Month: November 2012

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Subcap Methane Feedbacks, Part 1: Fossil methane seepage in Alaska

Originally published at Skeptical Science.

As permafrost thaws, methane is released as the vegetable matter in the soils decomposes. This methane bubbles to the surface in lakes and ponds and accumulates under the ice in the wintertime. New research has shown that the most vigorous methane seeps in Alaska are fed also by methane emitted by thermal decomposition of organic matter in deeper and much older sediments. Continuous permafrost acts as a top seal to this fossil methane, preventing it from reaching the surface and, as global warming melts and perforates this cap, we can expect the pent-up gas to be released more quickly. This source of methane, released from traps under the permafrost, is a potential third source of methane feedback in the Arctic, in addition to permafrost soils and methane hydrates. 

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Subcap Methane Feedbacks. Part 2: Quantifying fossil methane seepage in Alaska and the Arctic

Originally posted at Skeptical Science

The previous article in this series looked at the recent discovery of significant releases of fossil methane through the thawing permafrost in Alaska. In this second instalment we will look at the potential of the rest of the Arctic to produce subcap methane, and will compare the size of these seeps to other global methane-producing mechanisms.

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Subcap Methane Feedbacks. Part 3: Methane from beneath the ice

Originally posted at Skeptical Science

The previous two parts (one here and two here) of this series examined the evidence for seeps of geological methane through the cap provided by permafrost and looked at estimates of the magnitude of such seeps in relation to other sources of atmospheric methane. In this section, we will look at the emerging evidence for actual and potential methane releases related to glaciers and ice sheets. The sources of this methane are varied: fossil methane released through reactivated fractures; organic matter once buried and now exhumed; and possible methane hydrates lurking under the big ice sheets.

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Subcap Methane Feedbacks. Part 4: Speculations

Originally posted at Skeptical Science

Previous articles in this series have reviewed recent research on methane sources from beneath permafrost and ice sheets. Part 1 looked at subcap fossil methane seeps in Alaska;Part 2 provided a perspective for the size of these seeps in relation to other natural and human sources; and Part 3 looked at potential methane sources resulting from the withdrawal of glaciers and ice sheet. In this final section, I will try to make estimates of what subcap methane emissions may mean for future climate change; more as a speculative basis for discussion rather than an authoritative prediction. Firstly, though, I will argue for a role for subcap methane emissions on the East Siberian Arctic Shelf (ESAS). 

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Book review: Rising Sea Levels: An Introduction to Cause and Impact by Hunt Janin and Scott Mandia

Originally posted at Skeptical Science

“My other piece of advice, Copperfield,” said Mr. Micawber, “you know. Sea-wall height twenty feet, maximum storm surge nineteen feet six inches, result happiness. Sea-wall height twenty feet, maximum storm surge twenty feet six inches, result misery. The blossom is blighted, the leaf is withered, the god of day goes down upon the dreary scene, and — and in short you are for ever flooded.”

With apologies to Charles Dickens for the paraphrasing.

Wilkins Micawber knew from his own experience that a small but persistent excess of spending over income eventually leads to disaster; in his case, debtors’ prison. Similarly, a small and sustained rise in sea level—once it is combined with unusual weather and high tides—can push ocean waters, quite literally, over a tipping point; as the people in New York and New Jersey, in the wake of Hurricane Sandy, have just witnessed.

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