Methane flux estimates from continuous atmospheric measurements and surface-water observations in the northern Labrador Sea and Baffin Bay
Vast amounts of methane (CH 4 ) 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 CH 4 over pan-regional scales to detect early signs of CH 4 release. However, o...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
| Published: |
2022
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/egusphere-2022-545 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-545/ |
| Summary: | Vast amounts of methane (CH 4 ) 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 CH 4 over pan-regional scales to detect early signs of CH 4 release. However, our ability to monitor CH 4 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 CH 4 in North Atlantic waters, we collected continuous real-time atmospheric CH 4 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 CH 4 concentrations in the water column using discrete water samples at selected stations. Measured atmospheric mixing ratios of CH 4 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 CH 4 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 CH 4 fluxes ranged from 0.1−14.1 µmol m -2 d -1 indicating that the ocean acted as a CH 4 source to the atmosphere. Atmospheric CH 4 levels were also driven by meteorological, spatial, and temporal variations. Highest atmospheric CH 4 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 CH 4 data have the potential to provide ongoing monitoring in a region susceptible to CH 4 releases, as well as critical validation data for global-scale measurements and modelling. |
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