Climate change/variability and freshwater-ice systems

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Freshwater ice is an integral component of cold-regions lakes and rivers and an important modifier of related biological, chemical and physical processes.   Although serious concerns have been expressed about the impacts of climate change on ice-covered systems (e.g., the recent assessment by the Intergovernmental Panel on Climate Change and the Arctic Climate Impact Assessment), knowledge of such systems is relatively weak making it difficult to predict the nature of the effects of a changing climate.  This project will focus on filling some of our most important knowledge gaps by addressing three research areas: extreme hydrologic events; climatic controls; and effects on hydro-ecological systems.The focus of extreme hydrologic events will be river-ice breakup and associated ice jamming.  Such events can produce floods exceeding those possible under similar flow during the open-water period.  Although breakup flooding is known to produce significant economic damage and also to be critical to the environmental health of aquatic systems, no broad-scale assessment of its importance has been conducted.  This study will fill this gap by conducting a national and circumpolar evaluation of the historical frequency and magnitude of breakup floods and compare the results to those for the open-water period.  This will provide a basis for improved infrastructure planning and environmental management, as well as be the basis for the second objective of this research program: predicting how the frequency and magnitude of such extreme events will be affected by future climate change.   Major changes in river and lake ecology, particularly including the water quality, are also expected to result from climate-induced changes to river-ice cover.  Projected ecological changes, however, have been based primarily on guesstimates of changes in the ice cover, not on the results of physically-based models.  The final objective of this program will be to undertake such modelling so that we can more accurately forecast how northern aquatic systems will respond to climate change.