'The effects of climate change are visible in many places'

Mathias Göckede, a scientist at the Max Planck Institute for Biogeochemistry in Jena, talks about the consequences of global warming for permafrost soils

Climate change is changing many ecosystems; the Arctic permafrost, for example, could partially thaw. Such upheavals in turn would affect the volumes of greenhouse gases released or else sequestered in these areas. We asked Mathias Göckede, a scientist at the Max Planck Institute for Biogeochemistry in Jena, what the consequences of global warming are for permafrost soils.

Mr Göckede, what will happen when the Arctic permafrost regions thaw?

Enormous volumes of carbon are stored within the permafrost, which are removed from the active carbon cycle because they are deep-frozen and, therefore, locked away. If this “ice safe” were to thaw, the carbon in the soil would be partially activated and could then be released into the air or water.

How relevant would this be to climate change?

That depends on the various climate change scenarios. According to current calculations, only about one eighth of the carbon currently trapped in permafrost would be released by 2100 even if we were continue with the current CO₂ emission levels. Even this amount would noticeably exacerbate climate change. However, some studies estimate the Arctic's contribution to climate change to be marginal.

When or rather under which conditions will a tipping point be reached?

No one can say whether that will be in 20 or 200 years or never.

But what would happen then?

That would be a point from which the ecosystem could no longer return to its present state and we would no longer have any control over what would happen in future. The release of carbon from the permafrost would increase the greenhouse effect and climate change, further accelerating the thawing process in the Arctic and releasing even more carbon. There is certainly a risk of such a classic positive feedback loop.

 To what extent has the permafrost already changed?

One can already see the effects of climate change in many places. Where we work in Northern Siberia, for example, it is possible to identify the formation of so-called thermal karst lakes and the tree line has already shifted northwards.

What other ecological consequences does the loss of permafrost have for the hydrologic balance?

We currently have a thawing depth of a few decimetres to several metres depending on the location. Rainwater accumulates on the surface because it is unable to penetrate any deeper into the ground. If global warming were to increase the thawing depth, the water in the region’s extensive wetlands would seep away at a much greater rate. The formation of thermal karst lakes could also dry up large parts of the surrounding areas, which would radically change the appearance of some Arctic regions, in addition to which, the characteristic wetlands could shrink significantly.

Could climate change be slowed down by thawing permafrost through localized actions?

Difficult! Possible human intervention, such as manipulating the hydrological balance or vegetation, could easily lead to unexpected side effects in sensitive Arctic ecosystems. Some of our Russian colleagues are calling for the transformation of the region into an Arctic steppe landscape through the introduction of large herds of grazing animals. It has already been demonstrated on a small scale that this can improve the stability of permafrost soils, but whether or not it could provide a large-scale, climate-relevant solution remains to be seen.