Transport of CH4 through open-talik lakes in discontinuous permafrost aquifers
Abstract
As northern regions of the world experience warming climate, scientists look to permafrost, a crucial component of arctic and subarctic ecosystems, as a source and sink of atmospheric carbon. It is well-known that the thawing of permafrost from above as a result of warming climate is a considerable source of greenhouse gases. However, few studies have considered the production of methane, a potent greenhouse gas, beneath the permafrost. A rugged permafrost bottom is proposed to favor the storage of gas in "pockets" that have been formed through permafrost thaw and degradation from below. Sub-permafrost methane can migrate to reach the atmosphere when connections between the sub-permafrost and supra- permafrost (open taliks) form or when changing permafrost morphology opens pathways from the pocket to the bottom of an open-talik lake. We hypothesize that the migration of methane into open-talik lakes from the sub-permafrost can occur through advection and diffusion as a dissolved gas and by movement as an immiscible fluid. Two lakes with varying degrees of talik formation within Goldstream Cr. Basin, Fairbanks, Alaska, serve as the major study sites. To distinguish advection and diffusion of dissolved-phase methane we analyze dissolved methane concentrations, stable isotopes and major ions as tracers and through hydraulic gradient analysis. Monthly collection and analysis of water samples from surface, subsurface, and benthic sources allow for observation of seasonal changes in composition and flow dynamics. Observations and data collected to date indicate the occurrence of multiphase flow. We test the occurrence of immiscible-phase flow through measurement of displacement pressures and aging methane captured in desaturated pore channels beneath the lake bottom. Results to date also bring attention to the complexity of open-talik systems that has previously not been observed. Data obtained in this study will aid in the understanding of greenhouse gas fluxes, and thereby improve research in climate change predictions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.H43E1490E
- Keywords:
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- 1807 Climate impacts;
- HYDROLOGYDE: 1829 Groundwater hydrology;
- HYDROLOGYDE: 1831 Groundwater quality;
- HYDROLOGYDE: 1866 Soil moisture;
- HYDROLOGY