Retreating Arctic glaciers uncover a new source of methane

July 6 () –

As the Arctic warms, retreating glaciers expose springs that they can be an underestimated source of the potent greenhouse gas methane.

A study, led by researchers from Cambridge and the Svalbard University Center in Norway, identified large reserves of methane gas seeping from groundwater springs discovered by melting glaciers.

The investigation, published in Nature Geoscience, suggests that these methane emissions are likely to increase as Arctic glaciers recede and more springs become exposed. This, along with other methane emissions from melting ice and the frozen soil of the Arctic, could exacerbate global warming.

“These springs are a significant and potentially increasing source of methane emissions, which until now have not appeared in our estimates of the global methane balance,” says Gabrielle Kleber, lead author of the research and a member of the Department of Earth Sciences at the University of Cambridge.

Scientists fear that the additional methane emissions released by melting Arctic ice will increase human-induced global warming. The springs studied by the researchers had not previously been recognized as a potential source of methane emissions.

Kleber spent nearly three years observing the water chemistry of more than 100 springs in Svalbard, where air temperatures are rising twice as fast as the Arctic average. He likens Svalbard to the canary in the coal mine of global warming, “Since it’s warming faster than the rest of the Arctic, we can get a preview of the potential methane release that could occur on a larger scale throughout this region“, Explain.

For his part, Professor Andrew Hodson, co-author of the study at the Svalbard University Center, comments that “living in Svalbard exposes you to the front lines of Arctic climate change. Nothing more stark can come to mind than the sight of the degassing of methane in the immediate prelude to a receding glacier,” he adds.

Until now, research has focused on the release of methane from thawing permafrost. “Although attention is often focused on permafrost, this new finding tells us that there are other methane emission pathways that could be even more important in the global methane balance.”says study co-author Professor Alexandra Turchyn, also from Cambridge’s Department of Earth Sciences.

“Until this work was done, 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 there are no glaciers,” Hodson adds.

The methane springs they identified are fed by a system of pipes hidden under most glaciers, which taps into large groundwater reserves in the underlying sediments and surrounding bedrock. Once the glaciers melt and recede, springs appear where this network of groundwater pierces the surface.

The researchers found that methane emissions from Svalbard’s glacial groundwater springs could exceed 2,000 tonnes over the course of a year, which is equivalent to approximately 10% of the methane emissions resulting from Norway’s annual oil and gas energy industry.

This source of methane will likely become more important as more springs become exposed, Kleber says. “If global warming continues unchecked, the release of methane from glacial groundwater springs will likely be more extensive,” she says.

Glacial groundwater springs aren’t always easy to spot, so Kleber trained his eye to pick them out on satellite images. Zooming in on areas of land exposed by the retreat of 78 glaciers on Svalbard, Kleber searched for the telltale blue threads of ice. where groundwater had seeped to the surface and frozen.

He then traveled to each of these locations by snowmobile to take groundwater samples where the ice had blistered due to a buildup of pressurized water and gas.

When Kleber and his team analyzed the chemical composition of the water feeding these springs, they found that all but one of the locations studied had a high concentration of dissolved methane, meaning that when the spring water reaches the surface, there is an excess of methane that can escape into the atmosphere.

They also identified localized sources of methane emissions, closely related to the type of rock from which the groundwater emerges. Certain rocks such as shale and coal contain natural gases, including methane, produced by the decomposition of organic matter when the rocks were formed. This methane can rise through the fractures in the rock and reach the groundwater.

“In Svalbard we are beginning to understand the complex cascade reactions caused by melting glaciers; It seems likely that there are more results like this that we haven’t discovered yet,” Kleber says.

“The amount of methane escaping from the springs that we have measured will likely be dwarfed by the total volume of trapped gas that lies under these glaciers, waiting to escape,” Hodson adds. “That means we urgently need to establish the risk of a sudden increase in methane leakage, because glaciers they will only continue to recede as we fight to curb climate change.”