Report for methane monitoring in Arctic Lakes in Northwest Territories, Canada, August 2015

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 ninemonth
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.

研究人员计划采用自主采样设备（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的变化特征。甲烷是一种强效温室气体，北极来源的甲烷排放将随气候变暖而显著增加。本项目将在一项已取得成功的初步研究基础上拓展——该初步研究完成了自主式连续流体采样与传感器系统的首批测试。本次拓展研究将新增多项功能，并计划在加拿大北极地区马更些河三角洲（Mackenzie River delta）沿南北梯度分布的6个小型湖泊各部署一套采样单元，部署时长为9个月，覆盖整个冬季。通过采集这些数据，研究人员旨在表征冰盖下冬季湖水柱（water column）中的物理、化学与微生物环境，以阐明冬季季节内的水文、微生物及风化过程——此时甲烷会在冰盖下的湖水中持续累积。研究人员提出如下假说：春季融汛与冰盖破裂后，甲烷会出现时间尺度为数周、数天乃至数小时的突发性释放，由此产生的北极湖泊大气通量特征极易被忽略；这是因为当前多数符合作业可行性的采样活动多在夏季开展，而此时湖水中的甲烷浓度往往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源自土壤与小型湖泊，但此类估算仅依托少量直接观测数据，存在较大不确定性。本研究采用原位采样器与传感器（in situ samplers and sensors），将可支撑大规模的微生物、气体与离子分析计划，并结合物理与化学传感器网络数据，以评估冬季月份的时间动态特征；验证关键过程与速率；厘清微生物、地球化学与物理过程间的相互作用；并为开展更具普适性的研究制定方案——该方案将利用低成本替代指标来表征湖泊环境时间动态的核心过程。
本项目将通过开发新型原位采样（in situ sampling）技术，完善北极地区未来研究的基础设施。项目将资助多名本科生与研究生，为来自非科研密集型院校的学生提供宝贵的实验室研究实践经验。
研究团队还将开展两项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，团队计划与位于加拿大因纽维克的奥罗拉学院（Aurora College）及奥罗拉研究所（Aurora Research Institute）密切合作，以吸引原住民第一民族（First Nations）青年参与其中。