Hydrological discharges and motion of Fels and Black Rapids Glaciers, Alaska, U.S.A.: implications for the structure of their drainage systems

• Published in: Journal of Glaciology
• Main Authors: Raymond, C.F., Benedict, R.J., Harrison, W.D., Echelmeyer, K. A., Sturm, M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1995
• Subjects: Earth-Surface Processes; glacier; glaciers; Journal of Glaciology; Alaska
• Online Access: http://dx.doi.org/10.1017/s002214300001618x; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S002214300001618X

Abstract Characteristics of the hydrology and motion of Black Rapids and Fels Glaciers, Alaska, were observed from 1986 to 1989. Hydrological measurements included stage, electrical conductivity and suspended-sediment concentration in the discharge stream of each glacier, and were made at 0.5–1 h intervals continuously through most of the melt seasons. Variations in the glacier speed were monitored through the full year at a number of locations along the length of each glacier using time-lapse photography (1 d time resolution), strain meters (0.5–1 h resolution) and seismometers set up to count acoustic emissions. Both glaciers show similar seasonal, diurnal and short-term event changes in hydrological discharges and ice speed. The hydrological behavior is analyzed in terms of a “fast” sub-system composed of surface streams, moulins and large tunnels with discharge that responds rapidly and a “slow” sub-system composed of heterogeneous small passageways through the ice and distributed over the bed that maintain approximately uniform discharge over a day. The liming and amplitude of water discharge in the diurnal cycle indicate that roughly 10–40% of the water is routed directly into the fast system. The remaining 90–60% of the water enters the slow system. Dilution of the solute discharged from the slow system by the variable discharge in the fast system results in changes in water discharge and solute concentration that are approximately equal in relative amplitude and inversely related. A small time lag from discharge maximum (minimum) to solute minimum (maximum) suggests that the fast system is confined to roughly the lowermost 30–40% of the full glacier length. The residence time of water in the fast system is short compared to 1 d. The slow system contains both short- and long-residence time passages. Characteristics of the diurnal cycles are somewhat variable through the melt season, but no systematic evolutionary patterns were discerned even though large changes in the mean discharges of water and solutes ...