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Subject: C8) How will a hurricane be affected by an oil slick?
How will an oil slick be affected by a hurricane?
Contribution taken from this
NOAA factsheet.
How will a hurricane be affected by an oil slick?
- Most hurricanes span an enormous area of the ocean (200-300 miles) - far
wider than most oil spills.
- If the slick remains small in comparison to a typical hurricane's general
environment and size, the anticipated impact on the hurricane would be minimal.
- The oil is not expected to appreciably affect either the intensity or the
track of a fully developed tropical storm or hurricane.
- The oil slick would have little effect on the storm surge or near-shore
wave heights.
- Evaporation from the sea surface fuels tropical storms and hurricanes. Over
relatively calm water (such as for a developing tropical depression or
disturbance), in theory, an oil slick could suppress evaporation if the layer
is thick enough, by not allowing contact of the water to the air.
- With less evaporation one might assume there would be less moisture
available to fuel the hurricane and thus reduce its strength.
- However, except for immediately near the source, the slick is very patchy.
At moderate wind speeds, such as those found in approaching tropical storms
and hurricanes, a thin layer of oil such as is the case with the current slick
(except in very limited areas near the well) would likely break into pools on
the surface or mix as drops in the upper layers of the ocean. (The heaviest
surface slicks, however, could re-coalesce at the surface after the storm
passes.)
- This would allow much of the water to remain in touch with the overlying
air and greatly reduce any effect the oil may have on evaporation.
- Therefore, an oil slick is not likely to have a significant impact on the
hurricane.
Will there be oil in the rain related to a hurricane that
passed over an oil slick?
- No. Hurricanes draw water vapor from a large area, much
larger than the area covered by oil, and rain is produced in
clouds circulating the hurricane.
How will an oil slick be affected by a hurricane?
- The high winds and seas will mix and "weather" the oil which can help
accelerate the biodegradation process.
- The high winds may distribute oil over a wider area, but it is difficult
to model exactly where the oil may be transported.
- Movement of oil would depend greatly on the track of the hurricane.
- Storms' surges may carry oil into the coastline and inland as far as the
surge reaches. Debris resulting from the hurricane may be contaminated by oil
from the Deepwater Horizon incident, but also from other oil releases that may
occur during the storm.
- A hurricane's winds rotate counter-clockwise. Thus, in VERY GENERAL TERMS:
- A hurricane passing to the west of the oil slick could drive
oil to the coast.
- A hurricane passing to the east of a slick could drive the oil
away from the coast.
- However, the details of the evolution of the storm, the track,
the wind speed, the size, the forward motion and the intensity are all
unknowns at this point and may alter this general statement.
- All of the sampling to date shows that except near the leaking well, the
subsurface dispersed oil is in parts per million levels or less. The hurricane
will mix the waters of the Gulf and disperse the oil even further.
- Our previous experience has been primarily with oil spills that occured
because of the storm, not from an existing oil slick and an ongoing release of
oil from the seafloor.
- The experience from hurricanes Katrina and Rits (2005) was that oil
released during the storms became very widely dispersed.
- Dozens of significant spills and hundreds of smaller spills occurred from
offshore facilities, shoreside facilities, veseel sinkings, etc.
Learn more about NOAA's response to the Deepwater Horizon oil
spill
here.
Last Revised : June 9, 2010
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