Methane leaking into atmosphere at alarming rate
March 7th, 2010 by Jim JustMethane is leaking from the East Siberian Arctic Shelf into the atmosphere at an alarming rate, says a press release from the National Science Foundation.
Climate scientists have long worried that global warming could unlock the vast quantities of the greenhouse gas methane that are frozen in the Arctic permafrost, kicking off a feedback loop that could end in catastrophe. Now, an international research team led by University of Alaska Fairbanks scientists Natalia Shakhova and Igor Semiletov has found signs that it may already be happening.
The East Siberian Arctic Shelf is shallow, 50 meters (164 feet) or less in depth, which means it has been alternately submerged or terrestrial, depending on sea levels throughout Earth’s history. During the Earth’s coldest periods, it is a frozen arctic coastal plain, and does not release methane. As the Earth warms and sea level rises, it is inundated with seawater, which is 12-15 degrees warmer than the average air temperature.
The press release quotes Shakhova:
It was thought that seawater kept the East Siberian Arctic Shelf permafrost frozen. Nobody considered this huge area.
Top left: Bubble plumes (probably dominated by CH4) rising from the seafloor registered by geophysical instrumentation. Top right: Seismic image showing gas charged sediments and gas release from the bottom. Bottom left: Positions of oceanographic stations with bathymetry lines. Bottom right: Fluxes of CH4 venting to the atmosphere over the ESAS. Source: Shakhova et al.
The study, “Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf”, is published in the March 5 edition of the journal Science. It shows that the permafrost under the East Siberian Arctic Shelf, long thought to be an impermeable barrier sealing in methane, is perforated and is starting to leak large amounts of methane into the atmosphere. Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.
A quote from the study in article at Green Car Congress captures the scientific community’s reluctance to sound alarmist:
Although the oceanic CH4 flux should be revised, the current estimate is not alarmingly altering the contemporary global CH4 budget. These findings do change our view of the vulnerability of the large sub-sea permafrost carbon reservoir on the ESAS; the permafrost “lid” is clearly perforated, and sedimentary CH4 is escaping to the atmosphere.
To discern whether this extensive CH4 venting over the ESAS is a steadily ongoing phenomenon or signals the start of a more massive CH4 release period, there is an urgent need for expanded multifaceted investigations into these inaccessible but climate-sensitive shelf seas north of Siberia.
In this New York Times article, Dr. Shakhova reiterates the notes of scientific caution:
I would not go so far as to suggest any implications. We are at the very beginning of research.
The permafrost contains 1.5 trillion tons of frozen carbon – about twice as much carbon as contained in the atmosphere – much of which would be released as methane. As a greenhouse gas, Methane is 25 times more potent than CO2 over a 100 year time horizon but 72 times as potent over 20 years. Atmospheric concentrations of methane have more than doubled since pre-industrial times.