This study presents the first comprehensive global analysis of the variation in mercury (Hg) concentrations in cryoconite, a heterogenous and often organic-rich material found on the surface of glaciers. Samples of cryoconite were collected from 39 glaciers across both hemispheres, comprising 130 samples in total. The highest Hg concentrations were measured in cryoconite from Norway and Alaska (up to 0.965 μg g-1), followed by the European Alps (up to 0.498 μg g-1), reflecting the levels of atmospheric deposition from heavily industrialized and inhabited areas in relatively close proximity to these glaciated regions. To better assess the environmental distribution of Hg in the glacial environment, in addition to cryoconite we also considered other environmental matrices found in glacial and proglacial areas, including algae, soils, and riverine sediments. This included a novel analysis of Hg in red snow algae from Qaanaaq Gletsjer (Greenland). Of all the environmental matrices considered in this study, cryoconite samples contained the highest Hg concentrations. The Pollution Load Index, Geoaccumulation Index, and Target Values for the Netherlands were used as pollution indices to identify hot spots of sediment contamination. According to these pollution indices, samples from the Northern Hemisphere were slightly and moderately polluted by Hg, while those from the Southern Hemisphere were unpolluted. Of the Northern Hemisphere samples, cryoconite from Sweden, Norway and Svalbard had the highest pollution status, while samples from Alaska and the European Alps were generally only slightly polluted. These results highlight the importance of improving our understanding of dynamic and rapidly changing glacial environments in the accumulation, transport, and re-emission of mercury.

The Beyond EPICA–Oldest Ice Core (BE-OIC) project successfully recovered the oldest continuous Antarctic ice core, extending back to at least 1.2 million years. This landmark achievement provides an unprecedented opportunity to address long-standing questions regarding the mechanisms underlying the Mid-Pleistocene Transition (MPT) (Barbante & Beyond EPICA Team, 2025). Among others, this core could be used to study past changes in atmospheric aerosol composition and here, in particular the geochemical composition of mineral dust.However, deep ice is increasingly recognized as a “geochemical reactor”, in which primary mineral impurities undergo post-depositional transformations into secondary phases such as jarosite (Baccolo et al., 2021; Lanci et al., 2025). These alterations pose a major challenge for extracting reliable paleoclimate signals from the analysis of mineral dust trapped into old ice. As such, to avoid misinterpretation of dust-related proxy records, we need to better constrain the nature and extent of deep-ice geochemical processes.Here, we investigate post-depositional geochemical alterations in the EPICA Dome C (EDC) ice core through elemental analysis of ten sections (55 or 110 cm long) spanning the depth of 282 to 3137 m. For the first time, we apply single-particle inductively coupled plasma time-of-flight mass spectrometry (sp-ICP-TOFMS) coupled to the Bern continuous flow analysis (CFA) system to EDC ice core analysis. This approach allows the separate quantification of dissolved and particulate elemental fractions and enables the characterization of the chemical composition of individual particles. Our results reveal extensive dissolution of primary minerals (e.g. hornblende-like phases), accompanied by the precipitation of secondary insoluble and soluble sulfates (e.g. jarosite, alunite), and possibly other Fe-oxide phases. These transformations are likely driven by localized acidic and oxidative microenvironments that develop during the metamorphism of deep ice, depending, to first order, on the growth of ice grains.Our findings provide new insights into post-depositional geochemical processes in deep Antarctic ice and are crucial for ensuring robust paleoclimate reconstructions from dust records in the oldest ice cores, including BE-OIC. Notably, significant geochemical alteration is observed in EDC sections at temperatures of approximately −15 °C and above, indicating that, at the conditions encountered at EDC, these changes emerge at around −15 °C and intensify under warmer conditions. Given that BE-OIC ice of comparable age to EDC is colder while exhibiting similar dust concentration, the BE-OIC ice core may preserve a less geochemically altered, and therefore higher-quality, dust archive for periods already covered by the EDC record (

