Meltwater flushed frozen methane hydrates out of the sediment at the edge of the Greenland ice sheet after the last glacial maximum, which occurred 29,000 to 19,000 years ago, raising fears that melting glaciers could soon release huge amounts of this planet-warming gas.

Methane hydrates form when gas molecules are trapped in a cage of water molecules, freezing into an ice-like substance. They are sometimes called “fire ice” because they can despite being 85 per cent water.

They form under the high pressure and low temperature found in sediments beneath the ocean, permafrost or glaciers. Some suggest methane hydrates contain twice as much carbon as all coal, oil and conventional gas on Earth.

But global warming is disrupting some of the cold, pressurised conditions in which methane hydrates exist. For example, some scientists think a mysterious 50-metre-deep discovered in the Russian Arctic in 2014 was caused when permafrost thaw suddenly relieved the pressure on a methane hydrate. This would have released it in a “violent physical explosion”, wrote the authors of .

Now, researchers have found that flows of glacial meltwater in Greenland can also unleash methane hydrates. “We found a new way of releasing methane that we thought was in the bank,” says at the University of Manchester, UK, who led the research. “It is methane we thought was stable.”

Huuse and his colleagues knew methane hydrates were common in the spaces between grains of sediment at the bottom of Melville Bay in north-western Greenland. In seismic surveys done by oil and gas companies in 2011 and 2013, they noticed 50 large pockmarks in the seafloor, each up to 37 metres deep, clustered near a long berm of earth called a grounding zone wedge. During the last glacial maximum, this wedge was where the floating tongue of the ice sheet met the ocean bottom.

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The researchers initially thought the pockmarks had been scoured by overturning icebergs. But when they drilled sediment cores in the area, they found the top layers of sediment were mostly free of methane, even though the temperature and pressure were perfect for methane hydrates.

They also found large volumes of fresh water in the sediments, rather than the seawater they expected. This could only have come from ice sheet melt. The team thinks that during the last glacial maximum, meltwater flowing under the glaciers in Melville Bay was forced through the grounding zone wedge, flushing out the methane hydrates.

In the future, meltwater could wash out hydrates at the edges of other glaciers as they retreat under climate change, says Huuse. Similar grounding zone wedges exist across the Arctic.

“In the not-so-distant past – could be 12,000, could be 15,000 years ago – a large amount of methane was released, and that same thing could happen tomorrow or in the next century, basically, of receding ice sheets,” he says. “And that’s bad news, because it’s not something we’d considered before.”

The research didn’t include an estimate of how much methane was released in Melville Bay, but Huuse figures it could have been on the order of 130 million tonnes. That’s the equivalent of about two years of from the US, although he notes this methane could have been released over the course of a century, rather than a year or two, and it was a one-time emission.

In addition, the methane would have been dissolved in seawater and, depending on the saturation, it may not all have been emitted to the atmosphere, he says.

The Antarctic ice sheet probably sits on top of even more methane hydrates than Greenland. The polar regions as a whole are to hold anywhere between 100 billion to 760 billion tonnes of methane in subglacial and marine hydrates. The release of even a fraction of that could rival the 48.7 million tonnes of methane currently released by the Arctic and boreal biomes each year – mostly from wetlands, lakes and streams – and speed up climate change.

Methane is already being unlocked from under the Greenland ice sheet. A published this month found meltwater streams across western Greenland are emitting an estimated 715 tonnes of methane per year. While some of this could be coming from hydrates, it is more likely to come from ancient plant carbon converted to methane gas by bacteria under the ice, says at the UK Centre for Ecology and Hydrology, who led the study. This will probably increase.

“If you’re getting enhanced melt, you’re potentially tapping into areas of subglacial system that… have got well-preserved organic carbon stocks that then have the potential to be converted into methane,” she says. “There is the potential of relatively large future release.”

Warmer Atlantic water from near Greenland is heating up the depths of the Arctic Ocean, which was previously thought of as one of the few places not significantly affected by climate change.

The sea ice on top of the Arctic Ocean has shrunk by about 40 per cent in four decades, due largely to the effect that atmospheric warming has on the surface of the ocean. Now researchers from the Ocean University of China have analysed the latest measurements taken using icebreaker ships to estimate warming at the bottom of the ocean.

In one of the ocean’s two major basins – the Eurasian basin – the waters between 1500 and 2600 metres deep have warmed by 0.074°C since 1990.

