Horizon - Backing Off Optimism

OK, so first of all, somebody I've heard of (a physical oceanographer whose opinion on such matters I'd trust more than my own) is worrying about long-range transport of oil:

Niiler is not speculating. He has studied the way ocean currents and winds moved hundreds of "drifter" buoys around the Gulf. In the drifters' 90-day lifespan, he has seen them scatter to all parts of the Gulf with the help of a tropical storm with 40-knot winds.

Some drifters were found as far west as Texas and others were caught in the Loop Current that carries Gulf water out and around to the East Coast of North America.

What's more, said Niiler, there's no evidence that oil will be diluted by the time it reaches the East Coast.

"We see Mississippi water in the Loop Current all the way to Cape Cod," said Niiler. "It's not mixed up."

And neither will any oil slicks that are sucked into the Loop, he said, unless there is something causing the water to mix, like a hurricane. A powerful hurricane can cause the ocean waters to mix down to 150 meters.

Is this right? I'm not sure. The Mississippi delivers more than 100 K barrels/day. So the fact that Mississippi water is detectable offshore in the east doesn't settle the question whether the oil will be noticeable, never mind troublesome.

Actually, this brings me to one of the things I've been thinking about. We really need to think about four sorts of oil in this situation:

1. oil in colloidal suspension in the deep
2. oil in two dimensional configuration on the surface
3. oil in two dimensional configuration on the sea floor
4. oil in linear configuration on a beach

Each of these will have different impacts. So far, it seems like we are getting a lot of #1, and I still think this is a lucky break. Suppose for the sake of argument we have 100,000 barrels divided into four equal parts of 25,000 barrels each. So each portion is about a million gallons (four million liters). Now suppose a gallon of oil is floating in a thin film, about a centimeter thick, it will cover about a third of a square meter. The whole mess will cover 33000 m^2 or an area of about 181 meters on a side. Of course, it doesn't do us the kindness of staying in a neat square. So suppose we consider a coverage of about 1/1000; that will probably be enough to provide a sheen on everything. The mess will cover a square about 5.7 km on a side and will be very depressing.

Now let's distribute that same amount of oil over the water column. This will be those "plumes" we are talking about. Presume the water column is 2000 meters thick. Here we have a gallon of oil over 1000 m^2 * 2000 m = 2,000,000 m^3. What is the density of oil in the column? Well a gallon is 4 liters is .004 m^3, so the concentration of oil in the water column is .004/2e6 = 2 parts per billion. Ho hum.

Of course, that is a bit generous. Suppose the plume is constrained to a 2 meter thickness instead of a 2 km thickness. 2 parts per million. Still hard to lose sleep over. Here, the dimensionality of the problem is on our side. So if these plumes get into the loop current, they will get sheared out and nobody will ever hear of them again.

The question is whether the colloidal suspension is stable on time scales comparable with the surface weathering of oil. I guess some of it is buoyant and gets to the surface. I get the impression that it is.

On the other hand, there is the sea floor. If some of the oil gets there, or some of the colloid settles down to the bottom, the lifetime is probably very long. And if a significant amount of colloid gets dragged past the coral formations off the Florida Keys, surely that won't help the corals which are already stressed by lots of things. Both of those things convert from 3 D back to 2 D.

But the dimensionality of the problem cuts the other way on the shoreline. If a gallon is essentially trivial in a 3D column, and unpleasant on a 2 D surface, it is catastrophic on a shoreline. There, 25,000 barrels of oil can make a huge mess. The entire Santa Barbara spill amounted to 100,000 gallons. If we are approaching such quantities on a daily basis, the amount of shoreline damage can be spectacular.

This is why it has been such good news that the oil has been kept offshore until the last couple of days, and such bad news that it is beginning to accumulate.

So I'm not as optimistic as I was a few days ago. But I'm sticking to my guns on this part: I think the main issue is the shoreline. The bottom is a secondary issue. Stuff that remains in suspension is not a big worry, and so the exact measure of the flux through the hole is not an immediate concern. Some aquatic birds and animals will get oiled at the surface, but not many.

We will be able to measure things better when it all settles down. Certainly it's important to do that, to gain experience if this ever happens again.

On the other hand, most of what I've seen indicates that this was entirely avoidable. Like Chernobyl, it tells us how bad things can get if people really screw up badly. That's pretty bad, so the best thing to do is to avoid screwing up. So I still think the measurement issue is a red herring.

This isn't to defend or attack BP's post-spill actions. I really don't have the information or skills to judge, much as I enjoyed the forthrightness of the f***ing booming rant.

I think it's important to understand that the engineers are not pleased. I think it's important to understand that an entity the size of BP is a lot of people and a lot of decision-makers. Inevitably with an organization of that size some of its members take their responsibilities more seriously than others do. The culpability and liability of the organization itself I leave to the lawyers and others who like to cast blame at inanimate objects.

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Image: NASA via SkyTruth h/t Hank. Note that the darker area in the east is not oil, but rather an area of calm water where the waves are too small to reflect sunlight directly to the satellite.