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Glacier phototroph blooms on the surfaces of ice sheets and glaciers cause albedo reduction, leading to increased melting rates. We observed seasonal changes in the abundance of phototrophs on the Qaanaaq Ice Cap in northwestern Greenland from June to August 2014, and reproduced these changes using numerical and empirical models. The phototroph community on the ice surface mainly consisted of the glacier alga Ancylonema nordenskioldii and the cyanobacterium Phormidesmis priestleyi. The glacier alga appeared on the ice surface in late June, after which its abundance increased exponentially throughout the melting period. A logistic growth model designed for snow algal growth reproduced the measured exponential increases, suggesting that growth could be explained using the model as a function of the ice melting duration. Cyanobacteria appeared and their abundance increased in late July but did not change exponentially thereafter. The abundance of cyanobacteria was explained with an empirical model expressed as a function of the amount of mineral dust on the bare ice surface. Our numerical and empirical models for reproducing glacier algae and cyanobacteria could be useful for quantifying the albedo reduction caused by their growth and the melt rates of the Greenland ice sheet and glaciers in the future.

The 13th Symposium on Polar Science/Ordinary sessions [OM] Polar meteorology and glaciology, Wed. 16 Nov.

Key Points: • First ever measurements with a high‐accuracy single‐particle soot photometer of black carbon (BC) concentrations in Arctic snowpack • Topography and BC emission flux strongly influenced latitudinal variations of mass concentrations and size distributions of BC • Measured BC mass concentrations 2–25 times lower than previously reported show the importance of revalidating climate models Black carbon (BC) deposited on snow lowers its albedo, potentially contributing to warming in the Arctic. Atmospheric distributions of BC and inorganic aerosols, which contribute directly and indirectly to radiative forcing, are also greatly influenced by depositions. To quantify these effects, accurate measurement of the spatial distributions of BC and ionic species representative of inorganic aerosols (ionic species hereafter) in snowpack in various regions of the Arctic is needed, but few such measurements are available. We measured mass concentrations of size-resolved BC (CMBC) and ionic species in snowpack by using a single-particle soot photometer and ion chromatography, respectively, over Finland, Alaska, Siberia, Greenland, and Spitsbergen during early spring in 2012–2016. Total BC mass deposited per unit area (DEPMBC) during snow accumulation periods was derived from CMBC and snow water equivalent (SWE). Our analyses showed that the spatial distributions of anthropogenic BC emission flux, total precipitable water, and topography strongly influenced latitudinal variations of CMBC, BC size distributions, SWE, and DEPMBC. The average size distributions of BC in Arctic snowpack shifted to smaller sizes with decreasing CMBC due to an increase in the removal efficiency of larger BC particles during transport from major sources. Our measurements of CMBC were lower by a factor of ~13 than previous measurements made with an Integrating Sphere/Integrating Sandwich spectrophotometer due mainly to interference from coexisting non-BC particles such as mineral dust. The SP2 data presented here will be useful for constraining climate models that estimate the effects of BC on the Arctic climate. Plain Language Summary Black carbon (BC) particles, commonly known as soot, are emitted from incomplete combustion of fossil fuels and biomass. They efficiently absorb solar radiation and thus heat the atmosphere. BC particles emitted at midlatitudes and in the Arctic are deposited onto snow in the Arctic, accelerating snowmelt in early spring by absorbing solar radiation. These processes contribute to warming in the Arctic. Calculations of this warming effect by using numerical models need to be validated by comparison with observed BC concentrations in snowpack. However, there are very few accurate records of concentrations of BC in snow because of technical difficulties in making these measurements. We developed a new laser-induced incandescence technique to measure BC concentrations in snowpack and applied it for the first time in six Arctic regions (Finland, Alaska, North and South Siberia, Greenland, and Spitsbergen). The BC concentrations we measured were highest in Finland and South Siberia, which are closer to large anthropogenic BC sources than the other regions, where our measured BC concentrations were much lower. On average, our BC concentrations were much lower than those previously measured by different techniques. Therefore, previous comparisons of modeled and observed BC concentrations need to be re-evaluated using the present data.

