Wednesday, May 28, 2008

The Termination of Snowball Earth

Snowball Earth termination by destabilization of equatorial permafrost methane clathrate. 2008. M. Kennedy, et al. Nature 453,: 642-645.

Dolomite cement, formed from oxidized methane as it evolved from melting methane hydrates at the end of the snowball Earth glaciation, present in wave-cut platforms at Marino Rocks, South Australia. The dolomite is orange-red and formed vertical plumbing of tubes and vugs as methane passed upward and disrupted overlying sediment. Credit: M. Kennedy/UC Riverside.
From the press release:
An abrupt release of methane about 635 million years ago from ice sheets that then extended to Earth’s low latitudes caused a dramatic shift in climate, triggering a series of events that resulted in global warming and effectively ended the last “snowball” ice age.
The researchers posit that the methane was released gradually at first and then in abundance from clathrates – methane ice that forms and stabilizes beneath ice sheets under specific temperatures and pressures. When the ice sheets became unstable, they collapsed, releasing pressure on the clathrates which began to degas.

“Our findings document an abrupt and catastrophic means of global warming that abruptly led from a very cold, seemingly stable climate state to a very warm also stable climate state with no pause in between,” said Martin Kennedy.

According to the study, methane clathrate destabilization acted as a runaway feedback to increased warming, and was the tipping point that ended the last snowball Earth. (The snowball Earth hypothesis posits that the Earth was covered from pole to pole in a thick sheet of ice for millions of years at a time.)