Arctic hydrate dissociation as a consequence of climate change: determining the vulnerable methane reservoir and gas escape mechanisms
Lead Research Organisation:
University of Southampton
Department Name: Sch of Ocean and Earth Science
Abstract
Along the western margin of Spitsbergen, where the northern extension of Gulf Stream system conveys warm Atlantic water into the Arctic Ocean, hundreds of plumes of bubbles of methane gas were discovered in 2008, rising from the seabed at a depth close to that of the landward limit of the methane hydrate stability zone. Methane hydrate is a solid with the appearance of ice, in which water forms a cage-like structure enclosing molecules of methane. Methane hydrate is stable under conditions of low temperature and high pressure such as those found in regions of permafrost or under the ocean in water deeper than 300-600 metres, depending on the water temperature. Over the past thirty years, the ocean's temperature at the seabed has increased by 1 degree C, causing the zone in which hydrate is stable to contract down the continental slope, with the apparent consequence that hydrate has broken down and released methane, which has migrated to the seabed and into the ocean. At present, the rate of release of methane is generally too slow to overcome dissolution and oxidation in the ocean to reach the atmosphere, except in very small quantities. However, catastrophic gas venting, which is known to occur elsewhere, could release large amounts of methane over a short period of time. The strength of such venting depends upon the how much gas is stored locally beneath the seabed and the kinds of pathways that bring gas to the seabed. The proposed research seeks to define these pathways and to quantify the amount of gas. A marine research expedition will use a deep-towed, very high-resolution seismic system to image the small-scale structures that convey gas to the seabed and to detect the presence of gas in the sediments beneath the seabed. This will be done in conjunction with an electromagnetic exploration system that uses a deep-towed transmitter and receivers on the seabed to derive the variations in electrical resistivity in the sediments beneath the seabed. Higher-than-normal resistivity is caused by both gas and hydrate, whereas the presence of gas reduces seismic velocity and hydrate increases it. In combination, the two techniques can distinguish the separate amounts of hydrate and gas. The deep-towed seismic system, SYSIF, which uses a piezo-electric chirp source that gives very-high-resolution images and deeper sub-seabed penetration than similar systems mounted on a ship's hull, will be supplemented by the use of ocean-bottom seismometers to provide precise measurements of the variation of seismic velocity with depth, and seismic profiles with small airgun (mini-GI gun) to provide deeper high-resolution seismic imaging. Multibeam sonar will be used to improve definition of the shape of the seabed and high-frequency, fish-finding sonar will image plumes of gas bubbles and define their positions, providing, in many cases, comparisons with the images obtained in 2008 when they were first discovered. Two areas will be investigated, the region of the landward limit of the methane hydrate stability zone, where many bubble plumes occur in water shallower than 400 metres, and, for comparison, a pockmark in the Vestnesa Ridge, at a depth 1200 metres, from which gas is escaping and is underlain by 'chimneys' that convey gas to the seabed through the hydrate stability zone, where the gas would normally form hydrate. Geological and geophysical data, including 96-channel seismic reflection profiles, acquired in both areas during a research cruise in 2008, will complement the new data. The project will provide the sub-seabed context for a seabed observatory (MASOX Monitoring Arctic Seafloor - Ocean Exchange), which will be established in the shallow plume area in summer 2010 by a European scientific consortium to monitor the activity of the plumes and the physical and chemical fluxes through the seabed.
