Variability of natural methane bubble release at southern hydrate ridge
Variability of natural methane bubble release at southern hydrate ridge
Current estimations of seabed methane release into the ocean (0.4–48 Tg yr−1) are based on short-term observations and implicitly assume that fluxes are constant over time. However, the intensity of gas seepage varies significantly throughout a seep lifetime. We used instruments operated by the Ocean Observatories Initiative's Regional Cabled Array to monitor variations of gas emissions over the entire Southern Hydrate Ridge summit. We show that bubble plumes emanate from distinct and persistent vents. Multiple plumes can occur within each vent and the location of their outlets may shift progressively. Active bubble plumes vary temporally in number and intensity, even within single vents. Gas emission fluctuations are partly periodic and linked to the local tide. However, short-term variability and high ebullition events unrelated to tidal cycles are also commonly observed. Our data indicate that small-scale processes beneath or at the sediment surface are responsible for the short-term variability of the venting activity that is otherwise modulated by tides. Furthermore, a decrease of venting at one vent may coincide with an increase in plume activity at other vents. Our results depict a spatially and temporally dynamic seep environment, the variability of which cannot be fully characterized without systematic and comprehensive monitoring of the entire area. These results indicate that flux estimations may be largely overestimated or underestimated depending on the time, duration, and place of observation. Although sudden ebullition bursts are hardly predictable, we argue that tidal cycles must be taken into consideration when estimating gas fluxes.
bubbles, methane, multibeam, plume, tides, variability
Marcon, Yann
f4d58db2-fb88-415a-9abe-9047175ab71e
Kelley, Deborah
d45031db-9833-4d78-8eea-7f9d8a24c0e5
Thornton, Blair
8293beb5-c083-47e3-b5f0-d9c3cee14be9
Manalang, Dana
ecce97f5-0c1b-4a63-ad61-827429b6c180
Bohrmann, Gerhard
02353b02-389c-4b34-b9cf-5af207a38615
October 2021
Marcon, Yann
f4d58db2-fb88-415a-9abe-9047175ab71e
Kelley, Deborah
d45031db-9833-4d78-8eea-7f9d8a24c0e5
Thornton, Blair
8293beb5-c083-47e3-b5f0-d9c3cee14be9
Manalang, Dana
ecce97f5-0c1b-4a63-ad61-827429b6c180
Bohrmann, Gerhard
02353b02-389c-4b34-b9cf-5af207a38615
Marcon, Yann, Kelley, Deborah, Thornton, Blair, Manalang, Dana and Bohrmann, Gerhard
(2021)
Variability of natural methane bubble release at southern hydrate ridge.
G3: Geochemistry, Geophysics, Geosystems, 22 (10), [e2021GC009894].
(doi:10.1029/2021GC009894).
Abstract
Current estimations of seabed methane release into the ocean (0.4–48 Tg yr−1) are based on short-term observations and implicitly assume that fluxes are constant over time. However, the intensity of gas seepage varies significantly throughout a seep lifetime. We used instruments operated by the Ocean Observatories Initiative's Regional Cabled Array to monitor variations of gas emissions over the entire Southern Hydrate Ridge summit. We show that bubble plumes emanate from distinct and persistent vents. Multiple plumes can occur within each vent and the location of their outlets may shift progressively. Active bubble plumes vary temporally in number and intensity, even within single vents. Gas emission fluctuations are partly periodic and linked to the local tide. However, short-term variability and high ebullition events unrelated to tidal cycles are also commonly observed. Our data indicate that small-scale processes beneath or at the sediment surface are responsible for the short-term variability of the venting activity that is otherwise modulated by tides. Furthermore, a decrease of venting at one vent may coincide with an increase in plume activity at other vents. Our results depict a spatially and temporally dynamic seep environment, the variability of which cannot be fully characterized without systematic and comprehensive monitoring of the entire area. These results indicate that flux estimations may be largely overestimated or underestimated depending on the time, duration, and place of observation. Although sudden ebullition bursts are hardly predictable, we argue that tidal cycles must be taken into consideration when estimating gas fluxes.
Text
Marcon 2021 G3
- Accepted Manuscript
Text
Marcon 2021 G3 Supplementary
More information
Accepted/In Press date: 12 September 2021
Published date: October 2021
Additional Information:
Funding Information:
We thank the University of Washington OOI Regional Cabled Array team and the captains and crew of R/V Roger Revelle and R/V Atlantis for their invaluable assistance during the VISIONS'18 and VISIONS'19 expeditions. The 3D mosaic data used in this work were collected using the AUV AE2000f during the Schmidt Ocean Institute's FK180731 #Adaptive Robotics campaign. We thank the crew of the R/V Falkor and in particular Kazunori Nagano and Tetsu Koike (University of Tokyo) for the AUV operations. We also thank the two anonymous reviewers for their constructive reviews of the manuscript. This work is supported by the German Federal Ministry of Education and Research (BMBF) under the grant numbers 03F0765A and 03F0854A and is based upon work supported by the National Science Foundation under Cooperative Agreement No. 1743430 (which supports the OOI).
Funding Information:
We thank the University of Washington OOI Regional Cabled Array team and the captains and crew of R/V and R/V for their invaluable assistance during the VISIONS'18 and VISIONS'19 expeditions. The 3D mosaic data used in this work were collected using the AUV AE2000f during the Schmidt Ocean Institute's FK180731 #Adaptive Robotics campaign. We thank the crew of the R/V and in particular Kazunori Nagano and Tetsu Koike (University of Tokyo) for the AUV operations. We also thank the two anonymous reviewers for their constructive reviews of the manuscript. This work is supported by the German Federal Ministry of Education and Research (BMBF) under the grant numbers 03F0765A and 03F0854A and is based upon work supported by the National Science Foundation under Cooperative Agreement No. 1743430 (which supports the OOI). Roger Revelle Atlantis Falkor
Publisher Copyright:
© 2021. The Authors.
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
Keywords:
bubbles, methane, multibeam, plume, tides, variability
Identifiers
Local EPrints ID: 452999
URI: http://eprints.soton.ac.uk/id/eprint/452999
ISSN: 1525-2027
PURE UUID: aff9199a-6b9b-4879-924e-9ce827543d4e
Catalogue record
Date deposited: 07 Jan 2022 12:12
Last modified: 17 Mar 2024 12:49
Export record
Altmetrics
Contributors
Author:
Yann Marcon
Author:
Deborah Kelley
Author:
Dana Manalang
Author:
Gerhard Bohrmann
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics