Methane Dynamics in Marine Sediment Systems

Methane in marine sediments originates from microbial decomposition of organic matter (biogenic sources), release from deeper geological reservoirs (thermogenic sources) and dissociation of gas hydrates. Once produced, methane migrates through porewaters and fractures, forming focused flows at cold seeps or diffuse emissions across broad margins. Along this pathway, microbial communities mediate anaerobic oxidation of methane (AOM), converting methane to carbon dioxide and sulphide, thus limiting oceanic and atmospheric fluxes. Variations in temperature, pressure and sediment composition control the stability of gas hydrates, while glacial history and isostatic rebound modulate hydrate dissociation over millennia. Methane bubbles reaching the water column may dissolve or bypass microbial filters, influencing pelagic ecosystems and air–sea gas exchange. Emerging research highlights dynamic feedbacks between sedimentary methane release, ocean stratification and global carbon cycling. Understanding these processes is critical for assessing the impact of natural seepage and potential anthropogenic disturbance of deep-sea environments, for evaluating methane’s role in past and present climate change, and for informing responsible use of subsea hydrocarbon resources.

Research from Nature Portfolio

Recent studies document extensive natural methane and oil leakage from submarine Arctic reservoirs, revealing thousands of persistent seeps that partly penetrate the water column and may reach the sea surface. These findings indicate that formerly glaciated basins, stripped of sedimentary seals by ice erosion, host widespread hydrocarbon release that has persisted for millennia. Elsewhere, evidence from the southern hemisphere demonstrates that contemporary ocean warming is driving gas hydrate dissociation at upper continental slopes, producing advective methane fluxes that overwhelm the capacity of anaerobic oxidation. This work challenges assumptions that most hydrate-derived methane is consumed before reaching the seafloor and underscores the sensitivity of hydrate stability zones to ocean temperature changes over both decadal and millennial timescales.

Methane Dynamics in Marine Sediment Systems publication trend

The graph below shows the total number of articles in methane dynamics in marine sediment systems across all publications each year (not limited to Nature Index journals).

Technical terms

Gas hydrate stability zone (GHSZ): Sediment interval where low temperatures and high pressures stabilise methane-water ice lattices.

Anaerobic oxidation of methane (AOM): Microbial process coupling methane consumption to sulphate reduction in anoxic sediments.

Cold seep: Seafloor site of focused fluid and gas discharge, often hosting chemosynthetic communities.

Pycnocline: Layer in the water column where density changes sharply, influencing vertical mixing and gas trapping.

Ebullition: Release of gas bubbles through sediments into overlying water, bypassing dissolution pathways.

Thermogenic methane: Methane formed at depth by thermal breakdown of organic matter, distinct from microbial sources.

References

1. Widespread natural methane and oil leakage from sub-marine Arctic reservoirs. Nature Communications (2023).
2. Gas hydrate dissociation off Svalbard induced by isostatic rebound rather than global warming. Nature Communications (2018).
3. Gas hydrate dissociation linked to contemporary ocean warming in the southern hemisphere. Nature Communications (2020).
4. Effects of climate change on methane emissions from seafloor sediments in the Arctic Ocean: A review. Limnology and Oceanography (2016).
5. A water column study of methane around gas flares located at the West Spitsbergen continental margin. Continental Shelf Research (2014).
6. Timescales of methane seepage on the Norwegian margin following collapse of the Scandinavian Ice Sheet. Nature Communications (2016).