Glacier-fed river thermal regimes vary markedly in space and time; however, knowledge is limited on the fundamental processes controlling alpine stream temperature dynamics. To address the research gap, this study quantified heat exchanges at the water surface and bed of the Taillon glacier-fed stream, French Pyrénées. Hydro-meteorological observations were recorded at 15-min intervals across two summer melt seasons (2010 and 2011), and energy balance components were measured or estimated based on site-specific data. Averaged over both seasons, net radiation was the largest heat source (~80% of total flux); sensible heat (~13%) and friction (~3%) were also sources, while heat exchange across the channel–streambed interface was negligible (<1%). Latent heat displayed distinct interannual variability and contributed 5% in 2010 compared with 0.03% in 2011. At the sub-seasonal scale, latent heat shifted from source to sink, possibly linked to the retreating valley snowline that changed temperature and humidity gradients. These findings represent the first, multiyear study of the heat exchange processes operating in a glacier-fed stream, providing fundamental process understanding; the research highlights the direct control antecedent (winter) conditions that have on energy exchange and stream temperature during summer months. In particular, the timing and volume of snowfall/snowmelt can drive thermal dynamics by the following: (1) altering the length of the stream network exposed to the atmosphere and (2) controlling the volume and timing of cold water advection downstream. Finally, this study highlights the need to develop long-term hydro-meteorological monitoring stations to improve the understanding of these highly dynamic, climatically sensitive systems.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)