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About the project

Project objectives

The key objective of this project is to quantify the mobility of Arctic marine gas hydrate reservoirs. The hypotheses to be tested are:

  1. The quantity of gas hydrate-bound methane in the climatically-sensitive part of the gas hydrate stability zone is significant in terms of its possible effect on climate.
  2. Some gas hydrate has moved out of its stability field as a result of post-glacial warming, producing methane gas on dissociation, and current venting is the result of this change in pressure and temperature conditions
  3. Future bottom-warming will induce gas hydrate dissociation on the Svalbard margins

For more information about the science concepts behind these hypotheses, please go to our background science page.


Methodology

To test these hypotheses, the team will carry out an extensive and interdisciplinary investigation of the Arctic gas hydrate system off Svalbard, focusing on the zone where the base of the past and present gas hydrate stability zone intersects the seabed. A major cruise to the region aboard RRS James Clark Ross (right) will enable detailed seismic surveys to be carried out, which will help determine whether extensive gas hydrates are present in this zone or not. Multibeam bathymetry data and sidescan sonar imagery, combined with 2D seismic reflection profiling will be used to examine the extent of subsurface sediment mobilisation as a result of fluid expulsion, and the pattern of present-day and past fluid/gas escape structures on the seabed. Seafloor photography, bottom water and atmospheric methane sampling will verify these results.

Seismic experiments using ocean bottom seismometers (OBS) will be used to determine the physical properties of the upper few hundred metres below the seafloor and hence to estimate how much methane hydrate and/or gas is present. These experiments will also determine whether these physical properties vary with direction, for example due to aligned cracks resulting from incipient slope instability.

A series of sediment cores will be taken at carefully-chosen locations in order to reconstruct the history of bottom-water temperature changes in the region and to characterise the physical and chemical properties of the sediment itself. This information will then be used in calculating the effect of changes in bottom-water temperature on the stability of gas hydrates in the area, and the potential for future methane release as a result of climatic warming.

The present-day and likely future methane emissions will be assessed by characterising modern methane sources in the region using carbon isotope anaylsis of both seawater and Arctic air samples. Anomalous concentrations of methane in seawater and air will assist in mapping present-day venting and verify the results of the seabed surveys.


The study area

The study site for this project is the area west of Svalbard (shown on map, left), primarily chosen because the region is known to contain significant quantities of gas hydrate and active venting of both biogenic and thermogenic gas has been reported. Previous seismic surveys carried out in the area strongly indicate the presence of gas hydrate, with ocean bottom seismometer experiments indicating that around 10% of the pore space within the sediments is filled with hydrate. Seismic data also show significant subsurface disturbance of the sediments - indicative of fluid flow - and this is supported by the presence of seafloor pockmarks identified on multibeam bathymetry maps, and localised bacterial mats observed by seafloor photography.


Right: Map showing the approximate location of
the seismic and mutlibeam surveys (grey shaded
area), and the OBS experiments (red dots).


Publications

Westbrook, G. K., et al. (2009), Escape of methane gas from the seabed along the West Spitsbergen continental margin, Geophys. Res. Lett., 36, L15608,
doi:10.1029/2009GL039191

 

 


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