Posted on 02/26/2003 11:23:11 AM PST by blam
Source: Woods Hole Oceanographic Institution
Date: 2003-02-26
Fossil Records Show Methane In Seafloor Sediments
Released During Periods Of Rapid Climate Warming Scientists have found new evidence indicating that during periods of rapid climate warming methane gas has been released periodically from the seafloor in intense eruptions. In a study published in the current issue of the journal Science, Kai-Uwe Hinrichs and colleagues Laura Hmelo and Sean Sylva of the Woods Hole Oceanographic Institution (WHOI) provide a direct link between methane reservoirs in coastal marine sediments and the global carbon cycle, an indicator of global warming and cooling.
Molecular fossils from methane-consuming bacteria found in sediments in the Santa Barbara Basin off California deposited during the last glacial period, (70,000 to 12,000 years ago), indicate that large quantities of methane were emitted repeatedly from the seafloor during warmer phases of the last ice age. Methane, one of the major greenhouse gases, is stored on the seafloor as an ice-like solid known as methane hydrate.
Previous evidence for such massive eruptions was based on isotopic properties of calcite shells of foraminifera, microscopic marine animals commonly called forams. Because a variety of factors could lead to very similar signals in their shells, that evidence has remained controversial.
The preserved molecular remnants found by the WHOI team result from bacteria that fed exclusively on methane and indicate that large quantities of this powerful greenhouse gas were present in coastal waters off California. The team studied samples that were deposited between 44,000 and 37,000 years ago.
"For the first time, we are able to clearly establish a connection between distinct isotopic depletions in forams and high concentrations of methane in the fossil record," Hinrichs, an assistant scientist in the Institution's Geology and Geophysics Department, says. "The large amounts of methane presumably released during one event about 44,000 years ago suggest a mechanism different from those underlying the emissions at warmer periods, i.e. slow decomposition of methane hydrate triggered by warming of bottom waters. The sudden release of these enormous quantities of methane was probably caused by landslides and melting of the methane hydrate."
Since there was already indirect evidence of methane eruptions in the Santa Barbara Basin area, Hinrichs and colleagues looked for fossil remnants of bacteria that would have flourished only under high concentrations of methane. In a 44,000-year-old sediment sample, a distinct type of biomarker representing bacterial communities that oxidize methane in the absence of oxygen provided evidence for an abrupt, catastrophic release of methane, presumably trapped as hydrate below the sea floor.
The WHOI team's data, from sediment cores taken by the Ocean Drilling Program off southern California, show that substantial quantities of methane were released at least several times during the past 60,000 years, leading to periodic fluctuations in the levels of methane in deep waters in the Santa Barbara Basin.
The researchers say increased bottom water temperatures could mobilize or release significant amounts of methane hydrate in shallow waters. According to some current estimates, there are about 10,000 billion tons of methane stored beneath the ocean and on continents. In comparison, the contribution of humans to the atmosphere's inventory of greenhouse gases by fossil-fuel burning amounts to about 200 billion tons of carbon in the form of carbon dioxide. If even a small portion of the stored methane were to escape into the atmosphere, the resulting greenhouse warming would be catastrophic.
"It was a surprise to find this sort of evidence," says Hinrichs, who was originally looking for evidence indicating mechanisms other than methane. "Although this research tells us something about the amount of methane consumed by bacteria in the ocean, it doesn't tell us anything about methane emissions into the atmosphere because neither forams nor methane biomarkers record the portion of methane that escaped out of the ocean. But one thing is for sure, our results clearly show that relatively minor environmental changes can have a major impact on sensitive coastal regions with yet unknown consequences for climate and biota."
Hinrichs plans to look for similar evidence elsewhere to determine whether this process, as a driver of climate variation, happened simultaneously at other locations around the world. This work, Hinrichs says, is just the beginning of better understanding of the role of methane in the carbon cycle and ultimately on climate on geologic time scales.
"We have a very poor understanding of the biogeochemical mechanisms that control production, destruction and accumulation of methane in sediments underlying the ocean," he notes. "We need to understand the big picture of what drives methane and the carbon cycle and the actual impact of methane emissions from hydrates on climate."
WHOI is a private, independent marine research and engineering, and higher education organization located in Falmouth, MA. Its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the ocean's role in the changing global environment. Established in 1930 on a recommendation from the National Academy of Sciences, the Institution is organized into five departments, five interdisciplinary institutes and a marine policy center, and conducts a joint graduate education program with the Massachusetts Institute of Technology.
The new-to-the-area pilot instructor made a navigation error and they all ran out gas before making it back to land - no mystery involved at all. IIRC, their course was reconstructed and they went out and photographed them on the bottom.
warming temps-->released methane-->global warming-->(repeat)
Positive feedbacks are not stable, and would not just now be showing up after 6 billion years of earth history.
I plead brain-fart.
The more general version goes something like this:
I found one expert who says something my cult can at least spin it its favor. The statements of this expert are the only real evidence. Utter and absolute proof is required that this evidence is false and/or that anything else is true.
If you mean the link to the USGS article by Gold of the same title, it does not answer my questions. Gold points to oil found in the well he drilled in Europe's largest meteor crater, the Siljan Ring. The fractured rock there did indeed contain an oil. Gold's paper does report the relative ratios of sterane compounds commonly used for the purposes of pinpointing the origin of the oil.
You might be interested in the following excerpts from a report on the oil found in Gold's well by a panel of US and Swedish geologists, petroleum geochemists, and geophysicists (from All that Glitters):
Unmistakable evidence found by geochemical analysis of oils, oil-stained rocks, and organic rocks points to the Ordovician bituminous Tretaspis Shale as the source for the oil found in the Siljan crater. [The] contention that the oil is abiogenic is without merit.Siljan data show little evidence that abiogenic gas exists. The Siljan oil, which [is claimed] to be abiogenic is clearly not...
I'm no expert in this field (I'm an engineer not a geochemist), but that is my conclusion too, based on the plot of sterane data in Gold's article. I've used those particular sterane compounds before to resolve issues of petroleum origin. I suspect the oil Gold found migrated through fractures caused by the meteor.
It could. Such happens in barns around the world all the time. One spark and disasster.
The French are presently installing pipes to the bottom of the two culprit lakes to release the gasses slowly.
Professor Mike Baille in his book, Exodus To Arthur, reveals ancient Irish and English legends about 'the lands without life' and speculated that one of these gas clouds may have settled over that area and killed everything. He goes into some pretty convincing details that I won't here.
LOL. Methane is odorless. But other gases aren't.
Actually, it does. Two factors: 1) large methane bubble displaces air/oxygen--airplane engine doesn't run any more, 2) if airplane flies thru big enuff bubble, and pilots don't have oxygen mask--pilots lose consciousness. Result in both cases is "...disappearance of Flight 19..."
Interesting. What about the interference from water on IR? Has anyone in the last 10 years measured an ambient increase in CO2?
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