At the edge of the Arctic ice in pursuit
of pingos and pockmarks
Charlie Paull, Ph.D.
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
project devoted to the detection of methane leakage from the Arctic
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
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