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Friday, September 2, 2011

Radar Satellite Image Shows Oil Slicks Seen August 30

An Envisat ASAR satellite radar image of the Gulf taken at about 10:50 pm local time on August 30 shows distinctive slicks corresponding with video and photos taken during an overflight earlier that day by Bonny Schumaker / On Wings of Care.  This image is complicated - NOAA/NODC data buoys in the area recorded very low wind speed (2-3 meters/sec) when the satellite passed overhead, near the lower limit for oil slick detection.  The thin spaghetti-like strands of dark slick throughout this area are most likely tendrils of natural surfactants that commonly appear on low-wind radar images of the ocean surface.  But the size, shape and appearance of a 14-mile-long slick that seems to originate at the 23051 Site matches many observations we've made on satellite imagery since we discovered a chronic leak at that location. And the large dark patch at the location of the August 30 overflight apparently confirms Bonny's observations with an area of slick covering about 122 square kilometers. Given a minimum observable thickness on radar of 0.1 microns under these low-wind conditions, that would represent a minimum of 3200 gallons of oil.

First, here's what the August 30 radar looks like.  The Mississppi Delta is the bright birds-foot pattern on the left edge of the image.  Water is medium-gray; slicks are black:
Envisat ASAR image taken August 30, 2011 about 10:50 pm local time. Image courtesy European Space Agency.
Here's the same chunk of image with markers showing the chronically leaking 23051 site, the Deepwater Horizon wreckage site, and the location of Bonny's August 30 oil slick photos and video. Seafloor pipelines in yellow; recently troubled Destin pipeline shown in brown; active oil and gas platforms and other structures, including seafloor manifolds, are orange dots; natural seep locations are green dots:
Same area with features of interest marked. Image courtesy European Space Agency.
Zooming in, here's the August 30 radar image again showing a distinct patch of slick about 16 miles northeast of the BP / Deepwater Horizon oil spill site.  Orange dots are active oil and gas production facilities (platforms, manifolds):

Detail from Envisat ASAR image taken August 30, 2011 about 10:50 pm local time. Image courtesy European Space Agency.
Same area with other features marked for reference (pipelines in yellow, natural seeps are green dots). The brown highlighted pipeline is part of the Destin gas pipeline network, operated by BP, that was coincidentally (?) shut down on August 30:

Detail from Envisat ASAR image taken August 30, 2011 about 10:50 pm local time. Image courtesy European Space Agency.
Here's what the same patch of Gulf looked like on a radar image taken four days earlier, on August 26.  A small, 4-mile-long slick is visible just above the word "wreckage" - it's about equidistant from a subsea manifold in the area and a couple of natural seeps, so either of these could be the source.  But this slick doesn't seem related to the large patch observed on August 30:
Detail from Envisat ASAR image taken August 26, 2011. Image courtesy European Space Agency.
As usual, we'll keep looking at this area as we get new imagery and information, and will let you know what we learn.

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