Glacier retreat creates new sources of methane

Researchers say another feedback effect in the climate change system is emerging: as Arctic glaciers retreat, groundwater flows out from the exposed subsoil, releasing vast amounts of the potent greenhouse gas methane. This is evidenced by investigations in the glacier retreat area in Spitsbergen. Scientists say it is an important and growing factor in climate processes that must now be included in the calculations.

Fossil burning, agriculture and environmental degradation: Humans are still responsible for massive emissions of greenhouse gases. But as it becomes increasingly clear, the problem is compounded fatally by feedback loops. The particularly anxious outlook focuses on the Arctic’s underground methane reserves caused by cold and pressure. Until now, the focus has been on the increased release of particularly powerful greenhouse gases as permafrost thaws. But researchers led by Gabriel Kleber of the University of Cambridge are now turning attention to the impact of retreating glaciers in the Arctic.

Focus on groundwater sources

The scientists’ findings are based on investigations of the glacier retreat zone of the Spitsbergen archipelago in the Arctic Ocean. The impact of climate change can be particularly felt there: the archipelago’s many glaciers have retreated significantly in recent decades. As the researchers report, there are a surprising number of springs rising from underground in the exposed areas. This is fed by groundwater that arises from sediments and rocks that were previously under the influence of the glacier in question. So it was assumed that methane that was previously associated with cold and pressure is increasingly flowing into the water and can reach the surface through springs and thus into the atmosphere.

To explore the magnitude of this effect, the team studied the water chemistry of more than a hundred springs in 78 glaciers in Svalbard. In some cases, the researchers were able to locate them with the help of satellite images because, they explained, the exit zones were indicated by some ice structures in the retreating regions of the glaciers. They were able to drive to the springs with snowmobiles to take water samples.

bubbling climate danger

The results of their analysis revealed that spring water is sometimes rich in methane, which can then leach out. So the concentration of gas dissolved in water can be up to 600,000 times higher than in the atmosphere. The scientists were also able to relate the extent of the methane content to the local characteristics of the rocks from which groundwater feeds into the glacier retreat zone. Some formations, which are characteristic of slate, for example, contain a particularly large amount of methane and then release it into groundwater through cracks.

Based on their results, Kleiber and her colleagues estimated that about 2,000 tons of methane bubbles escape from the groundwater sources of glacial lands throughout Spitsbergen each year. According to them, this indicates that the effect is of great importance: since many other regions of the Arctic region are affected by the retreat of glaciers and the process continues to increase, it may be an important and increasing factor in climatic events, scientists say.

“There is evidence that these sources can be an important and growing potential source of methane emissions that have not been previously accounted for in global budget estimates of this greenhouse gas,” Kleber concludes. “While the focus is often on permafrost, this new result now shows us that there are also other pathways of methane emissions that could be important to the global methane balance,” says co-author Alexandra Turchin of the University of Cambridge. the world.

Source: University of Cambridge, professional article: Nature Geoscience, doi: 10.1038/s41561-023-01210-6

© wissenschaft.de – Martin Vieweg