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The sensitivity of gas hydrate reservoirs to climate change : perspectives from a new combined model for permafrost-related and marine settings

Thomas Mestdagh UGent, Jeffrey Poort and Marc De Batist UGent (2017) EARTH-SCIENCE REVIEWS. 169. p.104-131
abstract
Gas hydrate reservoirs store large quantities of gas in sediments on continental margins, in deep lakes, and in continental and relic sub-shelf permafrost. The gas hydrate structure is only stable at sufficiently low temperature and high pressure, and may therefore collapse under changing climatic conditions. If a temperature rise or pressure drop (e.g. through falling sea level) is effective enough to dissociate hydrate deposits, methane (the most common gas component in hydrates and a potent greenhouse gas) is released from the hydrate structure and may eventually enter into the atmosphere. This may generate a positive feedback effect, as resulting enhanced greenhouse gas levels would additionally warm the atmosphere and hence maintain or reinforce hydrate dissociation. The significance of this mechanism has been debated over the past decades, often within the framework of geologically rapid Quaternary climatic oscillations and present-day climate warming. An extensive set of studies has addressed the climate-sensitivity of gas hydrate reservoirs in various study areas and geological settings, and by means of various approaches. No real consensus has yet been reached on the matter. In this study, we seek to evaluate the sensitivity of gas hydrate reservoirs to changes in global climate from a more general perspective, by firstly reviewing the available literature, and secondly developing a new numerical model to quantify gas hydrate destabilization under changing environmental conditions. Qualities of the model include the wide applicability to both marine and permafrost-related hydrate reservoirs and the integrative approach, combining existing hydrate formation models with a dissocation model that accounts for the consumption of latent heat during hydrate dissociation. To determine which settings are most vulnerable, and to acquire insight into the extent, fashion and rates of hydrate dissociation, we apply the model to four distinct types of hydrate reservoirs across a hypothetic high-latitude continental margin under two specific cases of climate change: the last deglaciation following the Last Glacial Maximum and present-day climate warming. The simulations indicate that hydrates on the upper continental slope and in association with thin, sub-shelf permafrost are most sensitive to the imposed climatic variations, whereas deepwater and onshore permafrost-related reservoirs react in a more stable way. However, the deep (i.e. at several tens to hundreds of meters subsurface depth) stratigraphic-type hydrates considered in this study constitute by far the largest fraction of the global gas hydrate volume, but dissociate on slow timescales of thousands to hundreds of thousands of years, even in the most sensitive environments. In contrast, shallow (i.e. at, or a few meters below the surface or seafloor) structural-type hydrates are able to respond to climatic variations on sub-millennial timescales, but the volumes of gas they may release are probably insignificant to the global carbon cycle and climate. Quaternary and present-day climate change do affect the stability of gas hydrate reservoirs, but at long timescales where hydrate volumes are large, and on short timescales where hydrate volumes are small. Consequently, gas hydrates dissociate to an extent that is too small or at a pace that is too slow to create a strong positive feedback effect. While the release of methane from the disintegration of gas hydrates is observed on different margins today, it is not likely to have played a leading role in Quaternary climatic variations or to become a significant process in the coming centuries as a result of present-day rising temperatures.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
Gas hydrate, Climate change, Methane, Modelling, Marine, Permafrost, GULF-OF-MEXICO, OCEANIC METHANE HYDRATE, CONTINENTAL-SLOPE, SEA-FLOOR, NUMERICAL-MODEL, CARBON-CYCLE, NORTH SLOPE, DOUBLE BSR, BLACK-SEA, ICE-SHEET
journal title
EARTH-SCIENCE REVIEWS
Earth-Sci. Rev.
volume
169
pages
104 - 131
Web of Science type
Article
Web of Science id
000403427800005
ISSN
0012-8252
1872-6828
DOI
10.1016/j.earscirev.2017.04.013
language
English
UGent publication?
