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Preprints
https://doi.org/10.5194/egusphere-2022-545
https://doi.org/10.5194/egusphere-2022-545
12 Jul 2022
 | 12 Jul 2022

Methane flux estimates from continuous atmospheric measurements and surface-water observations in the northern Labrador Sea and Baffin Bay

Judith Vogt, David Risk, Kumiko Azetsu-Scott, Evan N. Edinger, and Owen A. Sherwood

Abstract. Vast amounts of methane (CH4) stored in permafrost and submarine sediments are susceptible to release in a warming Arctic, further exacerbating climate change in a positive feedback. It is therefore critical to monitor CH4 over pan-regional scales to detect early signs of CH4 release. However, our ability to monitor CH4 is hampered in remote northern regions by sampling and logistical constraints and few good baseline data exist in many areas. To create a baseline study of current background levels of CH4 in North Atlantic waters, we collected continuous real-time atmospheric CH4 data, along with ambient air temperature and wind parameters over 22 days in summer 2021 on a roughly 5100 km voyage in the northern Labrador Sea and Baffin Bay up to 71° N. In addition, we measured CH4 concentrations in the water column using discrete water samples at selected stations. Measured atmospheric mixing ratios of CH4 ranged from 1944.7 ppb to 2012.0 ppb, with a mean of 1966.0±7.4 ppb and a baseline of 1954.2−1980.6 ppb. Dissolved CH4 concentrations in the near-surface water peaked at 56.58±0.05 nM within 1 km down-current of a known cold seep at Scott Inlet but were consistently super-saturated throughout the water column in Southwind Fjord, which is an area recently affected by submarine landslides. Local sea-air CH4 fluxes ranged from 0.1−14.1 µmol m-2 d-1 indicating that the ocean acted as a CH4 source to the atmosphere. Atmospheric CH4 levels were also driven by meteorological, spatial, and temporal variations. Highest atmospheric CH4 mixing ratios were detected in the Cumberland Sound in Nunavut, suggesting onshore sources from nearby waterbodies and wetlands, whereas ocean-based contributions at this location could not be ruled out. Coupled real-time measurements of marine and atmospheric CH4 data have the potential to provide ongoing monitoring in a region susceptible to CH4 releases, as well as critical validation data for global-scale measurements and modelling.

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Journal article(s) based on this preprint

16 May 2023
Sea–air methane flux estimates derived from marine surface observations and instantaneous atmospheric measurements in the northern Labrador Sea and Baffin Bay
Judith Vogt, David Risk, Evelise Bourlon, Kumiko Azetsu-Scott, Evan N. Edinger, and Owen A. Sherwood
Biogeosciences, 20, 1773–1787, https://doi.org/10.5194/bg-20-1773-2023,https://doi.org/10.5194/bg-20-1773-2023, 2023
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

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The release of the greenhouse gas methane from Arctic permafrost and submarine sources could...
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