BP / Gulf Oil Spill – What Did Bonnie Do?

The center of Bonnie’s circulation appears close to the Macondo well site on a CSK radar satellite image taken July 24. CSK and MODIS satellite images the next day, July 25, show remnants of the BP oil slick scattered around the Mississippi Delta. No new oil is seen around the well site; it’s been tightly capped since July 15.

COSMO-SkyMed radar satellite image showing center of circulation of tropical depression Bonnie, July 24, 2010. CSK-1 image courtesy CSTARS. Backdrop (color) is MODIS/Aqua image from earlier the same day.

The center of circulation for tropical depression Bonnie was located about 15 miles (24 km) south-southeast of the Macondo well site when this CSK-1 radar satellite image (black-and-white) was taken, at 6:44 pm local time. Weather station 42364, on the Ram-Powell oil platform about 27 miles (43 km) northeast of the Macondo well, recorded sustained wind speed of 22 mph (10 m/s) at that time. Station 42887 on the Thunder Horse oil platform about 39 miles (63 km) south of the well recorded winds at 11 mph (5 m/s).

Radar images show the “roughness” of the ocean’s surface, revealing the pattern of Bonnie’s counterclockwise-circulating winds. The strongest winds are generally in the northeast quadrant of cyclones in the northern hemisphere. This is reflected by the overall gray tone in the radar image: the area of stronger winds north and east of the storm’s center is brighter than the area to the south and west.

Two distinct storm bands are also apparent; these are lines of strong thunderstorms with gusty winds. A narrow line of oil slick is also visible – possibly related to the BP / Deepwater Horizon spill, although we think most of the slick and sheen from that spill is obscured on the radar image by the strong wind conditions.

COSMO-SkyMed radar and MODIS/Terra satellite images taken July 25, 2010, showing remnants of BP oil slick. CSK-1 image courtesy CSTARS.

CSK radar and MODIS / Terra satellite images taken on July 25, 2010, show the effects of tropical depression Bonnie’s passage on the oil slicks and sheen from the spill. No new oil is seen in the immediate vicinity of the well. But remnants of the oil slick are visible around the Mississippi Delta.

The MODIS image also shows dozens of small oil slicks from natural oil and gas seeps. These seeps appear unusually active, possibly due to seafloor disturbance caused by Bonnie. A bright area of slicks or sheen between the spill-related oil slicks (orange line) and the area of active seeps (dashed red line) could be where oil from both sources is mingling.

See all of SkyTruth’s images related to the BP / Deepwater Horizon spill in our gallery.

BP / Gulf Spill – Buh Bye, Bonnie

More good news for the Gulf: Bonnie was a bust. She blew over the BP / Deepwater Horizon spill site Saturday morning as a rapidly weakening tropical depression. NOAA weather buoys and stations in the eastern Gulf barely registered her passing, with sustained winds at the leak site only briefly exceeding 14 meters per second (about 31 mph). Fellow weather-geeks, check out the data from Station 42364 (located on the Ram-Powell oil platform operated by Shell) and Station 42376 (on the Marlin platform operated by BP).

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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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




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.