Highest methane concentrations in an Arctic river linked to local terrestrial inputs

• Published in: Biogeosciences
• Main Authors: K. Castro-Morales, A. Canning, S. Arzberger, W. A. Overholt, K. Küsel, O. Kolle, M. Göckede, N. Zimov, A. Körtzinger
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Arctic; Kolyma; Global warming; kolyma river; permafrost; Siberia
• Online Access: https://doi.org/10.5194/bg-19-5059-2022; https://doaj.org/article/000c1ab89ca34629b8fd9d40c6167ae0

Large amounts of methane ( CH 4 ) could be released as a result of the gradual or abrupt thawing of Arctic permafrost due to global warming. Once available, this potent greenhouse gas is emitted into the atmosphere or transported laterally into aquatic ecosystems via hydrologic connectivity at the surface or via groundwaters. While high northern latitudes contribute up to 5 % of total global CH 4 emissions, the specific contribution of Arctic rivers and streams is largely unknown. We analyzed high-resolution continuous CH 4 concentrations measured between 15 and 17 June 2019 (late freshet) in a ∼120 km transect of the Kolyma River in northeast Siberia. The average partial pressure of CH 4 ( p CH 4 ) in tributaries (66.8–206.8 µatm ) was 2–7 times higher than in the main river channel (28.3 µatm ). In the main channel, CH 4 was up to 1600 % supersaturated with respect to atmospheric equilibrium. Key sites along the riverbank and at tributary confluences accounted for 10 % of the navigated transect and had the highest p CH 4 (41 ± 7 µatm ) and CH 4 emissions (0.03 ± 0.004 <math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">mmol</mi><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">m</mi><mrow><mo>-</mo><mn mathvariant="normal">2</mn></mrow></msup><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">d</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="67pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="d4c2ee668fea12b7ca233e9f97025a6f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-5059-2022-ie00001.svg" width="67pt" height="13pt" ...