ST. PETERSBURG — Two years before the Deepwater Horizon explosion, scientists from SRI International took readings on the levels of methane in the Gulf of Mexico less than 10 miles from the rig. Last year, they went back and did it again.
Now, after the rig blew up and gushed oil for more than 80 days, SRI's scientists from St. Petersburg have returned to the same area just northwest of the disaster and taken fresh readings.
They found levels of methane — a particularly potent greenhouse gas — are now 100 times higher than normal, SRI scientists said. They can't say for sure it's from BP, said SRI director Larry Langebrake, but "it is a sign that says there are things going on here that need to be researched."
Higher levels of methane can cause problems both in the gulf and around the globe.
Seeps in the ocean floor put small amounts of methane into the water, where it's consumed by naturally occurring microbes. Higher concentrations of methane can cause the microbe population to boom, gobbling up oxygen needed by other marine life and producing dead zones in the gulf.
The other problem, said Langebrake: "Methane is a stronger greenhouse gas than carbon dioxide."
In fact, it's 20 times worse than carbon dioxide, trapping lots more heat close to the earth, contributing to climate change. And it can hang around in the atmosphere for up to 15 years.
In addition to the increased amount of methane, the SRI tests "did show indications that the methane was further up in the water column than we had seen it before," said Carol Lutken of the University of Mississippi, which is part of a consortium with SRI that has been doing the tests.
The findings from SRI are not the first to suggest that Deepwater Horizon is gushing methane as well as oil. Scientists from Texas A&M who tested the water within 5 miles of Deepwater Horizon reported finding methane concentrations that were 100,000 times higher than normal.
However they do suggest that the methane may be spreading throughout the gulf just like the underwater plumes of oil found by oceanographers from the University of South Florida and other academic institutions.
SRI is still analyzing the results. "We're still trying to understand what those things are telling us," Langebrake said.
SRI, based in Menlo Park, Calif., is the nonprofit scientific research institute that began as the research arm of Stanford University. In 2006 St. Petersburg persuaded the company to open a marine technology operation here to take advantage of research being produced at nearby state and federal facilities. Its offices opened last year near Albert Whitted Airport.
SRI is part of a consortium of institutions that has been studying natural seeps in the ocean floor for what until recently was known as the U.S. Minerals Management Service. The seeps come from deposits of methane gas that, because they are so deep beneath the ocean, have frozen into icy crystals.
Disturbing those deposits — say, by drilling an oil well through them — can turn that solid methane into a liquid, leaving the ocean floor unstable, explained Lutken.
Worse, the freed gas may explode. One theory on the cause of the Deepwater Horizon disaster blames a methane gas bubble for causing the explosion and fire that sank the rig. There have been rumors that a similar methane explosion could cause a tsunami, a concern that government officials say is unfounded.
Generally the oil industry tries to avoid methane areas during drilling for safety reasons. But the U.S. Energy Department wants to find a way to harvest fuel from those methane deposits, Lutken said.
For its research, the consortium persuaded the government to let it take over an area of the gulf floor that turned out to be in the same deepwater canyon as BP's well, Lutken said. But they're to the northwest and on a slope, just over half a mile deep, while Deepwater Horizon's well is a mile below the surface.
That means that the methane in higher levels that SRI discovered during the most recent tests on June 25 and 26 has apparently been flowing upslope, Lutken said.
What may turn out to be as important as those higher methane readings, though, are the earlier test results from research cruises before the oil rig explosion, she said, because they offer a snapshot of what "normal" should look like.
"We have what it was like in the neighborhood before Deepwater Horizon occurred," she said.