Collaborative Research: The East Siberian Arctic Shelf as a Source of Atmospheric Methane: First Approach to Quantitative Assessment

来自三个机构的六名研究人员提议研究东西伯利亚北极大陆架（ESAS）的甲烷释放，该大陆架是世界海洋中最大（约占世界海洋大陆架面积的10%）和最浅（平均深度小于50 m）的大陆架。ESAS储存了世界？这是北极地区最大的碳氢化合物储量，主要是北极浅层水合物，因此代表了一个巨大的潜在甲烷大气来源，可能是全球变暖引发的永久冻土退化造成的。甲烷通量的增加可能以大量弱渗漏或大面积强气泡羽流的形式出现。由于ESAS的深度较浅，大部分释放的甲烷可能会避免氧化并逃逸到大气中。研究人员将调查甲烷的迁移路径特征，并确定甲烷从海底、水柱和大气中流出的控制因素。核心假设是，海底甲烷通量是全年的重要来源，而大气通量仅在无冰期才很重要。将通过夏季和冬季考察对水柱和海底进行取样，以及通过直升机调查对大气层进行取样，解决甲烷源、汇、通量的时空变化等问题。PI还将在嵌套范围的声纳尺度上评估6个控制点和2个测试点的海底直接气泡通量，并结合使用气泡视频成像和气泡建模。建模的目的是建立一个区域通量模型。拟议活动的更广泛影响包括国际合作、研究生和本科生培训以及公众宣传。

Six investigators from three institutions propose to study methane release over the East Siberian Arctic shelf (ESAS), the largest (about 10% of the world ocean shelf area) and the shallowest (mean depth less than 50 m) continental shelf of the world ocean. The ESAS stores the world?s largest hydrocarbon stocks, mostly as shallow Arctic hydrates, and thus represents a large potential methane atmospheric source that could result from global warming-triggered permafrost degradation. Increased methane fluxes could occur as numerous weak seeps or as strong bubble plumes over large areas. Due to the shallow depth of the ESAS, it is possible that the majority of methane released avoids oxidation and escapes to the atmosphere. The PIs will investigate the migration pathway characteristics and identify the controlling factors of methane flux from the seabed, in the water column, and to the atmosphere. The central hypothesis is that seabed methane fluxes are significant year-round sources while atmospheric fluxes are only significant during ice-free periods. The questions of methane sources, sinks, spatial and temporal variations in fluxes will be addressed through summer and winter expeditions to sample the water column and seabed, and helicopter surveys to sample the atmosphere. The PIs will also assess seafloor direct bubble flux over 6 control and 2 test sites on a nested range of sonar scales and using a combination of bubble video imaging and bubble modeling. Modeling will aim to develop a regional flux model. Broader impacts of the proposed activity include international collaboration, graduate and undergraduate student training, and public outreach.