Gulf Oil Spill Likely to Hit U.S. Atlantic Coast This Summer

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Environmental News Service

Gulf Oil Spill Likely to Hit U.S. Atlantic Coast This Summer

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An image from the NCAR computer model of the flow of Deepwater Horizon oil. (Image courtesy NCAR)

BOULDER, Colorado - Oil from the massive
spill in the Gulf of Mexico is likely to extend along thousands of miles
of the Atlantic coast and into the open ocean as early as this summer,
according to a detailed computer modeling study released today by the
National Center for Atmospheric Research.

The research was supported in part by the National Science Foundation,
NCAR's sponsor. The results were reviewed by scientists at NCAR and
elsewhere, although not yet submitted for peer-review publication.

"I've had a lot of people ask me, 'Will the oil reach Florida?'" says
NCAR scientist Synte Peacock, who worked on the study. "Actually, our
best knowledge says the scope of this environmental disaster is likely
to reach far beyond Florida, with impacts that have yet to be
understood."

The computer simulations indicate that, once the oil in the uppermost
ocean has become entrained in the Gulf of Mexico's fast-moving Loop
Current, it is likely to reach Florida's Atlantic coast within weeks.

It can then move north as far as about Cape Hatteras, North Carolina,
with the Gulf Stream, before turning east to the open ocean.

Whether the oil will be a thin film on the surface or mostly subsurface
due to mixing in the upper ocean is not known. The flow in the model
represents the best estimate of how ocean currents are likely to respond
under typical wind conditions.

More model studies are underway that will indicate what might happen to
the oil in the Atlantic Ocean.

"We have been asked if and when remnants of the spill could reach the
European coastlines," says Martin Visbeck, a member of the research team
from the Leibniz Institute of Marine Sciences at the University of
Kiel, Germany.

"Our assumption is that the enormous lateral mixing in the ocean
together with the biological disintegration of the oil should reduce the
pollution to levels below harmful concentrations," said Visbeck. "But
we would like to have this backed up by numbers from some of the best
ocean models."

To model the flow of oil, NCAR scientists are using the Parallel Ocean
Program, the ocean component of the Community Climate System Model, a
powerful software tool developed by scientists at NCAR in collaboration
with the Department of Energy. They are conducting the simulations at
supercomputers based at the New Mexico Computer Applications Center and
Oak Ridge National Laboratory.

The NCAR scientists simulated how a liquid released at the spill site
would disperse and circulate, producing results that are not dependent
on the total amount released.

The scientists tracked the rate of dispersal in the top 65 feet of the
water and at four additional depths, with the lowest just above the sea
bed.

"The modeling study is analogous to taking a dye and releasing it into
water, then watching its pathway," Peacock says.

The dye tracer used in the model has no actual physical resemblance to
true oil. Unlike oil, the dye has the same density as the surrounding
water, does not coagulate or form slicks, and is not subject to chemical
breakdown by bacteria or other forces.

Peacock and her colleagues stress that the simulations are not a
forecast because it is impossible to accurately predict the precise
location of the oil weeks or months from now.

Instead, the simulations provide possible scenarios for the oil
dispersal. The timing and course of the oil slick will be affected by
regional weather conditions and the ever-changing state of the Gulf's
Loop Current, neither of which can be predicted more than a few days in
advance.

The dilution of the oil relative to the source also will be impacted by
bacterial degradation and other conditions, which are not included in
the simulations.

What is possible, is to estimate a range of possible trajectories, based
on the best understanding of how ocean currents transport material. The
oil trajectory that actually occurs will depend on both on the
short-term evolution of the Loop Current, which feeds into the Gulf
Stream, and on the state of the overlying atmosphere.

Oil has been spilling into the Gulf of Mexico since April 20 when the
oil rig Deepwater Horizon exploded and caught fire. Oil giant BP, which
leased the rig to drill a test well 18,000 feet below the seafloor has
not been able to stem the flow of oil from the broken wellhead.

Now, 45 days after the spill began, an estimated 540,000 to 1.25 million
barrels of oil have entered the waters of the Gulf of Mexico, according
to statements by the National Incident Command's Flow Rate Technical
Group and an addition estimate given by Incident Commandert U.S. Coast
Guard Admiral Thad Allen in a news briefing this week. Some of this oil
has evaporated or been collected by skimmer boats or burned on the
surface of the water.

The spill is located in a relatively stagnant area of the Gulf, and the
oil so far has remained relatively confined near the Louisiana and
Alabama coastlines, although there have been reports of small amounts in
the Loop Current. Oil has come ashore in Louisiana, Alabama and
Mississippi.

The model simulations show that a liquid released in the surface ocean
at the spill site is likely to slowly spread as it is mixed by the ocean
currents until it is entrained in the Loop Current. At that point,
speeds pick up to about 40 miles per day, and when the liquid enters the
Atlantic's Gulf Stream it can travel at speeds up to about 100 miles
per day, or 3,000 miles per month.

The six model simulations released today all have different Loop Current
characteristics, and all provide slightly different scenarios of how
the oil might be dispersed. The simulations all bring the oil to south
Florida and then up the East Coast. However, the timing of the oil's
movement differs depending on the configuration of the Loop Current.

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