Clathrates Fingered for PETM

[Schneibster]

For a long time, geophysicists and paleontologists have had trouble accounting for the PETM.

It happened about nine million years after the end of the dinosaurs. There's been no smoking gun found to account for it; massive peat fires have been postulated, but there's no band of ash to indicate them; a carbon meteorite was proposed, but no debris band like the one from the Chicxulub impact has been found in the geologic record; and volcanic activity has been proposed, but no volcanic ash has been found. The important thing to remember is that there is geologic evidence of the release of some 2,500 Gt of carbon into the atmosphere. The point is, there's been no explanation found for where it came from.

Release of methane clathrates from the ocean floor had previously been proposed, but due to high ocean temperatures before the beginning of the PETM, and the fact that clathrates only exist in a very narrow temperature band which would have been much less physically thick under the ocean floor, it had been dismissed until now. New studies have shown, however, that the higher temperature would have meant that the bacteria creating the methane would have been much more active, thus creating a higher density of methane than we see in the modern ocean, so the clathrates have been returned to the top of the list of potential culprits.

One of the things to keep in mind about this is that there are methane clathrates under the ocean floor today, and that they represent about the same amount of carbon as was released that created the PETM. During that time, the temperature rose 6° C and a mass extinction occurred as a result. And this means that we have evidence that if the clathrates in today's oceans are released, which they will be if things rise a few more degrees- some of them are already subliming- then we can expect the same thing to happen again. This is one of the abrupt climate change scenarios that geophysicists have been warning of for decades, that may occur as a result of global warming. Scary shit. The PETM was not a good time to live on Earth.

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