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Melting Arctic glaciers are unearthing a new source of potent greenhouse gas, warns new research.
As the Arctic gets warmer, scientists found shrinking glaciers are exposing bubbling groundwater springs which could provide an underestimated source of methane.
It is the second most important greenhouse gas contributor to climate change after carbon dioxide.
The new study, published in the journal Nature Geoscience, identified large amounts of methane gas leaking from groundwater springs unveiled by melting glaciers.
The research, led by Cambridge University scientists and colleagues from University Centre in Svalbard, Norway, suggests that these methane emissions will likely increase as Arctic glaciers retreat and more springs are exposed.
The team say that that the emissions along with other methane leaks from melting ice and frozen ground in the Arctic, could further increase global warming.
Study lead author Gabrielle Kleber, from Cambridge’s Department of Earth Sciences, said: ‘These springs are a considerable and potentially growing source of methane emissions – one that has been missing from our estimations of the global methane budget until now.’
Scientists are concerned that additional methane emissions released by the Arctic thaw could ‘ramp-up’ human-induced global warming.
The springs the researchers studied hadn’t previously been recognised as a potential source of methane emissions.
Ms Kleber, a PhD research student, spent nearly three years monitoring the water chemistry of more than 100 springs across Svalbard, where air temperatures are rising two times faster than the average for the Arctic.
She likens Svalbard to the ‘canary in the coal mine’ of global warming,
Ms Kleber said: ‘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.’
Co-author Professor Andrew Hodson, from the University Centre in Svalbard, said: ‘Living in Svalbard exposes you to the front-line of Arctic climate change.
‘I can’t think of anything more stark than the sight of methane outgassing in the immediate forefield of a retreating glacier.’
Previous research has centred on methane release from thawing permafrost.
Co-author Professor Alexandra Turchyn, also from Cambridge’s Department of Earth Sciences, said: ‘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.’
Prof Hodson said: ‘Until this work was conducted, we didn’t understand the source and pathways of this gas because we were reading about studies from completely different parts of the Arctic where glaciers are absent.’
The methane-delivering springs the team identified are fed by a ‘plumbing system’ hidden beneath most glaciers, which taps into large groundwater reserves within the underlying sediments and surrounding bedrock.
Once the glaciers melt and retreat, springs appear where the groundwater network punches through to the surface.
The researchers found that methane emissions from glacial groundwater springs across Svalbard could exceed 2,000 tonnes over the course of a year – which equates to around 10 per cent of the methane emissions resulting from Norway’s annual oil and gas energy industry.
The team warned that this source of methane will likely become more significant as more springs are exposed.
Ms Kleber said: ‘If global warming continues unchecked then methane release from glacial groundwater springs will probably become more extensive.’
Glacial groundwater springs aren’t always easy to recognise, so she trained her eye to pick them out from satellite images.
Zooming in on the areas of land exposed by the retreat of 78 glaciers across Svalbard, Ms Kleber looked for tell-tale blue trickles of ice where groundwater had leaked to the surface and frozen.
She then travelled to each of the sites by snowmobile to take samples of the groundwater at locations where the ice had blistered due to pressurised water and gas build up.
When the team profiled the chemistry of the water feeding the springs, they found that all bar one of the sites studied were ‘highly concentrated’ with dissolved methane – meaning that, when the spring water reaches the surface, there is plenty of excess methane that can escape to the atmosphere.
Ms Kleber said: ‘In Svalbard we are beginning to understand the complex and cascading feedbacks triggered by glacier melt – it seems likely that there are more outcomes like this which we have yet to uncover.’
Prof Hodson added: ‘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.
‘That means we urgently need to establish the risk of a sudden increase in methane leakage, because glaciers will only continue to retreat whilst we struggle to curb climate change.’
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