Shipborne eddy covariance observations of methane fluxes constrain Arctic sea emissions

• Main Authors: Thornton, BF, Prytherch, J, Andersson, K, Brooks, IM, Salisbury, D, Tjernström, M, Crill, PM
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Association for the Advancement of Science (AAAS) 2020
• Subjects: Arctic; Arctic Ocean; Laptev Sea; East Siberian Sea; Chukchi; laptev
• Online Access: https://eprints.whiterose.ac.uk/156269/; https://eprints.whiterose.ac.uk/156269/1/eaay7934.full.pdf

We demonstrate direct eddy covariance (EC) observations of methane (CH4) fluxes between the sea and atmosphere from an icebreaker in the eastern Arctic Ocean. EC-derived CH4 emissions averaged 4.58, 1.74, and 0.14 mg m−2 day−1 in the Laptev, East Siberian, and Chukchi seas, respectively, corresponding to annual sea-wide fluxes of 0.83, 0.62, and 0.03 Tg year−1. These EC results answer concerns that previous diffusive emission estimates, which excluded bubbling, may underestimate total emissions. We assert that bubbling dominates sea-air CH4 fluxes in only small constrained areas: A ~100-m2 area of the East Siberian Sea showed sea-air CH4 fluxes exceeding 600 mg m−2 day−1; in a similarly sized area of the Laptev Sea, peak CH4 fluxes were ~170 mg m−2 day−1. Calculating additional emissions below the noise level of our EC system suggests total ESAS CH4 emissions of 3.02 Tg year−1, closely matching an earlier diffusive emission estimate of 2.9 Tg year−1.