Frozen methane could be boon or disaster

Ice that burns?
Such ice exists, and it may soon provide the world with a vast amount of fuel – or its melting may speed up climate change and increase Arctic temperatures to tropical levels not seen for 55 million years.

Picture snowdrifts on the sea floor or icy layers buried deep under permafrost. That’s what frozen methane gas hydrates look like.

But if you put a match to this ice, it burns because there’s gas in the ice.

And if you take this ice up from under the water or permafrost and increase its temperatures even by one degree, it becomes unstable and will eventually dissolve, releasing methane gas – a potent, heat-trapping greenhouse gas – into the atmosphere.

Methane gas hydrates can stay frozen at temperatures warmer than the melting point of ice, but they need high pressures to stay in this solid form. Increase the temperature too much, or remove the gas hydrates from this pressure, and they fizz and vaporize into the air.

In November 2000, while trawling an undersea canyon off the coast of British Columbia, fishermen on the commercial fishing ship Ocean Selector were shocked to find their nets bobbing to the surface, filled with a catch of gas hydrates frothing and hissing “like Alka-Seltzer.”

Yet this is what could happen if greenhouse gases warm the planet enough. Then, warm seawater could trigger melting of vast deposits of undersea methane hydrate off the coast of most continents.

If the ocean warmed enough to melt these gas hydrate ices, the collapse of the formations could cause huge underwater landslides and tsunamis. At the same time, methane gas would bubble to the surface.

And if the planet warmed enough, releases of methane could come from both under the water and permafrost on the land. This would doubly accelerate global warming.

A massive meltdown of underwater hydrates may, for example, have released enough methane to drive up global temperatures by five to 10 degrees Celsius 55 million years ago.

Scientific studies suggest the impact of gas hydrates on global climate may be as important as orbital wobbling, volcanic eruptions and ocean currents.

Michael Riedel, a professor at McGill University in Montreal, is one of many scientists keenly interested in gas hydrates because they believe these deposits have played an important role in ancient global climate change.

Riedel is involved in several efforts to map and monitor hydrates, and to better understand, for example, why a small snowdrift of gas hydrates manages to stay frozen on an isolated undersea patch off Vancouver.

Riedel is co-chief of the joint Canada-U.S. Integrated Ocean Drilling Program, an international marine research program that explores sea floor sediments and rocks. The IODP recently announced it had found deposits of methane gas hydrates off the coast of British Columbia at less depth than expected.

The discovery, published in the Aug. 15, 2006 edition of the American Geophysical Union’s EOS, may have implications for future energy use as well as climate change. That’s because if gas hydrate deposits are near the seafloor, this could mean that they are less stable and more susceptible to melting, increasing the risk of “catastrophic releases of methane.”

Riedel said that there’s too short an observation span to tell if the hydrates are decomposing yet or not.

“But we know what will happen if we continue to warm the planet and the oceans,” Riedel said. “The hydrates will respond to the warming within decades. They are pretty quick to respond, so they could potentially make things worse.”

But methane trapped near the surface in a special type of permafrost is already bubbling up into the atmosphere at a rate five times faster than originally measured, the Sept. 7 edition of Nature says.

The effect is seen mostly in Siberia in a type of permafrost, called yedoma, flash-frozen about 40,000 years ago. In Siberia, meltwater lakes warm and thaw the permafrost even more, creating what one of the study’s authors calls “a slow-motion time bomb.”

At 600 metres below the ocean surface, an increase of even one degree is enough is enough to make the undersea hydrates unstable and lead to a “catastrophic release.”

Gas hydrates are also found “all over the Arctic” in permafrost, Riedel said.

“If there’s gas and if there’s enough pressure and low enough temperatures you can assume they are hydrates.”

The gas, locked up in ice under high pressure and low temperature, comes from the tissue of phytoplankton that once lived on the sea surface. Microorganisms converted this organic matter to methane gas.

Methane gas hydrates are now estimated to be twice as numerous as the world’s known oil, coal and natural gas deposits.

As oil prices rise, methane gas is now being considered as a source of energy on par with coal, hydroelectric power and nuclear energy. Many countries are mounting research projects into gas hydrates because the global deposits may contain enough energy to meet the world’s needs for up to 3,500 years.

But extracting gas from undersea hydrates is still tricky to do in a safe economic way, which reduces possible spills, the chance of fire and the release of methane into the atmosphere.

As it stands now, methane gas hydrates under permafrost in the Arctic are likely more economically viable for drilling than deep sea hydrates, due to their higher concentration and location near oil fields and planned pipeline routes.