Podcast: Measuring methane above the Arctic

Arctic landscape

Abisko, Sweden

1 April 2014 by Sue Nelson

This week in the Planet Earth podcast, Michelle Cain of the University of Cambridge and Stéphane Bauguitte of the Facility for Airborne Atmospheric Measurements (FAAM) explain how and why they're measuring methane in the atmosphere above the Arctic - a region that's warming twice as fast as anywhere else on our planet.

To assist those who find text-based content more accessible than audio, a transcript of this recording is available below.

Sue Nelson: This time in the Plant Earth podcast, monitoring methane in the Arctic to find out why it is warming twice as fast as anywhere else on our plant. I'm Sue Nelson and I am in one of the hangars at Cranfield University in Bedfordshire, the only UK university with its own operational airport. Now it is used for aerospace training and scientific research and I am beside a plane that is run by the Facility for Airborne Atmospheric Measurements. It is used by atmospheric scientists across the UK, including those who work on the methane in the Arctic Measurements and Modelling project. Dr Michelle Cain from the University of Cambridge is one of them, as is Dr Stéphane Bauguitte who as well as being the flight manager at the Facility for Airborne Atmospheric Measurements also operates the greenhouse gas instrument on board this plane. I think I've got to start with this plane, because this is the size you would expect to go on your holiday.

Dr Stéphane Bauguitte: That's right. This is actually a regional aircraft built in the 80s by BA systems and carries about 100 or so passengers. It is actually the prototype. It was converted as a research platform in 2004. As you will see in a minute it is fully kitted, both in the cabin and also using pylons which are hanging from the wing for remote sensing as well.

Sue Nelson: Michelle, methane in the Arctic, where does this methane come from?

Dr Michelle Cain: The biggest source of methane in the Arctic is from the wetlands, so things like bogs and marshes, fens and actually in the summertime the Arctic is full of them, it is not always completely frozen like it is in the winter and further north. So large parts of Scandinavia, large parts of Canada, Russia, Siberia actually have very big wetlands which are seasonally wetlands so in the wintertime they won't be a big source of methane but in the summertime they will when the temperatures increase and the snow melts.

Sue Nelson: How serious a problem is the methane over the Arctic?

Dr Michelle Cain: Methane is a greenhouse gas and the largest source in the
Arctic and possibly worldwide actually is from wetlands. So it is definitely a big factor. Referring to it as a problem is difficult because it is a natural process. Things like paddy fields are also wetlands and they are a large source that is not really natural because we are growing the rice. The interesting thing about wetlands is that if we're changing the climate from what humans are doing we could be changing what is traditionally seen as a natural process, which is actually about the same size as the anthropogenic source, the manmade source of methane, so it is not just greenhouse gasses are coming from human's, it is actually coming from natural sources as well.

Sue Nelson: Well there is quite a lot of engineering going on at the other planes that are in this hangar and there are two smaller ones right beside us and it looks like there is some pretty hardcore equipment coming out, so why don't we go onboard and it may or may not be quieter but Stéphane you led the way.

Dr Stéphane Bauguitte: Okay, let's go then.

Sue Nelson: Go up the steps into the aircraft itself. Oh yes, there are some people at the end there also doing some work and it has been gutted basically hasn't it? It is filled with boxes and stacks of scientific equipment.

Dr Stéphane Bauguitte: Yes. We are right in the middle of changing the configuration of the cabin for another greenhouse gas project starting next month, in the UK this time.

Sue Nelson: Where is your greenhouse gas instrument?

Dr Stéphane Bauguitte: We've got two systems that are used and if we walk down the cabin you've got one on your left here which is quantum cascade laser, spectrometer, and basically this one measures methane and also nitrous oxide as well which is another greenhouse gas.

Sue Nelson: How sensitive is it?

Dr Stéphane Bauguitte: We can measure to half a billion. We've got another system as well which measures carbon dioxide further down there and other molecules as well like ozone and carbon monoxide, so we have a second methane measurement in this system as well and this is also a spectrometer similar to the quantum cascade laser. They both operate in the infrared spectrum which is where methane absorbs and this is what gives you the global warming is the ability of methane to absorb the energy from the infrared and store it in the atmosphere, and these are in situ measurements. We are drawing the air from outside the cabin into the cabin through those windows and-

Sue Nelson: Oh yes, underneath the windows there is equipment and pipes.

