Unseen Emissions: Methane Rising from the Seabed of the Southern Ocean

As global temperatures continue to rise, we are increasingly paying attention to methane—a powerful greenhouse gas—and its role in accelerating climate change. One important, but often overlooked, source of this gas lies beneath the ocean floor in the form of methane hydrates.

These ice-like solids form when methane gas is trapped inside a lattice of water molecules, stable only under specific low-temperature, high-pressure conditions typically found in deep-sea sediments along continental slopes, especially in polar regions like Antarctica. But as ocean temperatures rise and sea levels shift, those stable conditions are disrupted, potentially triggering methane release.

Methane hydrate bearing sediment preserved in liquid nitrogen at MARUM. When exposed to a flame, the trapped gas ignites, creating the stunning effect of fire burning on ice. ©Maria De La Fuente

In polar regions, these changes are especially pronounced. Since the Last Glacial Maximum, about 21,000 years ago, Antarctica has seen the retreat of massive ice sheets. In West Antarctica, two-thirds of the ice sheet’s mass has disappeared, and the Earth’s crust has been rebounding in response—a process known as isostatic uplift. This affects the pressure conditions on the seafloor and, combined with warming waters, could have destabilized methane hydrates, releasing methane into the ocean—and possibly the atmosphere.

To investigate this possibility, the ICEFLAME project, led by the Institut de Ciències del Mar (ICM-CSIC) and the Spanish Geological and Mining Institute (IGME-CSIC), and conducted in collaboration with the Université libre de Bruxelles  (Belgium) and the National Institute of Oceanography and Experimental Geophysics (Italy), set sail in January 2025 for the Antarctic Peninsula. After a month-long expedition through the Drake Passage, we returned on 14 February with new insights into what lies beneath the seabed off the South Shetland Islands.

The scientific crew of the ICEFLAME project in front of the research vessel Sarmiento de Gamboa, just before departure. ©Pedro M. Prestel

Using sediment cores, gas and water sampling, and high-resolution acoustic imaging, we mapped the seafloor and its underlying structures to identify methane-rich hydrate reservoirs and the pathways through which gas escapes into the water column. What we discovered was striking: towering methane bubble flares reaching up to 350 metres—roughly as tall as the Eiffel Tower. These are the first massive methane flares ever documented in Antarctica.

Air gun system used to generate acoustic waves that helped image subsurface structures and detect gas accumulations - Seismic data collected during the ICEFLAME expedition showing clear bottom simulating reflectors (BSRs) with inverted polarity—key indicators of subsurface gas accumulation and the presence of gas hydrates beneath the seafloor. ©Maria De La Fuente

This discovery raises critical questions about how much of the released methane could eventually reach the atmosphere. While some of the gas is likely dissolved in seawater or consumed by seafloor microbes—processes whose impact on ocean carbon cycling is still poorly understood—the rapid warming of the Western Antarctic Peninsula, with air temperatures rising nearly 3°C since 1951 and surface ocean temperatures by over 1°C, may further threaten the stability of Antarctic hydrate reservoirs in the near future.

We are now entering a crucial phase of the project. Back in the laboratory, the team is analyzing samples and data to reconstruct the evolution of these methane hydrate systems and to model how they might respond to ongoing climate change. These findings will help assess the potential role of seafloor methane emissions in global carbon feedbacks—an urgent question as the planet continues to warm.

More about the campaign here: https://www.youtube.com/watch?v=hnIWLJGXzfU

Written by Maria De La Fuente

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Methane Matters by Maria