Abstract
Abstract. Worldwide, the rapid shrinking of glaciers in response to ongoing climate change is modifying the glacial meltwater contribution to hydrosystems in glacierized catchments. Determining the influence of glacial runoff to streams is therefore of critical importance to evaluate potential impact of glacier retreat on water quality and aquatic biota. This task has challenged both glacier hydrologists and ecologists over the last 20 yr due to both structural and functional complexity of the glacier–stream system interface. Here we propose quantifying the diurnal cycle amplitude of the streamflow to determine the glacial influence in glacierized catchments. We performed water-level measurements using water pressure loggers over 10 months at 30 min time steps in 15 stream sites in 2 glacier-fed catchments in the Ecuadorian Andes (> 4000 m a.s.l.) where no perennial snow cover is observed outside the glaciers. For each stream site, we performed wavelet analyses on water-level time series, determined the scale-averaged wavelet power spectrum at 24 h scale and defined three metrics, namely the power, frequency and temporal clustering of the diurnal flow variation. The three metrics were then compared to the percentage of the glacier cover in the catchments, a metric of glacial influence widely used in the literature. As expected, we found that the diurnal variation power of glacier-fed streams decreased downstream with the addition of non-glacial tributaries. We also found that the diurnal variation power and the percentage of the glacier cover in the catchment were significantly positively correlated. Furthermore, we found that our method permits the detection of glacial signal in supposedly non-glacial sites, thereby revealing glacial meltwater resurgence. While we specifically focused on the tropical Andes in this paper, our approach to determine glacial influence may have potential applications in temperate and arctic glacierized catchments. The measure of diurnal water amplitude therefore appears as a powerful and cost-effective tool to understand the hydrological links between glaciers and hydrosystems better and assess the consequences of rapid glacier shrinking.
Highlights
In view of the accelerated glacier shrinking worldwide (Lemke et al, 2007; Rabatel et al, 2013; Sakakibara et al, 2013), coupling glacier and glacier-fed hydrosystem dynamics is a timely research thematic
While we focused on the tropical Andes in this paper, our approach to determine glacial influence may have potential applications in temperate and arctic glacierized catchments
We proposed using the diurnal cycle amplitude as a quantitative measure of glacial influence in hydrosystems located in glacierized catchments
Summary
Glacial river discharges have shown both increasing and decreasing trends, depending on ice cover in the catchment, the study region, and where the glacier stands along the deglaciation trajectory (Fleming and Clarke, 2003; Stahl and Moore, 2006; Casassa et al, 2009; Moore et al, 2009; Dahlke et al, 2012; Fleming and Weber, 2012) In this context, a growing number of studies have quantitatively explored the potential future impacts of various climate change and glacier recession scenarios upon water resources, using modern glaciological and hydrological modeling techniques (e.g., Schaefli et al, 2007; Huss et al, 2008; Stahl et al, 2008; Villacis, 2008; Jost et al, 2012; Yao et al, 2013). Modifications in water regimes may have significant consequences on water quality, aquatic biota and water security for human populations (Barnett et al, 2005; Brown et al, 2010; Kaser et al, 2010)
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