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Snow-ice microbes, which adapted to harsh conditions such as low temperature and high dose of UV, inhabit the cryospheric environments. They cause unique phenomena represented by colored snow and ice occurring with blooms of snow and glacier ice algae, and cryoconite holes formed by filamentous cyanobacteria with inorganic matter. These phenomena also darken glacial surface and have a significant effect on the albedo of snow and ice. It is important to understand factors controlling the abundance of all microbes including consumers of algae and cyanobacteria (tardigrades and rotifers) for evaluating the collective influence of biological communities on albedo (biological albedo reduction: BAR). However, most studies have focused only on each taxon (algae, cyanobacteria, fungi or heterotrophic bacteria), and there is a lack of information on whole microbial communities. In this study, we aimed to describe spatiotemporal changes of microbial communities, and discuss the process of their growth and the factors determining their distribution. The fieldworks were carried out from June to September of 2022 on Gulkana Glacier in the Alaska Range, Alaska. Three different types of samples (snow, bare-ice, cryoconite) were collected spatially at maximum 51 points across the glacier. Microscopic observation and analysis of Chlorophyll a concentration, which is a proxy for the total abundance of snow and glacier ice algae, revealed that the algae were most abundant around the snow line and that their maximum occurred in the end of July (1.0 × 103 μg/m2) and in the middle of August (7.8 × 103 μg/m2) on the snow and ice surfaces, respectively. Their distribution in the ice area showed a similar spatial pattern throughout the season, higher abundance in the upper right side and lower in the left side. Consumers of algae (tardigrades and rotifers) were found only in the upper parts of the glacier. These results suggest that each microbial species on the glacier have different distribution and that their growth is associated with local characteristics such as microtopography of the glacier surfaces. In this presentation, we will show more data of spatial distribution of chemical composition, total impurities, and concentration of each microbe in all three surface types and discuss the factors of their growth and distribution.

Glacier retreat due to the warming climate is remarkable all over the world. In addition to climate warming, the “biological albedo reduction”, which the pigmented algae reduce the albedo of the glacier, enhances ice melting. Therefore, the spatial distribution of those algae is important for the glacier's mass balance. Although the altitude result in the air temperature and the duration of snow cover is recognized as the factor to affect the spatial distribution, the distribution pattern is more heterogeneous in the same altitude area. To understand the heterogeneity of snow algae and associating microbes and their effects on the glacier albedo, both eukaryotic and prokaryotic communities were analyzed using an amplicon sequencing approach in the dense coverage of the ablation area of a single glacier (total 54 sites over Gulkana Glacier, AK, USA). Furthermore, microbial diversities were analyzed with environmental factors such as carbon contents and nutrients. As a result, we found the green algae amplicon sequence variants (ASVs) closely related to the pigmented algae, Sanguina nivaloides, and Chlainomonas sp. from the surface ice and cryoconite and will show the spatial variation of microbial community structures and diversities and the relationship between the environmental factors.

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.

Previous reconstructions of summer temperatures from ice cores have relied on a statistical relationship between a melt layer and temperature observed at nearby stations. This study presents a novel method for reconstructing summer temperatures from melt layers in ice cores using an energy balance model that incorporates heat conduction and meltwater refreezing in the firn. We use the seasonal patterns in the ERA‐Interim reanalysis data set for an ice core site to calculate the amounts of refreezing water within the firn under various summer mean temperature (SMT) and annual precipitation conditions, and prepared calibration tables containing these three variables. We then estimate the SMTs from the refreezing amount and annual accumulation, both of which can be obtained from an ice core. We apply this method to four ice cores that were recovered from sites with different climates: two sites on the Greenland Ice Sheet, one in Alaska, and one in Russian Altai. The reconstructed SMTs show comparable variations with those of observed temperatures at nearby stations. The nonlinear relationship between SMT and melt layer thickness differs between sites, indicating that a single linear approximation cannot be employed to estimate SMT. Sensitivity analyses suggest that the annual temperature range, amount of annual precipitation, and firn albedo (which is a time‐invariant value in the model) significantly affect the relationship between SMT and melt layer thickness. This new method provides an alternative to existing approaches and yields an independent estimate of SMT from ice cores that have been affected by melting.

