Apparent recent trends in hydrologic response in permafrost regions of northwest Canada

Abstract

Yukon air temperature trends have been observed to change over the last several decades with an increase in both summer and winter air temperatures. An assessment of streamflow response was carried out to determine if there are apparent trends in permafrost regions as a result of the observed temperature changes. Degrading permafrost places a greater reliance on the interaction between surface and subsurface processes. Annual mean, maximum and minimum flows were assessed using the Mann–Kendall test to statistically validate observed trends. Annual mean flows are observed to have slight positive trends over the last three decades within continuous and discontinuous permafrost zones, with variable results within sporadic permafrost regions. These results are generally in keeping with similar trends in annual precipitation, which has increased slightly. Though not generally statistically significant, annual peak flows have largely decreased within continuous permafrost regions, and lesser so within discontinuous regions. Results are variable within sporadic permafrost zones. These trends are likely associated with increased annual precipitation; however, it is conceivable that there may be increased infiltration amounts as a result of degrading permafrost. Winter low flows have experienced significant apparent changes over the last three decades. The greatest changes in winter low flows appear to be occurring within the continuous permafrost zone, where flows from the majority of sampled streams have increased. Winter low flows trends in streams within the discontinuous permafrost zone generally exhibit positive significant trends, but are more variable. Winter streamflow trends within the sporadic permafrost zone are not consistent.