Collaborative Research: Degrading offshore permafrost as a source of methane on the East Siberian Arctic Shelf

在北冰洋沉积盆地内，北冰洋地区含有大量的有机碳，被称为北极碳超级池。这一区域拥有有记录以来最高的沿海沉积速率，每年的有机碳累积速率约为1000万公吨，大约相当于整个世界大洋中上层区域的沉淀量。由于该地区的沉积和成岩作用的特殊性，大部分有机碳在分解后幸存下来，并埋藏在海底沉积物中。这些沉积物每年或季节性地冻结，代表着潜在的不稳定有机碳的大量储藏。据预测，未来几十年，北极地区的全球变暖将是巨大的，而且可能是快速的。在永冻层融化后，储存的旧碳将重新进入现代碳生物地球化学循环，可能成为上覆水乃至大气中甲烷的强大来源。此外，大量更古老的(更新世)甲烷以天然气水合物的形式被困在永久冻土内和之下。这项研究旨在阐明东西伯利亚北冰洋陆架地区沉积物和永冻土的甲烷通量潜力。由于全球变暖，东西伯利亚北极大陆架沿线的海底永久冻土可能会经历明显的热状况变化。温度升高可能会在几个方面影响永久冻土，最终导致其降解和甲烷释放增加。一个跨学科的国际研究小组将确定东西伯利亚北冰洋大陆架上永久冻土的分布和稳定性，并评估该地区是否为北极地区的甲烷来源。将使用干式钻井技术从11个地点获得岩心。生物甲烷的产生和消耗(氧化)的速率将在原地和高温下在永冻土和沉积物中量化。自然丰度稳定的碳和氢同位素测量将被用来量化从不同地点和深度收集的甲烷的年龄和来源。这些数据将被用作数值模型的输入，这些数值模型将被开发来描述永久冻土甲烷动力学的热力学和生物地球化学方面。利用现场数据和模型，将确定近海永久冻土甲烷当前和未来的潜在释放量，并将建立东西伯利亚北极大陆架的甲烷收支。

The Arctic region contains a huge amount of organic carbon, referred to as the Arctic Carbon Hyper Pool, within the Arctic Ocean sedimentary basin. This area has the highest documented rates of coastal sedimentation with annual accumulation rates of about 10 million metric tons organic C per 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 frozen annually or seasonally, 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 the melting of permafrost, old stored carbon 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 research aims 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. An international, interdisciplinary research team will determine the distribution and stability of permafrost on the East Siberian Arctic Shelf and evaluate this area as a methane source to the arctic region. Cores from eleven locations will be obtained using dry drilling techniques. Rates of biological methane production and consumption (oxidation) will be quantified in permafrost and sediments at in situ and elevated temperatures. Natural abundance stable carbon and hydrogen isotope measurements will be used to quantify the age and source of methane collected from different sites and depths. These data will be used as input to numerical models, which will be developed to describe the thermodynamic and biogeochemical aspects of permafrost methane dynamics. Using field data and modeling, the current and future potential release of methane from offshore permafrost will be determined and a methane budget for the East Siberian Arctic Shelf will be constructed.