Increasing surface air temperatures from anthropogenic forcing are melting permafrost at high latitudes and intensifying the hydrological cycle. Long-term streamflow records (≥30 yrs) from 23 stream gauges in the Canadian Northwest Territories (NWT) indicate a general significant upward trend in winter baseflow of 0.5–271.6 %/yr and the beginning of significant increasing mean annual flow (seen at 39% of studied gauge records), as assessed by the Kendall-τ test. The NWT exports an average discharge of ≥308.6 km3/yr to the Beaufort Sea, of which ≥120.9 km3/yr is baseflow. We propose that the increases in winter baseflow and mean annual streamflow in the NWT were caused predominately by climate warming via permafrost thawing that enhances infiltration and deeper flowpaths and hydrological cycle intensification. To provide hydroclimatic context, we present evidence of a statistically significant positive link between the Northern annular mode and annual NWT streamflow at the interannual-to-decadal timescales.