Modelling Multi-Year Carbon Fluxes in the Arctic Critical Zone

Vegetation and soil regulate the terrestrial carbon cycle and contribute to the atmospheric CO2 concentration and Earth climate. The Arctic soil plays a major role in this cycle as the extension of permafrost areas is around 25% of the land in the Northern hemisphere and it is estimated that permafrost stores 2-3 times the atmospheric carbon. In the Holocene, the tundra has acted as a carbon sink, but it is not clear if the fast Arctic climate change will turn it into a carbon source. Yet, data regarding Arctic carbon fluxes are scarce and modelling of their fate is affected by large uncertainties. With the aim of investigating the tundra carbon fluxes dynamics on the high Arctic, CNR established the Bayelva Critical Zone Observatory at the Ny Ålesund research station in Svalbard since 2019, equipped with an Eddy Covariance tower and portable flux chambers for the measurement of Gross Primary Productivity (GPP) and of Ecosystem Respiration (ER) variability at the point scale, making it possible to build empirical models that correlate such variables to climate and environmental parameters such as temperature, irradiance, moisture and phenology. A first model, published in 2022, identified temperature, solar irradiance, soil moisture and green fractional cover as drivers. Further measurements done in 2021 and 2022 adding further sites in the Bayelva basin, allowed us to enlarge the scale of application of the model. A further step will be the use of the high-resolution satellite data of the VENmS mission (4 meters, 1 day revisit time) to extend the modelling of GPP over the entire Broegger peninsula, facilitating the spatial upscaling of measured fluxes,identifying the main variables to be used in general vegetation models and allowing future projections of carbon fluxes under different climate change scenarios in the high Arctic tundra.