One might ask, by looking at this title, just what good there can be that comes from methane. Not only is it the smelly export product of the world’s beef population, but it is also a more potent warmer of the planet’s atmosphere than carbon dioxide.
Well, there isn’t much good to say about methane. But what one can say is that its affects on the ocean from deep ocean seeps is less than previously feared.
Let’s start off by explaining what it is I’m talking about first, before we get in to why what I said is good news. A seep, or at least one type, is according to Wikipedia the movement of liquid hydrocarbons to the surface through fractures and fissures in the rock and between geological layers.
So when I say that there are deep ocean seeps of methane, I refer to the seeps that exist on the ocean floor. Seeps can expel anything from oil to methane, and the results of the latter have been hitherto unstudied.
Researchers at the University of California, Santa Barbara have rectified that however, by studying one of the largest seeps, the Coal Oil Point seep off their coastline. About three square kilometers, the seep releases around two million cubic feet of methane per day, according to David Valentine, associate professor of Earth Science at UC Santa Barbara.
Until now however, just how much of that methane makes it to the surface and in to the atmosphere has been unknown. Valentine and his team have found however that, thankfully, only about one percent of the dissolved methane escapes in to the surrounding atmosphere from the Coal Oil Point seep.
This research will be published as the cover story in Volume 34 of Geophysical Research Letters, and is the first time that a study has focused on the plume – the gas that dissolves and moves away from the seep.
Part of the study was explaining just how the methane dissipates. Valentine hypothesized that the methane was oxidized by microbial activity in the surrounding ocean, and went about proving his hypothesis with the aid of lead author Susan Mau, a postdoctoral fellow in Valentine’s lab. Together, they tracked the plume down the current from the seeps from 79 surface stations, in a study area 280 square kilometers.
They found that the methane plume which dissipates from the seep point spread over 70 square kilometers of the ocean. Sampling the water on a monthly basis, they found variable methane concentrations that corresponded with changes in surface currents. They also found that the more wind there is above the ocean, the more methane is then released in to the atmosphere.
Backing up their findings was a mass spectrometer that was towed behind their boat. This allowed them to acquire very high resolution chemical information about the methane. “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.
University of California, Santa Barbara via ENN – Good News About Ocean Methane