Arctic winter observations show higher-than-expected methane emissions
A new study led by researchers fromNASA's Jet Propulsion Laboratory (JPL) and San Diego State University(SDSU) has examined the amount of methane gas escaping from theArctic – a key component of global warming. The results go againstconventional theory, finding that a much larger amount of the gas escapes during the Arctic winter than previously thought.
The observations focused on the amountof methane – a greenhouse gas that has a big impact of atmosphericwarming – escaping from the Arctic tundra, caused largely by thedecomposition of embedded organic matter. It's important to monitorthese emissions, as it's thought that climate change maysignificantly increase the amount of gas escaping, especially thatcurrently caught in a stable layer of frozen soil called permafrost.
The new readings aren't the first timethat we've looked at the Arctic methane emissions. In fact,scientists have been using specialized equipment to accurately recordthe level of emissions for decades. However, there's one big problemwith how things have been done up until this point – nearly allrecordings have been made during the short Arctic summer.
For the winter months, which accountfor 70 to 80 percent of the year, climate change models have beenrelying purely on speculation. Those predictions generally follow atheme – that because of the frozen ground, methane emissions dropto almost zero during the winter.
Unfortunately, and thanks to the newstudy, we now known that the assumption isn't just too simplistic,but it's actually entirely wrong. While the ground does freeze upmore in the winter than the summer, it's a little more complicatedthan current models predict. When temperatures drop to around 32 °F (0 °C), the top and bottom parts of theuppermost layer of the ground – known as the active layer –freeze, but the central section remains insulated, continuing tobreak down organic matter throughout the coldest periods of the year.
To determine exactly how much methaneis emitted by that central layer, the researchers upgraded fivesampling towers above the Arctic Circle in Alaska, enabling them togather data throughout the year, making recordings between June 2013and January 2015. The results were instantly alarming, with the studyfinding that a large part of the total methane emissions from theregion occurred during the colder months.
To check that their results wererepresentative of the entire Arctic region, the researchers comparedtheir findings to readings taken by aircraft, flying over the regionas part of NASA's Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE). Aligning the two sets of data, the team foundthat the CARVE readings supported those of its own work, showing thatmethane continues to be emitted long after the surface freezes during the wintermonths.
With the results varying sosignificantly from predictions, and given that methane is such asignificant driver of atmospheric warming, it's now essential thatclimate models be adjusted accordingly.
"It is now time to work more closelywith climate modellers and assure these observations are used toimprove model predictions, and refine our prediction of the globalmethane budget," said SDSU's Donatella Zona.