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.