Greenland's Melting Ice: Ticking Time Bomb of Methane 'Fire Ice' Under the Seafloor

Beneath the vast Greenland ice sheet, a slumbering menace stirs. Scientists have discovered that the melting of this ice could unlock massive stores of methane, a potent greenhouse gas, trapped as 'fire ice' in the seafloor. Evidence from ancient pockmarks—giant craters on the ocean bed—shows that similar releases occurred after the last glacial maximum. Now, as climate change accelerates ice loss, researchers warn history may repeat itself with severe consequences for our planet. Below, we answer key questions about this alarming discovery.

What are pockmarks and how are they linked to methane release?

Pockmarks are large, crater-like depressions on the seafloor, often ranging from tens to hundreds of meters wide. They form when fluids or gases—particularly methane—erupt from beneath the seabed, displacing sediment. In the waters around Greenland, seismic surveys and sediment cores reveal dozens of these pockmarks. Chemical analysis of the cores shows they were created when ancient methane hydrates (also called 'fire ice') destabilized and released gas. This explosive process leaves distinctive scars on the ocean floor, acting as a permanent record of past methane events.

What evidence do scientists have that methane was released after the last ice age?

Researchers used seismic surveys to map the seafloor structure and collected sediment cores from pockmarks. By analyzing the age and composition of sediments, they found that the pockmarks formed around 11,700 to 15,000 years ago—just after the last glacial maximum. During that period, warming caused Greenland's ice sheet to shrink, reducing pressure on the seabed. This triggered the dissociation of methane hydrates, leading to massive gas blowouts. The data shows a clear correlation: ice retreat equals methane release.

What exactly is methane 'fire ice' and why is it a concern?

Methane 'fire ice' is a solid, ice-like compound called methane hydrate, where methane molecules are trapped inside cages of water molecules under high pressure and low temperatures. It burns if lit, hence the name. Huge deposits lie buried under seafloor sediments, especially in Arctic regions. If disturbed by warming or pressure changes, the hydrates can rapidly break down, releasing methane gas. Since methane is 25 times more powerful than CO₂ over a century, a large release could supercharge global warming, creating a dangerous feedback loop.

How could the melting Greenland ice sheet trigger a new methane release today?

Today, the Greenland ice sheet is losing ice at an unprecedented rate due to climate change. As the ice melts, it reduces the weight pressing down on the underlying bedrock and seafloor. This unloading effect decreases the pressure on methane hydrate deposits stored in sediments beneath the ocean. When pressure drops below a critical threshold, hydrates destabilize and dissociate into methane gas. The gas can then migrate upward and erupt, creating new pockmarks or reviving old ones. Scientists worry this process is already underway.

What do scientists warn about the potential global consequences?

Scientists caution that if large amounts of methane escape from the seabed, it could accelerate climate change significantly. The methane from ancient events was released in pulses, not all at once, but even a gradual increase would spike atmospheric greenhouse gas levels. This could push Earth past tipping points, including further ice loss and permafrost thaw. The study's authors emphasize that while the exact amount of modern methane hydrate vulnerability is uncertain, the historical record proves the risk is real and that continued ice melting must be monitored closely.

What technologies are used to study these pockmarks and methane risks?

To investigate the pockmarks, scientists rely on two main tools. First, seismic surveys use sound waves to create detailed images of the seafloor layers, revealing the shape and depth of pockmarks. Second, sediment cores are drilled from the ocean bed; they contain microscopic fossils and chemical signatures that show past methane leakage. Advanced submersibles and autonomous underwater vehicles also help map these features. Combining these data with climate models allows researchers to assess current and future threats under different warming scenarios.