubbs, Ch., Nicolsky D., Tumskoy V., and Ö. Gustafsson (2013). Ebullition and storm-induced methane release from the East Siberian Arctic Shelf, *Nature Geosciences*, DOI:10.1038/NGEO2007。
2. Chuvilin, E.M., Bukhanov, B.A., Tumskoy, V.E., Shakhova, N.E., Dudarev, O.E., and I.P. Semiletov (2013). Thermal conductivity of bottom sediments in the region of Buor Khaya Bay (Shelf of the Laptev Sea), *Earth Cryosphere*, 17(2), 32-40。
3. Semiletov, I.P., Shakhova, N.E., Pipko, I.I., Pugach, S.P., Charkin, A.N., Dudarev, O.V., Kosmach, D.A., and S. Nishino (2013). Space-time dynamics of carbon and environmental parameters related to carbon dioxide emissions in the Buor-Khaya Bay of the Laptev Sea, *Biogeosciences*, 10, 5977-5996, www.biogeosciences.net/10/5997/2013/doi:10.5194/bg-10-5977-2013。
4. Nicolsky, D.J., Romanovsky, V.E., Romanovskii, N., Kholodov, A.L., Shakhova, N.E., and I. Semiletov (2012). Modeling sub-sea permafrost in the East Siberian Arctic Shelf: The Laptev Sea Region, *Journal of Geophysical Research*, doi:10.1029/2012JF002358。
5. Nicolsky, D., and N. Shakhova (2010). Modeling sub-sea permafrost in the East-Siberian Arctic Shelf: the Dmitry Laptev Strait, *Env. Res. Lett.*,5, doi:10.1088/1748-9326/5/1/015006。
6. Semiletov, I.P., Shakhova, N. E., Sergienko, V.I., Pipko, I.I., and O. Dudarev (2012). On carbon transport and fate in the East Siberian Arctic Land-Shelf-Atmosphere System, *Environment Research Letters*, 7, doi:10.1088/1748-9326/7/1/015201。
7. Semiletov, I.P., Pipko, I.I., Shakhova, N.E., Dudarev, O.V., Pugach, S.P., Charkin, A.N., McRoy, C.P., Kosmach, D., and Ö. Gustafsson (2011). Carbon transport by the Lena River from its headwaters to the Arctic Ocean, with emphasis on fluvial input of terrestrial particulate organic carbon vs. carbon transport by coastal erosion, *Biogeosciences*, 8, 2407-2426。
8. Karlsson, E.S., Charkin, A., Dudarev, O., Semiletov, I., Vonk, J.E., Sánchez-García, L., Andersson, A., and Ö. Gustafsson (2011). Carbon isotopes and lipid biomarker investigation of sources, transport and degradation of terrestrial organic matter in the Buor-Khaya Bay, SE Laptev Sea, *Biogeosciences*, 8, 1865-1879, doi:10.5194/bg-8-1865-2011。
9. Shakhova, N., Nicolsky, D., and I. Semiletov (2009). Current state of sub-sea permafrost on the East-Siberian Shelf: Testing of modeling results by observational data, *Doklady Earth Science* 429 (2), 1518-1521。
10. Semiletov, I., Shakhova, N., Lobkovsky, L., Dmitrevsky, N., Dudarev, O., Tumskoy, V., Grigoriev, M., Ananiev, R., Charkin, A., Koshurnikov, A., and E. Chuvilin . Degradation offshore permafrost as a source of methane on the East Siberian Arctic shelf, *Science*, in preparation