365 Days of Climate Awareness 296 – Siberia and Methane

The extreme north of Siberia, across virtually its entire east-west extent, is tundra. Further, during the last glacial age, much of the current Arctic Ocean was land (if much of that was under glacial ice). The tundra and large portions of the Arctic Ocean are underlain by permafrost, which produces the massive swamps in the larch-dominated western taiga—water has nowhere to drain with the ice beneath it, the same as for Canada’s muskeg—but this is changing.

Arctic tundra.

Methane, CH₄, a greenhouse gas 23 times as insulative as carbon dioxide, though shorter-lived in the atmosphere, is common in swamps where dead organic materials pile up in anoxic environments. Methane would oxidize (by burning if there’s enough present) or escape into the atmosphere if it were free to do so. But when the methane is either trapped in ice, or frozen solid itself as a hydrate—a mixture with water molecules--on the sea floor, it remains immobile, but with the potential to enter the atmosphere, with possibly destructive effects. (And in addition, carbon dioxide is also stored within tundra sediment, not just methane.)

Global seafloor where methane hydrates are found (the absence around Antarctica and northern Siberia is due more to lack of measurment, due to the presence of ice).

The concept behind the widespread angst, in scientific circles and increasingly in the public’s awareness too, is that of the runaway feedback, where an effect of a process can amplify its own cause, and so lead to a situation out of control and worsening rapidly. Methane, being such a powerful greenhouse gas, could potentially add enough warmth to the atmosphere, ocean and ground to encourage the escape of still more methane and carbon dioxide, and so on.  The potential escape of large amounts of methane from frozen tundra and seafloor methane deposits is a real likelihood which scientists struggle to assign probability to.

Swamp gas (mostly methane).

Seafloor methane hydrates are estimated to total 1000-5000 GT, 100-500 times current annual carbon emissions. Total global carbon—both CO₂ and CH₄—stored in the top 3 m of arctic sediment is estimated at 1,400-1,600 PG (= 1,400-1,600 billion metric tons), or 40 times the world’s annual carbon emissions. Arctic and seafloor sediments represent significant and possibly dangerous reservoirs of greenhouse gases.

Methane hydrate (left: picture; right: diagram)

In recent years, spontaneous emissions from land and marine sources have been happening throughout the Siberian Arctic. Ocean measurements north of eastern Siberia have shown elevated amounts of methane, likely having escaped from warming hydrate deposits. On land, permafrost covers 65% of Russian territory. Craters have begun appearing at various locations, largely circular, straight-walled, and showing clear signs of a blast, not an impact. It is theorized these craters are being caused by methane deposits sublimating instantly.

Siberian (theorized) methane crater.

Tomorrow: introduction to Mongolia.

Be brave, and be well.