Links Between Proglacial Stream Suspended Sediment Dynamics, Glacier Hydrology and Glacier Motion at Midtdalsbreen, Norway

Abstract

Two-hourly suspended sediment concentration variations observed during the summer of 1987 in the proglacial stream draining Midtdalsbreen, Norway are modelled using multiple regression and time series techniques. Suspended sediment fluctuations are influenced by stream discharge variations, diurnal hysteresis effects, medium-term sediment supply and transport variations and the recent suspended sediment concentration history of the stream. They do not appear to be influenced by seasonal exhaustion or rainfall variations. Possible reasons for this are discussed. Large positive residuals from the fitted models are major pulses of suspended sediment unrelated to discharge variations; these sediment flushes correlate with periods of enhanced glacier motion. They cannot be explained by enhanced sediment production by subglacial erosion, but are probably due to the tapping of subglacially stored sediment during sudden changes in the hydraulics and/or configuration of the subglacial hydrological system. Seasonal changes in the lag between glacier motion peaks and suspended sediment flushes suggest that the subglacial hydrological system evolves over the summer from a distributed to a more channelized configuration.

Regional and Annual Variability in Subglacial Sediment Transport by Water for Two Glaciers in the Swiss Alps

“…As a result, subglacial sediment transport is not only a function of water discharge (e.g., Rickenmann, 2001), but also of ice dynamics, as pressurized water flow can exhibit higher velocities (Walder and Fowler, 1994). The access of fast flowing meltwater to subglacial sediment is another major factor impacting subglacial sediment discharge (e.g., Collins, 1996;Willis et al, 1996;Herman et al, 2015).…”

Hydrologic controls on coastal suspended sediment plumes around the Greenland Ice Sheet

“…Sediment-rich meltwater from land-terminating outlet glaciers may encounter lakes, outwash plains, or braided river valleys, all of which can act as traps or sources for sediment (Busskamp and Hasholt, 1996;Hasholt, 1996); these land-terminating fjords tend to be dominated by surface meltwater (Dowdeswell and Cromack, 1991). While sediment transport in rivers from landterminating glaciers have been commonly studied through a relationship between river discharge and suspended sediment concentration (SSC) or total sediment load, some hysteresis has been found, where limitations in sediment supply result in decreased SSC despite increased meltwater runoff (Hammer and Smith, 1983;Schneider and Bronge, 1996;Willis et al, 1996). For marine-terminating outlet glaciers, sediment export to the ocean is dominated by the distinctly different mechanisms of iceberg rafting and/or en-and sub-glacially transported meltwater runoff (Andrews et al, 1994).…”

Estimating fluvial sediment transport: The rating parameters

“…A river dominated by snow discharge may show a positive hysteresis loop since it experiences its highest sediment concentrations during the spring freshet [Syvitski et al, 1987]. These and other studies on hysteresis [Richards, 1984;Kostaschuk, 1989;Willis, 1996] indicate that suspended sediment concentration is dependent on the runoff source (snow melt, glacial melt, rain, and groundwater).…”