Aeolian dusts serve as ice nucleating particles in mixed-phase clouds, and thereby alter the cloud properties and lifetime. Glacial outwash plains are thought to be a major dust source in cold, high latitudes. Due to the recent rapid and widespread retreat of glaciers, high-latitude dust emissions are projected to increase, especially in the Arctic region, which is highly sensitive to climate change. However, the potential contribution of high-latitude dusts to ice nucleation in Arctic low-level clouds is not well acknowledged. Here we show that glacial outwash sediments in Svalbard (a proxy for glacially sourced dusts) have a remarkably high ice nucleating ability under conditions relevant for mixed-phase cloud formation, as compared with typical mineral dusts. The high ice nucleating ability of the sediments is probably governed by the presence of small amounts of organic matter (

Seasonal changes of meteorological and ground surface conditions can cause seasonal changes of source area of mineral particles supplied to the Greenland ice sheet. Difference in metal composition and size distribution of them reflects their source area difference. To clarify seasonal changes in the source area of mineral particles, we examined the metal composition and size distribution of them in snow pit samples obtained from EGRIP (East Greenland Ice Core Project).In summer 2017, we dug a 2.01 m snow pit at EGRIP camp. Snow samples were collected at 0.03 m intervals. The snow samples were melted, then fractions of them were analyzed for the particle size distribution (0.52-12μm) with a Coulter counter (Beckman Coulter: Multisizer 4). Other fractions of the samples were treated with a microwave acid digestion method to decompose particulates. Total concentrations of Al, Ca and Na in samples were measured by inductively coupled plasma mass spectrometry.Total concentrations of Al (t-Al) and concentrations of non-sea-salt Ca (nssCa) showed peak values in winter to spring layers. In those layers, nssCa/t-Al ratios and volume fractions of fine particles (

Temporal variability in surface mass balance (SMB) on the Greenland ice sheet is important for understanding the mass balance of the ice sheet. Additionally, knowledge of the spatial variability in SMB at ice core drilling sites helps to interpret the spatial representativeness of SMB data obtained from a single ice core. In this study, to investigate the spatiotemporal variability in recent SMB in the East Greenland Ice Core Project (EGRIP) area in the northeastern Greenland ice sheet, pit observations were made at six sites in the summers of 2016–2018. In all pits, depth profiles of water isotope ratios showed clear seasonal variations. The annual SMB differed from site to site, which is probably due to post-depositional redistribution of snow caused by wind erosion and snowdrift. However, the multiple-site averages of annual SMBs, which ranged from 134 to 157 mm w. e. yr−1 (average 146 mm w. e. yr−1) during 2009–2017, were very similar. This indicates that annual SMBs in the EGRIP area were nearly constant in this period. The seasonal SMBs in the EGRIP area tended to be larger in the summer–winter period than in the winter–summer period.

The 11th Symposium on Polar Science/Ordinary sessions: [OM] Polar Meteorology and Glaciology, Thu. 3 Dec.

Our study is the first to demonstrate a high-temporal-resolution record of mineral composition in a Greenland ice core over the past 100 years. To reconstruct the past variations in the sources and transportation processes of mineral dust in northwestern Greenland, we analyzed the morphology and mineralogical composition of dust in an ice core from 1915 to 2013 using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS). Analysis of the SEM-EDS reveals that the ice core dust mainly consisted of silicate minerals and the composition varied substantially on multi-decadal and inter-decadal scales, suggesting that the geological origin of the ice core minerals changed periodically during the past 100 years. The multi-decadal variation trend differed among mineral types: kaolinite generally formed in low- or middle-latitude areas were abundant in the colder periods (1950 to 2000), whereas mica, chlorite, feldspars, mafic minerals, and quartzes formed in arid, high-latitude, and local areas were abundant in the warmer periods (1915 to 1949 and 2005 to 2013). This indicates that the multi-decadal variation of the relative abundance of the minerals can be attributed to the local temperature changes in Greenland. The trajectory analysis shows that the minerals were mainly transported from the western coast of Greenland in the two warming periods, which was likely due to an increase of dust sourced from local ice-free areas. On the other hand, the abundant kaolinite was likely derived from old sediments at higher latitudes in North America, rather than from low and middle latitudes.

The 11th Symposium on Polar Science/Special session: [S] Accelerating Arctic research: Recent progress and future prospect of Arctic research, Poster presentations, Mon. 16 Nov. - Fri. 18 Dec.

