Large concentrations of spilled oil 1,000 meters below Gulf surface
By Science journalist Mark Schrope, aboard the research vessel Pelican
“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. In 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. …
