First results from Acoustic Doppler Current Profiler measurements of meltwater flux in a large supraglacial river in western Greenland compared with downstream proglacial river outflow

Abstract:

A vast network of seasonally evolving, thermally eroding supraglacial rivers on the southwestern Greenland Ice Sheet (GrIS) is the preeminent transporter of meltwater across this area of the ablation zone. Supraglacial rivers are important for estimating surface water storage and transport into moulins and into the en-, sub-, and proglacial environments. Yet, little is known about their role in the GrIS cryo-hydrologic system. To that end, supraglacial river discharge in a large river, the “Rio Behar” (67.05°, -49.02°; ~75 km from the Kangerlussuaq International Airport), was measured in situ over 300 times: approximately four times per hour over three consecutive days from July 19 – 22, 2015. The Rio Behar drains a ~ 70 km² ice catchment and enters a large moulin in the Watson River land-ice watershed in western Greenland. River discharge was measured using a Sontek M9 Acoustic Doppler Current Profiler. Each profile records water temperature, depth-integrated velocity, channel width and channel bathymetry. This novel dataset can be used to assess diurnal variations in river discharge, slope, velocity, stream power, and channel incision in order to enhance process-level understanding of GrIS meltwater routing, storage and transport. Future work will compare supraglacial river discharge in the Rio Behar with in situ estimates of proglacial river outflow upstream of the Watson River bridge in Kangerlussuaq, Greenland.