arch 05 6:12 AM

 

Methane bubbles in Arctic seas stir warming fears – (Reuters) — Large amounts of a powerful greenhouse gas are bubbling up from a long-frozen seabed north of Siberia, raising fears of far bigger leaks that could stoke global warming, scientists said. It was unclear, however, if the Arctic emissions of methane gas were new or had been going on unnoticed for centuries — since before the Industrial Revolution of the 18th century led to wide use of fossil fuels that are blamed for climate change. The study said about 8 million tonnes of methane a year, equivalent to the annual total previously estimated from all of the world’s oceans, were seeping from vast stores long trapped under permafrost below the seabed north of Russia. "Subsea permafrost is losing its ability to be an impermeable cap," Natalia Shakhova, a scientist at the University of Fairbanks, Alaska, said in a statement. She co-led the study published in Friday’s edition of the journal Science.
 

– Abstract  – Remobilization to the atmosphere of only a small fraction of the methane held in East Siberian Arctic Shelf (ESAS) sediments could trigger abrupt climate warming, yet it is believed that sub-sea permafrost acts as a lid to keep this shallow methane reservoir in place. Here, we show that more than 5000 at-sea observations of dissolved methane demonstrates that greater than 80% of ESAS bottom waters and greater than 50% of surface waters are supersaturated with methane regarding to the atmosphere. The current atmospheric venting flux, which is composed of a diffusive component and a gradual ebullition component, is on par with previous estimates of methane venting from the entire World Ocean. Leakage of methane through shallow ESAS waters needs to be considered in interactions between the biogeosphere and a warming Arctic climate.

 

Natalia Shakhova, Igor Semiletov: Arctic seabed methane stores destabilizing, venting –  

– The research results, published in the March 5, 2010, edition of the journal Science, show that the under the East Siberian Arctic Shelf, long thought to be an impermeable barrier sealing in , is perforated and is leaking large amounts of methane into the atmosphere. Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming. “The amount of methane currently coming out of the East Siberian Arctic Shelf is comparable to the amount coming out of the entire world’s oceans,” said Shakhova, a researcher at UAF’s International Arctic Research Center. “Subsea permafrost is losing its ability to be an impermeable cap.” Methane is a more than 30 times more potent than carbon dioxide. It is released from previously frozen soils in two ways. When the organic material—which contains carbon—stored in permafrost thaws, it begins to decompose and, under oxygen-free conditions, gradually release methane. Methane can also be stored in the seabed as methane gas or methane hydrates and then released as subsea permafrost thaws. These releases can be larger and more abrupt than those that result from decomposition.
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