Content provided by Douglas Main, OurAmazingPlanet
A research cruise has discovered 40 previously unknown gas seeps on the
seafloor off the U.S. East Coast. The plumes of gas are almost
certainly methane, also known as natural gas, according to government
scientists.
Methane is a potent greenhouse gas
due to its ability to absorb heat, but the released gas is not likely
to reach the ocean surface in significant quantities and affect the
climate, said Carolyn Ruppel, a researcher with the U.S. Geological
Survey, which collaborated in the research. Neither is the amount of gas
likely to warrant commercial interest, she said.
The seeps were found in four clusters, three of them about 100 miles
(160 kilometers) southeast of Nantucket, Mass. The other cluster,
consisting of 17 of the seeps, was mapped about 90 miles (147
kilometers) east of Cape Henry, Va., according to a release from the
National Oceanographic and Atmospheric Administration, which led the
expedition.
Methane seeps are important to find and study since they involve the
transfer of carbon from the ground to the atmosphere, which is important
for getting an accurate picture of climate change in terms of how much
gas is emitted naturally and how much is emitted by humans, Ruppel told
OurAmazingPlanet. Methane also can oxidize in water and contribute to ocean acidification, she said. (Video: Humans Hit the Oceans Hard)
The NOAA ship Okeanos Explorer mapped the locations between Nov. 2 and
Nov. 20 using multibeam sonar, which produces detailed images of the
seafloor by calculating the amount of time and distance it takes for
sound waves to travel from the ship to the seafloor and back. During
that time the ship and its instruments mapped 5,970 square miles (15,460
square kilometers) of seafloor, an area larger than Connecticut,
according to the NOAA release. The mapping was primarily done along the
continental slope, where the North American continent ends and drops
into the Atlantic Ocean basin. Sound waves were also used to visualize
the rising plumes of gas.
It's unclear exactly where the gas is coming from, Ruppel said. Methane
either can arise from microbial activity in shallow deposits of organic
material, or it can come from more deep-seated processes involving oil
formation. Probably both processes are at work in these different seeps,
she said.
A mere generation ago, methane seeps were virtually unheard of off the East Coast. Since the early 1980s, however, several seeps have been found.
"With advanced multibeam sonar, it may become routine to discover seeps
while we systematically explore our poorly known ocean," NOAA scientist
Stephen Hammond said in the statement.
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