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Saturday, 17 July 2010

The power of context, Part IV

Two anecdotes on remote sensing and environmental monitoring highlight some issues in measuring and predicting the current Gulf of Mexico oil rupture.

Last year as a consultant at AGIP KCO to Tony Battle, I spent some time with ice specialists in the north Caspian Sea. It freezes over every winter, and both navigation and oil platforms must be monitored for the safety of the environment as well as the infrastructure. But remote sensing specialists assured me how difficult it is to separate roughness in the water - such as white caps we see on any lake in brisk wind - that may also be caused by ice, oil or loose vegetation. Ground-truthing is a must through vessel observations, buoy measurements etc.

And that had been made patent, when Hurricane Katrina struck the Mississippi delta in the fall of 2005. Below is one of then US Department of the Interior Secretary Gail Norton's pictures from her visit in its aftermath (posted with permission). That aerial view of the river shows a different hue of brown/green working its way downriver shortly after the hurricane landfall. The press immediately suspected an oilslick - nothing like this spring's Macondo oilspill offshore, but a slick nonetheless - and that was not an unfair supposition: many oilwells aren't connected to a pipeline network, either because they're too old and/or they produce too little (stripper wells), or because the marshy environment made pipeline laying hazardous (more so in the past); production is thus collected in oiltanks, which may easily have been dislodged if not ruptured during the hurricane, by water pushed up the Mississippi by the storm surge, or by subsequent flooding from the sudden increase in rainfall.


click on image to see photo gallery

It's those two last events, however, that point to the real cause of the apparent slick observed from the air. David Gisclair of the Louisiana Oil Spill Coordinator's Office (LOSCO) / Office of the Governor told me at the time that ground crews were dispatched immediately. They found that the alleged slick seen from above was in fact marsh grass that had been torn up by the storm upsurge, then washed down in the subsequent flooding... marsh grass is anchored to sustain downstream not upstream currents, much like levees were built to sustain outward pressure from the river not inward pressure from the storm surge! Again, ground-truthing was a must.

[nearby Texas gulf coast a year earlier in the banner of my old website]
Fast forward to a space-shuttle view of the current oilspill in the Gulf of Mexico: a video of screenshots from the US EPA / Coast Guard's Deepwater Horizon Gulf Spill Response KMZ in Google Earth (link at end of video) from 11 May to 15 July:

best viewed on YouTube in full screen mode,
click lower right-hand corner then press F11


Notice as you step through this day-by-day (YouTube helps read the dates to the left):
  • first the spill spreads offshore, spelling fear of it reaching out of the Gulf into the Atlantic and perhaps the Gulf Stream
  • then it hugs the eastern shoreline, prompting the deploymeent of protective booms in red featured in the news
  • and it spreads far west along this shoreline (faint tracks to the west), perhaps a distant effect of Hurricane Alex
  • to start shrinking (?) toward the end perhaps as an effect of well capping, or offshore cleanup or wave dispersion
This is of course at a very macro scale, by no means the only place to see this as posted earlier, and relies on EPA's science and other agencies such as USGS. And the outcome of these events are just starting to be felt, such as passing the CLEAR Act in the US.