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 Vogt1,2, David Risk1, Kumiko Azetsu-Scott3, Evan N. Edinger4, and Owen A. Sherwood5 Judith Vogt et al.
  • 1Department of Earth Sciences, St. Francis Xavier University, Antigonish, B2G2W5, Canada
  • 2Environmental Science Program, Memorial University of Newfoundland, St. John’s, A1B3X7, Canada
  • 3Fisheries and Oceans, Bedford Institute of Oceanography, Dartmouth, B2Y4A2, Canada
  • 4Department of Geography, Memorial University of Newfoundland, St. John’s, A1B3X9, Canada
  • 5Department of Earth and Environmental Sciences, Dalhousie University, Halifax, B3H4R2, Canada

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.

Judith Vogt et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-545', Charel Wohl, 26 Jul 2022
    • AC1: 'Reply on RC1', Judith Vogt, 15 Nov 2022
  • RC2: 'Comment on egusphere-2022-545', Anonymous Referee #2, 01 Sep 2022
    • AC2: 'Reply on RC2', Judith Vogt, 15 Nov 2022

Judith Vogt et al.

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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, Owen A. Sherwood https://doi.org/10.5683/SP3/6IUECA

Judith Vogt et al.

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Short summary
The release of the greenhouse gas methane from Arctic permafrost and submarine sources could exacerbate climate change in a positive feedback. Continuous monitoring conducted over a 5100 km voyage in the western margin of the Labrador Sea and Baffin Bay highlighted both onshore and offshore sources of atmospheric methane. The ocean-atmosphere flux of methane was positive at all measured stations, suggesting that the region in summer 2021 was a net positive source of methane to the atmosphere.