Investigation on the effects of climate change on stream temperature and river ice thickness in the Nelson-Churchill and Mackenzie River basins

Abstract

The IPCC (Intergovernmental Panel on Climate Change) has predicted a median increase of 2.4 to 3.5 ℃ of median air temperature by 2100. The Arctic is predicted to be more severely affected due to arctic amplification, where higher latitudes are warming at a rate faster than the global mean. In Canada’s North, observed data are not readily available due to the remote nature of rivers, and accessibility issues. Therefore, modelling offers a solution as a way to estimate variables in remote locations. This project seeks to investigate the effects of climate change on stream temperature and river ice thickness in the Nelson–Churchill and Mackenzie River basins. These basins cover roughly one third of Canada and both drain to the Arctic Ocean.

The Arctic HYPE model was used to model five climate scenarios from 1981 to 2070, continuously. The Mann–Kendall trend test was used to determine the stream temperatures and river ice thickness trends, based on pre–whitened yearly mean data. Overall, stream temperatures are expected to increase at a mean rate of 0.022 ℃/year, increasing more quickly in the southern portions of the study area, and disproportionately in the summer months, at an average rate of 0.041 ℃/year. River ice thickness is expected to decrease at an average rate of 0.22 cm/year, and the number of days with river ice cover are expected to decrease at an average rate of 0.4 days/year. Due to increases in stream temperature, cold–water fish species will likely thrive, which would result in disrupting the ecosystem balance. Ocean and major lake inflows are expected to increase in temperature, causing potential harm to ice cover, flora and fauna, and processes such as mixing and stratification in these areas. Ice roads will be affected by shorter frozen river seasons and an overall decrease in ice thickness. Remote communities, and in particular Indigenous communities, will be affected by the decrease in river ice as they disproportionately rely on ice roads for transportation.