Melting Arctic glaciers are creating a ‘doom loop’ by washing old methane from rocks beneath the ice, a study has found.
Researchers collected 148 water samples from 19 glacier-fed rivers in Spitsbergen, a remote Norwegian archipelago in the Arctic Ocean.
Each river tested contained more methane than would be expected from contact with air alone.
Shockingly, the most polluted waterways contain up to 425 times the level of methane that would normally be expected.
Methane is a potent greenhouse gas that escapes from rivers into the atmosphere and contributes to it global warming.
As the planet warms and the glaciers melt faster, more methane will be released, leading to even faster warming and even greater melting.
Lead author Dr Gabrielle Kleber, researcher at the iC3 Polar Research Hub, said: ‘The amounts reported here are small compared to man-made emissions from fossil fuels, agriculture and waste.
‘But they are important because they reveal a natural feedback loop that is not limited to Svalbard, and that could grow as the Arctic warms.’
Melting glaciers in the Arctic are creating a ‘doom loop’ by flushing methane into rivers. Pictured: a glacial river on Spitsbergen
Importantly, the researchers found that this methane is not produced by microbes beneath the ice, as has been shown to be the case in Greenland.
The team analyzed the types of carbon found in the water, showing that many contained propane and ethane in addition to methane.
This is exactly what you would expect if the methane has a geological source, rather than a biological one.
Many parts of the Spitsbergen archipelago contain layers of ancient shale rock rich in organic carbon.
Over millions of years, heat and pressure underground can convert this carbon into methane and other gases such as propane and ethane.
Dr. Kleber says: These glaciers are mostly melting at the surface, but this meltwater finds its way to the bottom of the glaciers through crevices and holes.
‘This means it interacts with the rocks below, and where those rocks contain old gas, the water can wash methane into rivers.’
The researchers estimate that glaciers that end on land in Svalbard can transport about 182 to 368 tons of methane per year in meltwater.
Scientists used water samples and ground-penetrating radar measurements (pictured) to show that water from melting glaciers is washing old methane from the rocks below
This is especially concerning for the Arctic, because methane is a particularly potent greenhouse gas.
Over a 100-year period, one kilogram of methane is 21 times more effective than one kilogram of CO2 at trapping heat in the Earth’s atmosphere.
That adds to previous, much higher estimates of the amount of methane released by groundwater sources before glaciers.
Using ground-penetrating radar, the researchers also mapped ice conditions in some glaciers to see which factors led to the highest methane emissions.
The most methane-rich water came from glaciers that lay on rich layers of shale, but the condition of the glacier itself also played an important role.
Co-author Leonard Magerl, from UiT The Arctic University of Norway, says: ‘The temperature at the foot of glaciers is an important piece of the puzzle.
“We found that the largest methane emissions occurred where the right rocks and the right glacier conditions met.”
The big concern is that this extra boost in greenhouse gases will accelerate the already rapid melting of Arctic glaciers and cause even more methane to be released.
Some rivers contain up to 425 times as much methane as would be expected if they simply absorbed the greenhouse gas from the atmosphere. In the photo: Scientists take a sample from a glacial river on Spitsbergen
Previous studies have shown that Arctic glaciers such as the Geikie Plateau in eastern Greenland (pictured) contain almost twice as much ice as previously estimated, creating a significant risk that rapid melting will significantly raise sea levels.
As glaciers retreat and thin, more meltwater can reach their bottoms and come into contact with fractured bedrock, sediment and groundwater, flushing out more methane.
If so lead to accelerated melting in the Arcticthe resulting sea level rise could have serious consequences for the rest of the world.
The Greenland ice sheet, which is located within the Arctic Circle, contains sufficient fresh water increase sea level by 23 feet (7.4 m) if it were to melt completely.
With recent research estimating this Currently, more than 100 million people live below sea levelthis could cause a catastrophic displacement of people from coastal areas.
However, the researchers are not yet entirely sure whether this cycle will continue to accelerate in the future.
Some Svalbard glaciers are even getting colder at the base, as they shrink and melt at the surface.
If a glacier becomes frozen to bedrock, its ability to flush methane into rivers can decrease.
Dr. Kleber adds: ‘Our results show that future methane emissions will depend on both geology and glacier change. That’s why it’s important to know what lies beneath the ice, and not just how fast the ice is melting.’