Snow algae are photosynthetic microbes that inhabit the melting snow surface in alpine and polar regions. We analyzed the pigment and species composition of colored snow collected on Mt. Tateyama in Japan during the melting seasons of 2015 and 2016. High-performance liquid chromatographic analyses of the pigments extracted from the colored snow showed that their composition varied within the study area and were classified into four types: Type A (astaxanthin-monoester dominant), Type B (medium astaxanthin-monoester content), Type C (abundant primary carotenoids and free-astaxanthin), and Type D (abundant primary carotenoids and astaxanthin diesters). Types A and B were most commonly observed in the study area, whereas Types C and D appeared only at specific sites. Analysis of the 18S ribosomal RNA (18S rRNA) gene revealed six major amplicon sequence variants (ASVs) of snow algae, belonging to the Sanguina, Chloromonas, and Chlainomonas groups. The relative abundance of the algal ASVs showed that Sanguina was dominant (>48%) in both Types A and B, suggesting that the difference in astaxanthin abundance between the two types was caused by the production of pigments in the algal cells. The algal community structures of Types C and D differed from those of Types A and B, indicating that the primary carotenoids and astaxanthin diesters were derived from certain algal species in these types. Therefore, astaxanthin-rich Sanguina algae mostly induced the red snow that appeared widely in this alpine area; however, they were partially dominated by Chloromonas or Chlainomonas algae, causing different pigment compositions.

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.

Oxygen isotope ratios (δ18O) of tree-ring cellulose are a novel proxy of summer hydroclimate in monsoonal Asia. In central Japan, we collected 67 conifer wood samples, mainly Chamaecyparis obtusa, with ages encompassing the past 2,600 yr. The samples were taken from living old trees, excavated archeological wood, old architectural wood, and naturally buried logs. We analyzed stable isotope ratios of oxygen (δ18O) and hydrogen (δ2H) in tree-ring cellulose in these samples without using a pooling method, and constructed a statistically reliable tree-ring cellulose δ18O time-series for the past 2,500 yr. However, there were distinct age trends and level offsets in the δ18O record, and cellulose δ18O values showed a gradual decrease as an individual tree matures. This suggested it is difficult to establish a cellulose δ18O chronology for low-frequency signals by simple averaging of all the δ18O time-series data. However, there were opposite age trends in the cellulose δ2H, and δ2H gradually increased with tree age. There were clear positive correlations in the short periodicity variations between δ18O and δ2H, probably indicating a common climate signal. A comparison of the δ18O and δ2H time-series in individual trees with tree-ring width suggested that the opposite age trends of δ18O and δ2H are caused by temporal changes in the degree of post-photosynthetic isotope exchange with xylem water, accompanied by changes in stem growth rate (growth effect) that are influenced by human activity in the forests of central Japan. Based on the assumptions that cellulose δ18O and δ2H vary positively and negatively with constant proportional coefficients due to climate variations and the growth effect, respectively, we solved simultaneous equations for the climatological and physiological components of variations in tree-ring cellulose δ18O and δ2H in order to remove the age trend (growth effect). This enabled us to evaluate the climatic record from cellulose δ18O variations. The extracted climatological component in the cellulose δ18O for the past 2,600 yr in central Japan was well correlated with numerous instrumental, historical, and paleoclimatological records of past summer climate at various spatial and temporal scales. This indicates that integration of tree-ring cellulose δ18O and δ2H data is a promising method to reconstruct past summer climate variations on annual to millennial time-scales, irrespective of the growth affect. However, analytical and statistical methods need to be improved for further development of this climate proxy.

A 180 m long (ca. 274 years) ice core was drilled in the saddle of the Aurora Peak of Alaska (63.52° N; 146.54° W, elevation: 2825 m). The ice core samples were melt, concentrated and then derivatized with N,O-bis-(trimethylsilyl) trifluoroacetamide with 1 % trimethylsilyl chloride and pyridine followed by gas chromatography/mass spectrometry analyses. Levoglucosan, dehydroabietic acid, and vanillic acid are reported for the first time from the alpine glacier to better understand historical biomass burning activities in the source region of southern Alaska. These organic compounds showed higher concentrations with many sporadic peaks in the 1660s–1830s, 1913, and 2005. Moreover, there are few discrepancies of higher spikes among them after the 1970s with sporadic peaks in 1994–2007 for dehydroabietic acid. Historical trends of levoglucosan, dehydroabietic and vanillic acid showed that biomass burning activities from resin and lignin in boreal conifer trees, other higher plants and grasses were significant before the 1840s and after the 1970s in the source regions of southern Alaska, being different from previous ice core studies. Long-range atmospheric transport could be important for levoglucosan compared to dehydroabietic acid in the North Pacific Rim (NPR). We found weak or no correlations of levoglucosan with NO2− (r = 0.06), NO3− (0.04), nss-SO42− (0.08), nss-K+ (0.11), and NH4+ (0.11) from the same ice core, suggesting that these anions and cations do not represent a gleaming signal of biomass burning activities in the source regions for southern Alaska. Hence, this study revels a new dimension of biomass burning periodic cycles in the NPR.

