BP / Gulf Oil Spill – Here Comes Bonnie

3-day forecast track for Tropical Depression Bonnie, expected to strengthen over the weekend

The Bad News: Tropical Depression Bonnie is making a beeline through the eastern Gulf of Mexico, heading right for the Macondo well site. According to the National Weather Service, Bonnie should cross over the site on Saturday afternoon, strengthened by her trip over warm Gulf waters to a tropical storm with sustained winds over 40 miles per hour. Crews are being evacuated from the area, and progress on the relief wells has been brought to a halt.

GOES weather satellite image of Bonnie, taken at 5pm Central time on July 23, 2010

The Good News: The cap on the Macondo well has been shut tight for several days, and we no longer see signs of fresh oil upwelling around the site of the failed well. We have also noticed a significant reduction in the surface oil slicks in the Gulf since early July. Although we don’t know how much oil is lingering out of sight beneath the surface, we hope this means that far less oil is available to be thrown up onto the beaches and into the wetlands when Bonnie comes through.

On June 29, when Tropical Storm Alex was moving past in the southern Gulf, the area of slicks on satellite images spanned 19,000 square miles; the MODIS / Aqua image below, taken on July 21, shows a fragmented area of slicks and sheen covering 5,476 square miles:

MODIS / Aqua satellite image taken July 21, 2010

However, the large area of anomalous ocean color noted on a July 19 MODIS image is even more obvious. It shares spectral characteristics with the sediment-laden plume emerging from the Mississippi River, but it may also indicate changed water chemistry in the area affected by the spill – possibly due to oxygen depletion as a result of the elevated levels of methane (natural gas) dissolved in the water. The eastern edge of this anomaly is marked with a dashed brown line.See all of SkyTruth’s images of the BP spill here.
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Dalian Oil Spill, China

Sometime last week, two pipelines in the port city of Dalian, China, exploded and burned, and a large quantity of oil was released into the Yellow Sea. One firefighter lost his life. There are some harrowing pictures of oil-covered firemen being pulled from the water. Officials report that 165 square miles of ocean was covered with oil, but the pipelines are no longer leaking and cleanup is proceeding. Aquaculture is a huge business in China – Greenpeace estimates that 10,000 shellfish farms have been affected.

Envisat ASAR radar image (black-and-white) taken July 18, 2010

This Envisat radar satellite image appears to show patchy oil slicks spread out over a large area along the coast and islands near Dalian. China Central Television reported that the spill was estimated at about 400,000 gallons. If true this is far smaller than the BP /Deepwater Horizon spill in the Gulf of Mexico, although it’s worth noting that any spill greater than 100,000 gallons is labeled “major” by the US Coast Guard.

Some of the dark patches in this radar image may be areas of calm water rather than oil. This is a rugged coast, and strong topography can generate “wind shadows” on the downwind sides of rocky islands and coastal hills.

SkyTruth – In The News

We’ve been getting a lot of TV, radio, print and Web interviews and other coverage since the BP / Deepwater Horizon spill began back in April. Media interest focused on our early determination that the oil spill rate was much larger than official BP and government estimates; testimony in November 2009 warning Congress about the risks posed by offshore drilling; discovery of chronic leaks from other wells in the Gulf; and call for systematic, Gulf-wide pollution monitoring using satellite imagery.

We have been busy. You can download reports listing our media and web appearances in April, May, June, and (so far) July. You might also be interested in reading our brand-new newsletter (Volume 1, Issue 1 – a future collectible!). Here are a few of the highlights:

TV appearances

Radio

Print

Web

Satellite Imaging of Oil Slicks – A Primer

We get a lot of questions from folks interested in our work using satellite images to detect and monitor oil spills around the world. The Montara spill off Australia last year, and the ongoing BP / Deepwater Horizon spill in the Gulf of Mexico, are striking examples of how this technology can help us investigate and illustrate what’s happening far out to sea and in remote locations.

