Sea–air methane flux estimates derived from marine surface observations and instantaneous atmospheric measurements in the northern Labrador Sea and Baffin Bay
<p>Vast amounts of methane (CH<span class="inline-formula"><sub>4</sub></span>) stored in 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<...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-05-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/20/1773/2023/bg-20-1773-2023.pdf |
| Summary: | <p>Vast amounts of methane (CH<span class="inline-formula"><sub>4</sub></span>) stored in 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<span class="inline-formula"><sub>4</sub></span> over pan-regional scales to detect early signs of
CH<span class="inline-formula"><sub>4</sub></span> release. However, our ability to monitor CH<span class="inline-formula"><sub>4</sub></span> is hampered in
remote northern regions by sampling and logistical constraints, and few good
baseline data exist in many areas. From high-resolution atmospheric CH<span class="inline-formula"><sub>4</sub></span>
measurements and discrete surface water samples, we estimated instantaneous
sea–air CH<span class="inline-formula"><sub>4</sub></span> fluxes at various locations. We also created a baseline
study of current background levels of CH<span class="inline-formula"><sub>4</sub></span> in North Atlantic waters
based on the atmospheric CH<span class="inline-formula"><sub>4</sub></span> data over 22 d in summer 2021 on a
roughly 5100 km voyage in the northern Labrador Sea and Baffin Bay between
55 and 72<span class="inline-formula"><sup>∘</sup></span> N. In addition, we measured CH<span class="inline-formula"><sub>4</sub></span>
concentrations across the water column at various stations. Measured
atmospheric mixing ratios of CH<span class="inline-formula"><sub>4</sub></span> ranged from 1944 to 2012 ppbv,
with a mean of 1966 <span class="inline-formula">±</span> 8 ppbv and a baseline of 1954–1981 ppbv.
Dissolved CH<span class="inline-formula"><sub>4</sub></span> concentrations in the near-surface water peaked at 5.3 nmol L<span class="inline-formula"><sup>−1</sup></span> within 1 km down-current of a known cold seep at Scott Inlet and were
consistently oversaturated throughout the water column in Southwind Fjord,
which is an area that has been recently affected by submarine landslides. Local sea–air
CH<span class="inline-formula"><sub>4</sub></span> fluxes ranged from 0.003–0.119 <span class="inline-formula">µ</span>mol m<span class="inline-formula"><sup>−2</sup></span> d<span class="inline-formula"><sup>−1</sup></span>,
indicating that the ocean released only small amounts of CH<span class="inline-formula"><sub>4</sub></span> to the
atmosphere at all stations. Atmospheric CH<span class="inline-formula"><sub>4</sub></span> levels were also driven by
meteorological, spatial, and temporal variations, and both onshore and
ocean-based contributions to atmospheric CH<span class="inline-formula"><sub>4</sub></span> mixing ratios are likely.
Coupled high-resolution measurements of marine and atmospheric CH<span class="inline-formula"><sub>4</sub></span> data
have the potential to provide ongoing monitoring in a region susceptible to
CH<span class="inline-formula"><sub>4</sub></span> releases, as well as critical validation data for global-scale
measurements and modelling.</p> |
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| ISSN: | 1726-4170 1726-4189 |