Finnish Environment Institute
Palsas (peat mounds with a permafrost core) occur in ecologically valuable subarctic mires located at the outer margin of the permafrost zone. Palsas are expected to undergo rapid changes under global warming. This study presents an assessment of the potential impacts of climate change on the spatial distribution of palsa mires in northern Fennoscandia during the 21st century. A large ensemble of statistical climate envelope models was developed that deﬁne relationships between palsa occurrences and a set of climate indicators. The models were used to project areas suitable for palsas in the future. The sensitivity of these models to changes in air temperature and precipitation was analysed to construct impact response surfaces (IRS). These were used to assess the behaviour of models when extrapolated into changed climate conditions, so that new criteria, in addition to conventional model evaluation statistics, could be deﬁned for determining model reliability. IRS were combined with probabilistic climate change projections to quantify the risk of palsa loss.
In addition to future climate, structural differences in impact models appeared to be a major source of uncertainty. However, using the model judged most reliable according to the new criteria, results indicated that the area with suitable climatic conditions for palsas can be expected to shrink considerably during the 21st century. The risk of this occurring by the end of the 21st century was quantiﬁed to be between 43% (for the B1 low emissions scenario) and 100% (for the A2 high emissions scenario). The projected changes in areas suitable for palsas are expected to have a signiﬁcant inﬂuence on the biodiversity of subarctic mires and are likely to affect the regional carbon budget.
Fronzek, S. (2013) Climate change and the future distribution of palsa mires: ensemble modelling, probabilities and uncertainties, Monographs of the Boreal Environmental Research No. 44, ISBN 978-952-11-4204-8, pp. 35, http://hdl.handle.net/10138/40184