Satellite view of the Southern California oil spill

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October 3, 2021

Satellite imagers can aid in the detection of oil spills in open water.

When oil leaks or spills into the ocean, the surface of the water changes. It may seem obvious to anyone who has seen polluted water staining a beach or swamp, but in the vast, deep, deep blue ocean, oil is not always easy to spot. Some satellite imagers can help detect oil spills in open water.

At least two satellites sighted oil in the ocean off the coast of southern California on October 2-3, 2021. The first image above is a natural-color view captured at 11:22 a.m. PT (6:22 p.m. PDT) Universal Time) on October 3 by Operational Land Imager (OLI) on Landsat 8. In the midst of clouds and haze, along with white streaks of large freighters and boat wakes, traces of oil are faintly visible. Half a day earlier, the European Space Agency’s Sentinel-1B satellite acquired a radar image at 6:49 p.m. PDT on October 2 (01:49 UTC on October 3). The tablecloth stands out better in this view.

Synthetic aperture radar for oil spill in California, October 2021 annotated

October 3, 2021

Sentinel-1B uses Synthetic Aperture Radar (SAR) to observe differences in surface roughness on Earth. The rougher surfaces look the brightest, while the smoother surfaces look dark. Oil makes the ocean smoother by reducing the size and number of “capillary waves” on the surface. (If the angle of sunlight is correct, scientists can also use sunlight to plot large spills.)

Scientists from the National Oceanic and Atmospheric Administration interpreted and shared the Sentinel-1B images as part of a marine pollution monitoring report on October 3. The report showed oil slicks stretching for more than 50 kilometers along the coast. On October 6, scientists from ">NasaIts Jet Propulsion Laboratory flies an airborne radar – the Unmanned Aerial Vehicle Synthetic Aperture Radar (UAVSAR) – over coastal areas near the spill. (Data is not yet available.)

On October 2, 2021, federal and state agencies first reported oil on the ocean surface off Huntington Beach, California, about 40 miles south of Los Angeles. Investigations have since traced it to a ruptured pipeline about 8 kilometers offshore. According to media and institutional reports, crude oil and its tailings have spread along the coastline, affecting areas such as Huntington State Beach, Talbert Marsh and the mouth of the Santa Ana River. Many beaches have been closed to swimming from Huntington Beach to Dana Point, while skimmers and booms have been deployed to slow the movement of oil in marshes and coastal basins. Fishing in the area has been closed and crews are working to save and rehabilitate oil-affected seabirds.

The US Coast Guard and the California Department of Fish and Wildlife are working with local cities and private industry to mitigate the effects of the oil spill. NOAA regularly monitors U.S. coastal waters for potential spills and provides science and disaster response resources during such events.

NASA’s Earth Applied Sciences Disasters program is working to determine what NASA resources and capabilities may be available to support spill recovery efforts. The program also recently funded the Marine Oil Spill Thickness (MOST) Field Campaign near Santa Barbara, California, to improve remote sensing techniques for monitoring oil spills. Additional flights for the MOST campaign are planned for later in October.

Images from NASA’s Earth Observatory by Joshua Stevens, using Landsat data from the US Geological Survey and modified data from Copernicus Sentinel (2021) processed by the European Space Agency.


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