Surface albedo of snow and ice is substantially reduced by inorganic impurities, such as aeolian mineral dust (MD) and black carbon (BC), and also by organic impurities, such as microbes that live in the snow. In this paper, we present the temporal changes of surface albedo, snow grain size, MD, BC and snow algal cell concentration observed on a snowpack in northwest Greenland during the ablation season of 2014 and our attempt to reproduce the changes in albedo with a physically based snow albedo model. We also attempt to reproduce the effects of inorganic impurities and the red snow algae (Sanguina nivaloides) on albedo. Concentrations of MD and red snow algae in the surface snow were found to increase in early August, while snow grain size and BC were found to not significantly change throughout the ablation season. Surface albedo was found to have decreased by 0.08 from late July to early August. The albedo simulated by the model agreed with the albedo observed during the study period. However, red snow algae exerted little effect on surface albedo in early August. This is probably owing to the abundance of smaller cells (4.9×104 cells L−1) when compared with the cell abundance of red snow reported by previous studies in the Arctic region (∼108 cells L−1). The simulation of snow albedo until the end of the melting season, with a snow algae model, revealed that the reduction in albedo attributed to red snow algae could equal 0.004, out of a total reduction of 0.102 arising from the three impurities on a snowpack in northwest Greenland. Finally, we conducted scenario simulations using the snow albedo model, coupled with the snow algae model, in order to simulate the possible effects of red snow blooming on snow albedo under warm conditions in northwest Greenland. The result suggests that albedo reduction by red snow algal growth under warm conditions (surface snow temperature of +1.5 ∘C) reached 0.04, equivalent to a radiative forcing of 7.5 W m−2 during the ablation season of 2014. This coupled albedo model has the potential to dynamically simulate snow albedo, including the effect of organic and inorganic impurities, leading to proper estimates of the surface albedo of snow cover in Greenland.

Mass loss from ice sheets contributes to global sea level rise, and accelerated ice flow to the oceans is one of the major causes of rapid ice sheet mass loss. To understand flow dynamics of polar ice sheets, we need to understand deformation mechanisms of the polycrystalline ice in ice sheets. Laboratory experiments have shown that deformation of polycrystalline ice occurs largely by dislocation glide, which mainly depends on crystal orientation distribution. Grain size and impurities are also important factors that determine ice deformation mechanisms. Compared with ice formed during interglacial periods, ice formed during glacial periods, especially ice that forms cloudy bands, exhibits finer grain sizes and higher impurity concentrations. A previous report suggests the deformation rate of ice containing cloudy bands is higher than that of ice without cloudy bands. To examine the microstructures and deformation histories of ice in cloudy bands, we applied the electron backscatter diffraction (EBSD) technique to samples from the Greenland Ice Sheet using an environmental scanning electron microscope (ESEM) equipped with cold stages. Prior to the EBSD analysis, we optimised our ESEM/EBSD system and performed angular error assessment using artificial ice. In terms of c-and a-axis orientation distributions and grain orientation spread, we found little difference between samples taken from a cloudy band and those taken from an adjacent layer of clear ice. However, subgrain boundary density and orientation gradients were higher in the cloudy band, suggesting that there are more dislocations in the cloudy band than in the clear ice layer.

To understand the geological origins of minerals in cryoconite and the nutrients sources for microbes on glaciers, we analyzed the Sr–Nd isotopic ratios of the four mineral fractions in cryoconites including saline, carbonate, phosphate, silicate and the organic fraction obtained from Gulkana Glacier in Alaska. The isotopes in the silicate mineral fraction exhibited spatial variation within the glacier (87Sr/86Sr: 0.704533–0.709563, εNd (0): −16.0 to 0.5), which can be explained by the different mixing ratios of the two distinct sources: one of the sources is lateral and terminal moraines or soil, and the other is the medial moraine of the glacier. The minerals in the cryoconite at the lower sites in the glacier are likely derived from the former source, whereas those at the upper sites are from latter sources. The mineralogical and elemental compositions also support mixing of the silicate minerals from the two local sources. The Sr isotopic ratios of the organic fraction also showed spatial variation on the glacier in the middle sites – a trend similar to those of the phosphate fraction. The results suggest that the organic matter is mostly the byproducts of microbes using the phosphate minerals as a nutrient source.