The discovery of englacial diagenesis, involving neoformation of minerals at depth within ice sheets, has the potential to reshape the interpretation of insoluble dust records in ice cores and the origin of planetary ice-bearing deposits on Mars. Mineralogical changes in deep ice involve iron geochemistry, and are driven by the circulation of acidic fluids within pre-melted ice during ice metamorphism, leading to the authigenic formation of jarosite. Here we show that englacial diagenesis is a widespread process in deep Antarctic ice and involves the authigenic growth of mineral phases like goethite (lepidocrocite) and hematite (maghemite) in addition to jarosite. The coexistence of these neoformed phases reflects micron-scale variability in pH and water activity within the englacial brine network. Englacial diagenesis has major consequences: it introduces systematic biases in bulk mineralogical proxies used to reconstruct dust source conditions, and it provides a grounded explanation for the anomalously high dust magnetization observed in deep Antarctic ice. We further propose that repeated burial of dust within planetary ice reservoirs, as expected on Mars over orbital timescales, represents a viable and previously underexplored mechanism for the oxidation, aggregation and magnetic activation of Martian airborne dust, without requiring prolonged warm and wet surface conditions.

Abstract The Himalayas form a major atmospheric barrier between South Asia and Tibetan Plateau, yet cross‐barrier transport of anthropogenic metals remains poorly constrained. We use moss δ66Zn along a 750–4,100 m a.s.l. south‐north transect in Motuo to trace pollution sources and transport processes. On the southern slope, trace metals (Zn, Pb, As, Ni, Co) display pronounced altitudinal gradients, with low elevations showing high concentrations and light δ66Zn (−0.41‰ to −0.32‰) dominated by smelting (42%–50%). With increasing elevation, concentrations decrease and δ66Zn becomes heavier (0.20‰ to 0.29‰), reflecting greater coal combustion inputs (35%–50%). North of the crest, overall metal loads are lower, but high elevations (>3,500 m) show heavy δ66Zn (0.30‰ to 0.44‰) and strong coal contributions (43%–54%). Our results show that topography, anthropogenic emissions, and vegetation coverage regulate vertical pollutant distribution patterns, providing direct Zn isotopic evidence for transboundary transport of coal combustion emissions from South Asia to the Tibetan Plateau.

Abstract Temperate glaciers, characterized by ice at the pressure-melting point and the coexistence of solid and liquid water, are generally considered unsuitable as natural archives because meltwater undermines the paleoclimatic signals they hold. Historically, ice-core studies have favored cold glaciers. However, the ongoing atmospheric warming is driving many formerly cold portions of glaciers toward temperate conditions. As such, the relevance of temperate ice as potential paleoclimate archives is increasing. Assessing its ability to record environmental signals has become a priority for ice-core science. This review synthesizes more than 70 years of research on temperate ice cores, tracing the evolution of scientific approaches from pioneering efforts in the 1950s to recent projects across the globe. The behavior of ice-core proxies—including soluble and insoluble impurities, water stable isotopes, gases, radionuclides and organic compounds—is discussed in the context of meltwater-related post-depositional processes. By compiling and comparing evidence from diverse settings, this work highlights both the challenges and the emerging opportunities for retrieving meaningful information from temperate glaciers. Understanding how climatic and chemical signals are modified, preserved or lost in rapidly transforming glaciers is essential for sustaining the role of ice-core science in a warming world.

