| Summary: | A distinctive characteristic of proglacial streams is unsteady streamflow associated with diurnal ice melt. The role of discharge variability on downstream temperatures is not well understood. This study addressed the influence of diurnal discharge fluctuations on temperature by quantifying longitudinal heat advection and unsteady flow effects in a heat budget model for a proglacial stream in the Coast Mountains of British Columbia, Canada. Given advection has not been quantified in previous modeling studies, the dominant role of advection over surface heat fluxes found here was surprising. Advection was expected to have a considerable cooling effect due to the flow contributions from cold meltwater. This effect was confirmed while discharge generally increased; however, advection also exhibited a diurnal warming phase of similar magnitude and duration as the cooling phase, while flow generally decreased. The role of discharge variability on transverse mixing dynamics found in previous studies has been inconsistent. Here, transverse mixing lengths tended to be longer with greater tributary flow relative to the main channel. These findings need to be confirmed with further research.
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