Carbon fluxes in the Arctic Critical Zone: a study-case in Spitzbergen, Norway

We measured carbon fluxes in a few sites around Ny Ålesund, Spitzbergen, Norway, in the summers of 2019, 2021 and 2022, using portable accumulation chambers. The measurement procedure is capable of distinguishing between the Net Ecosystem Exchange, NEE, and Ecosystem Respiration, ER, thus allowing for an estimate of the Gross Primary Productivity, GPP=NEE-ER. The statistical analysis of the data, coupled with the construction of a family of empirical models for GPP and ER, allowed us to identify the main drivers of carbon flux variability and of Critical Zone processes at these Arctic sites. In particular, the results indicate the relevance of both the soil (or air) humidity and of the Green Fractional Cover, and point to the presence of small-scale heterogeneity of the fluxes. Important points concern the difference in the fluxes from vascular and non-vascular vegetation, which can be driven by different environmental parameters, and the different behavior of different vascular plants. We show that the use of the validated empirical model allows for future projections of the expected carbon fluxes under different climate change scenarios and for spatial upscaling of the measured fluxes.