Kleber and 7 co-authors reported in early 2023 that permafrost and glaciers in the high Arctic form an impermeable ‘cryospheric cap’ that traps a large reservoir of subsurface methane, preventing it from reaching the atmosphere. Cryospheric vulnerability to climate warming is making releases of this methane possible.
On Svalbard, where air temperatures are rising more than two times faster than the average for the Arctic, glaciers are retreating and leaving behind exposed forefields that enable rapid methane escape. Here we document how methane-rich groundwater springs have formed in recently revealed forefields of 78 land-terminating glaciers across central Svalbard, bringing deep-seated methane gas to the surface. Waters collected from these springs during February–May of 2021 and 2022 are supersaturated with methane up to 600,000 times greater than atmospheric equilibration.
Spatial sampling reveals a geological dependency on the extent of methane supersaturation, with isotopic evidence of a thermogenic source. The authors estimated annual methane emissions from proglacial groundwaters to be up to 2.31 kt across the Svalbard archipelago. Further investigations into marine-terminating glaciers indicate future methane emission sources as these glaciers transition into fully land-based systems.
Their findings revealed that climate-driven glacial retreat facilitates widespread release of methane, a positive feedback loop that is probably prevalent across other regions of the rapidly warming Arctic.
The authors concluded that the observed pace of warming in the Arctic has far exceeded climate model predictions, probably due to many feedback loops within the Arctic that the models fail to capture48. Their findings present a regionally important feedback loop related to climate-driven glacier melt that is currently not considered in the Arctic methane budget, where rapid glacial retreat is opening new pathways for methane escape. As Svalbard is warming at a rate more than twice the Arctic average13, its responses to warming are indicators of what can be expected in other regions of the Arctic and Antarctica.
Improving our understanding of possible pan-Arctic methane release from proglacial groundwater springs is necessary to assess the importance of such
emissions and their potential global climate impact. This is particularly relevant in regions where glaciers are capping large reservoirs of geologic methane, such as parts of Arctic Canada and the Russian Arctic1, where further melting of the cryosphere could lead to considerable seeps of this potent greenhouse gas.
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