| Summary: | 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.
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