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Is Gulf Oil Headed For The East Coast? A New Simulation Says: Maybe

Ocean Simulation Model, Credit: NCAR

As soon as it became clear that the Deepwater Horizon oil eruption was going to be gushing for a while, anyone with a basic understanding of regional ocean currents, from sea captains to oceanographers, began to wonder: what will happen if the oil gets into the Loop Current?  This whirling river of water mostly flows clockwise around the Gulf of Mexico, but it also sends a tendril down around the tip of Florida, where it feeds into the northward-flowing Gulf Stream. If substantial amounts of oil were to reach the Gulf Stream, it could in principle spread up along the US Atlantic coast, threatening the coastline from Key West to Cape Hatteras.

Now those speculations have become a little more concrete: a team of climate scientists at the National Center for Atmospheric Research (NCAR) have run computer models to simulate the spread of oil. It suggests that Gulf crude could indeed reach the Atlantic — as early as in the next few weeks. And once there, say the scientists, it could head up the East Coast at up to 100 miles per day. “Our best knowledge,” says NCAR’s Synte Peacock in a press release, “says the scope of this environmental disaster is likely to reach far beyond Florida, with impacts that have yet to be understood.”

But their best knowledge is still imperfect. The NCAR scientists warn that their simulations are idealized in a number of ways. For one thing, the “oil” in their computer models acts more like a dye, dissolving evenly in the water and staying dissolved. Real oil forms globules and doesn’t dissolve at all. Second, the simulation assumes the oil lies in the upper 65 ft. of ocean. The real spill is believed to be mostly deeper than that, and rises only slowly.

As for the ocean currents carrying the spill, those too are idealized, based on historical behavior of water motions. In real life, these vary every year, depending on weather and other factors. Right now, for example, there’s an eddy — a sub-swirl in the Loop Current — which may detach from the larger current and prevent the Atlantic connection from happening. Reliable predictions of the Loop Current’s evolution cannot be made far in advance. Also, if a hurricane should move into the area, or wind patterns should unexpectedly change, all bets would be off.

In short, the NCAR model has transformed some of the initial speculation into information. But it hasn’t quite risen to the level of a prediction.

Dr. Steve Pacala of the Princeton Environmental Institute, and Climate Central board member, highlights some of the uncertainties in the NCAR computer modeling study.

Dr. Steve Pacala of the Princeton Environmental Institute, and Climate Central board member, discusses how the NCAR computer modeling study illustrates how we are all interconnected.

From the NCAR Press Release:
This animation from NCAR shows one scenario of how oil released at the location of the Deepwater Horizon disaster on April 20 in the Gulf of Mexico may move in the upper 65 feet of the ocean. This is not a forecast, but rather, it illustrates a likely dispersal pathway of the oil for roughly four months following the spill. It assumes oil spilling continuously from April 20 to June 20. The colors represent a dilution factor ranging from red (most concentrated) to green (most diluted).  The dilution factor does not attempt to estimate the actual barrels of oil at any spot; rather, it depicts how much of the total oil from the source that will be carried elsewhere by ocean currents. For example, areas showing a dilution factor of 0.01 would have one-hundredth the concentration of oil present at the spill site.

The animation is based on a computer model simulation, using a virtual dye, that assumes weather and current conditions similar to those that occur in a typical year. It is one of a set of six scenarios released today that simulate possible pathways the oil might take under a variety of oceanic conditions. Each of the six scenarios shows the same overall movement of oil through the Gulf to the Atlantic and up the East Coast. However, the timing and fine-scale details differ, depending on the details of the ocean currents in the Gulf. The full set of six simulations can be found here. (Visualization by Tim Scheitlin and Rick Brownrigg, NCAR; based on model simulations.)