Cryoconite holes are water-filled cylindrical holes formed on ablation ice surfaces and commonly observed on glaciers worldwide. Temporal changes of cryoconite holes characteristically −2, 40–55% of the incoming flux). In contrast, holes developed in sunny conditions correspond to high solar radiation (186–278 W m−2, 63–88%). Results suggest that the dimensions of holes drastically changed depending on the weather conditions and that frequent cloudy, warm and windy conditions would cause a decay of holes and weathering crust, inducing an increase in the cryoconite coverage on the ice, consequently darkening the glacier surface.

The Tenth Symposium on Polar Science/Ordinary sessions: [OM] Polar Meteorology and Glaciology, Thu. 5 Dec. / 2F Auditorium , National Institute of Polar Research

The Tenth Symposium on Polar Science/Ordinary sessions: [OM] Polar Meteorology and Glaciology, Thu. 5 Dec. / 2F Auditorium , National Institute of Polar Research

The Tenth Symposium on Polar Science/Ordinary sessions: [OM] Polar Meteorology and Glaciology, Thu. 5 Dec. / 2F Auditorium , National Institute of Polar Research

The Tenth Symposium on Polar Science/Ordinary sessions: [OM] Polar Meteorology and Glaciology, Wed. 4 Dec. / Entrance Hall (1st floor) , National Institute of Polar Research

Surface albedo of snow and ice is substantially reduced by inorganic impurities, such as aeolian mineral dust (MD) and black carbon (BC), and also by organic impurities, such as microbes that live in the snow. In this paper, we present the temporal changes of surface albedo, snow grain size, MD, BC, and snow algal cell concentration observed on a snowpack in northwest Greenland during the ablation season of 2014 and our attempt to reproduce the changes in albedo with a physically based snow albedo model. We also attempt to reproduce the effects of inorganic impurities and the red snow algae (Chlamydomonas nivalis) on albedo. Concentrations of MD and red snow algae in the surface snow were found to increase in early August, while snow grain size and BC were found to not significantly change throughout the ablation season. Surface albedo was found to have decreased by 0.08 from late July to early August. The albedo simulated by the model agreed with the albedo observed during the study period. However, red snow algae exerted little effect on surface albedo in early August. This is probably owing to the abundance of smaller cells (4.9 × 104 cells L^-1) when compared with the cell abundance of typical red algal snow (~ 108 cells L−1). The simulation of snow albedo until the end of the melting season, with an algal growth model, revealed that the reduction in albedo attribute to red algae could equal 0.004, out of a total reduction of 0.102 arising from the three impurities on a snowpack in northwest Greenland. Finally, we conducted scenario simulations using the snow albedo model, coupled with the algal growth model, in order to simulate the possible effects of red algal blooming on snow albedo under warm conditions in northwest Greenland. The result suggests that albedo reduction by red snow algal growth under warm conditions (surface snow temperature of +1.5 °C) reached 0.04, equivalent to a radiative forcing of 7.5 W m−2 during the ablation season of 2014. This coupled albedo model has the potential to dynamically simulate snow albedo, including the effect of organic and inorganic impurities, leading to proper estimates of the surface albedo of snow cover in Greenland.

We collected snow samples from two pits with depths of 4.02 and 3.18 m at the East Greenland Ice Core Project camp (75°37′N, 35°59′W), Greenland in the summer of 2016 to estimate recent annual snow deposition and examine seasonal variation in major ion species, stable isotopes of water and microparticles (dust). Dating based on clear seasonal variation in chemical components indicated that the 4.02- and 3.18-m-deep pits included snow deposition corresponding to ten years from 2006 to 2016 and seven years from 2009 to 2016, respectively. The mean values for annual snow deposition for the 4.02-m-deep pit were 138 and 145 mm yr−1 in water equivalent (mm w.e. Yr−1) in 2006–2016 and 2009–2016, respectively. The average deposition for the 3.18-m-deep pit was 149 mm w.e. Yr−1 between 2009 and 2016. Seasonal variation in concentrations of major ion species and dust were similar to those previously reported for Greenland. The maximum Cl−/Na+ concentration ratios in the summer were much higher than the ratios at other sites in Greenland.

