Calling the Methane Bomb Squad
October 15, 2014
This is an important post, which I’ll be updating soon. This is part one. See other parts here.
It’s ironic that in the course of spending most of my time trying to raise awareness about how serious the climate issue is, recently I’ve had to be on the side of seeking to tamp down unnecessary alarm and fatalism that I’m seeing, particularly online.
I’ve been planning to do a piece on the whole “undersea methane bomb” idea, and have been interviewing key scientists in this area for quite a while. I was not planning to release a finished piece for some time- as this is an area where I feel the need to step very carefully.
I’ve posted before that I believe the cottage industry that has developed around catastrophic scenarios of methane bombs, burps, and belches is probably not accurate, and definitely not helpful at this time.
Now in the last two weeks there’s been a bit of a kerfuffle following Dr. Gavin Schmidt’s presentation at a conference in the UK, where he trained some pretty intense fire on the whole issue, and in the process made some pretty good points – most compellingly, that when we look back at previous interglacial periods, even when where it has been warmer than today for long periods, when we are pretty sure significant amounts of land ice melted, and sea levels were considerably higher, – we don’t see a methane belch.
Gavin has since been attacked in some rather conspiracy-flavored blog posts, basically with the idea that alternative views were somehow not allowed at the conference, although Dr. Peter Wadhams, who is associated with the so called Arctic Methane Emergency Group, and very much on the side of alarm for this issue, did present.
There is a rather vigorous back channel discussion going on around this, most serious people coming down on the side of some concern, no burning hair or clothing, but wanting more info.
I’m by no means ready to go with a carefully digested piece on this, but given the fooferaw going on now, I thought I would start sharing some of the interviews I have with credible scientists on this issue. Above, one of the most credible, Dr. Carolyn Ruppel, who chairs the US Geological Survey gas hydrates research group. Dr. Ruppel was an author of the recent, widely publicized finding of methane seepage along the US East Coast:
Natural methane leakage from the seafloor is far more widespread on the U.S. Atlantic margin than previously thought, according to a study by researchers from Mississippi State University, the U.S. Geological Survey, and other institutions.
Methane plumes identified in the water column between Cape Hatteras, North Carolina and Georges Bank, Massachusetts, are emanating from at least 570 seafloor cold seeps on the outer continental shelf and the continental slope. Taken together, these areas, which lie between the coastline and the deep ocean, constitute the continental margin. Prior to this study, only three seep areas had been identified beyond the edge of the continental shelf, which occurs at approximately 180 meters (590 feet) water depth between Florida and Maine on the U.S. Atlantic seafloor.
Cold seeps are areas where gases and fluids leak into the overlying water from the sediments. They are designated as cold to distinguish them from hydrothermal vents, which are sites where new oceanic crust is being formed and hot fluids are being emitted at the seafloor. Cold seeps can occur in a much broader range of environments than hydrothermal vents.
“Widespread seepage had not been expected on the Atlantic margin. It is not near a plate tectonic boundary like the U.S. Pacific coast, nor associated with a petroleum basin like the northern Gulf of Mexico,” said Adam Skarke, the study’s lead author and a professor at Mississippi State University.
The gas being emitted by the seeps has not yet been sampled, but researchers believe that most of the leaking methane is produced by microbial processes in shallow sediments. This interpretation is based primarily on the locations of the seeps and knowledge of the underlying geology. Microbial methane is not the type found in deep-seated reservoirs and often tapped as a natural gas resource.
Most of the newly discovered methane seeps lie at depths close to the shallowest conditions at which deepwater marine gas hydrate can exist on the continental slope. Gas hydrate is a naturally occurring, ice-like combination of methane and water, and forms at temperature and pressure conditions commonly found in waters deeper than approximately 500 meters (1640 feet).
“Warming of ocean temperatures on seasonal, decadal or much longer time scales can cause gas hydrate to release its methane, which may then be emitted at seep sites,” said Carolyn Ruppel, study co-author and chief of the USGS Gas Hydrates Project. “Such continental slope seeps have previously been recognized in the Arctic, but not at mid-latitudes. So this is a first.”
Most seeps described in the new study are too deep for the methane to directly reach the atmosphere, but the methane that remains in the water column can be oxidized to carbon dioxide. This in turn increases the acidity of ocean waters and reduces oxygen levels.
