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

合作研究：近海永久冻土层和北极水合物的退化是西伯利亚北极陆架当前和潜在的甲烷来源

• 批准号: 0909546
• 负责人: Igor Semiletov
• 金额: $ 60.9万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-15 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0909546&HistoricalAwards=false
• 关键词: Collaborative; Research; Degrading; Offshore; Permafrost

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.

北极地区在北冰洋沉积盆地内含有大量的有机碳，被称为北极碳超级池。这一地区有记录的沿海沉积速率最高，每年积累约1 000万公吨有机碳，大约相当于世界海洋整个水层区积累的沉积物量。由于这一地区沉积和成岩作用的特殊性，大部分有机碳在分解后仍然存在，并埋藏在海底沉积物中。这些沉积物每年或季节性冻结，代表着潜在不稳定有机碳的大量储存。据预测，在未来几十年，北极地区的全球变暖将是巨大的，而且可能是迅速的。在永久冻土融化时，旧的储存碳将被重新引入现代碳地球化学循环，可能作为甲烷的强大来源，进入上覆水和潜在的大气。此外，极大量的更古老的（更新世）甲烷被困在永久冻土层内和之下的气体水合物。本研究旨在阐明东西伯利亚北极大陆架地区沉积物和永久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着的海底永久冻土可能会经历明显的热状况变化。温度升高可能会以多种方式影响永久冻土，最终导致其退化和CH4释放增加。一个国际跨学科研究小组将确定东西伯利亚北极大陆架永久冻土的分布和稳定性，并评估该地区作为北极地区甲烷来源的情况。将使用干钻技术从11个地点获得岩心。生物甲烷生产和消耗（氧化）的速率将在永久冻土和沉积物中在原位和高温下进行量化。天然丰度稳定碳和氢同位素测量将用于量化从不同地点和深度收集的甲烷的年龄和来源。这些数据将被用来作为输入的数值模型，这将被开发来描述永冻层甲烷动力学的热力学和地球化学方面。利用现场数据和建模，将确定近海永久冻土目前和未来的潜在甲烷释放量，并构建东西伯利亚北极大陆架的甲烷预算。