Cryoconite granules are dark-colored biological aggregates on glaciers. Bacterial community varies with granule size, however, community change in space and their susceptibility to environmental factors has not been described yet. Therefore, we focused on bacterial community from four different granule sizes (30–249 μm, 250–750 μm, 750–1599 μm, more than 1600 μm diameter) in 10 glaciers in northwestern Greenland and their susceptibility to exogenous nutrients in cryoconite hole. A filamentous cyanobacterium Phormidesmis priestleyi, which has been frequently reported from glaciers in Arctic was abundant (10%–26%) across any size of granules on most of glaciers. Bacterial community across glaciers became similar with size increase, and whence smallest size fractions contain more unique genera in each glacier. Multivariate analysis revealed that effect of nutrients to beta diversity is larger in smaller granules (30–249 μm and 250–750 μm diameter), suggesting that bacterial susceptibility to nutrients changes with growth of granule (i.e. P. priestleyi was affected by nitrate in early growth stage).

Cryoconite granules, which are dark-colored biological aggregates on glaciers, effectively accelerate the melting of glacier ice. Bacterial community varies with granule size, however, community change in space and their susceptibility to environmental factors has not been described yet. Therefore, we focused on bacterial community from 4 different granule sizes (30-249 μm, 250- 750 μm, 750-1599 μm, more than 1600 μm diameter) in 10 glaciers in northwestern Greenland and their susceptibility for exogenous nutrients in cryoconite hole. A filamentous cyanobacterium Phormidesmis priestleyi, which has been frequently reported from glaciers in Arctic was abundant (10-26%) across any size of granules on most of glaciers. Bacterial community across glaciers became similar with size increase, and whence smallest size fractions contain more unique genera in each glacier. Multivariate analysis suggests that phosphate, which is significantly higher in one glacier (Scarlet Heart Glacier), is primary associated with bacterial beta diversity. Correlation coefficients between abundance of major genera and nutrients largely changed with granule size, suggesting that nutrients susceptibility to genera changes with growth process of granule (e.g. P. priestleyi was affected by nitrate in early growth stage).

The Ninth Symposium on Polar Science/Interdisciplinary sessions: [ID] Polar science developed by leading-edge analytical technology ～Beyond the micro meters and micro grams～, Thu. 6 Dec. / 3F Seminar room, National Institute of Polar Research

The Ninth Symposium on Polar Science/Ordinary sessions: [OM] Polar meteorology and glaciology, Wed. 5 Dec. / Entrance Hall (1st floor), National Institute of Polar Research

The Ninth Symposium on Polar Science/Ordinary sessions: [OM] Polar meteorology and glaciology, Wed. 5 Dec. / Entrance Hall (1st floor), National Institute of Polar Research

The Ninth Symposium on Polar Science/Ordinary sessions: [OB] Polar biology, Wed. 5 Dec. / Entrance Hall (1st floor), National Institute of Polar Research

The Ninth Symposium on Polar Science/Ordinary sessions: [OM] Polar meteorology and glaciology, Wed. 5 Dec. / 3F Multipurpose Conference room, National Institute of Polar Research

Snow algal bloom is a common phenomenon on melting snowpacks in polar and alpine regions and can substantially increase melting rates of the snow due to the effect of albedo reduction on the snow surface. In order to reproduce algal growth on the snow surface using a numerical model, temporal changes in snow algal abundance were investigated on the Qaanaaq Glacier in northwest Greenland from June to August 2014. Snow algae first appeared at the study sites in late June, which was approximately 94 hours after air temperatures exceeded the melting point. Algal abundance increased exponentially after the appearance, but the increasing rate became slow after late July, and finally reached 3.5 × 107 cells m-2 in early August. We applied a logistic model to the algal growth curve and found that the algae could be reproduced with an initial cell concentration of 6.9 × 102 cells m-2, a growth rate of 0.42 d-1, and a carrying capacity of 3.5 × 107 cells m-2 on this glacier. This model has the potential to simulate algal blooms from meteorological data sets and to evaluate their impact on the melting of seasonal snowpacks and glaciers.

