Greenland methane – New findings suggest glacial meltwater can flush methane hydrates from beneath Greenland, raising fears of future climate-warming emissions.
Melting at the edges of Greenland is not just shrinking ice and raising sea levels, it may also be freeing methane trapped in frozen “fire ice” under the seafloor.
In a study focused on Melville Bay in north-western Greenland. researchers report evidence that flows of glacial meltwater can dislodge methane hydrates from sediments where the conditions for these compounds to remain stable have been disrupted.. The work suggests a pathway for releasing methane that scientists previously believed was less likely during retreating ice-sheet conditions.
Methane hydrates are an ice-like form of methane, where gas molecules are locked inside a cage of water molecules.. They are often nicknamed “fire ice” because, despite containing roughly 85% water, they can burn.. Under the right combination of high pressure and low temperature. hydrates can persist in cold. dense environments found beneath oceans. within permafrost. and under glaciers or in sediments influenced by them.
The new concern is rooted in the way global warming is changing those cold, pressurized settings.. If hydrates destabilize, methane can escape—an outcome that would add to atmospheric greenhouse-gas levels.. Similar mechanisms have been discussed after unusual events in the Arctic. including a mysterious 50-metre-deep crater discovered in Russia in 2014. which has been interpreted as the result of permafrost thaw changing the pressure on methane hydrates.
Led by Mads Huuse at the University of Manchester, the Greenland research began with clues from earlier seismic surveys.. Oil and gas company data collected in 2011 and 2013 revealed around 50 seafloor pockmarks in the area. each reaching up to 37 metres deep.. These marks were clustered near a long structure on the seabed known as a grounding zone wedge. a region tied to where a floating tongue of the ice sheet met the ocean during the last glacial maximum.
The team initially considered a familiar explanation: pockmarks can form when disturbances such as overturning icebergs scour the seabed.. But drilling sediment cores in the area produced a different story.. The upper sediment layers were mostly free of methane, even though temperature and pressure there would ordinarily suit methane hydrates.. That mismatch pointed toward a process that had removed or flushed the hydrates after conditions formed for them.
More evidence came from the water chemistry in those sediment layers.. Rather than the seawater the researchers expected, the cores contained large volumes of fresh water.. The report concluded that the most plausible source was meltwater from the ice sheet.. According to the team’s interpretation. during the last glacial maximum. meltwater flowing beneath glaciers in Melville Bay was forced through the grounding zone wedge. flushing out methane hydrates that would otherwise have remained in place.
Looking ahead, Huuse said the same mechanism could operate as other glaciers retreat.. As meltwater increasingly travels under shrinking ice. it may wash out hydrates at the edges of glaciers where grounding-zone wedges occur.. The researchers note that similar structures exist across the Arctic. which means the potential pathway may not be confined to Greenland.
This matters because the Greenland ice sheet is only one part of a larger methane reservoir.. The report highlights that estimates for the polar regions collectively span a wide range. from 100 billion to 760 billion tonnes of methane stored in subglacial and marine hydrates.. Even releasing a fraction of that reservoir could meaningfully influence climate. potentially matching or exceeding the scale of methane emissions from Arctic and boreal wetlands currently released each year.
The team did not calculate how much methane was released in Melville Bay itself. but Huuse estimated it could have been on the order of 130 million tonnes.. He also cautioned that the timing might differ from a simple annual accounting. suggesting the methane could have been emitted over a longer period—potentially across a century rather than a couple of years.. He further noted that methane released into seawater may dissolve and. depending on how saturated the surrounding waters are. not all of it would necessarily reach the atmosphere.
At the same time, methane is already being detected near Greenland’s melting landscape.. A study published this month found meltwater streams across western Greenland emitting an estimated 715 tonnes of methane per year.. While the authors of that work said some of that methane could come from hydrates. they argued it is more likely to originate from ancient plant carbon that bacteria convert into methane under the ice.. That microbial pathway, they suggest, would likely intensify as melt increases.
Taken together, the findings paint a more complex picture of how warming affects the frozen systems beneath polar ice.. In one scenario, meltwater can physically flush methane hydrates from sediments where the gas was previously trapped.. In another, enhanced melting can feed biological processes that transform stored organic material into methane gas.. If ice loss continues. both routes could become more active—an outcome researchers say deserves closer attention because it was not traditionally treated as a key factor in the near-term methane story.
Greenland methane hydrates glacial meltwater fire ice Arctic methane grounding zone wedge climate change