Abstract. Aerosol-derived impurities in deep Antarctic ice cores provide high-resolution records of past climate and atmospheric variability. However, post-depositional englacial geochemical processes driven by impurity remobilization through ice metamorphism can perturb the originally deposited signals, challenging the interpretation of deep ice records. To address this, we investigate englacial mineral alterations by analyzing the elemental composition of 18 ice-core sections of the EPICA Dome C (EDC) ice core (ranging from 281.6–3137.1 m depth) using single-particle inductively coupled plasma time-of-flight mass spectrometry (sp-ICP-TOFMS) coupled to a continuous flow analysis (CFA) system. This reveals a deep-ice environment dominated by pervasive acid dissolution, leaving behind refractory mineral phases. We document the progressive neoformation of potassium-rich alunite-supergroup minerals (jarosite, alunite, and mixed phases) and the probable formation of Fe-(oxyhydr)oxide coatings. These secondary phases concurrently immobilize trace elements (iodine, arsenic, lead) via surface adsorption and structural substitution. These transformations occur within highly localized microenvironments and are accelerated by increasing in situ temperatures with depth. They are further enabled by the old age of deep ice, which provides hundreds of thousands of years for these reactions to occur. These findings underscore the importance of accounting for the effects of post-depositional geochemical transformation when interpreting impurity records from EDC and other old ice cores. The colder thermal regime of the Beyond EPICA Little Dome C is expected to lead to slower geochemical transformation, potentially providing a higher-fidelity impurity record for the epochs currently covered by EDC.

This study investigates uranium (U) and lithium (Li) isotope fractionation in suspended particulate matter (SPM) from glacial basins in the northeastern Tibetan Plateau, aiming to explore the coupling between physical and chemical weathering processes under glacial influence. The (234U/238U) activity ratio is correlated with parameters related to glacial activity, such as the elevation of the basin and glacier area. Samples from glacial watersheds are enriched in 234U (mean 1.28 f 0.11), indicating the efficient comminution of rocks. Conversely, non-glacial areas show lower (234U/238U) ratios due to weakened physical weathering (mean 1.09 f 0.04). The Li isotopes are sensitive to chemical weathering, providing complimentary information to U isotopes. In glacial watersheds, the variation of delta 7LiSP is minimal and compatible with the signature of unaltered bedrock (mean 1.58 f 0.87 %o). Samples from lower basins show a stronger fractionation (mean - 2.61 f 1.26 %o), pointing to a stronger chemical weathering. As for U, Li fractionation is also related to topographic variables influencing the degree of glacial activity. Where glaciers are active, physical weathering fractionates U isotopes but no Li isotopes. Where glaciers are not present, physical weathering is less important, while chemical alteration is more relevant, leading to a low fractionation of U isotopes and a strong fractionation of Li isotopes. The combined use of U and Li isotopes offers an effective tool for tracing weathering regimes shaped by geomorphic and climatic factors, highlighting the role of glaciers in silicate weathering and landscape evolution, and demonstrating the proxies' potential for reconstructing recent glacial weathering.

Over the last century, alpine glaciers have melted rapidly. According to current climate models, it is predicted that 80% of these glaciers will likely disappear between the 2060s and the 2080s. The storage of natural and anthropogenic contaminants in these ice masses, which might be released with water, creates a potential threat for communities, especially those closely related to glacierised regions, and the surrounding glacier habitats.In recent years, cryoconite – a mineral-organic debris that accumulates on the glacier surface - has been the subject of interest due to its ability to accumulate specific substances, surpassing levels found in other terrestrial ecosystems (e.g., proglacial, sediments, soil, lichens, mosses). This phenomenon is attributed to a combination of natural and anthropogenic factors, yet still not well-studied. The majority of artificial radionuclides released into the environment can be attributed to nuclear reactor accidents like Chernobyl (1986) and the stratospheric global fallout.Our main objective is to comprehensively understand the accumulation of natural (210Pb) and artificial (137Cs, 238,239,240Pu) radioisotopes in cryoconite and identify the different sources of contamination based on isotopic and mass ratios of subject radionuclides. To achieve these objectives, we analysed activity concentrations, their relation with the global and local signals, and their variability between glaciers. Samples were collected from eight glaciers in the European Alps, including the glaciers Blanc, Gries, Mandrone, Pastrze, Preda Rossa, Tsanteleina, Ventina, and Zebrù.The highest values of 210Pb were found in cryoconite from the Ventina and the Zebrù Glaciers (more than 11,000 Bq kg−1). The lowest values of 210Pb in individual samples (

