Pasadena Scientists Conduct Experiment in Middle of Oil Spill Exercise Off Coast of Norway

Three scientists from Pasadena, two of them from the Jet Propulsion Laboratory and one from Caltech, were able to run a science experiment in the middle of a North Sea oil clean-up exercise early this month to test the ability of NASA’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) to classify the oil in an oil spill.

It was an experiment that the three – Cathleen Jones and Ben Holt from Pasadena’s JPL and Brent Minchew from Caltech – have been trying to accomplish during the 2010 BP Deepwater Horizon Spill in the Gulf of Mexico but were not able to because of the limitations inherent in an actual oil spill. On June 8 through 11, Norway’s annual Oil on Water exercise provided just the right opportunity.

Jones, Holt and Minchew were part of a NASA team that participated for the first time in the North Sea exercise. The exercise has been held annually since the 1980s, weather and wildlife permitting. In these drills, oil is released onto the ocean and then recovered, giving responders experience with existing cleanup techniques and equipment and a chance to test new technologies.

In this exercise, the American scientists flew the UAVSAR, a specialized airborne instrument, on NASA’s C-20A piloted research aircraft to monitor a controlled release of oil into the sea, testing the radar’s ability to distinguish between more and less damaging types of oil slicks.

The local scientists were invited by Camilla Brekke, associate professor in the Department of Physics and Technology at the University of Tromsø, Norway.

“This year was special, because we had our own dedicated science experiment in the middle of the training exercise,” said Brekke.

In the 2010 Gulf oil spill, Jones, Holt and Minchew recognized UAVSAR’s potential to classify the oil in an oil slick during their observations. But since they had only estimates of how much oil was released in the disaster and of the rate of flow, they could not fully check UAVSAR’s accuracy.
“Radar has long been thought to be useful only for telling where oil is present,” said Jones. “That information is important, but it’s not all that’s needed to direct the response to an oil spill.”

The same accident can create both sheens of oil a few hundredths of an inch thick and heavy, sticky emulsions of oil and seawater, depending on factors such as the weather and length of time since the spill.

“Thick emulsions hang around in the environment much longer than a sheen does,” Jones explained. “They’re more likely to make it to shore to contaminate coastal and tidal zones and to oil sea animals. If we can identify where that high-environmental-impact oil is, cleanup crews can get the most out of the time and people they have.”

Radars “see” an oil spill because of a characteristic that the Greek philosopher Aristotle first wrote about 2,500 years ago: pouring oil on water smooths the surface. To an observer, returning radar signals — called backscatter — from a smooth, oily sea surface look darker than backscatter from a normal sea surface with small, bumpy waves.

In the Gulf oil spill, the NASA scientists discovered that the extremely sensitive UAVSAR could also detect another characteristic of oil: compared with seawater, it is a very poor conductor of electricity. Radar waves are reflected well by materials with good electrical conductivity, such as seawater, and not so well by poor conductors like oil. For that reason, the strength of the backscatter from different parts of an oil slick is related to the thickness of the emulsion in each part.

The Norwegian exercise released emulsions of differing thicknesses so that the scientists could have a range of conditions to calibrate the UAVSAR data. The experiment also tested the instrument’s ability to distinguish between petroleum and plant-based oil, found in algal blooms.

“In the Baltic Sea you will see plenty of these, and they look like oil slicks from [radar on] a satellite,” Brekke said.

The Norwegian Clean Seas Association for Operating Companies runs the Oil on Water exercise to keep its personnel and ships ready to respond to an emergency. This year, Oil on Water was held at the abandoned Frigg Oilfield, about 140 northwest of Stavanger, Norway.