Evaluation of the impact of climate change on the streamflow of major pan-Arctic river basins through machine learning models

Under a warmer climate, streamflow from the pan-Arctic River basins exhibits increasing trends in recent years. The higher streamflow would have a large impact on the atmospheric and oceanic circulation of the Arctic, even the globe. However, due to the limited observation data and the complex hydrologic processes in the polar river basins, it is challenging to simulate and to predict the streamflow under the impact of climate change. This study applied Support Vector Regression Model (SVR), Artificial Neural Network (ANN), and Multi-Variable Regression (MLR) model to simulate the monthly streamflow of four major pan-Arctic River basins: Mackenzie River basin, Ob’ River basin, Lena River basin, and Yenisei River basin. After validating the SVMs with datasets independent of the calibration experience, the SVMs were used to predict the monthly streamflow of the four large pan-Arctic river basins, under the climate projection scenarios, SSP245 and SSP585, of five CMIP6 GCMs: BCC-CSM2-MR, CAS-ESM2-0, CMCC-ESM2, FIO-ESM-2-0, and MPI-ESM1-2-HR, for 2020–2100. Results show that: 1) the precipitation and temperature are both projected to increase by almost five GCMs in almost river basins with larger amplitudes under SSP585 than SSP245; 2) with wetter and warmer climate, the annual streamflow was projected to increase continuously over the twenty-first century for Mackenzie, Lena, and Yenisei river significantly, with larger amplitudes under SSP585 than SSP245. The Ob’ river does not show significant increasing trends in its annual streamflow; 3) the higher annual streamflow of Lena and Yenisei river basins mainly come from the increase in summer streamflow, while for Meckanzie, the streamflow in summer and winter increases evenly. As its higher winter streamflow compenstates its lower summer streamflow, the annual streamflow of the Ob’ river is projected with minimal changes. In addition, the onset of spring snowmelt is also projected to occur earlier in all river basins due to warmer climate. Results of this study agree with previous findings that the Arctic streamflow is increasing, but this study also demonstrate different responses in seasonal streamflow between the river basins to warmer temperature and higher precipitation, which is largely controlled by the respectiver terrestrial environment of the river basins.