Hydrological processes in glacier and permafrost affected landscapes are highly variable in time and space and subject to rapid transformation during a changing climate. In order to gain a deeper understanding of the linkages between glaciers and hydrology on the watershed scale, a thorough measurement network was set up in the Jarvis Creek watershed (630 km2), which is a headwater basin of the Tanana River (12,000 km2), in semi-arid Interior Alaska. Runoff, glacier mass balance, end-of-winter snow depths, soil temperature, geochemistry, and meteorological variables have been measured since 2011, to reflect an elevation gradient from north (lowland) to south (mountain).
We hypothesize that glacier melt i) maintains lowland streamflow during summer months and ii) recharges the regional aquifer. Glacier coverage of Jarvis basin (3% of total area) has been reduced by about 34 % (1950-2000), while providing up to 19 % (2014) to 58 % (2013) of total specific runoff in the lowland. The reduction in glacier area coincide with increased mean annual air temperature (+1.9°C) and summer warmth index (+6.5 °C), which is the sum of all mean monthly air temperature above 0 °C, since 1947 (Delta Junction). Change in annual, summer and winter precipitation has been negligible. Our measurements also show that Jarvis Creek is a losing stream that recharges the regional aquifer.
We postulate that the reduced glacier coverage, via increased aquifer recharge, is the primary cause of the observed increase in late winter baseflow of the Tanana River (+24 % 1974-2006, Fairbanks). These results suggest that glaciers do not only directly support streamflow in the headwater basins during summer months, but are also significant contributors to groundwater recharge in permafrost-free soils, thereby affecting the large scale hydrological regime of subarctic glacierized watersheds.