Scientists Find That Tons Of Oil Seep Into The Gulf Of Mexico Each Year

[Cees Binkhorst]

REPLY TO: D66 at nic.surfnet.nl

Het verschil met de Deepwater spill is dus de hoeveelheid en concentratie.

Groet / Cees

http://www.sciencedaily.com/releases/2000/01/000127082228.htm
ScienceDaily (Jan. 27, 2000) — Twice an Exxon Valdez spill worth of oil
seeps into the Gulf of Mexico every year, according to a new study that
will be presented January 27 at the Ocean Sciences Meeting in San
Antonio, Texas.

But the oil isn't destroying habitats or wiping out ocean life. The ooze
is a natural phenomena that's been going on for many thousands of years,
according to Roger Mitchell, Vice President of Program Development at
the Earth Satellite Corporation (EarthSat) in Rockville Md. "The
wildlife have adapted and evolved and have no problem dealing with the
oil," he said.

Oil that finds its way to the surface from natural seeps gets broken
down by bacteria and ends up as carbon dioxide, a greenhouse gas. So
knowing the amount of fossil fuel that turns to carbon dioxide naturally
is important for understanding how much humans may be changing the
climate by burning oil and gas.

Using a technique they developed in the early 1990s to help explore for
oil in the deep ocean, Earth Satellite Corporation scientists found that
there are over 600 different areas where oil oozes from rocks underlying
the Gulf of Mexico. The oil bubbles up from a cracks in ocean bottom
sediments and spreads out with the wind to an to an area covering about
4 square miles.

"On water, oil has this wonderful property of spreading out really
thin," said Mitchell. "A gallon of oil can spread over a square mile
very quickly." So what ends up on the surface is an incredibly thin
slick, impossible to see with the human eye and harmless to marine animals.

When oil spreads out over water, surface tension causes it to act like a
super-thin sheet of Saran Wrap, flattening down small waves on the ocean
surface. To spot the oil slicks, EarthSat scientists use radar data from
Canadian and European satellites. The oil slicks stand out in the radar
image because they return less of the radar signal than the wavy surfaces.

To get an estimate of how much oil seeps into the Gulf each year, the
researchers took into account the thickness of the oil-only a hundredth
of a millimeter, the area of ocean surface covered by slicks, and how
long the oil remains on the surface before it's consumed by bacteria or
churned up by waves. "The number is twice the Exxon Valdez's spill per
year, and that's a conservative estimate," said Mitchell.

With funding from NASA, EarthSat researchers began this work in the
early 1990s using Landsat satellite and radar data to identify marine
oil seeps for petroleum exploration. The method has had amazing success.
Drilling for oil in the ocean is extremely expensive, and with radar
data, oil companies have a much better shot at finding oil deposits.

In the future, EarthSat hopes to refine this method using data from
NASA's new EO-1 satellite, set for launch in June 2000. A sensor aboard
EO-1 may be able to tell gas from oil and better pinpoint the source of
the slick.
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http://oils.gpa.unep.org/facts/natural-sources.htm
Crude oil and natural gas seeps naturally out of fissures in the ocean
seabed and eroding sedimentary rock. These seeps are natural springs
where liquid and gaseous hydrocarbons leak out of the ground (like
springs that ooze oil and gas instead of water). Whereas freshwater
springs are fed by underground pools of water, oil and gas seeps are fed
by natural underground accumulations of oil and natural gas (see USGS
illustration). Natural oil seeps are used in identifying potential
petroleum reserves.

As pointed out by the National Research Council (NRC) of the U.S.
National Academy of Sciences, "natural oil seeps contribute the highest
amount of oil to the marine environment, accounting for 46 per cent of
the annual load to the world's oceans. -- Although they are entirely
natural, these seeps significantly alter the nature of nearby marine
environments. For this reason, they serve as natural laboratories where
researchers can learn how marine organisms adapt over generations of
chemical exposure. Seeps illustrate how dramatically animal and plant
population levels can change with exposure to ocean petroleum".

# U.S. Geological Survey (USGS): Basics about oil and gas seeps • Seeps
and the environment • Natural oil and gas seeps in California.
# U.S. Minerals Management Service (MMS): Natural oil and gas seepage in
the coastal areas of California.
# Sciency Daily: "Scientists find that tons of oil seep into the Gulf of
Mexico each year". Article published in 2000.
# U.S. National Academy of Sciences: Oil in the sea III: Inputs, fates
and effects. Report 2002 by the National Research Council (NRC)
Committee on Oil in the Sea: Inputs, Fates, and Effects. See also U.S.
National Academies press release about the conclusions in the NRC
Report, and Web Extra on Oil (including summary of sources of oil). See
also references to the figures published in the 1985 NRC report: on the
Ocean Planet Exhibition web site, and on the web page Oil in the sea:
About offshore oil and gas. (U.S.) National Ocean Industries Association.
# U.S. NOAA: General oil spill questions (FAQs). U.S. National Oceanic
and Atmospheric Administration (NOAA) Office of Response and Restoration.
# Caspian Environment Programme: Natural oil seeps in the Caspian Sea.
# U.S. NASA: Tons of oil seep into the Gulf of Mexico each year. Earth
Observatory. U.S. National Aeronautics and Space Administration (NASA).
# APPEA: Discovery: Explore the world of oil and gas: Oceans and oil
spills. Australian Petroleum Production and Exploration Association (APPEA).
# GESAMP: "Impact of oil and related chemicals and wastes on the marine
environment". GESAMP Report 50, 1993. Not available online, but the
figures referred to can also be found in the online article "Oil
pollution of the sea".
# UN Atlas of the Ocean: The impact of marine pollution. Report (1980)
by Douglas J. Cuisine and John P. Grant. Table published on the UN Atlas
of the Oceans web site.
NOAA describe a natural seepage area in California: "One of the
best-known areas where this happens is Coal Oil Point along the
California Coast near Santa Barbara. An estimated 2,000 to 3,000 gallons
of crude oil is released naturally from the ocean bottom every day just
a few miles offshore from this beach".

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