Oil Spill--Big or Small?

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Several times in the last few weeks, I've heard executives from British Petroleum make statements that their spill (which, incidentally is now the largest in US history) is "small relative to the total volume of the ocean."  According to BP's original estimate of 5000 barrels per day, the spill has "only" released 185,000 barrels as of 5/27.  However, USGS just released a best estimate of 12,000 barrels per day (444,000 total), but says it could be as high as 25,000 barrels per day (925,000 total).  Using the USGS best estimate, 444,000 barrels amounts to only 0.000000000005% of the total ocean or 0.000000003% of the Gulf of Mexico.  As Nick put it, if the spill were actually big relative to the ocean, then we'd really be in trouble.

The problem with viewing the spill in this way is that it assumes the oil is spread evenly throughout the ocean.  Suppose the oil were confined to a layer 1m thick.  In this case, the oil would cover 0.07 square km.  This would be like covering 7.6 Fenway Parks with 1m of oil.  Again, doesn't seem like much, especially if you're a Yankee fan.  The problem, though is that reality is somewhere in between the "completely mixed" or "pure oil" alternatives.  

26MAY2010OilSM.jpg

One of the things that struck me about the comments from BP, is that the oil slick can be seen from space.  In my opinion, anything that can be seen from space is probably not small.  Roffer's Ocean Fishing Forecasting Service is issuing regular updates on the position of the oil slick using regular satellite images.  By my crude counting of the "oily" squares in their latest images, the oil slick now covers 135,531 square km.  If we assume that the slick is 10m deep, then the slick is about a 0.000005% oil-water mixture.  To me, this provides a rough guideline for the concentration of oil necessary to cause some effect (or at least, to make the water look oily).  Using these numbers, the slick now covers 8.5% of the surface area of the Gulf of Mexico and 0.005% of its total volume.  To put this in a more local perspective, if the slick were in the Gulf of Maine, it would cover 72% of the surface and affect 5% of its volume.  Sounds like a big deal to me.

Sources:
volumes & surfaces areas of World Ocean and Gulf of Mexico--wikipedia
flow rates of oil--New York Times

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4 Comments

Another interesting fact overlooked by the telemetry, is the impact of the so-called "Water Accommodated Fraction", the water-soluble fraction of the hydrocarbons, essentially naphthalene.
Apparently, from a quick and recent copepodo-centrist research of the literature, the impact of those compounds can be highly detrimental at very low concentrations !
And on top of that it seems to target the lipid metabolism (check the previous blog posts !).
(Hansen et al. 2008 Aquat Toxicol 86 157-165)

I'm sorry, but I must protest at the continuing use of "Fenway Parks" as a unit of area. I'm British, and I'm sure that there are many different sizes that you could use to approximate.

According to the Guardian, a British paper, the standard measurements for size are the London bus, the football (or soccer) pitch, or Wales. No, not the Free Willy kind, but the country. Others include Olympic swimming pools, the Isle of Wight, or Wembley stadiums.

At last estimate, I believe the slick reached half the size of Wales, but I have no idea how many Olympic sized swimming pools that is equivalent to...

Mind you, I think I've spotted a flaw in that plan - no one, ever, even tells you how big Wales is to start with.

Until here - http://www.guardian.co.uk/media/mind-your-language/2010/may/17/mind-your-language-david-marsh?CMP=twt_gu

I totally agree with Jon and strongly suggest a lab trip to Fenway Park, so that we'll finally all be on the same page !

For Jonathan's benefit, I recommend using "Royal Bafokeng Stadium" as the standard unit of area rather than Fenway Park. I think both Americans and Brits will remember that stadium for awhile, the former a little bit more fondly than the latter.

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This page contains a single entry by Andy Pershing published on May 27, 2010 5:45 PM.

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