Quantifying the effect of freeze-thaw on daily sediment transport in an alpine catchment

In cold mountain environments, freeze-thaw processes significantly influence sediment dynamics. With the rapid warming of high mountain areas observed in recent decades, such freeze-thaw processes are likely to be affected. Thus examining the relationship between fluvial sediment transport and catchment freeze-thaw, may inform our predictions of the future sediment transport regime in mountain landscapes. Freeze-thaw has the potential to both increase and decrease suspended sediment concentrations in rivers. Freeze-thaw-driven erosion increases the sediment supply and thus can elevate the suspended sediment load. However, as the key hydrological processes driving sediment transport are thermally regulated, temperatures at the freeze-thaw boundary will generally result in lower transport capacity and less catchment area contributing sediment to the streams. Here, we aim to examine this diverging effect of freeze-thaw at the daily scale in a high alpine catchment. We use Bayesian analysis to quantify the modulating effect of catchment freeze-thaw state and cycles on sediment transport in an alpine catchment. We use daily 1-km rasters of maximum and minimum temperature to determine the catchment area affected by daily freeze-thaw cycles and the frozen catchment area to determine freeze-thaw influenced days. With daily suspended sediment and streamflow data, we then analyse the sediment-discharge relationship on days with and without freeze-thaw influence.