Mechanisms behind the uneven increases in early, mid- and late winter streamflow across four Arctic river basins

•Winter streamflow increases were 1.7–5.2 times greater than annual streamflow.•Discharge in late winter is the lowest but is most sensitive to temperature.•The early winter streamflow reflects the changes in late summer precipitation.•Permafrost thawing gradually increases the winter streamflow. The increasing winter streamflow of major Arctic rivers has been well documented. However, the contribution of climate change to winter streamflow and associated mechanisms of streamflow generation during early, mid- and late winter are not fully understood. Among the Arctic rivers, we selected four rivers with relatively few dam effects (Lena, Kolyma, Yukon and Mackenzie rivers) and analysed their climate change-related responses in streamflow during early, mid-, and late winter. Our results showed that the winter streamflow (Qwin) of the Lena, Kolyma, Yukon and Mackenzie rivers increased from 1980 to 2019 by approximately 43%, 72%, 16% and 16% (1.7–5.2 times greater than increases in annual streamflow), respectively. In general, the rate of streamflow increase was the greatest in early winter, followed by mid- and late winter. The streamflow in late winter was particularly sensitive to air temperature changes, and permafrost degradation due to rising temperatures is likely a major factor driving late winter streamflow increases. In contrast to late winter streamflow, the larger rate of increase in early winter streamflow can be mainly attributed to the additional influence of increased late summer precipitation on streamflow generation. The different change rates in winter streamflow among the four river basins are highly determined by permafrost degradation and related baseflow discharge processes. Under warming climate conditions, winter streamflow generation is strongly associated with the enhanced hydrological cycle that is apparent in both the surface (e.g., precipitation and river ice) and the subsurface (the active layer and groundwater discharge).