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Science Discussion

A scientific discussion followed the presentations.  The focus of this discussion was on the current state of knowledge, outstanding scientific problems, and how and where to address them.  We started from a list of open problems:

• Gas hydrate distribution,

• Climate change,

• Slope stability,

• Stratigraphy of the Arctic margin,

• Arctic basin evolution.

The goal of the discussion was to develop hypotheses that could be tested by marine surveying and drilling.  The discussion concentrated on a few key topics.

Transition between land/shelf and marine gas hydrates.  In the Arctic environment, gas hydrates are found in two settings: within or below permafrost on land and beneath continental shelves that were above sea level during the last glacial (i.e., on both the McKenzie Mackenzie delta and the Alaskan Beaufort shelf), or on continental margins at depths greater than about 300 m.  Gas hydrates in permafrost are restricted to polar regions, whereas they are found in continental margin sediments worldwide.  In the Arctic, thermodynamic stability predicts that the permafrost and the continental margin gas hydrate domains should be separated by a gap.  The Alaska/Canada Beaufort Sea margin is an ideal setting to study the transition between permafrost and marine gas hydrates.  The focus of the study would be on mapping the gas hydrate distribution in the two domains, testing the predictions of thermodynamic models, and determining the effects of the last deglaciation on gas hydrate distribution and stability.

Submarine slides along the Beaufort Sea continental slope.  USGS seismic surveys have shown clear evidence of landslides  on the Beaufort Sea continental slope at depths between 200-400 and 2000 m.  The deformed sediments lay above a smooth bottom-simulating reflector, suggesting that overpressures due to gas hydrate dissociation may have contributed to or caused the slides.  The latest multichannel seismics in this area were collected in the late 1970s, and new surveys may provide key data to test the gas hydrate dissociation hypothesis for submarine slope instability.  On the other hand, gas hydrates and submarine slides are found on continental slopes worldwide, and there are much easier areas where this kind of slope instability may be studied (e.g., the US East coast).

Pingo-like features. “Pingo-like features” (PLFs) are mounds few tens of meters high and wide that seem to be related to release of methane gas from the permafrost. Charlie Paull reported that methane gas bubbling from an underwater PLF has been sampled on the MacKenzie Mackenzie delta shelf.  Charlie noted that at present these features are the only clearly documented examples of methane escaping from permafrostPLFs.  PLFs are found on the MacKenzie Mackenzie delta both on land and on the shelf, and they are key features to study how methane gas escapes from gas hydrates in Arctic regions.

Climate studies in the MacKenzie Mackenzie trough.  It has been recently proposed that during glacial periods the MacKenzie Mackenzie River transported large quantities of fresh water into the Arctic basin by flowing next to the ice sheet in Canada.  Kate Moran noted that an ideal location to test this hypothesis is the MacKenzie Mackenzie trough, which contains up to 3500 m of Plio-Pleistocene sediments.  The high sedimentation rate would provide an ideal high-resolution climate record for the Beaufort Sea region.