Submitted by Dr C.M. Martin-Jones on Mon, 24/04/2023 - 09:45
As the Artic warms, bubbling springs that emerge from beneath shrinking glaciers could provide an underestimated source of the potent greenhouse gas methane — according to new research presented today at EGU23.
The research — led by researchers from the University of Cambridge and the University Centre in Svalbard, Norway — identified large quantities of methane leaking from springs exposed by retreating glaciers across Svalbard in the high Arctic, which is the fastest warming region on Earth.
Gabby Kleber, lead author of the research from Cambridge’s Department of Earth Sciences, spent much of the past three years monitoring the water chemistry of over a hundred springs across Svalbard — identifying highly concentrated methane that can rapidly escape into the air once exposed.
The research found that methane emissions released from the springs totalled at least two kilotonnes over the course of a year — roughly equivalent to the methane released by two million cows over the same time frame. “We find that these springs could be a significant source of methane emissions — one that has been missing from the picture until now, and will become more significant if global warming continues unchecked,” said Kleber.
Methane gas is the third most important greenhouse gas in the atmosphere after water vapour and carbon dioxide. Although present in lower concentrations than carbon dioxide, methane is approximately 28-34 times more powerful in terms of its ability to warm the atmosphere.
Most methane on Earth is produced by microorganisms that convert organic matter to methane in oxygen-starved environments like natural wetlands. A significant proportion of the global methane budget, however, comes from human activities; including agriculture, waste disposal and fossil fuel burning.
The thaw of ice and frozen ground throughout the Arctic is another source of methane, and one that scientists are increasingly concerned about. That’s because melting could trigger a sudden release of trapped methane—rapidly warming our planet and ramping-up human induced global heating. The scale and pace of that release is difficult for scientists to pin-down, adding uncertainty to calculation of the global methane budget and how it might change in the future.
Most research up until now has focused on methane emitted when frozen ground (permafrost) thaws, because it contains large stores of organic material that feeds methane-releasing microrganisms. But the new study shows that there might be additional, and unaccounted for, methane emissions that are unveiled as glaciers in the Arctic shrink.
In Svalbard, scientists are getting an early warning of this new source of methane, because the pace of glacier melt is faster than elsewhere in the Arctic. “Svalbard is the canary in the coal mine — the changes we see give a preview of the potential methane release that could happen at a larger scale as temperatures increase in other regions of the Arctic,” said Kleber.
The springs Kleber studied are fed by a plumbing system hidden beneath all glaciers, one which extends down into large groundwater reserves within the underlying soil and rocks. Once the glaciers thaw and retreat, springs bubble up where this groundwater network punches through to the surface.
These groundwater springs aren’t always easy to recognize, so Kleber 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, she looked for tell-tale blue trickles of ice where groundwater had leaked to the surface and frozen, along with blisters of ice due to pressurized waters and gas build up. She then travelled to each of these sites by snowmobile to take samples of the groundwaters.
When Kleber profiled the chemistry of the water feeding these springs, she found that all bar one of the 123 sites were super-saturated with dissolved methane — meaning that, when the spring water reached the surface, there is plenty of excess methane than can escape to the atmosphere.
The researchers also identified localized hotspots of methane emissions, which were closely related to the type of rock underlying the glaciers — the same region where the spring water comes from. Certain rocks like shale and coal contain natural gases, like methane, that were produced by the breakdown of organic matter during the formation of the rocks. This methane can move upwards through fractures in the rock and into the groundwater.
“This phenomenon is likely to be prevalent across other regions of the rapidly warming Arctic,” said Kleber, who adds, “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.”
Kleber, G., Hodson, A., Magerl, L., Schytt Mannerfelt, E., Bradbury, H., Zhu, Y., Trimmer, M., and Turchyn, A.: Glacial retreat driving enhanced methane emissions in the high Arctic, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15412.