Modelling methane hydrate stability changes and gas release due to seasonal oscillations in bottom water temperatures on the Rio Grande cone, offshore southern Brazil
International audience The stability of methane hydrates on continental margins worldwide is sensitive to changes in temperature and pressure conditions. It has been shown how gradual increases in bottom water temperatures due to ocean warming over post-glacial timescales can destabilize shallow oce...
Published in: | Marine and Petroleum Geology |
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ftinsu:oai:HAL:hal-02362956v1 2024-02-11T10:05:48+01:00 Modelling methane hydrate stability changes and gas release due to seasonal oscillations in bottom water temperatures on the Rio Grande cone, offshore southern Brazil Braga, R. Iglesias, R.S. Romio, C. Praeg, D. Miller, D.J. Viana, A. Ketzer, J.M. Pontifícia Universidade Católica do Rio Grande do Sul Brasil = Pontifical Catholic University of Rio Grande do Sul Brazil = Université catholique pontificale de Rio Grande do Sul Brésil (PUC-RS) Aarhus University Aarhus Géoazur (GEOAZUR 7329) Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD France-Sud ) Petrobras Rio de Janeiro Linnaeus University 2020 https://hal.science/hal-02362956 https://hal.science/hal-02362956/document https://hal.science/hal-02362956/file/Braga%26al_JMPG_accepted.pdf https://doi.org/10.1016/j.marpetgeo.2019.104071 en eng HAL CCSD Elsevier info:eu-repo/semantics/altIdentifier/doi/10.1016/j.marpetgeo.2019.104071 hal-02362956 https://hal.science/hal-02362956 https://hal.science/hal-02362956/document https://hal.science/hal-02362956/file/Braga%26al_JMPG_accepted.pdf doi:10.1016/j.marpetgeo.2019.104071 info:eu-repo/semantics/OpenAccess ISSN: 0264-8172 Marine and Petroleum Geology https://hal.science/hal-02362956 Marine and Petroleum Geology, 2020, 112, pp.104071. ⟨10.1016/j.marpetgeo.2019.104071⟩ Methane hydrate Numerical simulation Bottom water temperature South Atlantic Ocean [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography info:eu-repo/semantics/article Journal articles 2020 ftinsu https://doi.org/10.1016/j.marpetgeo.2019.104071 2024-01-17T17:28:34Z International audience The stability of methane hydrates on continental margins worldwide is sensitive to changes in temperature and pressure conditions. It has been shown how gradual increases in bottom water temperatures due to ocean warming over post-glacial timescales can destabilize shallow oceanic hydrate deposits, causing their dissociation and gas release into the ocean. However, bottom water temperatures (BWT) may also vary significantly over much shorter timescales, including due to seasonal temperature oscillations of the ocean bottom currents. In this study, we investigate how a shallow methane hydrate deposit responds to seasonal BWT oscillations with an amplitude of up to 1.5 °C. We use the TOUGH + HYDRATE code to model changes in the methane hydrate stability zone (MHSZ) using data from the Rio Grande Cone, in the South Atlantic Ocean off the Brazilian coast. In all the cases studied, BWT oscillations resulted in significant gaseous methane fluxes into the ocean for up to 10 years, followed by a short period of small fluxes of gaseous methane into the ocean, until they stopped completely. On the other hand, aqueous methane was released into the ocean during the 100 years simulated, for all the cases studied. During the temperature oscillations, the MHSZ recedes continuously both horizontally and, in a smaller scale, vertically, until a permanent and a seasonal region in MHSZ are defined. Sensitivity tests were carried out for parameters of porosity, thermal conductivity and initial hydrate saturation, which were shown to play an important role on the volume of methane released into the ocean and on the time interval in which such release occurs. Overall, the results indicate that in a system with no gas recharge from the bottom, seasonal temperature oscillations alone cannot account for long-term gas release into the ocean. Article in Journal/Newspaper Methane hydrate South Atlantic Ocean Institut national des sciences de l'Univers: HAL-INSU Marine and Petroleum Geology 112 104071 |
institution |
Open Polar |
collection |
Institut national des sciences de l'Univers: HAL-INSU |
op_collection_id |
ftinsu |
language |
English |
topic |
Methane hydrate Numerical simulation Bottom water temperature South Atlantic Ocean [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
spellingShingle |
Methane hydrate Numerical simulation Bottom water temperature South Atlantic Ocean [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography Braga, R. Iglesias, R.S. Romio, C. Praeg, D. Miller, D.J. Viana, A. Ketzer, J.M. Modelling methane hydrate stability changes and gas release due to seasonal oscillations in bottom water temperatures on the Rio Grande cone, offshore southern Brazil |
