Glacierized headwater streams as aquifer recharge corridors, subarctic Alaska

• Published in: Geophysical research letters 2017-07, Vol.44 (13), p.6876-6885
• Main Authors: Liljedahl, A. K., Gädeke, A., O'Neel, S., Gatesman, T. A., Douglas, T. A.
• Format: Article
• Language: English
• Subjects: Annual; aquifer; Aquifer recharge; Aquifers; Arctic; Arid regions; Base flow; Climate; Coastal inlets; Coastal processes; Coastal waters; Corridors; Creeks & streams; discharge; Glacial runoff; glacier; Glacier melting; Glaciers; Glaciohydrology; groundwater; Groundwater recharge; Headwaters; Infiltration; Meltwater; Mineral nutrients; Mountain glaciers; Permafrost; River discharge; River flow; Rivers; Runoff; Sea ice; Sea ice growth; Semiarid climates; Semiarid lands; Semiarid zones; Shrinkage; Stream discharge; Stream flow; Streambeds; Streams; Summer; Travel; Water discharge; Winter
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2017GL073834

Arctic river discharge has increased in recent decades although sources and mechanisms remain debated. Abundant literature documents permafrost thaw and mountain glacier shrinkage over the past decades. Here we link glacier runoff to aquifer recharge via a losing headwater stream in subarctic Interior Alaska. Field measurements in Jarvis Creek (634 km2), a subbasin of the Tanana and Yukon Rivers, show glacier meltwater runoff as a large component (15–28%) of total annual streamflow despite low glacier cover (3%). About half of annual headwater streamflow is lost to the aquifer (38 to 56%). The estimated long‐term change in glacier‐derived aquifer recharge exceeds the observed increase in Tanana River base flow. Our findings suggest a linkage between glacier wastage, aquifer recharge along the headwater stream corridor, and lowland winter discharge. Accordingly, glacierized headwater streambeds may serve as major aquifer recharge zones in semiarid climates and therefore contributing to year‐round base flow of lowland rivers. Key Points Glacier meltwater discharge represents >15% of total annual streamflow in a subarctic headwater with 3% glacier coverage Headwater streams lose 38 to 56% of annual streamflow to recharge of lowland aquifers Glacier‐derived aquifer recharge via headwater streambeds may explain long‐term increases in lowland river base flow Plain Language Summary Observations of increased river discharge in summer and winter span the scientific community and Arctic residents. Changes in streamflow present implications for river travel throughout the year and impact sea ice growth and nutrient exports to Arctic Ocean coastal waters. Processes responsible for increasing river discharge are debated because no single process can explain increases in runoff of several rivers. Here we show that the ubiquitous mass loss from subarctic mountain glaciers feeds rivers not only in summer but also in the winter. We measured summer discharge at two places in the same glacier‐fed headwater stream in Interior Alaska and found that the discharge is lower downstream that upstream. The difference represents water that is lost to infiltration into ground and subsequent aquifer recharge. The aquifer in turn feeds the larger lowland river, like the Tanana River, during winter. As such, glaciers across the semiarid regions can be important sources of water to streams and aquifers and an overlooked source of increasing river discharge reported across the Arctic.