of Bp oil in gulf
two studies offer confusing
picture of deep-sea plumes
By Janet Raloff
Amajor deep-sea oil-mapping effort reports that as of June an enormous diffuse plume of crude oil generated by
the BP spill roamed deep in the Gulf of
Mexico and appeared disturbingly stable.
Data by a second research consortium
also detected a deep dispersed plume in
June — but its data indicate that the oil
was degrading quickly and may, by now,
be completely gone.
Chris German/Woods hole oCeanoGraphiC institution
Analyses by both groups, published
online in August in Science just a week
apart, point to the difficulty involved
in determining the fate of an estimated
4. 1 million barrels of oil (172.2 million gallons) that spewed into the Gulf following
the Deepwater Horizon accident. Because
most of this oil has never surfaced, concerns abound over its location and persistence, both of which could influence the
pollution’s potential to poison wildlife.
A report online August 19 in Science
describes a diffuse plume of hydrocarbons more than 35 kilometers long.
As this cloud of oil flowed roughly 1,100
meters below the surface, it maintained
a configuration roughly 200 meters high,
up to 2 kilometers wide and traveling at
about 6. 7 kilometers per day.
“We’re not sure why this plume set up
In June, researchers from the Woods Hole oceanographic Institution probed an oil
plume in the gulf of mexico using the Sentry autonomous underwater vehicle.
at this depth,” says lead author Richard
Camilli of the Woods Hole Oceanographic
Institution in Massachusetts, “but it
appears to have persisted for at least several weeks or months. And it appears very
stable, but we really don’t know why yet.”
The buildup of stable deep plumes
makes sense based on the evolving
science of interactions between high-velocity oil and cold, slow-moving waters,
comments Roberto Camassa, who directs
the Carolina Center for Interdisciplinary
Applied Mathematics at the University of
North Carolina at Chapel Hill.
“In our lab experiments, things mainly
get trapped based on their density,” says
Camassa. “So I would expect to find a
somewhat sharp transition in density
down there, and with such stratification
the oil could persist for a long, long time.”
Oil in the plume hasn’t ascended
to the surface, he explains, because if
droplets are small enough, they become
neutrally buoyant and move with the
water. Camassa’s lab studies suggest that
the high-velocity spray of oil from the BP
blowout would essentially have atom-
ized the crude oil into microdroplets.