Ancient Mass Extinction Linked to Oceanic Methane

Huge reservoirs of methane trapped beneath the ocean floor rapidly escaped during prehistoric global warming and depleted much of the sea’s oxygen, according to new research into why many forms of life suddenly vanished 183 million years ago.

The findings, reported in Thursday’s issue of the journal Nature, shed new light, not only on the disappearance of as many as 80% of some deep-sea species, but also on a process suspected in other prehistoric mass extinctions.

The study also raised questions about today’s sea floor reservoir of methane hydrate, which the federal government plans to study as a possible energy source.

Methane hydrate is formed beneath the sea floor when algae from the surface dies and sinks. Normally a gas, the methane is locked in an ice-like state but is susceptible to changes in pressure and temperature.

In the latest research, Oxford University scientists studied fossil wood deposits and identified a signal that they say indicates an unusual level of light carbon in the Earth’s atmosphere.

The researchers believe massive volcanic eruptions during the Jurassic period initiated global warming by spewing carbon dioxide and other greenhouse gases into the atmosphere. Deep-sea currents also were affected.

Methane, unlocked from its suboceanic state by warmer water, then used the oxygen in the water or atmosphere to form carbon dioxide. In either case, global warming would have been accelerated.