In northern thermokarst lakes, which form in depressions left as permafrost thaws, methane, a greenhouse gas, can be released from lake sediments to the atmosphere through bubbling, or ebullition.
Constraining the amount of methane released through bubbling would help scientists understand the role of thawing permafrost in the carbon cycle and global climate change.
However, bubbling is highly variable in both space and time and thus difficult to measure accurately, so there are large uncertainties in estimates of methane emissions from northern ecosystems.
Researchers sought to better understand the spatial distribution of bubbling in lakes. They note that in many northern lakes, the bubbling sources, which they call ebullition seeps, cluster together in regular spatial patterns.
They combined field data from individual seeps with models to describe the spatial patterns of ebullition in three thermokarst lakes in different regions of Alaska. The authors used these models to create simulated ebullition data sets, on which they tested various methods for estimating lake ebullition. They find that the standard method of measuring ebullition with randomly placed bubble traps is biased toward underestimating methane flux, while a method using survey transects to map ebullition bubbles trapped in lake ice only slightly underestimated methane flux.
The authors suggest that transect field data from a large number of widely distributed lakes can be combined to give a good estimate of regional lake ebullition.
Article: Katey M. Walter Anthony and Peter Anthony, 'Constraining spatial variability of methane ebullition seeps in thermokarst lakes using point process models', Journal of Geophysical Research-Biogeosciences,doi:10.1002/jgrg.20087