To better understand the reported paleoclimate features and underlying mechanisms in the lowest-latitude region (~28°N to 29°30′N), where 12 major river gorges cross the Himalayas, of the southern Tibetan Plateau, we aim to elucidate the major sources and behavior of modern monsoon air masses in the region based on spatial variations in the δ18O and δ2H of stream water and precipitation, and vegetation during the summer monsoon season. Our main findings were following: The river gorges, high mountain ranges bearing extensive dense vegetation, and stronger solar insolation characteristic of the lowest-latitude region may have functioned for an extended period as the essential geological settings for strongly drawing significant amounts of moisture from the Indian Ocean toward the region without passing through the Yarlung Zangbo basin. The combination of such geological settings specific to this region may have caused its earlier response to the climate amelioration after a cold/dry event, such as the Younger Dryas and Heinrich-1, compared to other regions on the Plateau. Furthermore, gorge-derived monsoon air masses that blew through the lowest-latitude region are highly likely to have more significantly influenced the onset of the climate amelioration after a cold/dry event even in the southwestern, south-central, and southeastern regions, rather than the Yarlung Zangbo-derived monsoon air masses. Therefore, this caused the subsequent expansion of the Indian summer monsoon (ISM) over the Plateau. Thus, with its unique geological setting, the lowest-latitude region has presumably played a critical role as the key region, i.e. the initiator, for the early evolution of the ISM on the Tibetan Plateau by responding to climate amelioration after cold/dry events more rapidly than any other region and drawing gorge-derived monsoon air masses strongly toward the region.

To improve surface mass balance (SMB) estimates for the Greenland Ice Sheet (GrIS), we developed a 5 km resolution regional climate model combining the Japan Meteorological Agency Non-Hydrostatic atmospheric Model and the Snow Metamorphism and Albedo Process model (NHM–SMAP) with an output interval of 1 h, forced by the Japanese 55-year reanalysis (JRA-55). We used in situ data to evaluate NHM–SMAP in the GrIS during the 2011–2014 mass balance years. We investigated two options for the lower boundary conditions of the atmosphere: an offline configuration using snow, firn, and ice albedo, surface temperature data from JRA-55, and an online configuration using values from SMAP. The online configuration improved model performance in simulating 2 m air temperature, suggesting that the surface analysis provided by JRA-55 is inadequate for the GrIS and that SMAP results can better simulate physical conditions of snow/firn/ice. It also reproduced the measured features of the GrIS climate, diurnal variations, and even a strong mesoscale wind event. In particular, it successfully reproduced the temporal evolution of the GrIS surface melt area extent as well as the record melt event around 12 July 2012, at which time the simulated melt area extent reached 92.4 %. Sensitivity tests showed that the choice of calculation schemes for vertical water movement in snow and firn has an effect as great as 200 Gt year−1 in the GrIS-wide accumulated SMB estimates; a scheme based on the Richards equation provided the best performance.

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. / 3F Multipurpose Conference room, National Institute of Polar Research

A 180.17 m ice core was drilled at Aurora Peak in the central part of the Alaska Range, Alaska, in 2008 to allow reconstruction of centennial-scale climate change in the northern North Pacific. The 10 m-depth temperature in the borehole was −2.2 °C, which corresponded to annual mean air temperature at the drilling site. In this ice core, there were many melt-refrozen layers due to high temperature and/or strong insolation during summer seasons. We analyzed stable hydrogen isotopes (δD) and chemical species in the ice core. The ice core age was determined by annual counts of δD and seasonal cycles of Na+, and we used reference horizons of tritium peaks in 1963 and 1964, major volcanic eruptions of Mount Spurr in 1992 and Mount Katmai in 1912, and a large forest fire in 2004 as age controls. Here, we show that the chronology of the Aurora Peak ice core from 95.61 m w.eq. to the top corresponds to the period from 1900 to the summer season of 2008, with a dating error of ±3 years. We estimated that the mean accumulation rate from 1997 to 2007 (except for 2004) was 1.88 m w.eq per year. Our results suggest that temporal variation in δD and annual accumulation rates are strongly related to shifts in the Pacific Decadal Oscillation index (PDOI). The remarkable increase in annual precipitation since the 1970s has likely been the result of enhanced storm activity associated with shifts in the PDOI during winter in the Gulf of Alaska.

