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Multiyear measurements of ebullitive methane flux from three subarctic lakes
Author(s) -
Wik Martin,
Crill Patrick M.,
Varner Ruth K.,
Bastviken David
Publication year - 2013
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/jgrg.20103
Subject(s) - subarctic climate , permafrost , flux (metallurgy) , environmental science , methane , atmospheric sciences , latitude , peat , thermokarst , hydrology (agriculture) , oceanography , physical geography , geology , geography , ecology , chemistry , geotechnical engineering , geodesy , archaeology , biology , organic chemistry
Ebullition (bubbling) from small lakes and ponds at high latitudes is an important yet unconstrained source of atmospheric methane (CH 4 ). Small water bodies are most abundant in permanently frozen peatlands, and it is speculated that their emissions will increase as the permafrost thaws. We made 6806 measurements of CH 4 ebullition during four consecutive summers using a total of 40 bubble traps that were systematically distributed across the depth zones of three lakes in a sporadic permafrost landscape in northernmost Sweden. We identified significant spatial and temporal variations in ebullition and observed a large spread in the bubbles' CH 4 concentration, ranging from 0.04% to 98.6%. Ebullition followed lake temperatures, and releases were significantly larger during periods with decreasing atmospheric pressure. Although shallow zone ebullition dominated the seasonal bubble CH 4 flux, we found a shift in the depth dependency towards higher fluxes from intermediate and deep zones in early fall. The average daily flux of 13.4 mg CH 4 m −2 was lower than those measured in most other high‐latitude lakes. Locally, however, our study lakes are a substantial CH 4 source; we estimate that 350 kg of CH 4 is released via ebullition during summer (June–September), which is approximately 40% of total whole year emissions from the nearby peatland. In order to capture the large variability and to accurately scale lake CH 4 ebullition temporally and spatially, frequent measurements over long time periods are critical.