Melting Siberian Yedoma permafrost could potentially release up to 500 Gt pure carbon, thereby posing one of the world’s most serious climate warming feedback threats.

Climate change in the Arctic is of global importance because sea ice melting lowers the planetary albedo (thereby amplifying warming) and because Greenland melting contributes to sea level rise in the world’s oceans (on average some 5 meters by the time the Greenland ice sheet has fully responded to reach its new equilibrium state).

But there is a third reason, one that is no less important and one which may present acute problems on a relatively short timescale. Arctic warming is a global threat because of the oddity that the small* band of permafrost soils bordering the Arctic Ocean contains just as much shallow carbon as all the world’s temperate and tropical forests, grass and shrubland ecosystems and agricultural land combined.

[*) don’t get fooled by the classical 2D map of the world, but always consider it is a sphere – therefore the highest latitude ranges have the smallest surface]

The Yedoma loess deposits: a thick layer of dust, fossil snow and up to 500Gt of carbon…

The highest concentration of this carbon can be found in an even smaller area, called the Yedoma* permafrost, named after a North East Siberian town in the middle of thick loess deposits in North East Siberia – permanently frozen soils that have accumulated carbon for as long as the Pleistocene has lasted – and which have been able to withstand the milder climates of the interglacials – like the pre-industrial Holocene – but not the present warming, which happens at least twice as fast in the High North as elsewhere.

[*) Some noteworthy facts about the Yedoma permafrost soils: they consist of as much as 50-90 percent ice per volume – and of about 2 percent carbon per weight. The sedimentary make-up suggests Yedoma contains layers of ‘fossil snow’, captured in loess storms – accumulating into a package of dust and ice – as this part of North Siberia was actually not covered by ice sheets during the Pleistocene ice ages. Over an area of ‘just’ one million square kilometers the Siberian Yedoma permafrost alone may contain about 500 gigatonnes of relatively unstable carbon. About half of the Yedoma permafrost is actually offshore, submerged (on the Eurasian continental shelf) in the Arctic Ocean – especially in such oxygen-deprived conditions the additional concern is that some of the carbon will not be released as CO2, but as methane, about 25 times as potent a climate forcer per atom of carbon. All in all the total Arctic tundra permafrost carbon store may be as large as 2000 gigatonnes – enough to create an entire climate catastrophe on its own.]

When the ice melts the loose sedimentary soils erode and the carbon is freely transformed to CO2 – and – just like the Arctic warming – this process too is happening a lot faster than expected, a Nature publishing group warns.

Winds and waves pound a once-frozen Arctic coastline

Especially the coastal Yedoma, along the Arctic Ocean, appears to be deteriorating fast, the researchers have found – as the now ice-free Arctic waters in summer allow for ample wind fetch and wave generation, eroding permafrost cliffs and leading to flooding events of more low-lying tundra.

The research group, which was led by Stockholm University, has calculated that the coastal Yedoma erosion currently destabilises around 44 megatonnes of the ice age carbon per year – ten times as much as previously thought – and that about two thirds of this end up as CO2 in the atmosphere, translating to annual CO2 emissions of about 0.165 gigatonnes*.

[*) This would imply currently the Yedoma CO2 emissions are about 40 times higher than the Yedoma methane emissions – and that currently Yedoma CO2 amplifies (global) climate warming roughly twice as strongly as Yedoma methane (which generally receives more media attention).]

Of course as the warming continues, so does the permafrost melting. The researchers therefore assume the Yedoma CO2 emissions will increase.

“Thermal collapse and erosion of these carbon-rich Pleistocene coastline and seafloor deposits may accelerate with Arctic amplification of climate warming”, the researchers write in their Nature publication.

© Rolf Schuttenhelm | www.bitsofscience.org