Natural seeps occur when crude oil leaks from beneath the
sea floor into the water. They form the largest single source of
petroleum in the marine environment, accounting for 45% of
all oil in the world’s oceans. Seeps have existed for millions of
years and are part of the ecosystem in many areas. There are
natural seeps off the coast of West Greenland, off California,
in the northern Mediterranean Sea, in the Caspian Sea and
in the Gulf of Mexico. These areas normally have a thriving
marine ecosystem, despite the natural seep of a significant
amount of oil into the water. Bacteria naturally present in the
seawater feed off this oil and effectively biodegrade it.
Mechanical containment and recovery
If a spill does occur, the rapid containment and recovery of oil
at or near the source is the first goal. Mechanical skimmers can
be used to remove oil from the water surface and transfer it to
a storage vessel. Skimmers work most efficiently on thick oil
slicks: floating barriers, known as oil booms, are used to collect
and contain spilled oil into a thicker layer. A variety of designs
for skimmer and booms have been adapted for Arctic sea
conditions and several have been proven to work well.
Controlled in situ burning
Oil on water or between layers of ice can also be tackled
quickly, efficiently and safely by controlled burning. This
technique works most efficiently on thick oil layers, so the oil
needs to be contained by fire-resistant booms, ice or by a
shoreline. On average, about 80-95% of the oil is eliminated
as gas, 1-10% as soot and 1-10% remains as a residue.
Following the burning, this residue can be recovered from
the water surface. Controlled burning is a proven response
developed over several decades by the oil industry, emergency
response authorities and scientists. This involved extensive
laboratory and tank testing, large-scale field experiments
and lessons from real incidents. Burns can eliminate 1,000
barrels of oil per hour. Through tests over several decades,
in situ burning has been proven to work well in the Arctic.
Dispersants
Chemical dispersants are another method of cleaning up
spills. They have proven highly effective in the Arctic through
extensive testing. Dispersants are like detergents designed