River ice under climate change: integrating modelling and data acquisition methods for detecting changes

Fluvial ice significantly impacts river hydrodynamics by increasing flow resistance, which leads to altered water levels, flow velocities, and turbulence characteristics. River ice also has socio-economic implications as it impacts energy production, flood risk management, and transportation. These effects have remarkable spatial extent: approximately one third of the Earth’s landmass is drained by seasonally freezing rivers. At the same time, the Earth system is experiencing rapid and dramatic changes due to changing climate and these changes are intense in northern areas due to even faster warming and fragile ecosystems. Despite the importance of understanding these changes, obtaining detailed information of ice-covered hydrodynamics remains challenging and potentially dangerous, resulting in limited data availability even under current conditions.

In this research, more comprehensive insights into fluvial ice and ice-covered hydrodynamics in Finland are achieved by integrating novel approaches in physical modelling, numerical modelling, and field data acquisition and processing. Information of current conditions in the studied subarctic rivers is gathered using conventional methods, such as flow velocity measurements, as well as emerging technologies including underwater drones. The study includes ice growth calculations under projected climate and flow conditions. Flume experiments in an indoor flume with proxy ice and bed topography and pressurised conditions are conducted to observe ice-covered hydraulics in a controlled environment. New methodologies and integration of different approaches allow for gathering more comprehensive information on seasonally freezing rivers and help in predicting future changes in response to climate change.