IMPACT OF CLIMATE CHANGE ON FUTURE DISCHARGES AND FLOW CHARACTERISTICS OF THE TANA RIVER, SUB-ARCTIC NORTHERN FENNOSCANDIA

Climate change is expected to have a substantial impact on hydrology on both a global and regional scale. Although the anticipated warming is expected to be greatest in the northern regions and cause alteration in the hydrological cycle, it has yet to be resolved, to what extent these hydrological changes will alter such flow characteristics as flow velocity, bed shear stress and stream power in Sub-Arctic rivers. Future changes in the fluvial erosion potential are studied in the Sub-Arctic Tana River, on the border of Finland and Norway. We modelled future discharge scenarios for the years 2070 to 2099 with a conceptual hydrological model incorporating three emission scenarios, with two global and one regional climate model. These simulated flood discharges were used as input hydrographs to model flow characteristics with a two-dimensional hydraulic model. Differences in the spatial distribution of flow characteristics between frequent (HQ1/2a) and infrequent floods (HQ1/250a) were examined. Compared to the present, in most simulations, both HQ1/250a and HQ1/2a flood discharges diminished, with spring floods occurring earlier also. Although the relative reduction in flow characteristics (velocities, bed shear stresses and stream powers per unit area) was more notable in 1/2a compared to 1/250a floods, the discharge peaks of the former would theoretically still be able to transport the fine sediments that form the river bed. Based on most of the climate scenarios, autumnal floods become more frequent in the future and hence, their role in sediment transport may become more significant compared to the present-day situation.