Global warming's pingo problem

Submarine mounds under Arctic seas could be harbingers of climate change.

Published February 5, 2007 7:28PM (EST)

The obituary for the renowned Arctic botanist Alf Erling Porsild notes that "he went through life with a rollicking, though curiously muted, sense of humor." Perhaps this is what happens when you spend your formative years studying reindeer and learning Inuit.

The Inuit word for "small hill," incidentally, is "pingo." A. E. Porsild borrowed the word to describe a particular formation of earth-covered ice mounds that dot the Arctic and sub-Arctic landscapes. In memory of his contributions, a pingo on the Tuktoyaktuk Peninsula in Northern Canada was named after him.

Porsild Pingo is near the shores of the Beaufort Sea. In the 1960s, researchers studying the submarine geology of the Beaufort Sea started using the term "pingo-like features" to describe mounds that had emerged from the sea floor that looked similar to the pingos on land.

The aboveground pingos are thought to have formed primarily through "expansion associated with ground ice formation," say researchers. But the pingo-like features on the sea bottom may be quite different. New research presented this month, in Geophysical Research Letters of the American Geophysical Union, suggests that the pingo-like features on the Beaufort Sea shelf are the result of decomposing methane gas hydrates. (Thanks to EnergyBulletin for the link.)

A methane gas hydrate is a solid substance composed of water and methane that is formed under conditions of low temperature and high pressure. In the Beaufort Sea, gas hydrate deposits are believed to have been created from the submersion of thick Arctic permafrost. But as warmer waters have "transgressed" upon regions of the long-submerged permafrost, the hydrate structures may, essentially, be melting. And as the gas pushes upward, pingo-like features are forming on the seabed.

Why should we care? Some geologists see gas hydrates as a source of energy, if ways can be found to safely mine them. But methane is also an especially virulent greenhouse gas. If warmer temperatures lead to the rapid unlocking of submarine methane hydrates, the pace of climate change could be considerably accelerated.

It's not at all clear that such an acceleration is occurring yet. The marine transgression referred to by the pingo-fascinated researchers has been occurring on a time scale that dates back to the last Ice Age, well before humans started influencing the climate. But as the researchers note, "because methane is a potent greenhouse gas, the fate of decomposing gas hydrate is of considerable interest in global warming scenarios."

So boil the oceans, release methane gas, boil even faster. Contemplating that prospect will mute just about anyone's rollicking.

By Andrew Leonard

Andrew Leonard is a staff writer at Salon. On Twitter, @koxinga21.

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