Time for an Arctic update and a bit of “original” research. There’s been quite a bit of polar news around, and a rapid freeze-up is underway in the Arctic – so rapid that some are declaring that the sea ice is “back to normal” for the time of year, based on this graph from the Arctic Regional Ocean Observing System in Norway, which shows sea ice area climbing up towards to the average for 1979-2007, within one standard deviation (the grey area). On the other hand, if you look at the equivalent graph at Cryosphere Today, you’ll see that ice area is 1.25m km2 below the average – which in CT’s case is 1979-2000. So the ice is approaching normal, only if you define “normal” as including the significant ice reductions over the last seven years. How encouraging. But this autumn’s freeze-up has been pretty rapid. Does that mean that it’s been unusually cold up there? I thought I’d take a look…
Tag: Siberia
Something in the air (methane mystery)
Atmospheric methane levels “shot up” in 2007, according to a paper in this week’s Geophysical Research Letters (MIT news release — Rigby, M., R. Prinn, et al (2008), Renewed growth of atmospheric methane, Geophys. Res. Lett., doi:10.1029/2008GL036037, in press. PDF here for AGU members.). This confirms NOAA’s announcement in April that methane levels were on the increase after a decade of stability, but adds a new twist to the data.
One surprising feature of this recent growth is that it occurred almost simultaneously at all measurement locations across the globe. However, the majority of methane emissions are in the Northern Hemisphere, and it takes more than one year for gases to be mixed from the Northern Hemisphere to the Southern Hemisphere. Hence, theoretical analysis of the measurements shows that if an increase in emissions is solely responsible, these emissions must have risen by a similar amount in both hemispheres at the same time.
A rise in Northern Hemispheric emissions may be due to the very warm conditions that were observed over Siberia throughout 2007, potentially leading to increased bacterial emissions from wetland areas. However, a potential cause for an increase in Southern Hemispheric emissions is less clear.
A possible explanation might be a global reduction in the amount of hydroxyl free radical (OH) in the atmosphere. OH “mops up” methane (and other stuff), and is sometimes called the atmosphere’s cleaner or “detergent”. Unfortunately, measuring atmospheric OH is difficult.
“The key thing is to better determine the relative roles of increased methane emission versus any decrease in the rate of removal,” Prinn said. “Apparently we have a mix of the two, but we want to know how much of each” is responsible for the overall increase.It is too early to tell whether this increase represents a return to sustained methane growth, or the beginning of a relatively short-lived anomaly, according to Rigby and Prinn.
Any increase in atmospheric methane is not good news. A possible reduction in OH is also disturbing, because it might indicate that pollution (from all sources, methane, industry, coal burning etc) is beginning to overwhelm the atmosphere’s ability to cleanse itself. Both together would be very bad news indeed.
[Update: Comments from a CSIRO scientist and co-author here.]
From Russia, with love
The work of the Swedish and Russian team on the Yakov Smirnitsky has finally found its way into the mainstream media, with Steve Connor at the Independent in London reporting the final post at the ISSS-08 blog I’ve been linking to for the last month or two. It’s not good news – they’ve found dramatic evidence of “methane chimneys” – bubbles of methane emerging form the sea floor and reaching the surface (instead of dissolving), and recorded atmospheric concentrations 100 times the normal background level. Connor reports on an email exchange with the Swedish team:
“We had a hectic finishing of the sampling programme yesterday and this past night,” said Dr Gustafsson. “An extensive area of intense methane release was found. At earlier sites we had found elevated levels of dissolved methane. Yesterday, for the first time, we documented a field where the release was so intense that the methane did not have time to dissolve into the seawater but was rising as methane bubbles to the sea surface. These ‘methane chimneys’ were documented on echo sounder and with seismic [instruments].”
At some locations, methane concentrations reached 100 times background levels. These anomalies have been seen in the East Siberian Sea and the Laptev Sea, covering several tens of thousands of square kilometres, amounting to millions of tons of methane, said Dr Gustafsson. “This may be of the same magnitude as presently estimated from the global ocean,” he said. “Nobody knows how many more such areas exist on the extensive East Siberian continental shelves.
In his piece, Connor uses the “standard” global warming potential for methane of 20 times CO2 (actually 25 is the official IPCC number), and correctly notes the short atmospheric lifetime of the gas. However, over that short lifetime (around 12 years), CH4’s GWP is more like 70 times CO2. Current global methane level is about 1750 ppb (1.75 ppm), so using a GWP of 25 it has the same warming effect as 43.75 ppm CO2. On the shorter 10 year time scale, that’s more like 122 ppm CO2. But Semiletov and his team on the Yakov Smirnitsky have measured concentrations 100 times greater than “normal”, which implies a local warming effect equivalent to 12,200 ppm CO2.
Luckily, it’s getting dark up there, but methane release on that scale might slow down the winter cooling in the region of the chimneys. Methane seeps in lakes can keep holes open in winter ice, so if persistent holes start appearing in the satellite maps of sea ice over the Siberian seas, we’ll know there’s a big issue (the holes would have to be huge to be seen in the data). We urgently need more info on the extent of the problem. There’s a lot of methane under the Siberian seas – we can only hope it stays there.
The NZ Herald reprints the Independent story, and the Guardian puts its own spin on it (a note of caution). This is a story that needs wider coverage, more informed scientific debate, and great deal more study. I hope Connor’s piece doesn’t get dismissed as hype, or “alarmism”. You don’t need to be an alarmist to find this stuff alarming…
I’m (possibly/probably) a loser
The National Snow & Ice Data Centre in the USA has declared that this year’s minimum Arctic sea ice extent has been reached – 4.52 million square kilometres on September 12th, only 390,000 km2 more than the record 2007 minimum (and 2.24 m km2 below the 1979-2000 average minimum). It looks as though their line may bump along the bottom of the graph for a while, so there may be some potential for that number to reduce a little. Their figure for Sept 12 is 9.4 percent above the 2007 minimum, so unless there’s some unprecedented melt over the next couple of weeks, I am prepared to accept that I have lost my bet with Malcolm (see comments here and at Poneke! here), which was based on NSIDC numbers. My cheque book is at the ready.
Dragging the river
In an update to my last post on Arctic methane, I linked to a Swedish team blogging their research on the Yakov Smirnitsky, a Russian vessel currently cruising the seas to the north of Siberia. The most recent post there is fascinating, but the Google translation rather difficult to follow, so I asked Magnus Westerstrand, who first drew my attention to the blog at Eli’s place, if he could tidy up the translation. And he did, overnight. Thanks Magnus, have a schnapps on me. Here are some extracts [full text at Magnus’ blog]:
At around 110 degrees easterly longitude, when we where wrestling with drift ice in western Laptev Sea, we discovered two new areas where methane concentrations in both the water and in the air above clearly exceeded the normal methane concentration in Arctic.
The blogger, Örjan Gustafsson, then goes on to describe how the methane deposits were formed, and how the gas might now be escaping.