Greening of the Arctic: gradual or abrupt?

Climate change is increasingly warming up Arctic ecosystems and removing climate envelops for vegetation. In response, a general increased vegetation productivity trend (‘greening’) has been observed in satellite imagery. However, this trend is not uniform with large areas exposing stability and even conflicting reduced productivity.

While there is ample evidence for widespread shrub encroachment and treeline movement into tundra ecosystems, there is also a significant time lag between projected and observed trends.

This is raising a conundrum as to why, despite driving forces of climate change pressuring these systems, we do not see a uniform linear response of vegetation.

In this project, I will investigate whether abrupt regime shifts and alternative stables states can explain conflicting patterns in Arctic greening.

I will test this hypothesis at local scale using an island treeline system marked by alternating patches of forest, shrubland and tundra, as well as at regional and circumarctic scale.

I will combine unmanned aerial vehicle (UAV) imagery, ground sampling, historic aerial photography and satellite time series to characterize the systems. The findings will be translated into models explicitly allowing for non-linearity and alternative stable states.

Finally, these will be linked to biogeochemical data (e.g. soil carbon storage, biomass, CO2 fluxes) to get a landscape understanding of future changes in Arctic carbon balances on a 100-year time horizon.