Project Summary

The scientific community is engaged in a lively debate over the importance of gas hydrate. Hydrates are believed to contain an enormous quantity (~10,000 Gt) of methane, a potent greenhouse gas. A central question is whether methane in gas hydrate reservoirs is mobile and can thus affect Earth’s climate. Scenarios that connect gas hydrate dynamics and climate are based on the fact that the stability of shallow gas hydrate deposits can be perturbed by temperature and pressure changes, and methane released from these deposits could contribute enough of this isotopically distinct greenhouse gas to alter global oceanic or atmospheric reservoirs. Carbon isotope excursions during the Late Paleocene and the Quaternary are believed to represent massive incursions of methane from hydrate into the world’s oceans. Yet the mechanisms, sites, and timing of methane transfer from hydrate reservoirs to oceanic and/or atmospheric systems are speculative.

One appealing mechanism to release methane from hydrate reservoirs is through large-scale sediment failures on continental margins. To test the hypothesis that submarine landslides can release methane from hydrate into the oceans and/or atmosphere, we need a detailed, focused study of a large submarine slide in an area believed to contain methane hydrate. In particular, we need accurate assessment of the amounts, distribution, and lateral variability of methane hydrate and gas in and around the slide, knowledge of the mechanical properties of sediments in and around the slide, well-constrained dates of the slide event, and high-resolution images of the slide structure.

We propose a coordinated seismic and coring study of the Støregga slide, which was produced by colossal slope failures on the Norwegian continental margin in the late Quaternary. The Støregga slide developed in sediments that are believed to have contained substantial amounts of gas hydrate. Thus, this is a prime location to assess whether significant quantities of gas can vent from hydrate-bearing sediments as a consequence of slope failure. We will test hypotheses associated with three interrelated questions: (1) How much hydrate and free gas is present in the Støregga region, and how is it distributed? (2) Did methane escape, and if so, how much, when and by what mechanism? (3) Does hydrate dissociation promote and/or localize submarine landslides? We propose a 43-day cruise of the R/V Ewing to acquire high-resolution, long-offset (6 km) multichannel seismic reflection data, three-component ocean-bottom seismic data, and jumbo piston cores.

This program is linked to a proposal to drill the Støregga slide which was highly ranked by SCICOM last year (8th global ranking) and is currently under consideration at IODP. Our program will add significant value to any scheduled drilling leg by providing a regional seismic, sedimentological, and geochemical context. Long-offset MCS and coring data will fill several crucial data gaps in site-survey information and enable the results of the drilling program to be extended beyond the immediate drill sites. However, our data will provide important stand-alone results and test, independently of the drilling leg, hypotheses regarding methane release (amounts and mechanism) and the role of hydrates in large-scale seafloor instability.

This project is a joint effort combining researchers at the University of Wyoming, the Monterey Bay Aquarium Research Institute, and the University of Tromsø, Norway.