If you stay up too long sampling, you tend to go a bit stir-crazy. Here on the bog front we go out every two hours, day and night, to collect air samples. It’s quite a balancing act, especially after hours and hours of no-sleep.
But now we’re seeing ghosts…too much night work? One ghost, to be specific. He’s a Ghost Reindeer. He haunts us all day (and days are very long indeed). He’s outside our cabin, then he pops up by the met tower, then by the Polaria building. I’m sure he has a name — Santa’s White Knight perhaps? He’s very elegant, almost white all over, with splendid velvety antlers, all clad in white plush. I’m sure he has a name, but we’re calling him Sammy. A bit to the south of us (yes, south) is Rovaniemi, the Santa Claus town where Santa seems to have a business running theme parks, so I suppose Sammy is on summer vacation. Now Santa Claus was the very proper Saint Nicholas of Myra, who attended the Council of Nicea (and would have known the Archbishop of York well, who was also there), so maybe Sammy was quietly sent here by Santa to look after us and NCAS, with its strong Yorkshire connections. Methane’s a bit like Sammy. It pops up unexpectedly in all sorts of places. Yes of course everyone knows about cows, for what is a cow but a walking tropical wetland (at least from a microbe’s viewpoint)? But wrong end – it’s cow breath, bovine eructation, not flatulence. Then there are gas leaks (methane doesn’t smell by the way – that smell is deliberately put in) and coal mine vents. But one of the biggest sources of methane pops up almost everywhere across the planet where rain falls – the swamps and wetlands. Like Sammy, look around and there it is next to you, bubbling away gently.
A great part of the north is covered in ‘boreal” forest wetlands (boreal is from Greek for north). When you try to work out the world’s methane emissions, we can measure how much is in the air. We can even make a good guess about how much is injected into the northern air, as compared with the tropics and the southern hemisphere. But that only gives us the total amount of northern methane production. What makes northern methane? There are giant gas fields in the north that leak; there are big fires making methane that’s carried in their smoke; there is methane leaking from permafrost lakes. And there are the vast soggy forests, the endless Canadian muskeg, the lakes of Finland, the swamps of western Siberia. How much do they make? Here carbon isotopes come to help. Carbon-12 is a little lighter and easier to fit into biological molecules. Carbon-13 is more abundant in methane from thermal sources, like fires or coalfields. But to use these isotopes we have to work out the isotopic signatures of the main sources; especially forest. How do we do that? Lots of ways, but one of the most direct is to sit up all night. Swamps make methane, and it is emitted into the air. In the daytime as the wind blows, methane mixes into the background. At night, and especially in the small still hours around dawn, the methane that is emitted from the wetlands sits close to ground, in the cold still air. We sample that, every two hours through the night and the day, over 24 hour periods. Plot up the results on a plot of methane isotope ratio versus 1/methane concentration (the reciprocal of the methane concentration) and the intercept on the 0 of the 1/conc axis (i.e. infinite concentration) is the isotopic signature of the wetland emission. Once you’ve got that you can use it is working out a global isotopic budget for methane. All methanes are NOT the same – some are ‘light’, rich in carbon-12 and come from wetlands (and probably differ according to where the wetland is, tropics or north); some are ‘heavy’, rich in carbon-13 and come from fires or coalmine leaks, and some are in the middle and are from landfills or maybe Russian gas (Dutch gas is much ‘heavier’). That means we can sniff a methane-rich wind, wind it back by reversing the weather forecast computer, and find where it came from, and identify the source of the methane. Well, it’s not as easy as that, but that’s the intention. It’s a methane telescope. For example, Rebecca Fisher and our team showed that the input of methane to Arctic air in summer seems mainly to come from wetlands.
That means staying up all night. Mary Fowler and I have just come back from two weeks in Canada, doing exactly that in northern Ontario and Saskatchewan. Now we’re at Sodankyla, doing the same thing. There’s a difference though – Sammy is here to look after us, and few mosquitoes. And the wonderfully welcoming saints of the Finnish Met Office (FMI) have most generously given us a fine cabin to sleep in and make strong coffee – a wonderful place by a riverside. Could science be more fun? Marvellous! (But please excuse the yawning – it’s been nearly 30 hours by now by the bogside, almost as bad as being a junior doctor.) And now off to collect the next samples… –Prof Euan Nisbet, Royal Holloway University of London