The effects of contemporary increases in riverine freshwater into the Arctic Ocean are estimated from ocean model simulations, using two runoff data sets. One runoff data set which is based on older climatological data, which has no inter-annual variability after 2007 and as such does not represent the observed increases in river runoff into the Arctic. The other data set comes from a hydrological model developed for the Arctic drainage basin, which includes contemporary changes in the climate. In the pan-Arctic this new data set represents an approximately 11% increase in runoff, compared with the older climatological data. Comparing two ocean model runs forced with the different runoff data sets, overall changes in different freshwater markers across the basin were found to be between 5-10%, depending on the area investigated. The strongest increases were seen from the Siberian rivers, which in turn caused the strongest freshening in the Eastern Arctic.

Lakes and reservoirs are an integral part of the terrestrial water cycle. In this work, we present the implementation of water balance models of lakes and reservoirs into mizuRoute, a vector-based routing model. The developments described here are termed mizuRoute-Lakes. The capabilities of mizuRoute-Lake in simulating the water balance of lakes and reservoirs are demonstrated. The main advantage of mizuRoute-Lake is flexibility in testing alternative lake water balance models within a given river and lake network topology. Users can choose between various types of parametric models that are already implemented in mizuRoute-Lake or data-driven models that provide time-series of the target volume and abstraction from a lake or reservoir from an external source such as historic observation or water management models. The parametric models for lake and reservoir water balance implemented in mizuRoute-Lake are Hanasaki, HYPE, and D{\"o}ll formulations. In general, the parametric models relate the outflow from lakes or reservoirs to the storage and various parameters including inflow, demand, volume of storage, etc. Additionally, this flexibility allows to easily evaluate and compare the effect of various water balance models for a lake or reservoir without needing to reconfigure the routing model. We show the flexibility of mizuRoute-Lake by presenting global, regional and local scale applications. The development of mizuRoute-Lake paves the way for better integration of water management models with existing and future observations such as the Surface Water and Ocean Topography (SWOT) mission, in the context of Earth system modeling.

This study investigates the impacts of climate change on the hydrology and soil thermal regime of ten sub-arctic watersheds (northern Manitoba, Canada) using the Variable Infiltration Capacity (VIC) model. We utilize statistically downscaled and bias-corrected forcing datasets based on 17 general circulation model (GCM) - representative concentration pathways (RCP) scenarios from phase 5 of the Coupled Model Intercomparison Project (CMIP5) to run the VIC model for three 30-year periods: a historical baseline (1981–2010), and future projections (2021–2050: 2030s and 2041–2070: 2050s), under representative concentration pathways (RCPs) 4.5 and 8.5. The CMIP5 Multi-Model Ensemble (MME) mean-based VIC simulations indicate a 15–20% increase and 10% decrease in the projected annual precipitation and snowfall, respectively over the southern portion of the basin and >20% rainfall increase over the higher latitudes of the domain by the 2050s. Snow accumulation is projected to decline across all sub-basins, particularly in the lower latitudes. Projected uncertainties in major water balance components (i.e., evapotranspiration, surface runoff, and streamflow) are more substantial in the wetland and lake-dominated Grass and Gunisao watersheds than their eight counterparts. Future warming increases soil temperatures >2.5°C by the 2050s, resulting in 40–50% more baseflow. Further analyses of soil temperature trends at three different depths show the most pronounced warming in the top soil layer (1.6°C 30-year-1 in the 2050s), whereas baseflow increases substantially by 19.7% and 46.3% during the 2030s and 2050s, respectively. These results provide crucial information on the potential future impacts of warming soil temperatures on the hydrology of sub-arctic watersheds in north-central Canada and similar hydro-climatic regimes.

A document by Tricia A. Stadnyk. Click on the document to view its contents.