Collaborative Research: Year-round autonomous sampling of methane in Arctic lakes, Northwest Territories, Canada, 2011-2017

The investigators propose to measure methane concentrations in frozen lakes continuously throughout the Arctic winter using autonomous sampling devices, to more thoroughly address the variability in the methane flux from Arctic lakes to the atmosphere. Methane is a potent greenhouse gas, the release of which from Arctic sources is poised to increase with climate warming. This project will expand upon a successful pilot study that included the initial testing of autonomous continuous fluid sampler and sensor systems. The proposed expansion will involve additional capabilities and the deployment of a sampling unit in each of six small lakes along a north-south gradient in the Mackenzie River delta in the Canadian Arctic for a nine-month period, spanning the winter season. With these data the investigators aim to characterize the physical, chemical, and microbial conditions in the water column to elucidate hydrologic, microbial, and weathering processes during the winter season, when methane builds in lake water under the ice cover. The investigators hypothesize that sudden (week, days, or even hours) releases of methane, following spring flooding and ice cover breakup, produce a distinct atmospheric flux from Arctic lakes that would otherwise be missed, since most logistically reasonable sampling occurs in the summer months when methane concentrations in these lakes are low or below detection. The majority of methane flux to the Arctic atmosphere is estimated to come from soils and small lakes, although these estimates are based on few direct observations with large uncertainties. This proposed study, using in situ samplers and sensors, will allow an extensive microbial, gas and ion analytical program coupled with a network of physical and chemical sensor data to assess temporal conditions during winter months; to confirm fundamental processes and rates; to determine the interplay among microbial, geochemical and physical processes; and to develop a plan for a more inclusive study that takes advantage of low cost proxies for significant processes that best characterize temporal aspects of lake conditions. The project will enhance infrastructure for future research in the Arctic through the development of novel in situ sampling. The project will support several undergraduate and graduate students, providing valuable lab-based experience for students from non-research-intensive institutions. The investigators also will conduct two informal outreach activities to communicate the importance of Arctic climate change to primary school students while also teaching them about design and engineering. They also intend to work closely with Aurora College and Aurora Research Institute based in Inuvik, Canada, to engage First Nations youth.研究人员拟采用自主采样装置（autonomous sampling devices），在整个北极冬季持续监测冰封湖泊的甲烷浓度，以更全面地解析北极湖泊向大气排放的甲烷通量（methane flux）的变化特征。甲烷是一种强效温室气体（greenhouse gas），北极地区的甲烷排放将随气候变暖而加剧。本项目将在一项已取得成功的先导研究基础上拓展，该先导研究完成了自主式连续流体采样与传感器系统的初步测试。本次拓展研究将新增相关功能，并在加拿大北极地区麦肯齐河三角洲沿南北梯度选取6个小型湖泊，每个湖泊部署一套采样装置，部署时长为9个月，覆盖整个冬季。借助这些观测数据，研究人员旨在表征水柱中的物理、化学与微生物条件，以阐明冬季冰层覆盖下甲烷在湖水中累积期间的水文过程、微生物过程与风化过程。研究人员提出假说：春季融汛与冰层破裂（ice cover breakup）后，甲烷会出现周、日乃至小时尺度的突发性释放，这会产生北极湖泊特有的大气甲烷通量，而这类通量在常规监测中往往会被遗漏——因为当前多数符合后勤可行性的采样活动均开展于夏季，此时湖水中的甲烷浓度较低甚至低于检测限。据估算，输入北极大气的甲烷通量主要来自土壤与小型湖泊，但这类估算仅基于少量直接观测数据，存在较大不确定性。本拟开展的研究采用原位采样器（in situ samplers）与传感器，将可开展大规模的微生物、气体与离子分析项目，并结合物理与化学传感器网络数据，评估冬季的时间动态特征；验证核心过程与速率；明确微生物过程、地球化学过程与物理过程之间的相互作用；并制定一套更全面的研究方案，借助低成本替代指标表征湖泊状况的时间动态特征，以体现关键过程的核心特点。本项目将通过开发新型原位采样技术，完善北极地区未来研究的基础设施。本项目将支持多名本科生与研究生开展研究，为来自非研究密集型院校的学生提供宝贵的实验室实践经验。研究人员还将举办两场非正式科普推广活动，向小学生讲解北极气候变化的重要性，同时传授设计与工程相关知识。此外，他们计划与加拿大因维克的奥罗拉学院及奥罗拉研究所紧密合作，以吸引第一民族青年（First Nations youth）参与其中。