Shallow-water seeps that may be related to offshore groundwater discharge were detected at the edge of the shelf and in the upper part of Hudson Canyon, an undersea gorge that represents the offshore extension of the Hudson River. Methane from these seeps could directly reach the atmosphere, contributing to increased concentrations of this potent greenhouse gas. More extensive shallow-water surveys than described in this study will be required to document the extent of such seeps.
Some of the new methane seeps were discovered in 2012. In summer 2013 a Brown University undergraduate and National Oceanic and Atmospheric Administration Hollings Scholar Mali’o Kodis worked with Skarke to analyze about 94,000 square kilometers (about 36,000 square miles) of water column imaging data to map the methane plumes. The data had been collected by the vessel Okeanos Explorer between 2011 and 2013. The Okeanos Explorer and the Deep Discoverer remotely operated vehicle, which has photographed the seafloor at some of the methane seeps, are managed by NOAA’s Office of Ocean Exploration and Research.
“This study continues the tradition of advancing U.S. marine science research through partnerships between federal agencies and the involvement of academic researchers,” said John Haines, coordinator of the USGS Coastal and Marine Geology Program “NOAA’s Ocean Exploration program acquired state-of-the-art data at the scale of the entire margin, while academic and USGS scientists teamed to interpret these data in the context of a research problem of global significance.”
The study, Widespread methane leakage from the sea floor on the northern US Atlantic Margin, by A, Skarke, C. Ruppel, M, Kodis, D. Brothers and E. Lobecker in Nature Geoscience is available on line
To the question of “what about undersea methane hydrates?” – most common answer heard is that microbial action takes a pretty substantial bite out of methane seeps. Now we have a new study focused on that, and finding a lot of previously unidentified actors.
CORVALLIS, Ore. – Since the first undersea methane seep was discovered 30 years ago, scientists have meticulously analyzed and measured how microbes in the seafloor sediments consume the greenhouse gas methane as part of understanding how the Earth works.
The sediment-based microbes form an important methane “sink,” preventing much of the chemical from reaching the atmosphere and contributing to greenhouse gas accumulation. As a byproduct of this process, the microbes create a type of rock known as authigenic carbonate, which while interesting to scientists was not thought to be involved in the processing of methane.
That is no longer the case. A team of scientists has discovered that these authigenic carbonate rocks also contain vast amounts of active microbes that take up methane. The results of their study, which was funded by the National Science Foundation, were reported today in the journal Nature Communications.
“No one had really examined these rocks as living habitats before,” noted Andrew Thurber, an Oregon State University marine ecologist and co-author on the paper. “It was just assumed that they were inactive. In previous studies, we had seen remnants of microbes in the rocks – DNA and lipids – but we thought they were relics of past activity. We didn’t know they were active.
“This goes to show how the global methane process is still rather poorly understood,” Thurber added.
The biochemical reactions involved when the microbes process the methane and sulphate causes the water surrounding the organisms to become more alkaline, which in turn leads carbonate ions to precipitate out of the water and form minerals such as calcium carbonate (CaCO3), the stuff of ordinary chalk. The presence of the minerals in sediments around methane seeps — sites where waters containing the dissolved gas leaks out of the sea floor — have long been used as evidence for past methane consumption, helping scientists to estimate the length of time such seeps have been or were active2.
But the study by Orphan and her colleagues strongly suggests that the carbonates are not just dead rock. The researchers analysed two dozen samples collected in and around deep-sea methane seeps off the coasts of Oregon, California and Costa Rica. Tests revealed the presence of genetic material associated with methane-consuming microbes, says Orphan.
Those results alone do not divulge whether the genes came from living or dead microbes, so the team ran further tests in the lab. They bathed samples of the carbonate rock in sea water infused with methane. But instead of ordinary methane, they used methane that included the radioactive isotope carbon-14, rather than the stable, and much more common, carbon-12. Over time, the carbon-14 was incorporated into the carbonate minerals. This was a sign that there were methane-munching microbes living in the samples — even in relatively nonporous rocks in which the microbes would have had little access to the radioactive methane, says Orphan.
Scientists already knew that such carbonates lock away carbon from a greenhouse gas that might otherwise warm the planet’s atmosphere. But the team’s results suggest that the reservoir is much more active than previously suspected.
“These data are very believable,” says John Pohlman, a biogeochemist with the US Geological Survey in Woods Hole, Massachusetts. “Maybe we’ve been underestimating the amount of methane oxidation going on in the sea-floor setting.”
I’ll be posting more excerpts from this and other interviews as I get them prepared. Juggling several balls here right now.
New Yale video coming very soon as well.