Variability of acoustically evidenced methane bubble emissions offshore western Svalbar
2019
Large reservoirs of methane present in Arctic marine sediments are susceptible to rapid warming, promoting increasing
methane emissions. Gas bubbles in the water-column can be detected and flow-rates can be quantified using
hydroacousticsurvey methods, making it possible to monitor spatiotemporal variability. We present methane (CH4) bubble flow-rates derived from
hydroacousticdatasets acquired during 11 research expeditions to the western Svalbard
continental margin(2008-2014). Three seepage areas emit in total 725–1125 t CH4 y-1 and bubble fluxes are up to 2 kg m-2 y-1. Bubble fluxes vary between different surveys but no clear trend can be identified. Flux variability analyses suggest that two areas are geologically interconnected, displaying alternating flow changes. Spatial migration of bubble-seepage was observed to follow seasonal changes in the theoretical landward limit of the hydrate stability zone, suggesting that formation/dissociation of shallow hydrates, modulated by
bottom watertemperatures, influences seafloor bubble release.
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