Like all data sources, satellite imagery has its strengths but also some important limitations. Few imaging satellites (the ones taking pictures of Planet Earth) are “turned on” all the time, so images are not necessarily available. Usually somebody has to contact the satellite operators – some operators are government agencies, some are commercial for-profit businesses – and request that images be collected over an area of interest. Often, you’ve got to pay to have this done. NASA makes images from their taxpayer-supported systems, including MODIS, available for free, but satellite images from private vendors can cost thousands of dollars each.

Imaging systems that operate at visible to infrared wavelengths of light, like the MODIS system we’ve used so often, can’t see through clouds, smoke, dust or haze. And oil slick imaging is sometimes dependent on the sunglint pattern, which varies considerably from one image to the next, and is also affected by wind and wave conditions on the water. Radar imagery gets around some of these problems, but NASA doesn’t operate any radar satellites so the cost can be prohibitive.

For all of these reasons, we haven’t been able to produce good images of the BP oil slick every day (NASA just published an excellent illustrated article on this topic). But at SkyTruth we have acquired good images often enough to illustrate the enormity of the spill and inadequacy of our initial spill response efforts; provide the first estimate of the spill size and rate that made any sense; to identify oil making landfall along the Alabama coast before it was being acknowledged by officials; to show clear entrainment of the spill in the Loop Current while officials were actively denying it; and to detect small but chronic leaks from other damaged wells, raising the related issue of inadequate plugging and abandonment.

This spill has also provided a unique opportunity to collect imagery from multiple different remote-sensing systems, both satellite and airborne, working at visible to infrared to microwave wavelengths, over a long period of time under a wide range of weather and illumination conditions. A systematic analysis of this dataset will yield a much better understanding of how imagery can be used to accurately measure and monitor oil pollution events in the future. We’re looking for funding opportunities to conduct such an analysis.

Because as long as we continue to produce and transport oil offshore, there will be a next time.

Hopefully not too soon.

BP / Gulf Oil Spill – Radar and MODIS, July 19, 2010

The cap on BP’s infamous Macondo oil well in the Gulf of Mexico is still shut, but small leaks have reportedly appeared on the seafloor around the well site. This is troubling because it suggests that the well casing is damaged and leaking somewhere below the seafloor. According to Coast Guard Admiral Thad Allen, one of those leaks is actually coming from an older abandoned well nearby – he goes so far as to say:

“it’s not unusual to have seepage around the old wells”

The AP recently did a story (featuring SkyTruth, among others) on the fact that there are 27,000 abandoned wells in the Gulf, and that abandoned wells on land leak so frequently that there is an ongoing need to re-plug them. I guess Admiral Allen confirms what the AP suspected – that this is also a problem with offshore wells. Who knew? Now we all do.

BTW, we wish folks would only use the term “seepage” when talking about natural oil and gas seeps on the seafloor, not human-caused leaks.

MODIS / Aqua and CSK radar satellite images taken on July 19 show oil slicks and sheen spanning about 7,868 square miles. This is almost twice as large as the area of slicks observed on satellite imagery from July 14, but still a lot smaller than it’s been on previous imagery.

MODIS / Aqua satellite image from July 19, 2010

Oil slicks and sheen appear through a complicated assortment of clouds and haze on the MODIS image, taken at about 2pm local time on July 19, 2010. An area of anomalous ocean color (dashed line marks its eastern edge) appears to mirror the eastern edge of the area covered by surface oil slicks. This may be an indication of changed water chemistry in the area affected by the spill – possibly due to oxygen depletion as a result of the elevated levels of methane (natural gas) dissolved in the water.

The edge of the ocean-color anomaly seen on the MODIS / Aqua image is shown for reference on the CSK radar images taken a few hours later that same day:

COSMO-SkyMed radar satellite images (black-and-white) taken July 19, 2010, superimposed on MODIS image from the same day (color). CSK images courtesy CSTARS.