The purpose of this collaborative research project was to continuously measure methane concentrations in seasonally ice-covered lakes in the Canadian Arctic (Mackenzie River delta) using autonomous sampling devices, to more thoroughly address the variability in methane flux from Arctic lakes to the atmosphere. Methane is a potent greenhouse gas, and its flux from Arctic environments is poised to increase with climate warming. The project leveraged site access through collaboration with Canadian scientists from Natural Resources Canada and Simon Fraser University, allowing a comparison of lake methane dynamics in permafrost lakes in the mid- and outer Mackenzie River delta as well as in a tundra setting on North Richards Island, Northwest Territories, Canada. Our approach was to deploy the autonomous sampling and sensor systems for an extensive microbial, gas, and ion analytical program. The experimental concept had been proven previously in deep-sea settings by our project team, and the goal of this project was to demonstrate the feasibility of the approach for frozen Arctic settings. An overview of the project goals and motivations was recently documented in a popular science article in Smithsonian Magazine: https://www.smithsonianmag.com/science-nature/climate-scientists-turn-to-unusual-partnerships-arctic-180965015/

We hypothesized that dissolved methane that builds up under lake ice cover can be suddenly released from Arctic lakes during the spring ice breakup, and that this pulse of methane to the atmosphere would be missed by other sampling approaches that commonly occur in the summer months when field work is easier. An annual time series of dissolved gases (methane and oxygen), ions, and lake properties (temperature, pressure, light) from lakes across the Mackenzie River region documented variations in methane concentration build up under ice, with patterns reflecting the different sources of methane (diffusion out of methane-rich sediment and/or ebullition of gas bubbles from deeper sources), the parallel cycling of redox species (like oxygen and metal oxides) as a function of lake loading and inputs, and the regional weather conditions controlling ice cover and flooding dynamics. Likewise, the time series also documented the timing of dissolved methane flux from these lakes, with the flux and timing dependent on ice loss dynamics. Overall, this collaborative dataset confirms the utility of the autonomous sampler packages for capturing a full annual time series of in seasonally ice-covered lakes, and provides valuable data from constraining the magnitude and timing of dissolved methane flux from Arctic lake settings, which are poorly constrained variables in current global climate models. A paper describing these results is in preparation.

In addition to the collaborative effort described above, the group at Bigelow Laboratory for Ocean Sciences also contributed an analysis of the microbial communities residing within the lakes, with a focus on the microbial groups involved in methane cycling. Initial results document the importance of season in structuring lake water communities, regardless of carbon load of the lakes or their connection to the river. Methanotrophic microbial groups appear to comprise a very small fraction of the total microbial community, but these groups do reveal variation with lake seasonal conditions. This work involved an international collaboration with a Masters student from Simon Fraser University, who learned DNA extraction, sequencing, and analysis techniques, and this student will be leading the publication of this work.  

Last Modified: 11/15/2017
Modified by: Beth Orcutt