Studies on the impacts and feedbacks in regions where rapid rates of human development trigger changes in the atmosphere or biosphere, and where rapid local and regional changes have global consequences are a central objective of the IGBP Analysis Integration and Modelling of the Earth System (AIMES) project as it seeks to understand and quantify the interactions and feedbacks between the biogeochemical and climate systems and the consequences of human activities and decisions. This includes coordinating and promoting research dedicated to improving Earth System Models through model development, parameterisation, testing and evaluation, with observations seen as a key contributor to this process. One of the key ‘trigger’ regions are the northern high latitudes (NHL) where there is strong palaeo-evidence that the Arctic and high-latitudes have responded dramatically to both external forcing and through internal feedbacks (vegetation, sea ice) in the past and they are known to be changing rapidly under both human pressures and the impacts of Global Change; the Arctic is predicted to warm faster and to a greater degree than any other part of the Earth. It is hypothesised that because of significant biogeochemical, hydrological and energetic feedbacks between the Earth system and the NHL, the future state of the entire Earth system will be strongly influenced by the response of the NHL to this warming. To understand further this coupling requires studies of:
- Changes in carbon storage and sequestration – in particular the vulnerability of the vast NHL soil carbon stocks to warming-induced nutrient mineralisation, which may accelerate CO2 accumulation in the atmosphere and thus act as a positive feedback on warming;
- Changes in albedo – reductions in albedo associated with reduced snow and ice, and increased forest cover, (enhanced absorption of radiation and elevated temperatures), increased albedo associated with removal of forest canopy through disturbance (e.g., wildfire, insect) and bare (snow covered) ground. Aerosols and their effect on haze and interactions with clouds are uncertain;
- Changes in terrestrial hydrology - the implications of altered precipitation and evaporation for permafrost dynamics (see 1. above) and ocean salinity gradients. Freshwater loading to the Arctic Ocean from river discharge is important in controlling the thermohaline circulation through deep-water formation.
- Changes in ocean circulation – potential changes in thermohaline circulation through surface warming, changes to the salinity gradient, altered CO2 uptake and changes to ocean solubility and uptake rates which may feed back on global climate;
- Changes in human behaviour – impacts on indigenous communities, changes in resource use, alterations in transport networks, including opening of new shipping routes.
- Develop close collaboration with a broad range of northern high latitude programmes and activities, and other IGBP and ESSP projects with a northern high latitude focus;
- Use this collaboration to identify and improve representation of key northern high latitude processes in global coupled carbon cycle climate models (C4MIP models) using local-to-regional northern high latitude experimental and modelling outputs;
- Initiate a regional/global model intercomparison with global C4MIP models to determine current uncertainties and key thresholds in Northern High Latitudes-Earth System climate-biogeochemical coupling.