Temporal Variability in Suspended Sediment
Variables representing variations in sediment availability were considered, including: coshr and sinhrto capture diurnal variability; ΔQ to represent other hysteresis effects; QE to represent sediment supply variability within a season; and H and ΣQ as indicators of seasonal trends (Table 1). Selection of coshr and -sinhr in the best-fit models for Carnivore and Chamberlin Creeks, respectively, are indicative of clockwise diurnal variability in the Q-SSC and NTU-SSC relations. Some Arctic sediment transfer studies have found no evidence of hysteresis control beyond covariation with discharge (Hodgkins, 1996; Hodgkins, 1999; Irvine-Fynn et al., 2005), while others have found prominent hysteresis effects over various time periods (Arnborg et al., 1967; Hodson et al., 1999; Lewkowicz & Wolfe, 1994; McDonald and Lamoureux, 2009; Richards, 1984; Schiefer et al., 2017; Østrem, 1975). Both coshr and -sinhr are likely related to the glacier meltwater cycle, during which sediment is entrained on rising daily discharge, resulting in higher SSCs on the rising limb, compared to when sediment is deposited farther downstream as meltwater discharge wanes (Lewkowicz & Wolfe, 1994; McDonald and Lamoureux, 2009; Richards, 1984). The diurnal SSC peak is later in Carnivore Creek than in Chamberlin Creek, which we attribute to the greater sediment transfer distance and lower slope of Carnivore Creek.
Suspended sediment exhaustion over the course of the open-channel season is suggested by the negative H coefficient in the Q-based model for Chamberlin Creek, but is not suggested for Carnivore Creek (Table 3), probably due to discrepancies in catchment characteristics. Chamberlin sub-catchment is small and steep, compared with the gently sloping lower valley of Carnivore Creek (Figure 2), with less potential for transient intra-annual sediment storage and remobilization. Differences among the glaciers’ thermal regimes (Bogen & Bønses, 2003; Hodson & Ferguson, 1999), or the pace of Quaternary-scale paraglacial denudation (Church & Ryder, 1972; Church & Slaymaker, 1989), could also explain seasonal exhaustion in the sub-catchment of Chamberlin Creek, but not in Carnivore Creek.