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As the Arctic warms, retreating glaciers expose boiling groundwater springs, which may provide an underappreciated source of the potent greenhouse gas methane, according to a new study published in Nature Geoscience. Researchers from the University of Cambridge and the University Centre in Svalbard, Norway, conducted the investigation, discovering enormous amounts of methane gas seeping from groundwater springs exposed by melting glaciers.
According to the study, methane emissions would certainly grow as Arctic glaciers recede and more springs are exposed. This, together with additional methane releases from melting Arctic ice and frozen permafrost, might accelerate global warming. "These springs are a significant, and potentially growing, source of methane emissions—one that has been missing from our estimates of the global methane budget until now," said Gabrielle Kleber, principal author of the study and professor of earth sciences at Cambridge.
Scientists are afraid that further methane emissions from the Arctic thaw would exacerbate human-caused global warming. The springs analysed by the researchers had not before been identified as a possible source of methane emissions.
Kleber spent nearly three years studying the water chemistry of over a hundred springs on Svalbard, where air temperatures are rising twice as fast as the Arctic norm. She compares Svalbard to a canary in the coal mine of global warming, saying, "Since it is warming faster than the rest of the Arctic, we can get a preview of the potential methane release that could happen at a larger scale across this region."
"Living in Svalbard exposes you to the front lines of Arctic climate change," said research co-author Professor Andrew Hodson of the University Centre in Svalbard. Nothing is more striking than the sight of methane outgassing in the immediate forefield of a receding glacier."
Previously, studies focused on methane emissions from melting permafrost (frozen ground). "While the focus is often on permafrost, this new finding tells us that there are other pathways for methane emissions, which could be even more significant in the global methane budget," said research co-author and Cambridge Department of Earth Sciences professor Alexandra Turchyn.
"We didn't understand the source and pathways of this gas until this work was done," Hodson continued, "because we were reading about studies from completely different parts of the Arctic where glaciers are absent."
The methane-producing springs discovered are fed by a plumbing system concealed beneath most glaciers that taps into vast groundwater supplies in the underlying sediments and adjacent bedrock. Springs develop as this groundwater network bursts through to the surface as glaciers melt and recede.
The scientists discovered that the yearly methane emissions from glacial groundwater springs in Svalbard might reach over 2,000 tonnes, which is equivalent to around 10% of the methane emissions from Norway's oil and gas industry. As more springs are revealed, this source of methane is expected to grow increasingly substantial, according to Kleber. Methane leakage from glacial groundwater springs will likely increase if global warming is left uncontrolled.
It's not always simple to spot glacial groundwater springs, thus Kleber developed the ability to spot them in satellite photos. Zooming in, Kleber searched for telltale blue trickles of ice where groundwater had spilled to the surface and frozen. 78 glaciers had retreated over Svalbard, exposing sections of land. Then, she took a snowmobile trip to each of these areas in order to collect groundwater samples at the spots where the ice blistered as a result of a buildup of pressurised water and gas.
All but one of the study sites had highly concentrated levels of dissolved methane, which means that when the spring water reaches the surface, there is plenty of extra methane that can escape to the atmosphere. This was discovered when Kleber and the team profiled the chemistry of the water feeding these springs. The kind of rock from which the groundwater originates was strongly associated with the researchers' localised hotspots of methane emissions. Methane is a natural gas that was created when organic matter broke down during the formation of certain rocks, such as coal and shale. Through rock fissures, this methane can ascend and enter the groundwater.
According to Kleber, "In Svalbard, we are starting to understand the complex and cascading feedbacks triggered by glacier melt—it seems likely that there are more effects like this that we have yet to uncover."
We urgently need to establish the risk of a sudden increase in methane leakage because glaciers will only keep retreating while we struggle to slow climate change, according to Hodson. "The amount of methane leaking from the springs we measured will likely be dwarfed by the total volume of trapped gas lying below these glaciers, waiting to escape," he said.
- The University of Cambridge's website served as the original publication for this press release.