Among the abiotic components, permafrost is the most widespread in the world (more than 25% of the land) and is also a good indicator of the impact on modern climate change and represents a natural archive of the past climate, providing a useful model for the study of the extraterrestrial climate and environmental conditions. Moreover,permafrost has been demonstrated to be highly susceptible to climate change. The influence of climate on permafrost is expressed by the combination of the surface energy balance and of the thermal offset. The first determines the ground surface temperature (GST), the latter the permafrost temperature from the input of the GST. The surface energy balance in particular is influenced by factors such as vegetation and snow cover, both acting as a buffering layer between the atmosphere and the ground. Land cover, and, above all, vegetation changes are among the more important factors able to modify permafrost distribution and its thermal regime due to the buffering effect exerted by vegetation and by the snow cover modifications due to the vegetation changes.
Among the terrestrial ecosystems, vegetation is one of the most sensitive components to climate change impacts, as climate is one of the most important factors influencing vegetation occurrence, structure and floristic composition and distribution. Past climate changes have affected vegetation at both species and community level,exerting significant impacts on its characteristics and distribution. Recent climate changes induced significant changes of vegetation floristic composition, structure and dominant functional types in the high latitude as well as in the high altitude areas, with impacts on biodiversity, vegetation dynamics and with species and community displacements. Moreover, vegetation changes are among the most important factors capable of modifying ground surface temperature and the related active layer thickness due to the buffering effect exerted by vegetation and the influence of the last on the snow cover. In the High Arctic climate change induced significant changes of vegetation floristic composition, structure and dominant functional types. Recent observations in the High Arctic show that different tundra types had different carbon budgets, acting as carbon sources or sinks and, hence,showing different potential responses to further climate changes. Climate-ecosystem feedbacks might amplify or dampen regional and global climate change. In particular, in the polar areas, changes of vegetation and permafrost as a result of warming climate are expected to exert strong feedbacks to climate change both through changes in the energy balance, in the permafrost conditions, in the snow cover thickness and duration, as well as through controls over ecosystem C storage. The effects of climate change on global soil carbon stocks are still unclear, predicting both positive feedbacks mainly associated to the higher increase of decomposition or negative feedbacks and/or impacts variable with time. Recently we demonstrated that, in Continental as well as in Maritime Antarctica the active layer thermal regime and its thickness are influenced by vegetation type and coverage and that changes of vegetation cover are able to influence the ground thermal regime and the snow depth and also to induce the thickening of the active layer. In particular, in the South Orkney Islands the documented increased rate of warming (2°C ± 1) since 1950 for recorded air temperatures suggests that the overall trend of active layer thickness increase will be around 1 cm/year.
Scientific objectives of this research activity will be:
- Assessment of climate change impacts on permafrost, active layer and vegetation through the monitoring of these indicators.
- Identification and quantification of the impacts induced by changes of key climatic factors such as air temperature and seasonal snow cover on the vegetation cover relating to its composition, structure, dynamics,distribution patterns and functional parameters linked to the budget of the greenhouse gasses and on the ground surface temperature (GST) in selected test sites around the CCT.
- Assessment of the thermal properties of the active layer in the same selected test sites around the CCT and analysis of their relationships to the changes of the GST.
- Setting-up of a new automatic active layer monitoring system and installation of new CALM grid for the short and long term monitoring of the active layer.
- Setting up of anew automatic permafrost monitoring system down to at least 30 m depth in correspondence of the CALM grid and on the CCT.
- Assessment and monitoring of the CO2, and CH4 fluxes associated to different vegetation types in selected test sites characterized by different permafrost and environmental conditions.
- Finally, the surface energy balance is relevant also for the connection between the surface energetic partitioning and the cloud coverage (topic of the third paragraph of this Science Plan).
