Methane Released from Under The Sea

Methane Released from Under The Sea

January 2008  - Methane, a potent 
greenhouse gas, is emitted in great quantities as bubbles from seeps on 
the ocean floor near Santa Barbara. About half of these bubbles dissolve 
into the ocean, but until now scientists have not known what happens to 
this dissolved gas. 
Today, researchers at the University of California-Santa Barbara said they 
have discovered that only one percent of the dissolved methane escapes 
into the air - a finding that is good news for the climate. 
Methane heats the Earth 23 times more than the most prevalent greenhouse 
gas, carbon dioxide, when averaged over a century, scientists have found. 
The potency of methane and the fact that thousands of seep fields exist in 
the sea floor around the world makes fate of methane bubbles from seeps an 
important environmental question. 
David Valentine, associate professor of Earth Science at UC Santa Barbara 
who led the study, said the one percent finding enabled the authors to 
conclude that most of the methane is transported below the ocean's surface 
- away from the seep area. 
Then it is oxidized by microbial activity. "We showed that the currents 
control the fate of the gas and supply it to bacteria in a way that allows 
them to destroy the methane," said Valentine. 
Coal Oil Point, COP, one of the world's largest and best studied seep 
regions, is located along the northern margin of the Santa Barbara 
Channel. 

The amount of methane released from COP seeps is around two million cubic 
feet per day, according to Valentine. About 100 barrels of oil oozes out 
of this area as well. 
"We found that the ocean has an amazing capacity to take up methane that 
is released into it - even when it is released into shallow water," said 
Valentine. 
"Huge amounts of gas are coming up here, creating a giant gas plume. Until 
now, no one had measured the gas that dissolves and moves away, the 
plume," he said. 
Valentine hypothesized that the methane is oxidized by microbial activity 
in the ocean, thus relieving the ocean of the methane "burden." 
To confirm this hypothesis, Valentine and lead author Susan Mau, a 
postdoctoral fellow in Valentine's lab, tracked the plume down current 
from the seeps at 79 surface stations in a 280 square kilometer study 
area. They found that the methane plume spread over 70 square kilometers. 
By boat, the authors sampled the water on a monthly basis. They found 
variable methane concentrations that corresponded with changes in surface 
currents. They also found that more wind releases more methane into the 
atmosphere. 
This research effort is the first time that the gas plume that dissolves 
and moves away from Coal Oil Point has been studied. 
The results will soon be published as a cover story in the journal 
"Geophysical Research Letters." 

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