The Tibetan Plateau (TP), known as the "Water Tower of Asia", is the source of many major rivers in Asia and an important ecological security barrier in western China. It's environmental sensitivity and unique high-altitude conditions make researching heavy metals critical. Copper (Cu) and Cadmium (Cd), as typical potentially toxic heavy elements, significantly influence biogeochemical processes in watershed ecosystems. This study systematically summarizes the composition, distribution, and enrichment characteristics of Cu and Cd in snow/cryoconite, soil, and river water within the TP. The results indicate that Cu-Cd in snow/cryoconite on TP shows moderate to heavy enrichments, which is mainly affected by local inputs and long-range pollutants via atmospheric circulation. Besides, the concentration and distribution patterns of Cu-Cd in river water of glacial watersheds varied considerably across regions, with both elements exhibiting notable enrichment. The Yarlung Zangbo River in particular, exhibited obvious impacts from anthropogenic activities. Moreover, the estimated atmospheric wet deposition fluxes of Cu and Cd in the glaciers of the TP are 127.62 μg m⁻² a⁻¹ and 2.56 μg m⁻² a⁻¹ , respectively; while the corresponding release fluxes from glacial meltwater runoff are 10.52 ∼ 3.9 × 10 ³ kg a⁻¹ for Cu and 0.23 ∼ 12.72 kg a⁻¹ for Cd. The Cu-Cd concentrations in the topsoils of the TP were unevenly distributed, with higher value in the east and lower in the west. The sources of heavy metals were complex and influenced by multiple factors, and the risk of Cd pollution in soil is widespread. Finally, we present a conceptual model illustrating the multi-source origins and migration dynamics of Cu and Cd in the glacial basins. While the TP is generally less polluted than many other global regions, Cu-Cd in glacial environments shows evident anthropogenic influence and elevated enrichment levels, potentially endangering downstream oasis ecosystems and human populations under the pressure of intensified glacier ablation.

Under climatic warming and increased melting, glaciers and ice caps are becoming secondary sources of contaminants deposited decades ago. Cryoconite, an organic-rich material found on the surface of many glaciers, is particularly efficient at accumulating airborne contaminants due to biogeochemical exchanges with the organic matter within cryoconite. Atmospherically derived radioactive isotopes, commonly referred to as fallout radionuclides, have now been found to accumulate in cryoconite globally. However, data from the polar regions, especially ice sheets and ice caps, is scarce. This study helps to address this regional gap in understanding fallout radionuclide accumulation in glacial settings. We present the first radioactivity dataset from cryoconite on a Greenlandic ice cap and assess the role of cryoconite in the distribution of radioactive species in the High Arctic. Forty-six cryoconite samples were collected from the Flade Isblink ice cap (NE Greenland) in August 2022. These samples were analysed via alpha and gamma spectrometry for atmospheric radionuclides, including 137Cs, 241Am, 210Pbexc., 207Bi, 7Be, and several plutonium isotopes. The results of this study confirm cryoconite's exceptional ability to accumulate fallout radionuclides, even in remote and relatively pristine regions such as Northern Greenland. The activities of radionuclides in cryoconite from Flade Isblink are among the highest reported across the High Arctic and the highest ever reported from Greenland. Flade Isblink's radioactivity source is compatible with the stratospheric reservoir established during atmospheric nuclear tests and with weapon-grade fissile fuel, likely originating from Novaya Zemlya. Our findings emphasise the necessity for continued research efforts on the release of legacy contaminants from glaciers, particularly given accelerated global warming and consequent glacier retreat.

