Much research over the last decade has focused on the potential impacts of thawing permafrost and the subsequent decomposition of previously frozen carbon stocks on global climate. The concern is that large releases of greenhouse gases such as carbon dioxide and methane could represent a so-called positive feedback on climate further accelerating the ongoing rapid warming. This research has been stimulated by recent new estimates indicating that large stocks of carbon are currently stored in the northern permafrost region.

Permafrost carbon is one of the key vulnerable carbon pools in the Earth System and the IPCC has recognized it is one of the main uncertainties in projections of future climate change. A first order control is the total amount of carbon stored in permafrost. In order to further improve estimates, we carry out soil carbon inventories across the northern permafrost region (Canada, Greenland, Svalbard, northern Europe, Russia). We realize that some carbon stocks (e.g. in forest soils on permafrost, deep Quaternary deposits) still need to be better quantified. Second, it is not only quantity but also quality that matters. Once carbon stocks are thawed out, how quickly will they decompose releasing greenhouse gases to the atmosphere. For this purpose, we characterize the decomposability of carbon stocks with simple geochemical techniques that can be applied at a circumpolar level.

Third, permafrost degradation will not only happen by a gradual warming and thawing of the permafrost. The permafrost region is characterized by so-called periglacial processes that can result in very fast changes in the landscape that are still poorly quantified. These are related to the unique zero-degree threshold at which ground ice melts, resulting in the collapse of surfaces and the formation of thermokarst lakes, rapid slope and coastal erosion, etc. We aim to contribute field data and process understanding to improve the representation of these key periglacial processes in Earth System models.

Peat plateau / thermokarst lake complex in N Russia (© P. Kuhry)
Peat plateau / thermokarst lake complex in N Russia (© P. Kuhry)