Abstract
We investigated characteristics of impurities and their impact on the ablation of Glacier No.31 in the Suntar-Khayata Mountain Range in Russian Siberia during summer 2014. Positive degree-day factors (PDDFs) obtained from 20 stake measurements distributed across the glacier’s ablation area varied from 3.00 to 8.55 mm w.e. K-1 day-1. The surface reflectivity measured with a spectrometer as a proxy for albedo, ranged from 0.09 to 0.62, and was negatively correlated with the PDDF, suggesting that glacier ablation is controlled by surface albedo on the studied glacier. Mass of total insoluble impurities on the ice surface varied from 0.1 to 45.2 g m-2 and was not correlated with surface reflectivity, suggesting that albedo is not directly conditioned by the mass of the impurities. Microscopy of impurities revealed that they comprised mineral particles, cryoconite granules, and ice algal cells filled with dark-reddish pigments (Ancylonema nordenskioldii). There was a significant negative correlation between surface reflectivity and algal biomass or organic matter, suggesting that the ice algae and their products are the most effective constituents in defining glacier surface albedo. Our results suggest that the melting of ice surface was enhanced by the growth of ice algae, which increased the melting rate 1.6 - 2.6 times greater than that of the impurity free bare-ice.
Highlights
Negative mass balance and recession have characterized the majority of glaciers worldwide over the last century, and are generally believed to result from global warming
The ice area of glaciers was extracted with band 5 image (0.845–0.885 μm), which can be used to distinguish between snow and ice surfaces (e.g., Hall et al, 1988)
Since the variation in Positive degree-day factors (PDDFs) can be attributed to difference in relative importance of individual energy components providing energy for melt (Hock, 2003), this significant correlation suggest that the absorbed shortwave radiation determined by surface albedo is the main energy source for melting on the glacier
Summary
Negative mass balance and recession have characterized the majority of glaciers worldwide over the last century, and are generally believed to result from global warming. The effect of impurities on melting appeared to be smaller on polar glaciers, studies have suggested that a dark colored ice surface appeared recently in the bare ice area and it is likely to contribute to the mass loss of glaciers in the Arctic region (Hodson et al, 2007; Mernild et al, 2014) and on the Greenland Ice Sheet (e.g., Bøggild et al, 2010; Wientjes and Oerlemans, 2010). Pigmented ice algae growing on the ice surface contribute to albedo reduction on the bare ice area of the Greenland Ice Sheet and on an Alaskan glacier (Yallop et al, 2012; Takeuchi, 2013; Lutz et al, 2014) These algal populations are usually dominated by Ancylonema nordenskioldii and Mesotaenium bergrenii, which are both commonly found on glaciers, in particular in the Arctic region (Remias et al, 2009, 2011). The thickness of the glacier derived seismically exceeded 100 m over its longitudinal profile (Koreisha, 1963)
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