This study concerns the 235U/238U ratios in environmental samples collected in the Pamir region (Central Asia). Cryoconite (a supra-glacial sediment), soil and river water were sampled in the Muztagh Ata Glacier Basin, a secondary basin belonging to Gaizi River watershed. The aim of the research is to assess the impact of anthropic nuclear activities in such a remote area, being the 235U/238U ratio highly sensitive to anthropogenic disturbances. Results indicate that the 235U/238U atomic ratio in the region ranges from 0.007256 to 0.007263, with an average of 0.007259 +/- 0.000002. Such values are slightly higher than the natural isotopic reference (0.007256), suggesting a modest enrichment of 235 U. This is related to the input of uranium with an anthropogenically modified isotopic signature. The 235U/238U ratios are higher in cryoconite compared to that of surface soil/sediment and river water, reflecting differences in the release, transmission and retention of 235U across various environmental media in the Pamir region. The variability of the isotopic ratio was also explored in relation to some key geographic parameters and compared with data from a wider geographic context. The altitude distribution of the 235U/238U ratio indicates that the deposition of 235U in the Muztagh Ata area primarily results from upper atmospheric deposition sources of the global fallout of radionuclides, which were probably released by historical human nuclear activities of global range, but without clear evidence of local uranium contamination. A conceptual model for interpretation of the 235U/238U ratios and profile distribution in eastern Pamir is provided. Comparative analysis of the 235U/238U ratios in our samples and in samples from other locations in the northern hemisphere shows that the level in the environment of the Muztagh Glacier area is cleaner, with subtle enriched uranium and not contaminated by depleted uranium. Therefore, this work is of importance in providing a complete view on the migration, dispersion, and removal of radionuclide 235U in the atmosphere and cryospheric glacier watershed of the remote Pamir region, thus offering new insights into the distribution and behavior of radionuclides in the Pamir.

Small Alpine glaciers located below the regional equilibrium line altitude are experiencing considerable ice loss and are expected to fragment into smaller glacial bodies and eventually disappear. Monitoring such glaciers by satellite remote sensing is often challenging because their size and surrounding topography are incompatible with the current spatial resolution of non-commercial satellites. The Italian Dolomites (southeastern Alps) are a region clearly illustrating such challenges and where no long-term glacier mass balance data are available. This renowned Alpine sector hosted tens of glaciers up until a few decades ago, with now only 12 remaining. This study presents a multi-decadal (1980s-2023) estimation of surface elevation change and geodetic mass balance of the current mountain glaciers present in the area. Calculations are based on geodetic data: high resolution and accuracy are obtained with uncrewed aerial vehicle (UAV), structure from motion (SfM), and airborne light detection and ranging (lidar) methods, from 2010 to 2023. SfM on historical aerial imagery is used for previous decades. We found an average cumulative surface elevation change of -28.7 +/- 2.6 m from 1980s to 2023, 33 % of which occurred between 2010-2023. The average geodetic mass balance rate for the whole period is -0.64 +/- 0.06 mw.e.yr-1 (water equivalent), varies widely among sites, and is less negative than the Alpine reference glaciers' mass balance. Regionally, 66 % of the volume loss is related to the Marmolada glacier alone. Losses of ice mass and area show that the Dolomites are rapidly losing their glaciers.