Publications
Goswami B
(2016)
Resistivity image beneath an area of active methane seeps in the west Svalbard continental slope
in Geophysical Journal International
Goswami B
(2017)
Variations in pockmark composition at the V estnesa R idge: Insights from marine controlled source electromagnetic and seismic data
in Geochemistry, Geophysics, Geosystems
Goswami B
(2015)
A joint electromagnetic and seismic study of an active pockmark within the hydrate stability field at the Vestnesa Ridge, West Svalbard margin
in Journal of Geophysical Research: Solid Earth
Marin-Moreno Hector
(2014)
The response of methane hydrate offshore Svalbard to ocean warming during the next three centuries
in EGU General Assembly Conference Abstracts
Marín-Moreno H
(2015)
Estimates of future warming-induced methane emissions from hydrate offshore west S valbard for a range of climate models
in Geochemistry, Geophysics, Geosystems
Marín-Moreno H
(2013)
The response of methane hydrate beneath the seabed offshore Svalbard to ocean warming during the next three centuries
in Geophysical Research Letters
Minshull T
(2012)
Leaking methane reservoirs offshore Svalbard
in Eos, Transactions American Geophysical Union
Minshull T
(2014)
Fine-scale gas distribution in marine sediments assessed from deep-towed seismic data
in Geophysical Journal International
Panieri G
(2014)
Record of methane emissions from the West Svalbard continental margin during the last 23.500yrs revealed by d13C of benthic foraminifera
in Global and Planetary Change
Veloso-Alarcón M
(2019)
Variability of Acoustically Evidenced Methane Bubble Emissions Offshore Western Svalbard
in Geophysical Research Letters
Description | The original aim of the project was to use novel exploration techniques to determine the amount of methane trapped beneath the seabed in a region offshore Svalbard and to determine how that methane can escape into the ocean. Additional funding was received to address an additional aim of using our results to estimate how much methane might be released from this area into the ocean over the next 300 years. We discovered that methane was widespread beneath the seabed, both in an ice-like form called hydrate and in gaseous form, and that it travels towards the seabed along dipping geological strata. Close to the seabed it may be trapped by glacial sediments, but can break through via fractures into the ocean. Sometimes such fluid escape is associated with the formation of small depressions in the seabed called "pockmarks". We estimated the amount of methane present in and beneath the hydrate by determining the electrical resistivity beneath the seabed. Using this method, we found that pockmarks that appear to be similar at the seabed can have very different amounts of gas beneath them. The flux of methane into the ocean from melting Arctic hydrates could be of similar magnitude to all other geological sources of methane globally. |
Exploitation Route | Our results have been presented at various industry-facing conferences and may contribute to the development of exploration techniques for hydrate and shallow gas in deep water. They may also contribute to the incorporation of methane release from hydrate beneath the seabed into global climate models - currently this source of methane is largely ignored. |
Sectors | Energy,Environment |
URL | http://www.southampton.ac.uk/oes/research/projects/arctic_hydrate_dissociation_as_a_consequence_of_climate_change.page |
Description | Invited to present results to a group of scientists at DECC. |
First Year Of Impact | 2014 |
Sector | Environment |
Impact Types | Policy & public services |
Description | DECC briefing |
Geographic Reach | National |
Policy Influence Type | Contribution to a national consultation/review |
Description | DECC briefing: AVOID2 |
Geographic Reach | National |
Policy Influence Type | Contribution to a national consultation/review |
Description | Determining the response of offshore Arctic hydrate to ocean warming during the next century |
Amount | £66,712 (GBP) |
Funding ID | NE/H022732/1 |
Organisation | Natural Environment Research Council |
Sector | Public |
Country | United Kingdom |
Start | 10/2012 |
End | 03/2013 |
Description | Collaboration with Ifremer |
Organisation | French Research Institute for the Exploitation of the Sea |
Country | French Polynesia |
Sector | Academic/University |
PI Contribution | Collaboration with Ifremer |
Start Year | 2011 |
Description | Collaboration with Tromsoe |
Organisation | University of Tromso |
Country | Norway |
Sector | Academic/University |
PI Contribution | Collaboration with University of Tromsoe |
Start Year | 2011 |
Description | 22nd EM Induction Workshop: A controlled source electromagnetic study of gas hydrates at the Vestnesa Ridge, West Svalbard continental margin |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | Talk led to some discussion None identified |
Year(s) Of Engagement Activity | 2014 |
Description | Chandlers Ford talk |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | Yes |
Geographic Reach | Local |
Primary Audience | Public/other audiences |
Results and Impact | Talk sparked questions and discussion afterwards. No direct impacts identified |
Year(s) Of Engagement Activity | 2012 |
Description | European Geophysical Union 2014: The response of methane hydrate beneath the seabed offshore Svalbard to ocean warming during the next three centuries |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | Talk led to questions and extensive discussion afterwards None identified |
Year(s) Of Engagement Activity | 2014 |
Description | Minerals of the Ocean and Deep Sea Minerals and Mining conference: Hydrate beneath the seabed offshore Svalbard, indirect evidence from seismic surveys and thermal modelling |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | Let to questions afterwards. None identified. |
Year(s) Of Engagement Activity | 2014 |
Description | Talk at DECC |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Policymakers/politicians |
Results and Impact | Talk led to extensive discussion. None that I am aware of. |
Year(s) Of Engagement Activity | 2014 |