The mineralogical composition of cryoconite on a glacial surface was investigated on six glaciers in northwest Greenland (Qaanaaq Qaqortaq Tugto Bowdoin Sun and Scarlet Heart. The X‑ray diffraction analysis showed that the cryoconites mainly contained seven silicate minerals: hornblende quartz potassium feldspar plagioclase illite kaolinite and chlorite. Semi‑quantitative mineralogical analysis of the silicate mineral composition on the Qaanaaq Glacier showed little variation among the samples collected from five different elevations. This indicates that the minerals on the glacier were probably dominated by dust from a unique source which is recently transported from local sediments including soil and moraine. On the other hand the mineral composition varied significantly among the glaciers. Based on the clay mineral content the glaciers could be classified into three groups. Type A: high clay mineral content composed of illite and kaolinite found on Qaanaaq Qaqortaq and Tugto; Type B: high clay mineral content composed of only kaolinite found on Sun; and Type C: lower clay mineral content composed of only kaolinite found on Bowdoin and Scarlet Heart. The geographical distribution of the types of glaciers did not correspond with the geology in this area indicating that the mineralogical composition is not determined just by the geologi‑ cal conditions around glaciers but also by other factors such as the redistribution of sediments by glacial fluvial or coastal processes.

Spatial variations in impurities (cryoconite) on the glacier surface were investigated on Qaanaaq Ice Cap and Tugto Glacier in the northwest Greenland in the melting season of 2012. Abundance of impurities ranged from 0.36 to 119 g m -2 (dry weight, mean: 18.8 g m -2 ) on bare ice and from 0.01 to 8.7 g m -2

In order to better understand the source of minerals on the dark-colored ice, located in the Greenland ice sheet ablation zone, we analyzed the Sr and Nd isotopic ratios of minerals in cryoconite, which were collected from glaciers in northwest and southwest Greenland. We focused on the following: (i) comparison of the isotopes of minerals in cyroconite with those in sediments from local and distant areas, (ii) regional variations in western Greenland, and (iii) spatial variations across an individual a glacier. The mineral components of the cryoconite showed variable Sr and Nd isotopic ratios (87Sr/86Sr: 0.711335 to 0.742406, εNd (0): −33.1 to −22.9), which corresponded to those of the englacial dust and moraine on and around the glaciers but were significantly different from those of the distant deserts that have been considered to be primary sources of mineral dust on the Greenland Ice Sheet. This suggests that the minerals within the cryoconites were mainly derived from local sediments, rather than from distant areas. The Sr ratios in the northwestern region were significantly higher than those in the southwestern region. This is probably due to geological differences in the source areas, such as the surrounding glaciers in each region. The isotopic ratios further varied spatially within a glacier (Qaanaaq and Kangerlussuaq areas), indicating that the silicate minerals on the glaciers were derived not from a single source but from multiple sources, such as englacial dust and wind-blown minerals from the moraine surrounding the glaciers.

Cryoconite granules are aggregations of microorganisms with mineral particles that form on glacier surfaces. To understand the processes by which the granules develop, this study focused on the altitudinal distribution of the granules and photosynthetic microorganisms on the glacier, bacterial community variation with granules size and environmental factors affecting the growth of the granules. Size-sorted cryoconite granules collected from five different sites on Qaanaaq Glacier were analyzed. C and N contents were significantly higher in large (diameter greater than 250 μm) granules than in smaller (diameter 30–249 μm) granules. Bacterial community structures, based on 16S rRNA gene amplicon sequencing, were different between the smaller and larger granules. The filamentous cyanobacterium Phormidesmis priestleyi was the dominant bacterial species in larger granules. Multivariate analysis suggests that the abundance of mineral particles on the glacier surface is the main factor controlling growth of these cyanobacteria. These results show that the supply of mineral particles on the glacier enhances granule development, that P. priestleyi is likely the key species for primary production and the formation of the granules, and that the bacterial community in the granules changes over the course of the granule development.

