As the world warms, methane trapped in ice beneath the Arctic Ocean is released. Methane is such a powerful greenhouse contributor that if the unfrozen gas reaches the atmosphere, the effects would be catastrophic. Thankfully, the methane in at least one location is being consumed by microorganisms before it can do damage.
Climatologists' greatest fear is of human-induced warming triggering feedback loops, leading to the release of even more gasses until the problem runs beyond hope of control. Several potential runaway sources have been considered, including vast fires in the Amazon and the release of carbon frozen in the Arctic tundra.
Probably the threat that frightens scientists the most, however, is methane in the Arctic Ocean, trapped in ice cages that are vulnerable to melting. Fifty-six million years ago, unknown forces triggered a major release of similar materials, transforming the Earth's climate for millions of years.
Past studies have shown some released methane is consumed by microorganisms before it reaches the surface of the ocean, softening the potential damage. The question of how much methane gets through is one of the most important unknowns in climate science and one that has proven very hard to answer. Now, Dr Katy Sparrow of Rochester University has provided encouraging news from Prudhoe Bay, northern Alaska.
The carbon in methane is mostly ordinary carbon-12, but on formation contains some heavier isotopes. Trapped at the bottom of the oceans for millenia, however, carbon-14 undergoes radioactive decay, giving old methane from the seafloor a different isotopic signature from gas of recent biological origin.
In Science Advances, Sparrow reports that the methane in the Prudhoe Bay water column indicates the surface methane is almost all new. The ancient material released from the seafloor is not reaching the place where it could be dangerous.
Sparrow told IFLScience that her team “make no attempt to upscale our findings to other areas of the Arctic,” and similar studies are needed elsewhere. Their site also has no known methane seeps, unlike those causing alarm in other parts of the Arctic. Nevertheless, the fact the Bay is quite shallow and yet the ancient methane Sparrow found near the seafloor is not reaching surface waters presents an encouraging sign for the deeper locations.
Sparrow also confirmed to IFLScience that, despite different methodology, her work is consistent with a study published last year that found that seafloor methane is not only not reaching the surface, but is stimulating the drawdown of atmospheric carbon dioxide.
Fellow Rochester researcher, Vasilii Petrenko, recently reported that during the last big warming event, most methane came from wetlands rather than the Arctic seafloor, in keeping with Sparrow's work.
The fight to stop disastrous climate change still appears in our hands.