To improve surface mass balance (SMB) estimates for the Greenland Ice Sheet (GrIS), we developed a 5 km resolution regional climate model combining the Japan Meteorological Agency Non-Hydrostatic atmospheric Model and the Snow Metamorphism and Albedo Process model (NHM-SMAP) with an output interval of 1 h, forced by the Japanese 55year Reanalysis (JRA-55). We used in situ data to evaluate NHM-SMAP in the GrIS during the 2011–2014 mass balance years. We investigated two options for the lower boundary conditions of the atmosphere, an "off-line" configuration using snow/firn/ice albedo and surface temperature data from JRA-55 and an "on-line" configuration using values from SMAP. The on-line configuration improved model performance in simulating 2 m air temperature, suggesting that the surface analysis provided by JRA-55 is inadequate for the GrIS and that SMAP results can better simulate snow/firn/ice physical conditions. It also reproduced the measured features of the GrIS climate, diurnal variations, and even a meso-scale strong wind event. In particular, it reproduced the GrIS surface melt area extent well. Sensitivity tests showed that the choice of calculation schemes for vertical water movement in snow and firn has an effect as great as 200 Gt year–1 in the GrIS-wide accumulated SMB estimates; a scheme based on the Richards equation provided the best performance.

Glaciological observations were conducted in 2012 and 2013 at the SIGMA-A site on the northwest Greenland ice sheet (78°03’06”N, 67°37’42”W, 1490 m a.s.l.) as part of the Snow Impurity and Glacial Microbe effects on abrupt warming in the Arctic (SIGMA) project. The meteorological conditions during the two observations were quite different. The meteorological condition during the 2012 observation period was warm, and heavy rainfall occurred during the observation period, thus the snow was very wet. In contrast, the meteorological condition during the observation period in 2013 was cold, with a blowing snow event, thus the snow was quite dry. The glaciological observations in 2012 consisted of 1) snow-stake measurements, 2) snow pit observations, 3) grain size observations for validation of satellite-derived snow products, 4) snow specific surface area measurements using a near-infrared camera, 5) snow sampling for chemical analyses, and 6) drilling of firn cores with a hand auger. The glaciological observations in 2013 consisted of 1) snow-stake measurements, 2) snow pit observations, and 3) snow sampling for chemical analyses.

AbstarctThe Sea of Okhotsk is the southernmost area in the Northern Hemisphere where seasonal sea ice is produced every year. The formation of sea ice drives thermohaline circulation in the Sea of Okhotsk, and this circulation supports the high productivity in the region. However, recent reports have indicated that sea-ice production in the Sea of Okhotsk is decreasing, raising concern that the decreased sea ice will affect not only circulation but also biological productivity in the sea. To reconstruct climatic changes in the Sea of Okhotsk region, we analyzed an ice core obtained from Ichinskaya Sopka (Mount Ichinsky), Kamchatka. We assumed that the remarkable negative peaks of δD in the ice core were caused by expansion of sea ice in the Sea of Okhotsk. Melt feature percentage (MFP), which indicates summer snowmelt, showed high values in the 1950–60s and the mid-1990s–2000s. The high MFP in the 1950–60s was assumed to be caused by an increase in cyclone activity reaching Kamchatka during a negative period of the Pacific Decadal Oscillation index, and that in the 1990–2000s may reflect the increase in solar irradiation during a positive period of the summer Arctic Oscillation index.

We present an approach for determining the major anaerobic bacterial processes in aquifers, using the combined stable isotope ratios of major elements (C, N, and S) as net recorders of the biogeochemical reactions. The Kumamoto groundwater is constituted of two major flow systems, A–A′ and B–B′, within 103 km-scale area. Previous study [Hosono, T., Tokunaga, T., Kagabu, M., Nakata, H., Orishikida, T., Lin, I-T., Shimada, J., 2013. The use of δ15N and δ18O tracers with an understanding of groundwater flow dynamics for evaluating the origins and attenuation mechanisms of nitrate pollution. Water Res. 47, 2661–2675.] investigated the nitrate sources and extent of denitrification using δ 15 N NO 3 and δ 18 O NO 3 tracers. In the present study, we studied a type of denitrification (heterogenic vs. autotrophic) and occurrence of sequential anaerobic processes along the flow systems with newly measured δ13CDIC and δ 34 S SO 4 . In A–A′ flow system, C, N, and S isotopic compositions did not change along the flow direction. However, in B–B′ flow system significant sulfate reduction (with a maximum δ 34 S SO 4 enrichment of +55‰) occurred along with denitrification (with a maximum δ 15 N NO 3 enrichment of +38‰) as the groundwater flowed down-gradient. Depletions in δ 34 S SO 4 (−8‰ maximum) were found only sporadically. These observations imply that autotrophic denitrification could occur in very limited parts of the study area. Moreover, the occurrence of methanogenic reactions was suggested by the enriched δ13CDIC signature (+8‰ maximum) at a denitrification hotspot. By characterizing C, N, and S isotope compositional changes in wide redox range (from aerobic oxidation of organic carbon, through denitrification, to sulfate reduction, until methanogenesis), we could develop the model of C, N, and S isotopic evolutional patterns under different redox scenarios. Proposed model is useful in obtaining a comprehensive understanding of the major anaerobic bacterial processes in aquifer systems, including distinguishing between heterotrophic and autotrophic denitrification.