Dr Stéphane Bauguitte: Yeah. So the air is coming through the holes, it goes into the spectrometer and it has got a very long path length inside the cavity, something like 150 metres long, and and we absorb the light from the infrared using the sample within the spectrometer and then looking at the spectroscopy we can tell how much methane is in the air that we draw into the cabin. So you've got large pumps which would be very noisy, so in the cabin we would have to wear a headset because it is a very noisy environment, not just the engines, we've got four engines, four jet engines, so it is quite loud.

Sue Nelson: It's quite loud now and this is when it is on the ground in a hangar. Oh, something has just been switched off as well. What was that being switched off?

Dr Stéphane Bauguitte: They've just switched off the [unintelligible] power in the cabin now for doing some maintenance at the back there, so what you heard there was the air circulation in the cabin, so as you can hear now it is a lot, lot quieter.

Sue Nelson: It's amazing. What is it like, Michelle, being on one of these missions effectively or being on one of these flights?

Dr Michelle Cain: It is really brilliant. As a modeller I normally sit in front of a computer all day and when I do the field work I sit in front of a computer on an aeroplane, but it's much better. It is really great to be there when the measurements are taken so you can really understand how difficult it is taking measurements and you know when you look at the data you have an understanding of what was going on when the data was being collected, it is not just some numbers on a page and the other great things about being a mission scientist, which is what I do on the aircraft, is that I call the shots or me and my team call the shots. So we don't have to worry ourselves with making the instruments work. So there are a number of instrument scientists on board who are slaving away over there-

Sue Nelson: Like you Stéphane.

Dr Michelle Cain: They are huge bits of kit and sometimes it is really hot, especially if you are in the tropics instead of the Arctic, they are slaving away over their instruments getting the best data there and we're just telling the aircraft where to fly really. So we forecast the weather, we plan the flights; we decide where we want to go to take our measurements so we can get the best data possible.

Sue Nelson: How are you using this on the ground, all the measurements that you would get from a flight?

Dr Michelle Cain: It can be quite complicated to analyse the data because you are not just in one place you are taking measurements at different times and different places, so it does make things a bit more complicated. What we're doing in this field campaign is looking at the methane concentrations and also methane isotopes which we use to fingerprint the air, so to try and find out where it has come from because each different source, for example, wetlands or fossil fuels have a different fingerprint, as it were, in the isotopes, so we can try and identify the sources. What I've been doing is using meteorological models to try and work out where the air has come from to try and connect the source locations, so the wetlands or maybe gas fields, with the measurements that we've got combining that with the different concentrations and the isotopic fingerprints.

Sue Nelson: When will this plane be going back to the Arctic?

Dr Stéphane Bauguitte: In June/July for a week long detachment. You follow through the work that has already been conducted in 2012 and 2013.

Sue Nelson: And are there any areas in the Arctic that are particular hotspots for methane?

Dr Michelle Cain: Yeah, this is one question that we're interested in because the wetlands are a very large area and they are not all the same. When you get down onto the ground and actually look there is a variety of different plants and different amounts of waterlogged soil and one question is whether different types of plants or different amounts of wetness or dryness in the soil, different soil types, does that make a difference to the amount of methane that is coming out. That's something that we're just starting to look at. We have colleagues who work on the ground and they get an even shorter straw, I think, going into the bogs, 24 hours a day, to try and see if it changes during the nights or the day and they go into the bogs and take measurements right there within centimetres of these wetlands. They're logging different types of plants that are growing and different amounts of wetness because it is the microbes within the soil that are producing the methane. So when they are waterlogged there is no oxygen so there can't be any aerobic activity. They call them Methanogens; they are just microbes that produce methane when there is no oxygen.

Sue Nelson: And there must be an awful lot of them.

Dr Michelle Cain: Anywhere where there is no oxygen actually, so landfill sites as well as the wetlands and the paddy fields. So we've started looking at this already and we've found that certain types of plants actually give different amounts of methane coming out. So if you look at the data based on what kind of plants go in there, certain plants like cotton grass-type plants seem to be producing more methane and as we were flying around actually we did find certain parts of Scandinavia, areas in Finland that seemed to have more methane above those areas.

Sue Nelson: Well, Dr Michelle Cain and Dr Stéphane Bauguitte, thank you both very much for allowing me to come on board this plane in the hangar and share your research with me. That's the Planet Earth podcast from the Natural Environment Research Council. You can follow us on Facebook and Twitter where we will post some pictures on today's recordings. I am Sue Nelson and thanks for listening.