Scientists recently found black gold bubbling up from an otherwise undistinguished mass of ocean imagery. Chuanmin Hu, an optical oceanographer at the University of South Florida, St. Petersburg, and colleagues from the National Oceanic and Atmospheric Administration (NOAA) and the University of Massachusetts–Dartmouth (UMass), found that they could detect oil seeping naturally from the seafloor of the Gulf of Mexico by examining streaks amid the reflected sunlight on the ocean's surface.
Most researchers usually discard such "sun glint" data as if they were over-exposed photos from a camera. "Significant sun glint is sometimes thought of as trash, particularly when you are looking for biomass and chlorophyll," said Hu. "But in this case, we found treasure."
The new technique could provide a more timely and cost-effective means to survey the ocean for oil seeps, to monitor oil slicks, and to differentiate human-induced spills from seeps.
Oil decreases the roughness of the ocean surface. Depending on the angles of the camera and of the light reflection, oil creates contrasting swaths that can show up in airborne images as either lighter or darker than the surrounding waters.
The detection and monitoring of oil spills and seeps by satellite is not new. Visible, infrared, microwave, and radar sensors have all been used, with synthetic aperture radar (SAR) being the most popular and reliable method in recent years according to the study authors. SAR imagery can be very expensive, the authors note, and timely, repeat coverage is not always possible, particularly in tropical regions.
Using imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA's Terra and Aqua satellites, Hu and colleagues assert, is far cheaper because the data is collected daily and provided freely by NASA, without the need for special observation requests. And the polar orbits of Terra and Aqua allow images of oil slicks to be collected several times per week in tropical regions and perhaps several times a day at higher latitudes. The description of the new technique was published in January in Geophysical Research Letters.
Hu actually happened upon the oil imagery while looking for signs of harmful algal blooms—commonly referred to as "red tide"—in the western Gulf of Mexico. Examining MODIS images, he kept noticing streaks across the sun glint reflections. After conferring with study co-authors Xiaofeng Li and William Pichel of NOAA and Frank Muller-Karger of UMass, Hu became aware that the streaks could be oil from natural seeps on the seafloor.
Hu and colleagues then defined a geographic area of the western Gulf and obtained MODIS images for the month of May for nine consecutive years (2000 to 2008) from NASA's Goddard Space Flight Center, Greenbelt, Md. The team reviewed more than 200 images containing sun glint, and found more than 50 with extensive oil slicks.
Exactly how much oil naturally seeps out of the seafloor is unknown, and most estimates are very crude because there has never been a proper global survey made for the public record. Researchers identified the natural seepage rate as a critical unanswered question when the National Academy of Sciences compiled its third Oil in the Sea report in 2003.
"This capacity for detecting oil in the ocean has great potential, not just for oil seeps but for responding to oil spills," said Chris Reddy, a marine chemist at the Woods Hole Oceanographic Institution in Massachusetts. "Scientists might be able to use this to forensically study old spills, to watch how new ones evolve in real time, and to rule out a spill when there is none. Ultimately, this could lead to a better use of our public resources."
The technique could be useful for detecting and monitoring oil spills from ships and other platforms, though Hu emphasized that the spills must be large enough (at least hundreds of meters or feet) to be visible in the MODIS imagery. If there is suspicion of a large human-caused spill, for instance, researchers would be able to review ocean imagery to see if the slick was present before the alleged spill, indicating a natural seepage. On the other hand, MODIS satellite imagery collected on a regular basis could help coastal managers track and mitigate the effects of large accidental spills.
The new method is not perfect, as cloud cover or a lack of sun glint can limit its use. Hu and colleagues suggest it may be best used as a complement to SAR, which penetrates cloud cover and can be tilted to get the necessary imaging angle.
"If you can get an image on a two- to three-day time frame and anywhere on the globe, that's pretty spectacular," said Reddy. "The first few days are critical to tracking oil in the ocean, so it helps to be able to use technology in real time to make informed decisions about cleanup."
Sarah DeWitt | EurekAlert!
Clear as mud: Desiccation cracks help reveal the shape of water on Mars
20.04.2018 | Geological Society of America
Hurricane Harvey: Dutch-Texan research shows most fatalities occurred outside flood zones
19.04.2018 | European Geosciences Union
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
20.04.2018 | Physics and Astronomy
20.04.2018 | Interdisciplinary Research
20.04.2018 | Physics and Astronomy