Oceanic Methane May Have Caused the PETM Event

A new study funded by the United States Department of Energy (DOE) uncovered that methane stored in the world's oceans may have been responsible for a drastic period of climate change and global warming that occurred more than 56 million years ago.

Researchers have been trying to figure out the most likely source of the event for years, but proposal made thus far have come up short in explaining all aspects of the issue. The new investigation focused on methane hydrate frozen under the seafloor.

Scientists with the Rice University say that the amount of carbon released from these methane deposits would have been more than sufficient to trigger a period of global warming. The event was disastrous to the world, occurring about 9 million years after the dinosaurs went extinct.

Controversy has surrounded the methane theory for many years, but the Rice team finally managed to produce tangible evidence that may put these discussions to rest. It is estimated that Earth's average temperature increased by as much as 6 degrees Celsius during the event.

It took the planet about 150,000 years to store the excess oceanic and atmospheric carbon into sediments, cleansing itself of the element, and restoring normal surface temperatures. This period is now called the Paleocene-Eocene Thermal Maximum (PETM).

The event severely affected habitats, food webs and ecosystems, and led to the extinction of numerous species. Scientists calculate that as many as 2,500 gigatons of carbon were released before PETM started changing the world.

Details of the new investigation were published in the latest issue of the esteemed journal Nature Geoscience. The main factor it proposes is that oceanic methane sediments could have contained just as much of the chemical as it does today.

“The critics said, 'No, this can't be. It's warmer; there couldn't have been more methane hydrate.' But we applied the numerical model and found that if the oceans were warmer, they would contain less dissolved oxygen and the kinetics for methane formation would have been faster,” George Hirasaki says.

The expert is the A.J. Hartsook Professor in Chemical Engineering at Rice, and a member of the research team that conducted the work. Rice professor of Earth science Gerald Dickens and the William W. Akers Professor in Chemical Engineering, Walter Chapman, were also a part of the group.

“We run the risk of reproducing that big carbon-discharge event, but faster, by burning fossil fuel, and it may be severe if hydrate dissociation is triggered again,” Rice graduate student Guangsheng Gu adds. He was the lead author of the Nature Geoscience paper.