Glacier thermal regime and suspended-sediment yield: a comparison of two high-Arctic glaciers

Abstract

ABSTRACT. This paper compares estimates of susp ended-sediment yield and discha rge from two glacier basins in Svalbard ex hibiting contrasting glacial thermal regimes: Austre Br0ggerbreen (",12 km 2), which is almost entirely cold-based, and Finsterwalderbreen (~4 km2), dominated by warm basal ice. There are marked differences in th e magnitude a nd temporal pattern o[ mean d ail y discharge a nd mean daily suspended-sediment concentration from the two glacier basin s. Specific suspended-sediment yields from Finsterwalderbreen (710-2900 t km 2 a I) were more than one order ofmagnitude greater than at Austre Br0ggerbreen (81 -110 t km 2 a-I). Th ese differences are ascribed to the influence o[ thermal regime upon the meltwater drainage system and the predominant sources of suspended sediment. The potential significance of glacier thermal regime is furth er explored using studies from other glacier basins in Svalbard. Variations in thermal regime resulting from mass-balance adjustments since the termination o[ the Little Ice Age are also examined.

Fluvial suspended sediment transport from cold and warm-based glaciers in Svalbard

“…Meltwaters entered the proglacial river after leaving a large subglacial conduit, a small supraglacial stream and a small subglacial upwelling in the glacier foreland. Other data collected during this study are described by Hodson et al (1997) and Wadham et al (1998). At Erdmannbreen, the proportion of bulk meltwaters routed through this upwelling-type reservoir was much greater than at Finsterwalderbreen.…”

“…During the early stages of the ablation season, the discharge-independent SSC maxima (e.g. JD 179±186: see Figure 2) most probably relate to periods early in the ablation season when sediment availability is at a maximum and interconnectivity in the subglacial drainage network is being established (Hodson et al, 1997). These maxima contribute significantly to the strong stochastic element observed in the proglacial suspended sediment concentration time series.…”

“…In physical terms, the SSClag n variable represents the increase in sediment availability associated with the contribution of newly tapped sediment stores (or`slugs') to SSC over several successive time periods. Examples of this behaviour causing residual autocorrelation include early season suspended sediment transport dynamics which generated several SSC maxima at Finsterwalderbreen basin in both 1994 and 1995 (Hodson et al, 1997). These SSC maxima occur independently of any discharge variability and may be seen in Figure 2E before JD 193.…”

“…However, since the 1980s, contributions from the Svalbard Archipelago have substantially increased the number of field studies conducted in glacier basins (e.g. Repp, 1988;Kostrzewski et al, 1989;Bogen, 1991Bogen, , 1996Vatne et al, 1992;Krawczyk and Opolka-Gadek, 1994;Barsch et al, 1994;Sollid et al, 1994;Hodgkins, 1996;Hodson et al, 1997Hodson et al, , 1998a. These studies, although mostly restricted to suspended sediment transport data, therefore enable comparison of the arctic glaciofluvial sediment transport regime with that of its better known temperate counterpart, reviewed below.…”

Direct effect of ice sheets on terrestrial bicarbonate, sulphate and base cation fluxes during the last glacial cycle: minimal impact on atmospheric CO2 concentrations

“…This is attributed to the high water flux (Anderson et al, 1997), high rock/water ratios, and reactive, freshly comminuted, silt and clay-sized surfaces with adhering microparticles (Tranter et al, 1993). A high flux of dilute, turbid runoff is a characteristic of present glaciated catchments, whether or not the runoff originates from warm-, polythermalor cold-based glaciers (Hallet et al, 1996;Hodson et al, 1997), since runoff accesses glacial debris in subaerial, ice-marginal, subglacial or proglacial environments. It is likely that runoff from the great ice sheets during the last glaciation (Arnold and Sharp, 1992;Tranter, 1996) was also turbid, since glaciogenic debris produced during either the last or previous glaciations could be accessed in subglacial, icemarginal and/or proglacial environments.…”