Modelling the long term impact of climate change on the carbon budget of Lake Simcoe, Ontario using INCA-C

This study presents a process-based model of dissolved organic carbon concentration ([DOC]) in catchments draining into Lake Simcoe, Ontario. INCA-C, the Integrated Catchment model for Carbon, incorporates carbon biogeochemical processes in a terrestrial system with hydrologic flow paths to simulate watershed wide [DOC]. The model successfully simulates present-day inter-annual and seasonal [DOC] dynamics in tributaries draining catchments with mixed or contrasting land cover in the Lake Simcoe watershed (LSW). The sensitivity of INCA-C to soil moisture, hydrologic controls and land uses within a watershed demonstrates its significance as a tool to explore pertinent environmental issues specific to the LSW. Projections of climate change under A1B and A2 SRES scenarios suggest a continuous monotonic increase in [DOC] in surface waters draining into Lake Simcoe. Large variations in seasonal DOC dynamics are predicted to occur during summer with a possibility of displacement of summer [DOC] maxima towards winter and a prolongation of summer [DOC] levels into the autumn. INCA-C also predicts possible increases in dissolved inorganic carbon in some tributaries with rising temperature suggesting increased CO2 emissions from rivers as climate changes. ► Despite their shortcomings, process-based model can be used to make useful conclusions about possible future conditions. ► Climate change scenarios suggest a monotonic increase in DOC concentration in surface waters draining into Lake Simcoe. ► Climate change may cause shifts in seasonality of DOC, with higher concentrations expected in the autumn and winter. ► Warmer temperatures may enhance mineralization of riverine DOC, suggesting a future increase in CO2 emission from rivers.