Significant methane undersaturation during austral summer in the Ross Sea (Southern Ocean)
Dissolved methane (CH 4 ) was measured at 9 stations along a transect at 75° S in the Ross Sea during austral summer in January 2020. CH 4 undersaturation (mean: 82 ± 20 %) was found in the water column, with a mean air-sea CH 4 flux density of −0.58 ± 0.48 μmol m −2 day −1 , which suggests that the...
Main Authors: | , , , , , , , , , |
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Format: | Text |
Language: | English |
Published: |
2022
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Subjects: | |
Online Access: | https://doi.org/10.5194/bg-2021-334 https://bg.copernicus.org/preprints/bg-2021-334/ |
Summary: | Dissolved methane (CH 4 ) was measured at 9 stations along a transect at 75° S in the Ross Sea during austral summer in January 2020. CH 4 undersaturation (mean: 82 ± 20 %) was found in the water column, with a mean air-sea CH 4 flux density of −0.58 ± 0.48 μmol m −2 day −1 , which suggests that the Ross Sea was a net sink for atmospheric CH 4 during the austral summer. Simple box-model calculations revealed that the CH 4 depletion should occur in the surface mixed layer because of CH 4 oxidation and advection of CH 4 -poor waters. We propose that freshwater injection caused by sea-ice melting in summer dilutes CH 4 concentrations within the surface layer and thus increases its potential for atmospheric CH 4 uptake in the Ross Sea. Thus, we argue that both CH 4 consumption and sea-ice melting are important drivers of CH 4 undersaturation, which implies that the high-latitude area of the Southern Ocean is a sink for atmospheric CH 4 . We estimated that the Southern Ocean (> 65° S) takes up about 0.02 % of the global CH 4 emissions and thus represents a minor sink for atmospheric CH 4 . |
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