Uncertainty in the impacts of projected climate change on the hydrology of a subarctic environment: Liard River Basin
Abstract. Freshwater inputs from the Mackenzie River into the Arctic Ocean contribute to the control of oceanic dynamics and sea ice cover duration. Half of the annual runoff from the Mackenzie River drains from mountainous regions, where the Liard River, with a drainage area of 275 000 km2, is especially influential. The impact of projected atmospheric warming on the discharge of the Liard River is unclear. Here, uncertainty in climate projections associated with GCM structure (2 °C prescribed warming) and magnitude of increases in global mean air temperature (1 to 6 °C) on the river discharge are assessed using SLURP, a well-tested hydrological model. Most climate projections indicate (1) warming in this subarctic environment that is greater than the global mean and (2) an increase in precipitation across the basin. These changes lead to an earlier spring freshet (1 to 12 days earlier), a decrease in summer runoff (up to 22%) due to enhanced evaporation, and an increase in autumn flow (up to 48%), leading to higher annual discharge and more freshwater input from the Liard River to the Arctic Ocean. All simulations project that the subarctic nival regime will be preserved in the future but the magnitude of changes in river discharge is highly uncertain (ranging from a decrease of 3% to an increase of 15% in annual runoff), due to differences in GCM projections of basin-wide temperature and precipitation.