The Effect of Impurities on the Surface Melt of a Glacier in the Suntar-Khayata Mountain Range, Russian Siberia

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.

The role of microbes in snowmelt and radiative forcing on an Alaskan icefield

“…Experimental results presented here, together with previous correlative observations [8][9][10][11][12][13][14][15][16] , laboratory experiments 17 , and theoretical calculations 18 , provide a compelling case for the magnitude of the glacier microbiome's effect on hydrology and climate. Snow algae amplify their albedo reduction through life history, population growth, dispersal, and physiology.…”

“…The generation of meltwater through microbes' albedoreducing properties motivates an hypothesis of bio-geophysical feedback on glacial landscapes 13,16 , such as the Greenland ice sheet. This feedback hypothesis, whereby microbes increase because they produce needed meltwater, is an active research area [13][14][15][16][17][18][19] , yet field experiments testing its assumptions are absent.Glacier microbiomes are water-limited 21,22 , because ice is generally not metabolically available, and oligotrophic, because their nutrient content equals that of precipitation plus deposition by airborne dust, pollen, and so on, with only limited N-fixation by local cyanobacteria 21,22 . Moreover, rapidly percolating water through large-grained snow may exacerbate both water-and nutrient limitation for algae in supraglacial snow-covered habitat 7 .…”

“…Fresh snow reflects >90% of visible radiation, but during melt its grain size and water content increase, reducing albedo and further increasing snowmelt 1 . Impurities, including black carbon 3 , dust 4 , and resident microbes [7][8][9][10][11][12][13][14][15][16][17][18][19] , also lower albedo; however, microbes differ from non-living particulates in several critical ways. Perennial populations of photosynthetic microbes actively resurface following overwinter burial by snow 20 , and depend on liquid water and nutrients for survival and reproduction 13,14,[20][21][22] .…”

“…The generation of meltwater through microbes' albedoreducing properties motivates an hypothesis of bio-geophysical feedback on glacial landscapes 13,16 , such as the Greenland ice sheet. This feedback hypothesis, whereby microbes increase because they produce needed meltwater, is an active research area [13][14][15][16][17][18][19] , yet field experiments testing its assumptions are absent.…”

Quantifying bioalbedo: a new physically based model and discussion of empirical methods for characterising biological influence on ice and snow albedo

“…Lutz et al, 2016), which is unsurprising, since the majority of the variation in albedo is due to physical characteristics of the snow or ice including internal factors such as ice crystal size and water content as well as external factors such as solar angle, atmospheric effects, shading and multiple reflections between surface roughness elements (Gardner and Sharp, 2010). Takeuchi (2002), Takeuchi and Kohshima (2004) and Takeuchi et al (2015) showed the albedo reduction resulting from biotic and abiotic impurities to vary between different glaciers, signifying that the mass and optical properties of abiotic impurities such as dust are also crucial determinants of surface albedo. This may be particularly relevant on the western Greenland Ice Sheet, where high concentrations of dust may be outcropping from melting Holocene ice (Bøg-gild et al, 2010;Wientjes et al, 2010Wientjes et al, , 2011.…”