Shrinking Arctic glaciers are unearthing a new source of methane

Date:
July 6, 2023
Source:
University of Cambridge
Summary:
As the Arctic warms, shrinking glaciers are exposing bubbling
groundwater springs which could provide an underestimated source
of the potent greenhouse gas methane, finds new research.


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As the Arctic warms, shrinking glaciers are exposing bubbling groundwater springs which could provide an underestimated source of the potent
greenhouse gas methane, finds new research published today in Nature Geoscience.

The study, led by researchers from the University of Cambridge and the University Centre in Svalbard, Norway, identified large stocks of methane
gas leaking from groundwater springs unveiled by melting glaciers.

The research suggests that these methane emissions will likely increase
as Arctic glaciers retreat and more springs are exposed. This, and other methane emissions from melting ice and frozen ground in the Arctic,
could exacerbate global warming.

"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," said Gabrielle Kleber, lead author
of the research who is from Cambridge's Department of Earth Sciences.

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 recognized as a potential
source of methane emissions.

Kleber spent nearly three years monitoring the water chemistry of more
than a hundred 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, "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." Professor Andrew Hodson, study co-author 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." Previously, research has centred on methane
release from thawing permafrost (frozen ground). "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," said study co-author Professor Alexandra
Turchyn, also from Cambridge's Department of Earth Sciences.

Hodson added, "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 they 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 this 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 roughly 10% of the methane emissions resulting
from Norway's annual oil and gas energy industry.

This source of methane will likely become more significant as more springs
are exposed, said Kleber, "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
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, Kleber looked for tell- tale blue trickles of
ice where groundwater had leaked to the surface and frozen. She then
travelled to each of these sites by snowmobile to take samples of the groundwater at locations where the ice had blistered due to pressurized
water and gas build up.

When Kleber and the team profiled the chemistry of the water feeding
these 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.

The researchers also identified localized hotspots of methane emissions,
which were closely related to the type of rock from which the groundwater emerges.

Certain rocks like shale and coal contain natural gases, including
methane, produced by the breakdown of organic matter when the rocks
formed. This methane can move upwards through fractures in the rock and
into the groundwater.

"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," said Kleber.

"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," said Hodson, "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."
* RELATED_TOPICS
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provided by University_of_Cambridge. Original written by Catherine Martin-Jones. The original text of this story is licensed under a Creative Commons_License. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Gabrielle E. Kleber, Andrew J. Hodson, Leonard Magerl, Erik Schytt
Mannerfelt, Harold J. Bradbury, Yizhu Zhu, Mark Trimmer,
Alexandra V.

Turchyn. Groundwater springs formed during glacial retreat are
a large source of methane in the high Arctic. Nature Geoscience,
2023; DOI: 10.1038/s41561-023-01210-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230706124515.htm

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