Hydrological response to warm and dry weather: do glaciers compensate?

Abstract

Abstract. Warm and dry summer days can lead to low streamflow due to a lack of rainfall and increased evaporation. In glacierized catchments, however, such periods can lead to a very different hydrological response as glaciers can supply an increased amount of meltwater, thereby compensating for the rainfall deficits. Here, we analyzed glacier-fed streamflow responses to warm and dry (WD) periods in long-term streamflow observations (>50 years). WD events during summer (June–September) were analyzed for catchments with varying glacier cover in western Canada, southwestern Norway, and the European Alps. WD events were defined by days with temperatures above a daily varying threshold, based on the 80th percentile of the respective long-term temperature data for that day in the year, and daily precipitation sums below a fixed threshold (<2 mm d−1) for a minimum duration of 7 d. Streamflow responses to these WD events were expressed as level of compensation (C) and were calculated as the event streamflow relative to the long-term streamflow regime. C≥100 % indicates that increased melt and other catchment storages could compensate, or even overcompensate, the rainfall deficit and increased evaporation. Results showed a wide range of compensation levels, both between catchments and between different WD events in a particular catchment. C was, in general, higher than 100 % for catchments with a relative glacier cover higher than 5 %–15 %, depending on region and month. June was the month with highest compensation levels, but this was likely more influenced by snowmelt than by glacier melt. For WD events in September, C was still higher than 100 % in many catchments, which likely indicates the importance of glacier melt as a streamflow contributor in late summer. There was a considerable range in C of different WD events for groups of catchments with similar glacier cover. This could be partly explained by antecedent conditions, such as the amount of snow fallen in the previous winter and the streamflow conditions 30 d before the WD event. Some decreasing trends in C were evident, especially for catchments in western Canada and the European Alps. Overall, our results suggest that glaciers do not compensate straightforwardly, and the range in compensation levels is large. The different streamflow components – glacier, snow and rain – and their variations are important for the buffering capacity and the compensating effect of glaciers in these high mountain water systems.

Hydrological process controls on streamflow variability in a glacierized headwater basin

“…Even though a glacier coverage of roughly 40% has been suggested to minimize inter-annual variability (and maximize the glacier compensation effect) (Chen & Ohmura, 1990;Fountain & Tangborn, 1985;Jansson et al, 2003), a recent analysis of streamflow in glacierized basins worldwide was not able to define a universal relationship between glacier coverage and streamflow variability and instead hinted at the range of hydrological processes that can complicate the relationship (van Tiel, Kohn, et al, 2020). Snow and ice melt in glacierized basins can also overcompensate for weather conditions and cause an increase in streamflow variability (van Tiel et al, 2021;van Tiel, Kohn, et al, 2020). In the Canadian Rockies, Hopkinson and Young (1998) showed that glacier meltwater does not always effectively augment streamflow during low flow, dry years.…”

“…compensated for declining precipitation and snowmelt in two Canadian Rockies glacierized catchments, resulting in increased discharge since the 1960s, showcasing the decadal capacity of the glacier compensation effect. On a weekly timescale, van Tiel et al (2021) found that glacier and snow melt in glacierized basins with a 5%-15% glacier cover could compensate for precipitation deficits and increased evapotranspiration in the European Alps. Even though a glacier coverage of roughly 40% has been suggested to minimize inter-annual variability (and maximize the glacier compensation effect) (Chen & Ohmura, 1990;Fountain & Tangborn, 1985;Jansson et al, 2003), a recent analysis of streamflow in glacierized basins worldwide was not able to define a universal relationship between glacier coverage and streamflow variability and instead hinted at the range of hydrological processes that can complicate the relationship (van Tiel, Kohn, et al, 2020).…”

Cuantificación del déficit hidrológico reciente en la región de Cuyo a partir de indicadores de caudales bajos

“…No obstante, como indican Crespo et al (2020), es necesario profundizar en el estudio de la interacción entre las componentes superficiales y subsuperficiales del ciclo hidrológico regional, considerando además mediciones más extensas y una mayor cantidad de cuencas para el estudio. Al respecto, una investigación reciente que considera cuencas de Canadá, Noruega y los Alpes, utilizando registros de los últimos 50 años, mostró un comportamiento heterogéneo en términos de la contribución de los glaciares a los caudales en períodos de sequía y elevadas temperaturas (Van Tiel et al, 2021). A fin de profundizar en el estudio de la contribución de las distintas componentes del ciclo hidrológico durante períodos de sequía, el uso de modelos hidrológicos como el recientemente desarrollado HBV.IANIGLA (Toum et al, 2021) podría permitir avanzar en el conocimiento de la hidrología regional.…”

Heat wave contribution to 2022’s extreme glacier melt from automated real-time ice ablation readings

“…Because glacier melt that occurs during heat waves can be important for mitigating drought conditions (Van Tiel et al, 2021;Ultee et al, 2022), the individual heat waves are compared to each other. The first heat wave occurred in early summer (17-21 June 2022), and glacier melt is categorized as extreme in four out of five days (Fig.…”