In the remote northern Arctic, greenhouse gas emissions are likely to come up through icy fissures. Flying over some of the most inaccessible parts of Alaska and northwestern Canada, NASA researchers have spotted a shocking amount of thawing in permafrost, the frozen layer of soil that covers much of the region.
A systematic review published in the journal Geophysical Research Letters it gives us no escape. If this tundra melts, it will release gases from millions of sources of methane and other carbon emissions into the atmosphere, further accelerating global warming.
Today we know the Arctic is heating up twice as fast as anywhere else on Earth, but given how cold and formidable the landscape is, we still don't know where more methane is emitted.
We consider hotspots to be areas that show an excess of 3.000 parts per million of methane in the sensing space between our aerial sensor and the ground. And in the observed area, we detected 2 million of these hotspots.
Clayton Elder, NASA's Jet Propulsion Laboratory.
Does it sound much more than you imagined? It's true. For many months of the year, much of the Arctic is inaccessible to scientists, so ground-based observations have so far only covered a fraction of the region. NASA researchers see this new technology as a breakthrough, which gives us a whole new perspective on the region. And it alarms us not a little.
Sources of methane in the arctic, the survey technique
Using a single infrared spectrometer (known as AVIRIS-NG), the researchers collected over 400 sets of data. The flights were made in the months of July and August 2017, covering approximately 30.000 square kilometers of Arctic land (12.000 square miles). In total, the trips have collected approx a billion careful observations of methane emissions and the results reveal a clear dispersion pattern centered on water.
"AVIRIS-NG was used in previous methane surveys. Those surveys had focused on man-made emissions in populated areas and with important infrastructures already known to produce emissions ", he claims Elder. 'In our study, the tool was used for the first time to find hotspots in areas where there is no intense human activity.'
On average these spots are clustered along the shores of lakes, ponds, streams and other wetland features, usually within 30-40 meters. From there on, the hotspots begin to fade, becoming rarer as they move away from the water, until eventually they almost completely disappear, some 300 meters away.
What are the causes?
The authors are still unclear as to why this phenomenon occurs. Previous research has indicated that some Arctic lakes, known as thermokarsts, can not only emit bubbles that release methane, but they can also melt the permafrost around them even faster.
Instead of centimeters of thaw, as for terrestrial environments, in the past 60 years we have seen 15 meters of thaw under newly formed lakes in the Goldstream Valley.
The factors of this further melting near wetlands and water bodies are still unknown, but there are several hypotheses on the merit.
One of these, the most accredited at the moment, is that methane sources could be clustered around streams as these facilitate the spread of plants. A sort of chain effect: carbon frozen for thousands of years melts, becomes food for microbes that transform everything into methane, and the phenomenon accelerates. The flatter areas of the Arctic were 'green' areas and therefore are more prone to the phenomenon.
Whatever the reason, it is clear that we need more research on the ground. The masses of water (or recent Arctic islands just because of the thaw) seem like a good starting point. Methane has a global warming potential about 30 times greater than carbon dioxide. Even if the Paris Agreement is respected, Arctic permafrost is expected to shrink by another 45%, unleashing these sources of methane and releasing another billion tons of carbon and methane into the atmosphere.
