Hydroclimatic dynamics in subarctic catchments
The water balance in arctic and sub-arctic catchments is often closely connected to the presence of permafrost and ice masses (i.e. ice caps, glaciers) that largely determine pathways of water flow through the landscape and timing of flood events. Climate change effects such as increasing precipitation and surface temperatures may lead to an increase in shallow subsurface flow, which may directly affect flood intensity and frequency in these catchments. Change in the timing and magnitude of hydrologic extremes may be one of the most significant consequences of climate change. Thus, understanding and quantifying the relation between local, physical controls and regional/global climatic forcings on stream discharge variability and flow pathways are key challenges to estimate climate change impacts in arctic and sub-arctic regions.
- Statistical investigation of hydro-climatic trends and risks, glacio-hydrological modeling, and experimental studies and field observations of water and biogeochemical fluxes.
- Improving the mechanistic understanding of the interactions between climate, the cryosphere and the terrestrial freshwater cycle in arctic and sub-arctic regions.
- Assessment of changes in rainfall-runoff partitioning and the hydrologic response to climate change through comparison of glacierized and non-glacierized catchments in a similar climate setting.
- Develop and test novel statistical analyses to decipher complex hydro-climatic trends.(Key-collaborators: Dr. Sean Fleming, Dr. Jery Stedinger)
- Glacierized (> 10% glacier cover) vs. non-glacierized catchments exhibit fundamentally different trends in the mean summer discharge, the flood magnitude and flood timing.
- Glacierized catchments in northern Sweden showed significantly increased mean summer discharges and flood magnitudes while non-glacierized catchments showed opposite trends.
- Increase in flood magnitudes is correlated to increase in extreme precipitation events in northern Sweden.
- Glacierized Norwegian and Canadian watersheds in the southern Canadian Rocky Mountains and arctic coastal Norway show stronger, more seasonally persistent, and more consistent declining late-summer flows than non-glacial basins, which is mainly due to progressive glacial area loss.
- Glacier-controlled, highly (non-monotonically) nonlinear (parabolic) streamflow teleconnections were identified between local air temperature and the Arctic Oscillation for the Norwegian basins or El Niño-Southern Oscillation for the Canadian basins yielding corresponding parabolic teleconnections in glacial melt production.
Figure left: Daily streamflow data for a Norwegian glacierized (40%) catchment. X-axis shows day-of-hydrologic-year (DOHY). Figure right: Example of a non-linear, parabolic relationship between late summer streamflow and the mean winter (DJF) El Niño-Southern Oscillation (ENSO) teleconnection.
- Dahlke HE, Lyon SW, Karlin T, Rosqvist G and P Jansson. 2013. Isotopic investigation of runoff generation in a glacierized catchment, northern Sweden. Hydrological Processes, doi: 10.1002/hyp.9668.
- Dahlke HE, Lyon SW, Stedinger JR, Rosqvist G and P Jansson. 2012. Contrasting trends in floods for two sub-arctic catchments in northern Sweden - does glacier presence matter?, Hydrology and Earth System Science 16, 2123-2141, doi:10.5194/hess-16-2123-2012, 2012.
- Fleming SW and HE Dahlke. 2013. Low- and high-frequency hydroclimatic dynamics of alpine rivers in Canada and Norway: strong nonlinearities, seasonal transients, and glacial controls. Canadian Journal of Water Resources (in press).