Not-So-Tiny Bubbles and Global Warming: News from UCSB

A team of UC Santa Barbara scientists went diving one day in 2002 in an area of the Santa Barbara Channel called Shane Seep, when the earth did something alarmingly rude, though not unexpected.

She belched — a “massive blowout of methane,” that “sounded like a freight train,” as Science Blog relates the story.

“Other people have reported this type of methane blowout, but no one has ever checked the numbers until now,” said Ira Leifer, lead author and an associate researcher with UCSB’s Marine Science Institute. “Ours is the first set of numbers associated with a seep blowout.” Leifer was in a research boat on the surface at the time of the blowouts.

Aside from underwater measurements, a nearby meteorological station measured the methane “cloud” that emerged as being approximately 5,000 cubic feet, or equal to the volume of the entire first floor of a two-bedroom house. The research team also had a small plane in place, flown by the California Department of Conservation, shooting video of the event from the air.

Leifer explained that when this type of blowout event occurs, virtually all the gas from the seeps escapes into the atmosphere, unlike the emission of small bubbles from the ocean floor, which partially, or mostly, dissolve in the ocean water. Transporting this methane to the atmosphere affects climate, according to the researchers. The methane blowout that the UCSB team witnessed reached the sea surface 60 feet above in just seven seconds. This was clear because the divers injected green food dye into the rising bubble plume.

Atmospheric methane is 20 times more potent than carbon dioxide as a greenhouse gas, and is the most abundant organic compound in the atmosphere. The ocean floor’s release of trapped methane hydrate — a form of ice that contains a large amount of methane within its crystal structure — in bubble form is both a symptom and a cause of global warming, according to UCSB geological science professor James Kennett’s theory.

When ocean temperatures rise, the methane releases are more likely to occur in the form of blowouts, like the one UCSB’s researchers saw. Those bubbles make a marked difference in the quantity of methane in the atmosphere, “thereby initiating a feedback cycle of abrupt atmospheric warming.”

Studies of seabed seep features suggest such events are common in the area of the Coal Oil Point seep field and very likely occur elsewhere.The authors explain that these results show that an important piece of the global climate puzzle may be explained by understanding bubble-plume processes during blowout events. The next important step is to measure the frequency and magnitude of these events. The UCSB seep group is working toward this goal through the development of a long-term, seep observatory in active seep areas.

(Not to make light of this disturbing news, but there is a bright side. Here’s one big blowout in Santa Barbara that can’t be blamed on Wendy McCaw.)