topic_facet |
Methane hydrate Numerical simulation Bottom water temperature South Atlantic Ocean [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
description |
International audience The stability of methane hydrates on continental margins worldwide is sensitive to changes in temperature and pressure conditions. It has been shown how gradual increases in bottom water temperatures due to ocean warming over post-glacial timescales can destabilize shallow oceanic hydrate deposits, causing their dissociation and gas release into the ocean. However, bottom water temperatures (BWT) may also vary significantly over much shorter timescales, including due to seasonal temperature oscillations of the ocean bottom currents. In this study, we investigate how a shallow methane hydrate deposit responds to seasonal BWT oscillations with an amplitude of up to 1.5 °C. We use the TOUGH + HYDRATE code to model changes in the methane hydrate stability zone (MHSZ) using data from the Rio Grande Cone, in the South Atlantic Ocean off the Brazilian coast. In all the cases studied, BWT oscillations resulted in significant gaseous methane fluxes into the ocean for up to 10 years, followed by a short period of small fluxes of gaseous methane into the ocean, until they stopped completely. On the other hand, aqueous methane was released into the ocean during the 100 years simulated, for all the cases studied. During the temperature oscillations, the MHSZ recedes continuously both horizontally and, in a smaller scale, vertically, until a permanent and a seasonal region in MHSZ are defined. Sensitivity tests were carried out for parameters of porosity, thermal conductivity and initial hydrate saturation, which were shown to play an important role on the volume of methane released into the ocean and on the time interval in which such release occurs. Overall, the results indicate that in a system with no gas recharge from the bottom, seasonal temperature oscillations alone cannot account for long-term gas release into the ocean. |
author2 |
Pontifícia Universidade Católica do Rio Grande do Sul Brasil = Pontifical Catholic University of Rio Grande do Sul Brazil = Université catholique pontificale de Rio Grande do Sul Brésil (PUC-RS) Aarhus University Aarhus Géoazur (GEOAZUR 7329) Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD France-Sud ) Petrobras Rio de Janeiro Linnaeus University |
format |
Article in Journal/Newspaper |
author |
Braga, R. Iglesias, R.S. Romio, C. Praeg, D. Miller, D.J. Viana, A. Ketzer, J.M. |
author_facet |
Braga, R. Iglesias, R.S. Romio, C. Praeg, D. Miller, D.J. Viana, A. Ketzer, J.M. |
author_sort |
Braga, R. |
title |
Modelling methane hydrate stability changes and gas release due to seasonal oscillations in bottom water temperatures on the Rio Grande cone, offshore southern Brazil |
title_short |
Modelling methane hydrate stability changes and gas release due to seasonal oscillations in bottom water temperatures on the Rio Grande cone, offshore southern Brazil |
title_full |
Modelling methane hydrate stability changes and gas release due to seasonal oscillations in bottom water temperatures on the Rio Grande cone, offshore southern Brazil |
title_fullStr |
Modelling methane hydrate stability changes and gas release due to seasonal oscillations in bottom water temperatures on the Rio Grande cone, offshore southern Brazil |
title_full_unstemmed |
Modelling methane hydrate stability changes and gas release due to seasonal oscillations in bottom water temperatures on the Rio Grande cone, offshore southern Brazil |
title_sort |
modelling methane hydrate stability changes and gas release due to seasonal oscillations in bottom water temperatures on the rio grande cone, offshore southern brazil |
publisher |
HAL CCSD |
publishDate |
2020 |
url |
https://hal.science/hal-02362956 https://hal.science/hal-02362956/document https://hal.science/hal-02362956/file/Braga%26al_JMPG_accepted.pdf https://doi.org/10.1016/j.marpetgeo.2019.104071 |
genre |
Methane hydrate South Atlantic Ocean |
genre_facet |
Methane hydrate South Atlantic Ocean |
op_source |
ISSN: 0264-8172 Marine and Petroleum Geology https://hal.science/hal-02362956 Marine and Petroleum Geology, 2020, 112, pp.104071. ⟨10.1016/j.marpetgeo.2019.104071⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1016/j.marpetgeo.2019.104071 hal-02362956 https://hal.science/hal-02362956 https://hal.science/hal-02362956/document https://hal.science/hal-02362956/file/Braga%26al_JMPG_accepted.pdf doi:10.1016/j.marpetgeo.2019.104071 |
op_rights |
info:eu-repo/semantics/OpenAccess |
op_doi |
https://doi.org/10.1016/j.marpetgeo.2019.104071 |
container_title |
Marine and Petroleum Geology |
container_volume |
112 |
container_start_page |
104071 |
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1790602992397844480 |