We return with some more info from the land of unknown, the land that is very important for our own land, but of which we do not seem to want to know more, as we are strangely comfortable with the unknown. I'm talking about methane, of course, the potent greenhouse gas of which enormous quantities lie stored under the frozen cap of Arctic soil and sea bed.
We regularly return to this topic, the last time being 4 months ago when this so-called Arctic time bomb was the centre of media and blogosphere attention for a couple of days. This time we hear again from East Siberian Arctic Shelf experts Natalia Shakhova (that image on the top right belongs to her) and Igor Semiletov who have a new paper out called Ebullition and storm-induced methane release from the East Siberian Arctic Shelf, published yesterday in Nature Geoscience.
Shakhova has spent the past decade compiling data on the East Siberia Arctic Shelf through research cruises and flyovers of the region. She published initial results in 2010, which showed that methane has been escaping at hot spots where vents have formed from a combination of geothermal heat as well as warmer river water flowing into the region. Those results showed that 7 teragrams of methane is bubbling to the surface annually. That's roughly the equivalent of 10 percent of the methane emissions from U.S. oil and natural gas production and transmission in 2012.
The new research refined those results, showing the amount of methane reaching the surface is more than double those previous estimates. In all, Shakhova and her colleagues estimate that 17 teragrams are escaping each year, though the new study says the estimates are likely on the conservative end. Shakhova said those totals are on par with emissions from the Arctic tundra.
One of the reasons for the revised estimates was more rigorous measurements using an unmanned underwater vehicle with advanced sonar technology. It provided a clearer image of the seafloor and the amount of methane escaping from vents.
Shakhova's research also shows that annual bottom water temperatures have increased 0.9°F over the past 14 years while summer temperatures have increased 1.8°F over the same period. That’s due in large part to increased runoff from rivers, which generally have warmer water than the Siberian Sea. Other research has pegged that increase at 7 percent from 1936 to 1999.
That the estimate of annual release is now twice as big than previously thought, is very interesting in itself, but personally I'm more intrigued by the claim that Arctic storms cause more methane to make it to the atmosphere, instead of dissolving in the water column.
In my survey of the literature on (persistent) Arctic cyclones back in June I noted how a lot of models predict that a combination of Arctic sea ice and land masses that become snow-free earlier and earlier in spring, could lead to more cyclonic activity in the Arctic. As we saw this melting season, it could be a negative feedback preserving more sea ice, but we learn now that it could also cause more methane from clathrates to reach the atmosphere. Every advantage has its disadvantage, it seems.
Stephanie Paige Oghbrun at Scientific American has this on storms:
Storms bring up more methane
Pulses of the methane bubbles are often triggered by storms, which churn up the water and allow the bubbles to quickly make their way up to the surface, the study found. Storms are already common in the area and may increase with climate change, leading to more methane pulses.
Shakhova's research team used sonar to target bubbles of methane rising up from the seafloor. They calculated the amount of methane being released from the bubbles to the atmosphere at 17 teragrams per year, which is close to the amount being released from the Arctic tundra.
"This means that the East Siberian Arctic Shelf is at least as significant a source of methane to the atmosphere as Arctic tundra, which is thought to be one [of the] major sources of methane in the Northern Hemisphere," Shakhova said.
Unfortunately, we're still stuck with the same caveats and uncertainty regarding the exact contribution of thawing methane deposits to the increase of greenhouse gases in the atmosphere. I hope this changes in years to come.
I for one am not comfortable with this unknown.
Remember, you can track methane yourself on MethaneTracker.org.
Update November 30th:
Commenter wili linked to this video from last summer showing an extended interview with lead author Natalia Shakhova: