High Mountain Glaciers Research Articles

Zn Isotope Tracing Unveils Primary Anthropogenic Zn Sources in Glacial Cryoconite of the High Asian Mountains

AbstractZinc (Zn) exerts a significant influence on the global environment, terrestrial ecosystems, and human health. The application of Zn isotopes (δ66Zn) has been suggested as a potent tool for tracing environmental contamination. However, studies focusing on Zn isotope tracing within the cryosphere areas are notably limited. Here we present the first data set on Zn isotopes in glacial cryoconite, based on observations over a large regional scale in High Asian Mountains (including Tibetan Plateau (TP) and its surroundings of western China). The results showed that glacial cryoconite had a general heavy Zn isotopic signature in various TP locations, with δ66Zn values ranging from −0.22‰ to +0.87‰. Employing the MixSIAR model, the overall Zn contribution source to the cryoconite was mineral dust (36%) > coal burning (33%) > non‐exhaust traffic emissions (22%) > industrial smelting (10%). We ascertained that anthropogenic sources account for the primary contribution (about 60%–73%) of Zn inputs in all glacial locations, with coal burning emerging as the foremost anthropogenic contributor (mean 33%). Anthropogenic Zn in various TP locations was primarily derived from Zn emissions resulting from coal combustion, though it is also predominantly influenced by industrial smelting source in cryoconite of the Tianshan Mountains. Our results aligned with coal combustion data from the energy inventory of western China, suggesting that regional coal burning likely represents the foremost source of atmospheric Zn pollutant emission and deposition in the High Asia mountain glaciers.

Characteristics of methane and carbon dioxide in ice caves at a high-mountain glacier of China

The exploration of the spatiotemporal distribution of greenhouse gas (GHG) exchange in the cryosphere (including ice sheet, glaciers, and permafrost) is important for understanding its future feedback to the atmosphere. Mountain glaciers and ice sheets may be potential sources of GHG emissions, but the magnitude and distribution of GHG emissions from glaciers and ice sheets remain unclear because observation data are lacking. In this study, in situ CH4 and CO2 and the mixing ratios of their carbon isotope signatures in the air inside an ice cave were measured, and CH4 and CO2 exchange in the meltwater of Laohugou glacier No. 12, a high-mountain glacier in an arid region of western China, was also analyzed and compared with the exchange in downstream rivers and a reservoir. The results indicated elevated CH4 mixing ratios (up to 5.7 ppm) and depleted CO2 (down to 168 ppm) in the ice cave, compared to ambient levels during field observations. The CH4 and CO2 fluxes in surface meltwater of the glacier were extremely low compared with their fluxes in rivers from the Tibetan Plateau (TP). CH4 and CO2 mixing ratios in the air inside the ice cave were mainly controlled by local meteorological conditions (air temperature, wind speed and direction) and meltwater runoff. The carbon isotopic compositions of CH4 and CO2 in the ice cave and terminus meltwater indicated δ13C-CH4 depletion compared to ambient air, suggesting an acetate fermentation pathway. The abundances of key genes for methanogenic archaea/genes encoding methyl coenzyme M reductase further indicated the production of CH4 by methanogenic archaea from the subglacial meltwater of high-mountain glaciers. The discovery of CH4 emissions from even small high-mountain glaciers indicates a more prevalent characteristic of glaciers to produce and release CH4 from the subglacial environment than previously believed. Nevertheless, further research is required to understand the relationship between this phenomenon and glacial dynamics in the third pole.

Monitoring a high mountain glacier through georeferenced time-lapse photography: Tapado, Dry Andes of Chile (30°S)

ABSTRACT Glaciers and snow cover provide freshwater for irrigated agriculture and urban consumption in the Dry Andes. Given the aridity of this environment, sublimation losses are significant, making precise monitoring techniques crucial in estimating glacier changes. Continuous monitoring of glaciers is typically conducted through the use of automatic weather stations (AWS). However, these stations may not capture the full extent of glacier changes, warranting the use of additional monitoring techniques such as close-range remote sensing and satellite imagery. This study utilizes time-lapse photography acquired from 2013 to 2015 to examine the temporal and spatial albedo variations across the Tapado Glacier, along with the surface changes in the debris-covered section. Sequential orthorectified images were used to observe the spatial evolution of ice cliffs and supraglacial ponds as they changed over time. High-resolution displacement measurements were obtained using feature tracking methods on the debris-covered glacier. Additionally, distributed albedo maps were produced by comparing photographic data with point albedo measurements from an AWS. The results indicate decreased albedo values during summer, along with the expansion of supraglacial ponds and ice cliffs in the debris-covered region. The study also proposes a cost-effective remote site monitoring approach using time-lapse photography for continuous observation and data collection.

Coupling of river discharges and alpine glaciers in arid Central Asia

Water resource is the primary factor impacting socio-economic development and security in arid Central Asia where high water stress occurs. Therefore, understanding the mechanism of water resource, particularly its associations with global warming, has unique importance for regional sustainable development. However, the dynamics of water resource is far from constrained in arid Central Asia indicated by the observed heterogenous trends of both alpine glaciers in high mountains (water tower) and river runoffs (dominant freshwater sources). Both meltwater and precipitations have been assumed to be the major contribution to the river runoff. Here, we make a systematic analysis on the 10Be exposure ages of the moraines in the high mountains and river terraces across Central Asia (n = 1057) to characterize the past changes of alpine glaciers and river discharges. The results show that the high river discharges are coupled with the alpine glacier expansions on both orbital and millennial scales, indicating a dominant contribution of meltwater to the freshwater supply. Both high river discharges and alpine glacier expansions occurred during the cold periods of the past 130 ka in Central Asia, indicating relatively low water stress under low-temperature conditions. This characteristic suggests that the water stress would increase with the decrease in both water reservoir and river discharges, and thus the environment would become drying with global warming in Central Asia.

Icequakes and Large Shear Wave Velocity Drop in the Kuoqionggangri Glacier of Tibetan Plateau Observed with Fiber Optic Seismometer Array

We developed a kind of fiber optic seismometer array for a high mountain glacier and first tested it on the Kuoqionggangri Glacier in the Tibetan Plateau. The array clearly recorded substantial passive seismic source signals of various icequakes, including shallow, deep and hybrid events. These fracturing activities indicate that crevasses and/or fractures developed in the glacier. We further obtained the glacial thickness of about 40 m by analyzing the active seismic source after hitting the glacier surface with a hammer based on the seismic scattering method. Most importantly, we observed a low shear wave velocity layer with a large velocity drop of ~28% and thickness of about ~7 m in the lower glacier. It is inferred that the low-velocity layer may represent a temperate ice layer. Our experiment provides a kind of feasible seismic observation to study icequakes and the englacial structure of Tibetan glaciers, offering new insights for evaluating glacier change in the Tibetan Plateau.

ONE OF THE VERSIONS ABOUT THE EXTRATERRESTRIAL ORIGIN OF VIRUSES ON PLANET EARTH

In this article, the author puts forward a version about the formation of planet Earth and the origin of life on it, as well as about the extraterrestrial origin of viruses. The appearance of viruses on Earth was associated with comets and meteor showers saturated with viral particles that arose from the destroyed hypothetical planet Phaeton, which periodically docked with the Earth's orbit, spraying them into its atmosphere, causing mass diseases. Alpine glaciers and permafrost zones also played an important role in the manifestation of viral diseases, in which, during the passage of meteor showers, viral particles accumulated in the form of layers. With global warming, the ancient viruses of glaciers and permafrost, being released, mutated with new viruses from flying meteor showers, causing new epidemics on Earth. In conclusion, the article proposes that scientists conduct space studies of comets and meteor showers, as well as ice of high-mountain glaciers and permafrost to study viral particles, to predict and prevent the next global catastrophes.

Reconstructing GRACE-like time series of high mountain glacier mass anomalies

High mountain glaciers (HMGs), called the water towers of the world, are vulnerable to the effects of climate change and thus are rapidly shrinking. Monitoring and evaluating large-scale glacier and snow (GS) mass changes are critical for humans and ecosystems. Although modern gravity satellites monitor GS on a global scale, the contemporary Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow−On (GRACE−FO) missions are only able to do so at coarse spatial resolutions and are restricted by their limited observation periods. Moreover, because of the complex mechanism behind a glacier's mass balance, existing reconstruction methods for GRACE-like mass anomalies, including machine learning approaches and statistical models, cannot be applied to HMGs. Here, we propose a precipitation and temperature data-driven statistical model combining hydrology and GS processes to reconstruct GRACE-like mass anomalies of HMGs, from which the hydrological and GS signals can be further separated. The prediction and reconstruction performance of this method was consistent with the GRACE/GRACE−FO observations (the median correlation coefficient/Nash-Sutcliffe efficiency: ~0.92/0.85). Additionally, the separated GS signals agreed with the independent external data used for comparison. Compared with machine learning methods, this method better reconstructed the long-term trend of GRACE-like mass anomalies. Our study provides an acceptable method for expanding mass anomaly time series on HMGs, thereby assisting in the sustainable management and protection of water resources in their downstream areas.

Redescription of the Caucasian endemic Diamesa caucasica Kownacki et Kownacka (Diptera: Chironomidae: Diamesinae)

Diamesa caucasica Kownacki et Kownacka was described from the watercourses of the Terek River basin flowing down from the high mountain glaciers of the Caucasus (alt. 20002700 m a.s.l.), namely from the Chkheri River (Ortsveri Glacier), the Suatisi River (Savitisi Glacier) and the Mnaisidon River (Mna Glacier) in Georgia (Kownacki Kownacka 1973). So far, no other finds of this species have been recorded in the Caucasus and other mountainous regions of Europe. Apparently, D. caucasica is endemic to the Caucasus and its distribution probably does not go beyond the glacial streams of the Terek River basin. This assumption is confirmed by the finds of adult males of this species made by Dmitry Palatov in 20182022 in the rivers at an altitude 14021980 m a.s.l., originating in the Mostocete, Tanantsete, Skazsky and Tseysky glaciers of North Ossetia and which also belong to the Terek River basin.

Large-area high spatial resolution albedo retrievals from remote sensing for use in assessing the impact of wildfire soot deposition on high mountain snow and ice melt

Soot deposition from wildfires decreases snow and ice albedo and increases the absorption of shortwave radiation, which advances and accelerates melt. Soot deposition also induces algal growth, which further decreases snow and ice albedo. In recent years, increasingly severe and widespread wildfire activity has occurred in western Canada in association with climate change. In the summers of 2017 and 2018, westerly winds transported smoke from extensive record-breaking wildfires in British Columbia eastward to the Canadian Rockies, where substantial amounts of soot were deposited on high mountain glaciers, snowfields, and icefields. Several studies have addressed the problem of soot deposition on snow and ice, but the spatiotemporal resolution applied has not been compatible with studying mountain icefields that are extensive but contain substantial internal variability and have dynamical albedos. This study evaluates spatial patterns in the albedo decrease and net shortwave radiation (K*) increase caused by soot from intense wildfires in Western Canada deposited on the Columbia Icefield (151 km2), Canadian Rockies, during 2017 and 2018. Twelve Sentinel-2 images were used to generate high spatial resolution albedo retrievals during four summers (2017 to 2020) using a MODIS bidirectional reflectance distribution function (BRDF) model, which was employed to model the snow and ice reflectance anisotropy. Remote sensing estimates were evaluated using site-measured albedo on the icefield's Athabasca Glacier tongue, resulting in a R2, mean bias, and root mean square error (RMSE) of 0.68, 0.019, and 0.026, respectively. The biggest inter-annual spatially averaged soot-induced albedo declines were of 0.148 and 0.050 (2018 to 2020) for southeast-facing glaciers and the snow plateau, respectively. The highest inter-annual spatially-averaged soot-induced shortwave radiative forcing was 203 W/m2 for southeast-facing glaciers (2018 to 2020) and 106 W/m2 for the snow plateau (2017 to 2020). These findings indicate that snow albedo responded rapidly to and recovered rapidly from soot deposition. However, ice albedo remained low the year after fire, and this was likely related to a bio-albedo feedback involving microorganisms. Snow and ice K* were highest during low albedo years, especially for south-facing glaciers. These large-scale effects accelerated melt of the Columbia Icefield. The findings highlight the importance of using large-area high spatial resolution albedo estimates to analyze the effect of wildfire soot deposition on snow and ice albedo and K* on icefields, which is not possible using other approaches.

Metagenomics reveals global-scale contrasts in nitrogen cycling and cyanobacterial light-harvesting mechanisms in glacier cryoconite

BackgroundCryoconite granules are mineral–microbial aggregates found on glacier surfaces worldwide and are hotspots of biogeochemical reactions in glacier ecosystems. However, despite their importance within glacier ecosystems, the geographical diversity of taxonomic assemblages and metabolic potential of cryoconite communities around the globe remain unclear. In particular, the genomic content of cryoconite communities on Asia’s high mountain glaciers, which represent a substantial portion of Earth’s ice masses, has rarely been reported. Therefore, in this study, to elucidate the taxonomic and ecological diversities of cryoconite bacterial consortia on a global scale, we conducted shotgun metagenomic sequencing of cryoconite acquired from a range of geographical areas comprising Polar (Arctic and Antarctic) and Asian alpine regions.ResultsOur metagenomic data indicate that compositions of both bacterial taxa and functional genes are particularly distinctive for Asian cryoconite. Read abundance of the genes responsible for denitrification was significantly more abundant in Asian cryoconite than the Polar cryoconite, implying that denitrification is more enhanced in Asian glaciers. The taxonomic composition of Cyanobacteria, the key primary producers in cryoconite communities, also differs between the Polar and Asian samples. Analyses on the metagenome-assembled genomes and fluorescence emission spectra reveal that Asian cryoconite is dominated by multiple cyanobacterial lineages possessing phycoerythrin, a green light-harvesting component for photosynthesis. In contrast, Polar cryoconite is dominated by a single cyanobacterial species Phormidesmis priestleyi that does not possess phycoerythrin. These findings suggest that the assemblage of cryoconite bacterial communities respond to regional- or glacier-specific physicochemical conditions, such as the availability of nutrients (e.g., nitrate and dissolved organic carbon) and light (i.e., incident shortwave radiation).ConclusionsOur genome-resolved metagenomics provides the first characterization of the taxonomic and metabolic diversities of cryoconite from contrasting geographical areas, highlighted by the distinct light-harvesting approaches of Cyanobacteria and nitrogen utilization between Polar and Asian cryoconite, and implies the existence of environmental controls on the assemblage of cryoconite communities. These findings deepen our understanding of the biodiversity and biogeochemical cycles of glacier ecosystems, which are susceptible to ongoing climate change and glacier decline, on a global scale.6g6EUUoWKnbiE9vByjupn9Video abstract

Automated Delineation of Supraglacial Debris Cover Using Deep Learning and Multisource Remote Sensing Data

High-mountain glaciers can be covered with varying degrees of debris. Debris over glaciers (supraglacial debris) significantly alter glacier melt, velocity, ice geometry, and, thus, the overall response of glaciers towards climate change. The accumulated supraglacial debris impedes the automated delineation of glacier extent owing to its similar reflectance properties with surrounding periglacial debris (debris aside the glaciated area). Here, we propose an automated scheme for supraglacial debris mapping using a synergistic approach of deep learning and multisource remote sensing data. A combination of multisource remote sensing data (visible, near-infrared, shortwave infrared, thermal infrared, microwave, elevation, and surface slope) is used as input to a fully connected feed-forward deep neural network (i.e., deep artificial neural network). The presented deep neural network is designed by choosing the optimum number and size of hidden layers using the hit and trial method. The deep neural network is trained over eight sites spread across the Himalayas and tested over three sites in the Karakoram region. Our results show 96.3% accuracy of the model over test data. The robustness of the proposed scheme is tested over 900 km2 and 1710 km2 of glacierized regions, representing a high degree of landscape heterogeneity. The study provides proof of the concept that deep neural networks can potentially automate the debris-covered glacier mapping using multisource remote sensing data.

Alpine glacier surface velocity measurement from UAV imagery – examining the effect of image resolution on the accuracy of results

The reliability and validity of the Glacier Surface Velocity (GSV) measurement results based on remote sensing datasets depends on the quality and spatial resolution of the image used. The typical pixel size of space-borne satellite imagery is often larger than the annual and inter-annual displacement of small alpine debris-covered glaciers. In addition, the pixel size of medium resolution satellite images (10–30 m), limits the size of a feature that can be matched. This is even more of an issue for glaciers located in arid and semi-arid environments (e.g. glaciers in Iran and high mountains of Asia) where flow velocities are not exceeding a few metres per year. Consequently, high-resolution data such as Unmanned Aerial Vehicle (UAV) images are required to calculate the surface velocity of such glaciers. However, the optimal resolution of UAV images is one of the most important challenges in GSV measurement. This paper explores the influence of UAV image resolution on the quality of GSV results. Analysis was carried out at 19 different resolutions of UAV images from 10 to 100 cm with a 5 cm bin over a debris-covered glacier, in Iran. COSI-Corr algorithm was used to perform the image correlation. To evaluate the accuracy of obtained results, manual digitisation was performed and the differences between manual GSV and frequency cross-correlator were assessed for all data sets. Moreover, displacement calculated for a stagnant off-glacier area was evaluated. While the quality of the results of the images between 10 and 30 cm is substantially the same, the obtained results indicate that the best result of GSV was not obtained using the finest image resolution. Results revealed that the highest correspondence between the measured GSV and manual digitisation was obtained in a 30 cm spatial resolution image. In addition, the 30 cm image resolution shows the minimum uncertainty over the off-glacier static area. Obtained results revealed that using too fine resolution images will lead to computational redundancy, while no improvement is observed in the accuracy of GSV results.

CH4 and CO2 observations from a melting high mountain glacier, Laohugou Glacier No. 12

With global warming, glaciers in the high mountains of China are retreating rapidly. However, few data have been reported on whether greenhouse gases from these glaciers are released into the atmosphere or absorbed by glacial meltwater. In this study, we collected meltwater and ice samples from Laohugou Glacier No. 12 in western China and measured CH4 and CO2 concentrations. Meltwater from the glacier terminus was continually sampled between 3 and 5 August 2020 to measure CH4 and CO2 concentrations. The results demonstrated that meltwater is a source of CH4 because the average saturations are over 100%. It could be concluded that CH4 in the atmosphere can be released by glacial meltwater. However, the CO2 saturations are various, and CO2 fluxes exhibit positive (released CO2) or negative (absorbed CO2) values because the water and atmospheric conditions are variable. More importantly, the CH4 and CO2 concentrations were higher in meltwater samples from the glacier terminus than in samples from the surface ice (including an ice core) and a surface stream. Although the meltwater effect from the upper part of the glacier cannot be excluded, we speculated that subglacial drainage systems with an anaerobic environment may represent the CH4 source, but it needs to be further investigated in the future. However, high mountain glaciers are currently ignored in global carbon budgets, and the increased melting of glaciers with global warming may accelerate the absorption of much more CO2 and lead to the release of CH4.

Holocene sedimentary evolution of a subaqueous delta off a typical tropical river, Hainan Island, South China

High-resolution seismic surveys were conducted off the eastern coast of Hainan Island to study the distribution and mass budget of Holocene subaqueous clinoform sediments. The Holocene subaqueous clinoform extends 45 km seaward across the shelf and more than 80 km northeastward along the shore. It covers an area of over 3,000 km2, which is almost equivalent to the expansion of large river systems. Overlying the transgressive surface, the deltaic sequence can be divided into a transgressive unit and a highstand unit separated by a downlap maximum flooding surface. The volume of sediments within the Holocene subaqueous clinoform is estimated to be 33.12×109 m3, equivalent to an annual accumulation of 3.61–3.31 Mt/yr, which is substantially higher than the global average. The high sediment yield presumably resulted from strong tropical weathering and active tectonics. The sediment flux during the transgression and sea-level highstand were 3.85–3.08 and 3.47 Mt/yr, respectively, suggesting no substantial changes in sedimentation. Compared to river systems originating from high mountain glaciers, the sedimentation variation of small tropical rivers throughout the Holocene is relatively minor. However, the sediment discharge of the Wanquan River has drastically decreased in recent decades because of increased human activity.

Combining UAV and Landsat data to assess glacier changes on the central Tibetan Plateau

AbstractIn recent years, researchers have focused on the applications of uncrewed aerial vehicles (UAVs) in environmental remote sensing tasks. However, studies on glacier monitoring using UAV technology are relatively scarce, especially for high mountain glacier monitoring. To explore the feasibility of UAV technology for high mountain glaciers, four UAV surveys were deployed on two glaciers of the central Tibetan Plateau. Based on the images retrieved by UAV in 2017 and 2019, orthomosaics and digital elevation models were produced to quantify the length, area and elevation changes in the ablation zone of these two glaciers at different times. Additionally, we utilized several Landsat scenes to derive glacier changes over the last 30 years and combined these with the UAV data to assess the advantages and disadvantages of UAV technology in mountain glacier monitoring.

UAV-Based Survey of Glaciers in Himalayas: Challenges and Recommendations

Role of Unmanned Aerial Vehicle (UAV)-based remote sensing (RS) applications in glaciology have increased in recent years. UAV-based RS studies on mountain glaciers are mainly focussing on obtaining accurate ultra-high-resolution data from UAV images for different glaciological applications. However, studies understanding the challenges involved during UAV surveys on complex terrains of high mountain glaciers are inadequate and they are not available for places like Himalayas. Therefore, this study aims to examine and derive strategies to minimize those challenges on such complex glacier and their margin topography. Here, UAV surveys were conducted using a fixed-wing commercial-grade off-the-shelf UAV (eBee series, SenseFly) on three glacier sites (East Rathong, Hamtah and Panchinala-A) located in different climate regimes within the Indian part of Himalayas. From the UAV collected images, ultra-high-resolution ortho-mosaicked images and Digital Elevation Models were generated at 0.1 m ground sample distance and their accuracies were assessed using the collected ground control points. Based on the challenges observed, the study recommends criteria for selection of best-suited take-off/landing locations on a mountain glacier and its margins for conducting efficient UAV surveys in the complex terrain such as in the Himalayas and possibly beyond. Recommendations reported in this article shall be useful to minimize the challenges and associated risks during UAV data acquisition using fixed-wing UAVs.

Soil development and spatial differentiation in a glacial river valley under cold and extremely arid climate of East Pamir Mountains

Melting glaciers release new ground surfaces, which may be either a source of greenhouse gas emissions or a sink for carbon dioxide. Studies carried out in subpolar and alpine ecosystems confirm the relatively rapid soil development and increase of carbon and nitrogen pools. However, observations from high-mountain glacier forelands in cold and dry climate are very scarce. This study analyses the impact of major environmental factors related to climate, topography, and vegetation, over a time-scale, on soil development and spatial soil differentiation in the foreland of Uisu Glacier, East Pamir Mountains. Moreover, the usefulness of the World Reference Base (WRB) and Soil Taxonomy in the classification of poorly developed soils in the ultracontinental climate was assessed. Geomorphological, pedological, and botanical surveys covered a sequence of terraces, alluvial fans, and end-moraines. Typical characteristics of the soils in the glacier foreland were: very high stoniness, coarse texture, high content of calcium carbonate, alkaline reaction, and low salinity. Soil development has extremely low intensity and was manifested in (a) soil organic carbon pools being among the lowest reported in the world (up to 1.4 kg m−2 in the layer 0–50 cm), and (b) the presence of cambic/calcic horizons only on landforms older than of Mid-Holocene age (estimated). It was concluded that both the extremely cold and extremely dry climate conditions in the Uisu Glacier foreland limit the water flux and availability, suppress vegetation density and variability, and slow down the rate of soil development. Both WRB and Soil Taxonomy were able to reflect the advances in soil development and spatial soil differentiation (Calcaric Hyperskeletic Leptosols – Calcaric Cambisols – Cambic Calcisols, and Gelifluvents – Haplocambids - Haplocalcids, respectively); however, highlighting different features developed under an extremely cold and dry climate conditions of the East Pamir Mountains.

Alkenone surface hydrographic changes of the subarctic Northwestern Pacific since the last glacial: proxy limitations and implications of non-thermal environmental influences

We investigated an alkenone-based sea surface temperature (SST) and the hydrographic change records of the subarctic Northwestern (NW) Pacific from the last glacial to interglacial. The core we investigated is a piston core (LV 63-41-2, 52.56° N, 160.00° E; water depth 1924 m) retrieved from the southern offshore east coast of the Kamchatka Peninsula, which is a location of high sedimentation rate, with highly dynamic interactions with the cold/warm water masses of the Bering Sea/the NW Pacific. Based on our alkenone analysis with a previously well-established chronology of the core, we found high glacial C37:4 contents suggesting larger freshwater influences prior to the last deglacial in approximately 27–16 ka BP. The most significant features of what we found are alkenone indicative of “warming” intervals with minimum alkenone productions that occurred prior to the stadial Heinrich event 1 and the Younger Dryas. In contrast, for the interval corresponding to the Bølling–Allerød period, our alkenone analysis shows relatively “colder” but maximum alkenone productions. We conclude that this particular subarctic alkenone SST proxy record is mainly masked by non-thermal environmental influences, such as strong shifts of timing and duration of the sea ice retreat and/or salinity changes in surface water at this site, which could cause changes in water stratification that affect nutrient supplies of the upper ocean that modulate growth durations of phytoplankton/coccolithophore productions. Our studies suggest that this subarctic alkenone “SST” proxy record is indicative of the changes of seasonality that control the timing and duration of the blooming seasons of coccolithophores. The alkenone “SST” proxy is also dominantly driven by water stratification effects that, instead of SSTs, reflect most likely a combination of the following local to regional climate and ocean current patterns: (1) the amount of meltwater inputs from high mountain glaciers at Kamchatka; (2) less saline, nutrient-rich Alaskan Stream waters from the Cordilleran Ice Sheet in the Gulf of Alaska; (3) downwelling waters associated with the interactions between the southward Eastern Kamchatka Current and the spinning-up of the North Pacific Subarctic Gyre; and (4) the strength of the Kuroshio Current since the last glacial.

LO STATO ATTUALE DEI GHIACCIAI ITALIANI E LA LORO RECENTE EVOLUZIONE

Mountain glaciers represent an important hydrological and touristic resource, and their recent evolution provides a dramatic evidence of climate change for the general public. Glacier inventories, quantifying glacier characteristics and evolution, are an important tool to describe and manage high mountain glacier environments and Italy has developed a long tradition in this sector. Our country was the first to provide itself with a glacier inventory, compiled by Comitato Glaciologico Italiano and CNR, showing a glacier surface of 530 km2. A recent project, coordinated by Università Statale di Milano with the support of private bodies and the cooperation of Comitato EvK2CNR and Comitato Glaciologico Italiano, led to the development of the new Italian Glacier Inventory, a national atlas produced from the analysis of color orthophotos at high resolution acquired between 2005 and 2011. The New Italian Glacier Inventory lists 903 glaciers, covering an area of 370 km2. The largest part of glacier area is located in Val d’Aosta (36.15% of the total), followed by Lombardia and South Tyrol. 84% of glaciers (considering the number of glaciers) have an area lower than 0.5 km2 and jointly account for 21% of the total glacier surface. Glaciers larger than 1 Km2 make up 9.4% of the total number, but cover 67.8% of the total glacier area. The comparison between data from the New Italian Glacier Inventory and the CGI-CNR inventory (1959-1962) shows a 30% reduction in glacier area in Italy; considering instead the World Glacier Inventory or WGI, published at the end of the ‘80s, which reported 1381 glaciers and an area of 609 km2, glacier loss sums up to 478 glaciers and an area of 239 km2 (-39%). This shrinkage has led to rapid and significant changes to high mountain landscapes, notably glacier fragmentation, an increase in deglaciated areas, the formation of proglacial lakes and the development of pioneer vegetation.

Occurrence of integrons and antibiotic resistance genes in cryoconite and ice of Svalbard, Greenland, and the Caucasus glaciers.

The prevalence of integrons and antibiotic resistance genes (ARGs) is a serious threat for public health in the new millennium. Although commonly detected in sites affected by strong anthropogenic pressure, in remote areas their occurrence, dissemination, and transfer to other ecosystems is poorly recognized. Remote sites are considered as a benchmark for human-induced contamination on Earth. For years glaciers were considered pristine, now they are regarded as reservoirs of contaminants, thus studies on contamination of glaciers, which may be released to other ecosystems, are highly needed. Therefore, in this study we evaluated the occurrence and frequency of clinically relevant ARGs and resistance integrons in the genomes of culturable bacteria and class 1 integron-integrase gene copy number in the metagenome of cryoconite, ice and supraglacial gravel collected on two Arctic (South-West Greenland and Svalbard) and two High Mountain (the Caucasus) glaciers. Altogether, 36 strains with intI1 integron-integrase gene were isolated. Presence of class 1 integron-integrase gene was also recorded in metagenomic DNA from all sampling localities. The mean values of relative abundance of intI1 gene varied among samples and ranged from 0.7% in cryoconite from Adishi Glacier (the Caucasus) to 16.3% in cryoconite from Greenland. Moreover, antibiotic-resistant strains were isolated from all regions. Genes conferring resistance to β-lactams (blaSHV, blaTEM, blaOXA, blaCMY), fluoroquinolones (qepA, qnrC), and chloramphenicol (cat, cmr) were detected in the genomes of bacterial isolates.