Climate and hydrological changes in the Ob River Basin during 1936-2017

Changes in the hydrological regimes of Arctic rivers could affect the thermohaline circulation of the Arctic Ocean. In this study, we analysed spatiotemporal variations in temperature and precipitation in the Ob River Basin regions during 1936-2017 based on data from the Global Precipitation Climatology Center. Changes in discharge and response to climate change were examined based on monthly observed data during the same period. It is indicated the Ob River Basin experienced significant overall rapid warming and wetting (increased precipitation) in the study period, with average rates of 0.20 degrees C (10 year(-1)) and 5.3 mm (10 year(-1)), respectively. The annual spatial variations of temperature and precipitation showed different scales in different regions. The discharge in spring and winter significantly increased at a rate of 384.1 and 173.1 m(3)/s (10 year(-1)), respectively. Hydrograph separation indicated infiltration and supported that deep flow paths increased the contribution of groundwater to base flow. Meanwhile, the variation of the ratio of Q(max)/Q(min) suggested that the basin storage and the mechanism of discharge generation have significantly changed. The hydrological processes were influenced by changes of permafrost in a certain in the Ob River Basin. An increase in the recession coefficient (RC) implies that the permafrost degradation in the basin due to climate warming affected hydrological processes in winter. Permafrost degradation affected the Q(max)/Q(min) more significantly in the warm season than RC due to the enhanced infiltration that converted more surface water into groundwater in the cold season. The impact of precipitation on discharge, including surface flow and base flow, was more significant than temperature at the annual and seasonal scales in the Ob River Basin. The base flow was more obviously influenced by temperature than surface flow. The results of this study are significant for analyses of the basin water budget and freshwater input to the Arctic Ocean.