When an ocean oil spill occurs, time is of the essence. Details about the slick—the type of oil, its thickness, and the extent of the discharge—are crucial information for responders who want to contain the spill.
Spotting an oil slick with satellites is an easy task under most conditions. But getting those important characteristics of the oil spill takes an additional step: field verification. Directly measuring spills can be problematic; it’s not always practical, safe, or quick to collect measurements after a spill.
Researchers have long been working on ways to boost the efficacy of satellite measurements of oil spills. Now a multiagency team of scientists has leveraged multiple remote sensing techniques to detect and characterize a spill from the dizzying heights of a satellite.
Researchers verified their remote sensing measurements with two on-site field tests. Their new method of rapid data collection could provide near-real-time information to tactical response teams after an oil spill.
Detecting an Oil Spill
The sheen, metallic reflection, or dark patch on the ocean surface left from an oil spill can be detected by satellites whizzing over our heads. While it’s important to know that a spill occurred, details about the spill are essential for containment responders. This need for knowledge became crystal clear in April 2010.
“Everything started with the Deepwater Horizon,” said Oscar Garcia-Pineda, geoscientist-owner of Water Mapping and lead author of a new paper in Remote Sensing of Environment. “One of the lessons learned was that, yeah, we could detect where the oil was, but there was very little knowledge we could share with the responders about where will be the most efficient or the most practical, effective position to disperse the oil.”
During the Deepwater Horizon containment efforts, “many times, unfortunately, the operations were directed towards areas that were not the most important,” said Garcia-Pineda. “In the past, we were limited to detecting the oil,” said Garcia-Pineda. “Now we’re aiming at where is the oil, what type of oil [is it], and how thick is it?” He explained that knowing those details will allow scientists to recommend the best containment efforts, such as skimming, dispersal, or burning.
Remote sensing allows researchers to see things that are not normally visible to the naked eye, said Garcia-Pineda. “We use sensors like microwave, thermal, hyperspectral, multispectral, and optical to study oil spills because oil and oil emulsions produce distinctive signatures depending on the platform/sensor in hand.”
He added that new technology advances, including the miniaturization of sensors, allow scientists to use satellites, aircraft, drones, and even handheld instruments to collect data. The multiple platforms allow scientist to understand the capacities of each method.
“For example, while we have managed to use satellite observations delivered to responders in a matter of minutes, drones can deliver crucial tactical information [in] real time,” Garcia-Pineda explained.
To verify their results, the researchers had two field verification sites: the National Oil Spill Response Research and Renewable Energy Test Facility in New Jersey, and the Mississippi Canyon 20 oil lease block, an open-water site in the northern Gulf of Mexico.
Samples are taken of whatever might be floating on the ocean by an instrument that “works like a cookie cutter,” Garcia-Pineda explained. “This basically cuts a profile of whatever is on the surface without disturbing that profile, and it preserves the oil inside that tube.” The team then takes the sample on board for testing and determines how thick and emulsified the oil is.
“In every case, using our in situ oil thickness measurement technology has been an important step to calibrate/validate our interpretation of the remote sensing data,” he noted.
Zoning in on Spills
“I think this paper is a major contribution, because when a spill occurs, you need to be able to see a very big footprint,” said Nancy Kinner, codirector of the Coastal Response Research Center at the University of New Hampshire. For example, blowouts like the Deepwater Horizon spread over hundreds of kilometers.
Remotely sensing oil spills can also be useful in harsh or remote environments, where getting people to a spill site is difficult or dangerous. “It’s one thing to have assets zipping down to the Gulf of Mexico,” said Kinner, but “[t]otally different to [have assets] zipping up to the Bering Sea where [there are] not places to deploy” seacraft or airplanes.
“That’s where the beauty of satellites comes in,” she said.
Kinner said the new study provides important information for big spills of “actionable oil”—thick and/or emulsified oil. She said she and her colleagues will be conducting their own blind remote sensing tests in other environments with unknown oil types. “We need to understand how these technologies work with different oils, different temperatures, and different states the oil might be in.”
Garcia-Pineda and his colleagues are also building on their research by expanding monitoring with drones, GPS drifters, and remote sensing. They are also working with the NASA Disasters Program to better monitor spills around the world.
—Sarah Derouin (@Sarah_Derouin), Science Writer
Derouin, S. (2020), Leveraging satellite sensors for oil spill detection, Eos, 101, https://doi.org/10.1029/2020EO141933. Published on 26 March 2020.
Text © 2020. The authors. CC BY-NC-ND 3.0
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