Oil spill science: The smoking gun

[depakid]

Science journalist Mark Schrope is aboard the research vessel Pelican, which is spending the week studying the Deepwater Horizon oil spill in the Gulf of Mexico. Check back to The Great Beyond for daily mission updates.

"You've got to see this," says Vernon Asper, an oceanographer with the National Institute for Undersea Science and Technology team, rushing into the main lab on board the Pelican. Soon after, to those gathering in the small room where readings from the sampling rosette come through on monitors, he points to the source of his excitement.

n a manner of speaking, the team had struck oil, or at least that was the best guess. Both the transmissometer, which measures particle levels, and the fluorometer, which detects dissolved oil (see previous posts), were showing very large concentrations of something at about 1,000 metres down, something we had not seen anywhere else.

"That, my friend, is the smoking gun," says Asper, "We've got to home in on this. You never see signals like that in the open ocean."

Certainly there are other possible explanations for what the team is seeing. But based on the limited information they've collected, their hypothesis, strengthened throughout the day, is that the instrument peaks had revealed a layer of dispersed oil. This could be coming straight from the 1,500 metre-deep gushing well, where the response team is now adding dispersants directly, and prevented from surfacing by the ocean's complex interplay of currents, density differences, and other factors.

The discovery defined the day's activities, and quite likely much of the rest of the expedition. The team is now on a quest to define the bounds of this strange plume. NIUST chief scientist Arne Diercks compares the effort to hunting shipwrecks, which is one of the things the group would have been doing on this expedition if they had not been diverted to oil research. "Except for us it's more fun," says Asper, adding, "That's a little weird. I admit it."

Later rounds of lowering and raising the sampling equipment would reveal even higher instrument readings at times, including one so high that Asper joked with a ship's technician, "At least your pumps will be well lubricated."

Eventually the team found that farther away from ground zero the layer was lower — in the 1,100 to 1,400 metre range. This might show the oil, likely aggregated with plankton and other organic material, is settling out over time.

In between sampling rounds we watch the carnival of ships and boats—I count 26 at one point—all doing their part to fight the spill. I'm in no position to assess whether enough is being done or whether the right things are being done, but I can say unequivocally that there are quite a few people with some very serious and expensive equipment doing a lot of something.

At times today we were downwind of this activity and ground zero, and it smelled like a refinery. Earlier in the trip you smelled the oil on deck, now at times the stench permeates the labs.

n most places, the oil has taken on a stringy form beneath the surface, but there are floating bands of dark brown in places. Diercks simply dragged a bucket through one of these to get samples of what looked and smelled like pure crude oil. Two inescapable results of this effort were a very messy bucket, and the spontaneous singing of the bubbling crude song from the old Beverly Hillbillies TV show. Almost as predictable, as Diercks dumped the remains from the sample bucket everyone began joking that he would be subject to fines and imprisonment because dumping oil in the sea is strictly prohibited.

For tonight, the team will be working a grid out from ground zero. Once they reach points with no plume, they'll cut over and start working back in.

More: http://blogs.nature.com/news/thegreatbeyond/2010/05/oil_spill_science_the_smoking.html