Changes in Arctic vegetation, precipitation and its effects on carbon emissions from thawing permafrost in the 21st century

Abstract

Context: The rapidly changing climate in the Arctic induces changes in Arctic ecosystems. The thawing of the permafrost may release large quantities of greenhouse gasses that accelerate warming even more. The Pleistocene Park aims to preserve the permafrost by restoring the ecosystem of the Pleistocene: the mammoth steppe. This will change the evaporation of the region, which will in turn change precipitation downwind. As the release of CH4 from permafrost depends on the water table depth, this will also change these emissions. Aims: In this thesis, I determine the degree of change in precipitation for the Arctic in various future scenarios. In some of these scenarios the tundra is completely replaced by mammoth steppe. An attempt to translate the precipitation changes to CH4 emission changes is also made. Methods: I use statistical models based on the current distribution of vegetation and evaporation therefrom to make predictions of evaporation in future scenarios. The evaporated water will be tracked using U-track to determine where it precipitates. Upscaling the equation for CH4 emission from Olefeldt et al. (2013) will provide insight in the release of CH4 from thawing permafrost. Results: The statistical models for evaporation deviate from reanalysis data from GLEAM on average with 20.8%. The precipitation change attributable to vegetation change is found to be much smaller than this average deviation in all scenarios (<5%), and therefore the resulting precipitation estimates are not significant. Conclusions: Precipitation that evaporated most recently from tundra regions does not fall in regions where the CH4 emission is estimated to be especially sensitive to added moisture. Although no significant estimate of CH4 emission change can be made, the increase in CH4 emission due to the large scale implementation of the Pleistocene Park method is therefore unlikely to exceed the reduction in emissions achieved otherwise.