Scientists Find Good News About Methane Bubbling Up From the Ocean Floor Near Santa Barbara

Dec 20, 2007

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 the fate of this dissolved methane remains uncertain. Researchers at the University of California, Santa Barbara have discovered that only one percent of this dissolved methane escapes into the air –– good news for the Earth's atmosphere.

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. Thousands of seep fields exist in the ocean bottom around the world, according to David Valentine, associate professor of Earth Science at UC Santa Barbara. Valentine along with other members of UCSB's seeps group studied the plume of methane bubbles that flows from the seeps at COP.

Their results will soon be published as the cover story in Volume 34 of Geophysical Research Letters. This research effort is the first time that the gas that dissolves and moves away from COP, the plume, has been studied.

The amount of methane release 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. Methane warms the Earth 23 times more than carbon dioxide when averaged over a century. Thus the fate of the methane bubbles from the seeps is an important environmental question.

"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."

Valentine hypothesized that the methane is oxidized by microbial activity in the ocean, thus relieving the ocean of the methane "burden."

To arrive at 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. Overall, they discovered that about one percent of the dissolved methane escapes into the atmosphere in the area they studied, a long-term average. This lead the authors to hypothesize that most of the methane is transported below the ocean's surface –– away from the seep area. Then it is oxidized by microbial activity.

To back up their findings of their surface sampling of the water, the scientists used a mass spectrometer hauled behind the boat as well. This equipment allowed for very high-resolution chemical information about the methane. This effort showed no significant difference in the numbers.

"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.

Valentine said that while the seeps at COP are among the largest in the world, they can be found just about anywhere.

Source: University of California, Santa Barbara

Explore further: Severe ozone depletion avoided

Related Stories

Ocean currents disturb methane-eating bacteria

May 04, 2015

Offshore the Svalbard archipelago, methane gas is seeping out of the seabed at the depths of several hundred meters. These cold seeps are a home to communities of microorganisms that survive in a chemosynthetic ...

Ocean currents impact methane consumption

Apr 20, 2015

Large amounts of methane - whether as free gas or as solid gas hydrates - can be found in the sea floor along the ocean shores. When the hydrates dissolve or when the gas finds pathways in the sea floor to ...

Scientists take aim at Four Corners methane mystery

Apr 08, 2015

Researchers from several institutions are in the Four Corners region of the U.S. Southwest with a suite of airborne and ground-based instruments, aiming to uncover reasons for a mysterious methane "hot spot" ...

Recommended for you

Evolution of the Antarctic ice sheet

31 minutes ago

ULB study sheds a new light on the stability of the Antarctic ice sheet. It shows for the first time that ice rises (pinning points that keep the floating parts of ice sheets in place) are formed during the transition between ...

Severe ozone depletion avoided

19 hours ago

We are already reaping the rewards of the Montreal Protocol, with the ozone layer in much better shape than it would have been without the UN treaty, according to a new study in Nature Communications.

Location matters in the lowland Amazon

May 25, 2015

You know the old saying: Location, location, location? It turns out that it applies to the Amazon rainforest, too. New work from Carnegie's Greg Asner illustrates a hidden tapestry of chemical variation across ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

quantum_flux
1.5 / 5 (2) Dec 20, 2007
They should capture the methane in solution and then treat it with heavy doses of chlorine to the breakpoint, and then capture the hydrogen gas that bubbles off.... for free hydrogen at the expense of recoverable chlorine residuals and dissolved carbon dioxide. or is my chemistry off!?
out7x
3 / 5 (2) Dec 21, 2007
A good reason to drill off SantaBarbara.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.