Modeling the impediment of methane ebullition bubbles by seasonal lake ice

S. Greene, K. M. Walter Anthony, D. Archer, A. Sepulveda-Jauregui, K. Martinez-Cruz
2014 Biogeosciences Discussions  
Microbial methane (CH<sub>4</sub>) ebullition (bubbling) from anoxic lake sediments comprises a globally significant flux to the atmosphere, but ebullition bubbles in temperate and polar lakes can be trapped by winter ice cover and later released during spring thaw. This "ice-bubble storage" (IBS) constitutes a novel mode of CH<sub>4</sub> emission. Before bubbles are encapsulated by downward-growing ice, some of their CH<sub>4</sub> dissolves into the lake water, where it may be subject to
more » ... y be subject to oxidation. We present field characterization and a model of the annual CH<sub>4</sub> cycle in Goldstream Lake, a thermokarst (thaw) lake in interior Alaska. We find that summertime ebullition dominates annual CH<sub>4</sub> emissions to the atmosphere. Eighty percent of CH<sub>4</sub> in bubbles trapped by ice dissolves into the lake water column in winter, and about half of that is oxidized. The ice growth rate and the magnitude of the CH<sub>4</sub> ebullition flux are important controlling factors of bubble dissolution. Seven percent of annual ebullition CH<sub>4</sub> is trapped as IBS and later emitted as ice melts. In a future warmer climate, there will likely be less seasonal ice cover, less IBS, less CH<sub>4</sub> dissolution from trapped bubbles, and greater CH<sub>4</sub> emissions from northern lakes.
doi:10.5194/bgd-11-10863-2014 fatcat:7uvdeqz3qbespa6oywpmnwxf4q