Tuesday 30 July 2013

Methane emissions in Siberia and seismic activity

Extended Interview Extracts With Natalia Shakhova - 2012


Earthquakes Contribute to 
Global Warming by 
Releasing Methane from 
Ocean Floor

Earthquakes contribute to global warming by releasing the highly potent greenhouse gas, methane, from the ocean floor

29 July, 2013

A study conducted by Swiss and German scientists has uncovered a natural source of greenhouse gas emission - methane.  Researchers emphasize that climate scientists need to consider the amount of methane being released as earthquakes rip open ocean floors, in order to better understand the various sources of greenhouse gases.

Researchers from the University of Bremen discovered that an underwater quake that occurred in Pakistan 70 years ago ripped opened the sea bed and released the potent greenhouse gas, 'methane', into the atmosphere.  

"We suggest there is a new source that they might want to consider in the future," David Fischer, a postdoctoral researcher at the University of Bremen in Germany and the lead author of the study, was quoted in The New York Times.

The researchers analyzed the sediment cores gathered in 2007 from two locations in the northern Arabian Sea. Referred to as the Makran Subduction zone, the plate boundary has triggered the most terrible and deadliest earthquakes like the one that occurred in 1945 in Pakistan. An 8.0 magnitude earthquake in Pakistan gave rise to a tsunami claiming around 4,000 lives, reports. LiveScience.

It is well known that sea floors are an ideal location for the formation of methane as deep ocean waters and sea beds are cold and methane hydrates are stable under excess pressure and low temperatures. The pressure below the water depth of 350 meters is just right to stabilize the hydrates.

For the present study, the researchers analyzed sediments taken from locations where the cores indicated the presence of large amount of methane. On calculating the rate of methane in the cores they estimated that there had been a significant increase in the level of gas since the 1945 earthquake.

The researchers calculated that over the past decade nearly 7.4 million cubic meters of methane has escaped to the surface.

"Based on several indicators, we postulated that the earthquake led to a fracturing of the sediments, releasing the gas that had been trapped below the hydrates into the ocean," Fischer said.  

Compared to carbon dioxide, methane is a more potent greenhouse gas. A recent study by researchers at the University of Cambridge and Erasmus University in the Netherlands states that the release of methane in the Arctic could increase the melting of sea ice and the resultant change in climate will cost the global economy up to $60 trillion in the coming decades.

From several years scientists have suspected a strong association between earthquakes and underwater methane bursts but this the first study that confirms this association and has been documented in the journal Nature Geoscience.

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