|August 14, 2013|
Arctic methane: What's the story?
|The Arctic. What pops into your head when you hear those words? Polar bears, icebergs, freezing temperatures? These days, you might also think about the declining sea ice, and the possibility of the Northwest Passage opening up for ships. In fact, the Arctic is warming twice as fast as the global average, so you might associate the Arctic with "warming" as well as "freezing" these days.|
One reason why the Arctic is warming faster than other areas is to do with "positive feedbacks", where any warming feeds more warming. For example, warmer summers mean more sea ice melts. The sea ice is white and reflects sunlight back out to space, whereas the exposed seawater is dark, meaning that it absorbs more sunlight and gets even warmer. Another positive feedback comes from the greenhouse gas methane. The amount of methane released by wetlands increases with temperature. As methane is a greenhouse gas, more methane causes more warming, leading to the release of even more methane. Small changes can be amplified by these positive feedbacks, so it's all the more important to try and quantify -- and maybe even predict -- them.
It's the methane emissions that we are trying to understand in the MAMM project (which stands for Methane in the Arctic -- Measurements and Modelling). The Arctic is a relatively unexplored wilderness, as it is vast and much of it difficult to reach. There are a handful of stations collecting continuous measurements of methane in the Arctic air, but there aren't nearly enough to get a good idea of what's going on.
This summer, we are going out to the Arctic to try and gather enough data to paint a better picture of how much methane is being released, and where it's ending up. On the ground, we'll have a team of fearless scientists in the wetlands (fearless against the huge mosquitoes at least), measuring how much methane is released by different types of wetland vegetation, essentially by placing a container over a patch of land and then measuring how much methane gets captured in the container. The wetland methane comes from microbes in the soil that produce it as a metabolic byproduct.
Then we've got the road trip, where some of the more adventurous among us will drive around remote parts of the European Arctic in a car, collecting bags of air along the way. Of course these aren't just the kind of plastic bags that you get in the supermarket -- they are airtight and coated with a non-stick, unreactive material (like your frying pan at home), so the air remains intact and can be taken back to the lab for analysis.
One of the things we will analyse is the isotopic signature in the methane, which is a bit like taking the fingerprint of the air samples. Different sources of methane (CH4) have different fractions of the carbon-13 isotope (carbon with 7 neutrons instead of the more common 6), so by measuring how much carbon-13 is in a sample you can tell if it's from biological sources like wetlands, or from other sources like fossil fuels.
For example, the gas that we burn in our homes has a higher fraction of carbon-13 compared to wetland methane. This is an incredibly powerful way of knowing the source of the methane you have measured, so we will be able to tell whether any methane we measure has come from wetlands, gas fields or other sources.
The wetland measurements will look in detail at the local methane, then the road trip will sample across the whole region, and finally we'll be taking the UK's atmospheric research aircraft (ARA) to take measurements across an even wider swathe of the Arctic. The converted jet plane, run by the Facility for Airborne Atmospheric Measurements (FAAM), has most of the passenger seats replaced by large pieces of instrumentation to measure the atmosphere. There's an excitingly-named quantum cascade laser, which measures methane from air that is sucked in from outside into the instrument. Other instruments measure methane at a distance below the aircraft ("remote sensing"), or back in the lab from samples. These instruments on-board the aircraft will help us to see the bigger picture, to try and scale up the detailed local measurements and see what impact the Arctic has on methane worldwide. We will use computer models to help us do this, alongside the measurements.
The ARA will be taking off and landing from Kiruna airport in northern Sweden, so most of the MAMM team will be based there in August and September 2013. The team is made up of: instrument scientists, who look after and calibrate the instruments on board; the team who run the aircraft, including pilots, engineers and cabin crew (scientists need caffeine and air sickness pills to function properly, especially when it's a bit bumpy!); and mission scientists, who coordinate where to fly to get the best data, and make sure the whole thing comes off smoothly. Be it the weather not playing ball, travel sickness, or some essential bit of kit breaking at an inopportune moment, there is usually something to keep us busy! As much as we want to make super precise and accurate measurements, we still have to go out in to the real world to get the data, and we all know how messy the real world can be! But dealing with that is part of the job, and part of the fun of it.