At the edge of the Arctic ice in pursuit
 of pingos and pockmarks

Charlie Paull, Ph.D.
MBARI

Wednesday, October 29, 2003
Pacific Forum – 3:00 p.m.

In August and September two NSF supported cruises were conducted on the Canadian Coast Guard vessels Nanidik and Sir Wilfred Laurier in the Beaufort Sea. This was an MBARI led US-Canadian project  devoted to the detection of methane leakage from the Arctic shelf. 

The Arctic shelf was targeted because it is an area currently undergoing dramatic thermal changes caused by the continuing warming associated with the Holocene sea level rise. During this transgression, comparatively warm waters flooded over relatively cold Arctic permafrost areas. The resulting thermal pulse is still propagating down into the submerged sediment and should be decomposing gas hydrates. We were specifically looking for evidence of gas venting from the Arctic seafloor during these cruises. Because the entire shelf is a prohibitively large area to systematically search, the primary focus was features which might be localized conduits for gas venting; in particular, offshore pingo–like features (PLF) and pockmarks to the northeast of the Mackenzie River Delta. Eighty-one vibracores were collected, primarily from the crests and flanks of eight PLF and two pockmark fields.  Methane concentrations were systematically elevated in cores from the PLF, sulfate depletion occurred in as little as one meter sub-bottom, and ROV surveys revealed that streams of gas bubbles composed predominately of methane are coming from the crests of at least two PLF. Gas was also venting from the pockmarks. While it is premature to conclude that this methane is related to gas hydrate decomposition, the methane is venting where we predicted it would occur if it was coming from decomposing gas hydrate.

Because we have just been back for a month and our samples are still in transit, only initial scientific results are available. While the scientific objectives of these expeditions will be introduced and the origins of pingos discussed; this talk will primarily be an Arctic travel log. Pictures of various Arctic images and experiences, including sea-ice, icebreaking, polar bears, side trips to pingos, the coming of winter in the Arctic, Northern Lights, and a yacht race, will occupy most of the seminar.

Next: Genetics as a window to the past: How many whales before whaling?