“Natural” release of methane from methane hydrates by earthquakes is more common and more significant than has been thought or accounted for in climate models.
The inescapable conclusion is that effects being attributed by the demonisation of carbon to man made carbon dioxide emissions (even if real) may well be partly due to the natural release of such methane. The global temperature pause for the last 17 years or so and the clear but small decline in global temperatures for the last 5 years is quite clear. At the same time emissions from fossil fuel combustion have been steadily increasing. These are a clear indication that the supposed linkage between carbon dioxide concentration and man-made carbon dioxide emissions on climate is very suspect if not completely broken.
It is also becoming increasingly clear that climate models – even though very complicated – are far too simplistic and just don’t (can’t) take all factors into account. Clouds, aerosols, particulates, solar effects, lunar cycle effects through the tides, ocean cycles and now earthquakes are all poorly understood and largely ignored in climate models. There is far more in the realms of the unknown about the climate than is known. We don’t even know what we don’t know.
David Fischer, José M. Mogollón, Michael Strasser, Thomas Pape, Gerhard Bohrmann, Noemi Fekete, Volkhard Spiess & Sabine Kasten, Subduction zone earthquake as potential trigger of submarine hydrocarbon seepage, Nature Geoscience (2013) doi:10.1038/ngeo1886
Here we present geochemical analyses of sediment cores retrieved from the convergent margin off Pakistan. We find that a substantial increase in the upward flux of gas occurred within a few decades of a Mw 8.1 earthquake in 1945—the strongest earthquake reported for the Arabian Sea. Our seismic reflection data suggest that co-seismic shaking fractured gas-hydrate-bearing sediments, creating pathways for the free gas to migrate from a shallow reservoir within the gas hydrate stability zone into the water column. We conservatively estimate that 3.26×108 mol of methane have been discharged from the seep site since the earthquake. We therefore suggest that hydrocarbon seepage triggered by earthquakes needs to be considered in local and global carbon budgets at active continental margins.
Dr. Fischer and his colleagues analyzed sediment cores taken in 2007 from two locations in the northern Arabian Sea where hydrates were present and seepage was occurring. They found chemical signatures in the cores suggesting that the methane flow greatly increased sometime in the mid-20th century. Looking through seismic records, Dr. Fischer found that a magnitude 8.1 quake occurred in the area in 1945. The quake, which was centered less than 15 miles from where the cores were taken, and a resulting tsunami, killed up to 4,000 people.
The conclusion was inescapable, Dr. Fischer said. “The quake broke open gas-hydrate sediments and the free gas underneath migrated to the surface.” The hydrates themselves did not dissolve. “They remain there,” he said.
Dr. Fischer said the researchers chose the core locations in the Arabian Sea because they wanted to get a better understanding of how methane seepage was related to tectonics, and the area is in an active zone where one of the earth’s tectonic plates slides beneath another. But they were not thinking about the effect of individual earthquakes, and his discovery of the 1945 quake in the records “was probably a moment I’ll never forget,” he said.
The upward flow of methane is continuing today, and the researchers do not know when it might stop. All told, they estimate that nearly 10 million cubic yards of methane have been released from the core sites over the years. But that is a conservative figure, Dr. Fischer said, because immediately following the quake the flow would have been much higher.
Tags: Earthquake, methane, methane emissions, methane hydrates, Subduction
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