Stable-isotopic ratios of strontium (Sr), neodymium (Nd) and lead (Pb) provide a means of identifying a geological source of substances and are used as tracers of elements in biological and geochemical processes. We analyzed these isotopic ratios of surface dust (cryoconite) collected on Ürümqi glacier No. 1 , Tien Shan, China. The dust was separated chemically into five fractions (four minerals and organic matter), and the isotopic ratios of each fraction were measured. The Sr and Nd isotopic ratios in the fractions extracted with ultrapure water (saline minerals), hydrogen peroxide solution (organic matter) and acetic acid (carbonate minerals) were low and invariable, whereas those extracted by hydrochloric acid (phosphate minerals) and the residual fraction (silicate minerals) were higher. The difference was likely due to the original source of each fraction. The isotopic ratios of the surface dust collected from different sites showed no significant difference, suggesting that they were spatially uniform across the glacier. The isotopic ratios of the silicate fraction were closer to those of desert sand reported in China than those of the soil and bedrock around the glacier. This suggests that the silicate minerals on the glacier were derived from distant deserts. The isotopic ratios in saline, carbonate and phosphate fractions were also close to those of evaporites and apatite in that desert region, suggesting that these minerals were also derived from that source. The Sr isotopic ratios in the organic fraction were closer to ratios in the saline and carbonate fractions rather than the silicate or phosphate fractions and may therefore reflect the isotopic ratios of the elements when they are incorporated into living microbes on the glacier.

第6回極域科学シンポジウム分野横断セッション：[IB2] 地球環境変動の解析と地球生命システム学の構築11月19日（木） 統計数理研究所 セミナー室1（D305）

第3回極域科学シンポジウム/特別セッション「これからの北極研究」11月28日（水） 国立極地研究所 2階大会議室

Psychrophilic yeasts have been isolated from supra- and subglacial ice at many sites worldwide. To understand the ecology of psychrophilic yeasts on glaciers, we focused on their adaptation to wide range of nutrient concentrations and their distribution with altitude on the Gulkana Glacier in Alaska. We found various culturable psychrophilic yeasts on the ice surfaces of the glacier, and 11 species were isolated with incubation at 4 °C in four different dilutions of agar medium. Some of our isolated species (Rhodotorula psychrophenolica, Rhodotorula aff. psychrophenolica, Rhodotorula glacialis, and Basidiomycota sp. 1) can grow on the low dissolved organic matter (DOC) concentrations medium (7.6 mg L(-1)) which is close to the typical level of supraglacial melt water, suggesting that these species can inhabit in any supraglacial meltwater. Otherwise, most of other species were isolated only from higher DOC concentration medium (183 mg L(-1) -18.3 g L(-1)), suggesting that these are inhabitant around the cryoconite, because DOC concentrations in melted surface-ice contained cryoconite is much higher than in melted water. Similarity of altitudinal distribution between culturable yeast and algal biomass suggests that the ecological role played by the cold-adapted yeasts is as organic matter decomposers and nutrient cyclers in glacier ecosystem.

Cryoconite is a dark-coloured surface dust deposited on glaciers that consists of wind-blown mineral particles, as well as organic matter derived from microbes living on glaciers. In this paper, we analyse the Sr and Nd isotopic ratios of four mineral fractions (i.e., the saline, carbonate, phosphate, and silicate mineral fractions), as well as the organic fraction, of cryoconite samples obtained from six Asian glaciers (the Altai, Pamir, Tien Shan, Qillian Shan, and Himalayan regions), and discuss their geographical variations in terms of the geological origins of the mineral particles and the biogeochemical processes on the glaciers. The silicate mineral fraction showed lower Sr and higher Nd ratios for the glaciers located to the north (Altai, 87Sr/86Sr: 0.713?490?0.715?284, ?Nd(0): ?6.4 to ?5.6), while higher Sr and lower Nd ratios for the glaciers located to the south (Himalayas, 87Sr/86Sr: 0.740?121?0.742?088, ?Nd(0): ?16.4 to ?15.7); the ratios were similar to those of desert sand, loess, and river sediments in the respective regions of the glaciers. This result suggests that the silicate minerals within the cryoconites were derived from different sources depending on the geographical locations of the glaciers. The isotopic ratios of the saline, carbonate, and phosphate mineral fractions were distinct from those of the silicate fraction, and were similar to those of evaporites and apatite deposits from the Asian deserts, but also varied geographically, indicating that they are likely to reflect their geological origin. The Sr isotopic ratios of the organic fraction were similar to those of the saline and carbonate fractions from glaciers in the central area (Tien Shan and Qillian Shan), but were higher than those of the saline and carbonate fractions, and lower than the phosphate mineral fraction, in the northern and southern areas. The ratios of organic fraction may be determined from the mixing ratio of calcium sources incorporated by microbes on the glaciers.