That means 200,000,000 years ago The Methane Bomb went off.
As this in turn led to the extinction of 23 percent of all families and 48 percent of all genera the ocean clathrates can now officially be regarded as mass murderer – also (still) a main suspect in Life on Earth’s 635 million year old cold case and ‘likely guilty’ of the PETM, some 56 million years ago – classified as a ‘lesser mass extinction’.
Methane clathrates, or methane hydrates, are bubbles of methane caught within structures of crystallised water. These are formed over millions of years and are abundant at parts of the ocean floors. The crystallised water – much like ice – depends on constant (high) pressure and (low) temperature to keep intact.
We however no longer live on a constant planet – we see it sliding into a transitional phase. And based on findings in the Earth’s fossil record, witnesses of such –really rather rare– phases usually don’t live to tell.
Indeed, climate change, feedback
Atmospheric warming leads to ocean warming, and that can in turn lead to ‘melting’ of the methane clathrates whereby the greenhouse gas is released to the atmosphere, acting as a positive climate feedback on the initial warming.
Life on Earth must have grown used to the peace and quite of the Triassic period, 205 millions ago. Things had been green, lush, undisturbed and simple for tens of millions of years, with the ocean and –‘right in the middle’– the continent, the one supercontinent, Pangaea.
Then the rift valleys came and geological forces tore Pangaea apart, leading to massive volcanism over extended periods of time – and the release of large amounts of CO2 into the atmosphere. So far this release has been directly linked to the T-J mass extinction.
‘It was the methane feedback’
But the volcanic CO2, the Utrecht scientists say, must have led to no more than an initial warming. Once the warming penetrated to the ocean floors it disturbed the clathrates.
Their measurements, published in Friday’s edition of Science, indicate at least 12,000 gigatonnes of C13-depleted carbon entered terrestrial biology, indicating the release of a minimum of around 16,000 gigatonnes methane “within only 10,000-20,000 years.”
That they think is what created dramatic climate change – and what led to the massive biodiversity decline.
In the same sediments the scientists have also researched fossil spores and pollen, which showed vegetation changes reflecting “strong warming and an enhanced hydrological cycle.”
Modern climate-methane feedback?
The question resounds: could this happen again? Since the PETM the Earth’s oceans have once again had plenty of time to stockpile methane – and the physical mechanisms of warming and melting will not have changed since the Triassic. So the answer should be yes.
So far we are safe, simply because the clathrates are deep. We know the oceans are already warming, but this warming takes time to reach the bottom of the ocean.
Faster CO2 rise, quicker methane release?
Then again the speed with which the ‘temperature shock wave’ travels down through the water depends on the speed of the atmospheric CO2 concentrations increase.
According to lead author Micha Ruhl this speed is now ‘several times faster’ than in the period he researched. So perhaps not count on any delay like the 10,000-20,000 year methane release period at the end of the Triassic.
Sometimes the biggest limitation of paleoscience does not seem to be the fact that we have to look back over all these millions of years, but that even then full analogies to our own little experiment with planet Earth simply do not seem to exist.
© Rolf Schuttenhelm | www.bitsofscience.org