While that doesn’t sound like much, it represents the transfer of almost 500 trillion megajoules of energy. If that amount of energy were present at the surface, it could melt as much as a third of the minimum sea ice extent.

“The deep ocean is much more active than what we thought,” says , a member of the research team. “I thought the deep ocean could be warming, but not so fast.”

An underwater mountain range running between Greenland and Siberia divides the Arctic Ocean into two basins. While the Amerasian basin is largely walled off from the Pacific by the shallow Bering Strait, an extension of the Atlantic Meridional Overturning Circulation, or AMOC, brings warm Atlantic water northwards along the coast of Scandinavia and into the upper layers of the Eurasian basin. As seawater freezes in the winter, the salt in it is ejected from the crystals. This forms dense water that sinks to the depths, taking some of the warm water from the Atlantic with it.

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The geothermal heat of Earth also warms deep water in the Eurasian basin.

Previously, these warming processes have been offset by an influx of cold deep water from the basin immediately to the east of Greenland. But as the Greenland ice sheet melts, more freshwater has entered the Greenland basin. This has slowed the sinking of cold, salty water to the deep and helped raise the deep water temperature in the Greenland basin from -1.1°C to -0.7°C – one of the fastest warming rates in the deep ocean. As a result, the movement of Greenlandic deep water into the Arctic Ocean no longer cancels out the geothermal bottom heat and sinking of warm Atlantic water.

“The warming of the Greenland basin has extended to the Arctic,” says , part of the research team.

This research has shown a new heating process in the deep Arctic Ocean, “implicating global warming in yet another location”, says at the University of California, Los Angeles.

This warming could eventually begin to contribute to sea ice melt or even thaw sub-sea permafrost, he adds. The permafrost includes ice-like deposits known as clathrates that could release methane into the atmosphere if disturbed, a process that has been hypothesised as a cause of the Permian mass extinction.

The Arctic is at the forefront of the climate crisis, with the central basin of the Arctic Ocean warming three times faster than the global average. However, its hostile and challenging environment, particularly during the polar winter, means much of this region is left unstudied for almost half of the year. Now, the construction of Tara Polar Station, a new long-term drifting observatory and laboratory designed to study the central Arctic Ocean, is pushing the boundaries of research in the region. This vessel, specially adapted to the harsh polar conditions, will shelter scientists as they embark on a transpolar drift, monitoring the sea ice year-round over multiple years. The expedition will be crucial in better understanding the impact of climate change on the Arctic’s ecosystem and the change it would have on the rest of the planet.

Read more: A floating laboratory will uncover the secrets of Arctic winter

The Arctic is a land of riches – not just in its beauty, wildlife and cultural heritage, but in the kinds of commodities we value most: oil, gas, lithium, cobalt, gold and more.

Yet those treasures are no good to us. As our special report on polar science reveals (see “Why vanishing sea ice at the poles is a crisis for the entire planet”), extracting the abundant resources of the Arctic for commercial gain is tricky.

Trying to haul oil and gas from the region is an expensive business, even with the dubious tailwind of melting sea ice helping to clear new patches of ocean for drilling. As industry and transport gradually shift to electric and hydrogen power, oil demand will fall, making the expense ever harder to justify.

It is a similar story for minerals, too. Greenland is a hotspot for in-demand materials, perhaps one reason why US President Donald Trump is aggressively pursuing its takeover. But even leaving aside Greenland’s lack of infrastructure – roads are hard to come by on this icy island – this is a risky place to invest. The landscape is changing fast as glaciers melt, revealing new, precarious coastlines that threaten landslides and tsunamis.

For a hard-nosed business executive, there are easier, less hazardous places to mine

Across the terrestrial Arctic, melting permafrost is destabilising existing roads, buildings and industrial sites. For a hard-nosed business executive, there are easier, less hazardous places to mine.

Viewing the Arctic as a ticket to bountiful economic growth is a fool’s errand. Instead of seeing it as a region ripe for exploitation, we should treat it as a scientific wonder, while also respecting the people who live there. After all, as the fastest-changing region on Earth, it is at the vanguard of our climate future. And there is so much still to learn: how quickly might the ice disappear? How fast will sea levels rise? And what happens if and when the ice is gone?

On a more positive note, researchers are pioneering ever more inventive ways to unlock these mysteries, from a new “drifting” laboratory to ultra-deep ice drills and state-of-the-art submarines. The Arctic is overflowing with opportunities for exploration and discovery. We just need to let go of the idea of monetising them.