NSF-OPP ARC-102328: Collaborative Research: The East Siberian Arctic Shelf as a Source of Atmospheric Methane: First Approach to Quantitative Assessment

The East Siberian Arctic shelf (ESAS) is the largest (~10% of the world ocean shelf area) and the shallowest shelf (mean depth <50 m) of the world ocean. Until this study, the ESAS was not considered a source of methane (CH4) to the atmosphere due to subsea permafrost’s impermeability, which completely isolated it from modern biogeochemical cycles. The ESAS stores the world’s largest hydrocarbon stocks, mostly as shallow Arctic hydrates, and thus represents an enormous potential CH4 atmospheric source that could result from global warming-triggered permafrost degradation. Increased CH4 fluxes could occur as numerous weak seeps or strong bubble plumes over large areas. Due to the shallow nature of the ESAS, the majority of ESAS CH4 likely avoids oxidation and escapes to the atmosphere. To assess whether sudden, large-scale CH4 release occurs or is likely to occur in the future, we investigated spatial and temporal variability as well as the controlling factors of CH4 flux to the water column, and to the atmosphere. This data set contains results of CH4 measurements performed in the water column using headspace analysis (ppm in gaseous phase) during the expeditions 2009-2010 and observed mixing ratios of CH4 in the atmospheric boundary layer above the water surface (ppm).

东西伯利亚北极陆架（East Siberian Arctic shelf, ESAS）是全球面积最大（约占世界海洋陆架总面积的10%）且最浅的海洋陆架，平均水深不足50米。在本研究开展之前，由于海底永久冻土的隔水特性，东西伯利亚北极陆架被认为不会向大气排放甲烷（methane, CH₄），完全隔绝于现代生物地球化学循环之外。该陆架储存着全球规模最大的碳氢化合物储量，且多以浅层北极水合物形式赋存，因此全球变暖引发的永久冻土退化可能使其成为极具潜力的大气甲烷排放源。甲烷通量的增加可能以大范围分布的弱渗漏或强气泡羽流的形式出现。鉴于东西伯利亚北极陆架的极浅水深特征，绝大多数甲烷大概率不会经历氧化过程，可直接逸散进入大气。为评估当前是否存在突发性大规模甲烷释放，或未来是否可能发生此类事件，本研究针对甲烷向水柱及大气的通量的时空变化特征与控制因素展开了调查。本数据集包含2009-2010年考察航次期间采用顶空分析法（气相浓度以ppm计）测得的水柱甲烷测量结果，以及水面上方大气边界层中观测到的甲烷混合比（单位：ppm）。