yes
classification
A1
copyright statement
I have transferred the copyright for this publication to the publisher
id
8526429
handle
http://hdl.handle.net/1854/LU-8526429
date created
2017-07-05 11:31:09
date last changed
2017-10-03 14:18:10
@article{8526429,
  abstract     = {Gas hydrate reservoirs store large quantities of gas in sediments on continental margins, in deep lakes, and in continental and relic sub-shelf permafrost. The gas hydrate structure is only stable at sufficiently low temperature and high pressure, and may therefore collapse under changing climatic conditions. If a temperature rise or pressure drop (e.g. through falling sea level) is effective enough to dissociate hydrate deposits, methane (the most common gas component in hydrates and a potent greenhouse gas) is released from the hydrate structure and may eventually enter into the atmosphere. This may generate a positive feedback effect, as resulting enhanced greenhouse gas levels would additionally warm the atmosphere and hence maintain or reinforce hydrate dissociation. The significance of this mechanism has been debated over the past decades, often within the framework of geologically rapid Quaternary climatic oscillations and present-day climate warming. An extensive set of studies has addressed the climate-sensitivity of gas hydrate reservoirs in various study areas and geological settings, and by means of various approaches. No real consensus has yet been reached on the matter. In this study, we seek to evaluate the sensitivity of gas hydrate reservoirs to changes in global climate from a more general perspective, by firstly reviewing the available literature, and secondly developing a new numerical model to quantify gas hydrate destabilization under changing environmental conditions. Qualities of the model include the wide applicability to both marine and permafrost-related hydrate reservoirs and the integrative approach, combining existing hydrate formation models with a dissocation model that accounts for the consumption of latent heat during hydrate dissociation. To determine which settings are most vulnerable, and to acquire insight into the extent, fashion and rates of hydrate dissociation, we apply the model to four distinct types of hydrate reservoirs across a hypothetic high-latitude continental margin under two specific cases of climate change: the last deglaciation following the Last Glacial Maximum and present-day climate warming. The simulations indicate that hydrates on the upper continental slope and in association with thin, sub-shelf permafrost are most sensitive to the imposed climatic variations, whereas deepwater and onshore permafrost-related reservoirs react in a more stable way. However, the deep (i.e. at several tens to hundreds of meters subsurface depth) stratigraphic-type hydrates considered in this study constitute by far the largest fraction of the global gas hydrate volume, but dissociate on slow timescales of thousands to hundreds of thousands of years, even in the most sensitive environments. In contrast, shallow (i.e. at, or a few meters below the surface or seafloor) structural-type hydrates are able to respond to climatic variations on sub-millennial timescales, but the volumes of gas they may release are probably insignificant to the global carbon cycle and climate. Quaternary and present-day climate change do affect the stability of gas hydrate reservoirs, but at long timescales where hydrate volumes are large, and on short timescales where hydrate volumes are small. Consequently, gas hydrates dissociate to an extent that is too small or at a pace that is too slow to create a strong positive feedback effect. 
While the release of methane from the disintegration of gas hydrates is observed on different margins today, it is not likely to have played a leading role in Quaternary climatic variations or to become a significant process in the coming centuries as a result of present-day rising temperatures.},
  author       = {Mestdagh, Thomas and Poort, Jeffrey and De Batist, Marc},
  issn         = {0012-8252},
  journal      = {EARTH-SCIENCE REVIEWS},
  keyword      = {Gas hydrate,Climate change,Methane,Modelling,Marine,Permafrost,GULF-OF-MEXICO,OCEANIC METHANE HYDRATE,CONTINENTAL-SLOPE,SEA-FLOOR,NUMERICAL-MODEL,CARBON-CYCLE,NORTH SLOPE,DOUBLE BSR,BLACK-SEA,ICE-SHEET},
  language     = {eng},
  pages        = {104--131},
  title        = {The sensitivity of gas hydrate reservoirs to climate change : perspectives from a new combined model for permafrost-related and marine settings},
  url          = {http://dx.doi.org/10.1016/j.earscirev.2017.04.013},
  volume       = {169},
  year         = {2017},
}

Chicago
Mestdagh, Thomas, Jeffrey Poort, and Marc De Batist. 2017. “The Sensitivity of Gas Hydrate Reservoirs to Climate Change : Perspectives from a New Combined Model for Permafrost-related and Marine Settings.” Earth-science Reviews 169: 104–131.
APA
Mestdagh, T., Poort, J., & De Batist, M. (2017). The sensitivity of gas hydrate reservoirs to climate change : perspectives from a new combined model for permafrost-related and marine settings. EARTH-SCIENCE REVIEWS, 169, 104–131.
Vancouver
1.
Mestdagh T, Poort J, De Batist M. The sensitivity of gas hydrate reservoirs to climate change : perspectives from a new combined model for permafrost-related and marine settings. EARTH-SCIENCE REVIEWS. 2017;169:104–31.
MLA
Mestdagh, Thomas, Jeffrey Poort, and Marc De Batist. “The Sensitivity of Gas Hydrate Reservoirs to Climate Change : Perspectives from a New Combined Model for Permafrost-related and Marine Settings.” EARTH-SCIENCE REVIEWS 169 (2017): 104–131. Print.