Mercury (Hg) is a chemical element recognized as one of the most toxic among all naturally occurring elements, with health risks depending on its form, concentration, route and time of exposure. Mercury appears in the environment as a result of human activities, which include burning coal or lignite, improper waste disposal, oil refining, use of mercury-containing pesticides and fertilizers, and industrial development such as mining, chemical, pharmaceutical and paper industries. The element also appears in the environment as a consequence of natural phenomena, among which are volcanic emissions, rock erosion, biomass burning and geothermal processes, but also as a result of re-emissions. Mercury can persist in the atmosphere for up to several months, which promotes the transfer of the element to areas far from the emitting source.Cryoconite, a sediment accumulating on the surface of glaciers, is known to accumulate atmospheric contaminants such as Hg likely due to biofilm producing extracellular polymeric substances. Mercury is a contaminant of primary concern in the global environment, including cryosphere environments such as glaciers, due to its high toxicity to biota. This study, for the first time, presents a comprehensive global analysis of the variation in Hg concentrations, observed in cryoconite holes and deposits from the surface of 27 glaciers in both hemispheres, comprising 105 samples in total. Concentrations of Hg were determined through ICP-MS/MS. The results indicate a higher Hg content in cryoconite from glaciers located in the Northern Hemisphere, which can be linked to the proximity of highly industrialized areas, which contrasts to glaciers located in the Southern Hemisphere. The highest Hg content was measured in cryoconite located in Norway and Alaska (up to 0.7 ppm), and the Alps (close to 0.5 ppm), correlated with the levels of industrialization in these regions. Our results reveal a broad pattern of reduction in Hg concentrations in cryoconite with altitude, which may be related to the topographical relief affecting the transport of contaminants from higher altitudes to lower.As a result of global warming, the majority of glaciers are retreating. The accumulated Hg in the cryoconite can be released during melting of glaciers and thus may also contribute to contamination of the downstream ecosystems and local communities through consumption of contaminated food and water in polar and alpine regions. Therefore, studies like this are needed to monitor the levels and fate of Hg in glaciers and ice caps.

The pattern of atmospheric and climate changes recorded by coastal Antarctic ice core sites and the processes they illustrate highlight the importance of multiproxy studies on ice cores drilled from such peripheral areas, where regional- to local-scale processes can be documented. Here, we present a 2 kyr long record of aeolian mineral dust and diatoms windblown to Roosevelt Island, obtained from the Roosevelt Island Climate Evolution project (RICE) ice core. Mineral dust and diatoms are highly complementary at RICE, since they are related to the large-scale South Pacific atmospheric circulation regime, carrying dust-rich air masses that travelled above the marine boundary layer, and local oceanic aerosol transport by low-level marine air masses, respectively. The period from 550 to 1470 CE is marked by increased mineral dust transport from Southern Hemisphere continents, a reduction in sea ice cover in the Eastern Ross Sea (ERS) and Amundsen Sea (AS), and more frequent incursions of humid air masses, which contributed to a relative rise in snow accumulation. After 1470 CE, relatively lower dust and snow deposition at RICE suggests an increase in pack ice in the eastern Ross and Amundsen seas. This period is characterized by prominent peaks of sea-ice-related aeolian diatoms that are unprecedented over the last 2 kyr, indicating a rapid reorganization of atmospheric circulation. Data suggest an eastward enlargement of the Ross Sea polynya culminating with the opening of the proposed Roosevelt Island polynya and an increased influence of low-level marine air masses to the site during the Little Ice Age (LIA).

Glaciers are well known for providing valuable climatice and environmental information which are made available through the retrieval of ice cores. Not all glaciers are equal in this respect, however. The best sites to drill ice cores for paleoclimatic purposes are the cold portions of accumulation basins. The term cold, when referred to ice, indicates ice whose temperature is constantly below the pressure melting point. The importance of cold sites for ice core science is related to the fact that under cold conditions, the stratigraphic signals used for paleoclimatic reconstructions are best preserved because of the absence of meltwater. Because of climate change, cold portions of mountain glaciers are rapidly changing. The rise of atmospheric temperature is impacting the thermal properties of ice and firn, leading to their warming. As a consequence of this, many cold accumulation basins of high-altitude glaciers are turning to temperate and their mass balances are approaching negative values. This is posing issues on the ability of glaciers to preserve climatic and environmental signals. This is related to two distinct processes. At first, temperate ice, by definition contains a fraction of liquid water which can interfere with the preservation of chemical and physical signals. Secondarily, negative mass balances related to increased melt rates, imply the loss of upper ice layers, obliterating the most recent stratigraphic signals normally used for calibration with instrumental data. The possibility to retrieve reliable paleoclimatic records from mountain glaciers in the future, is thus questionable. This will only be possible if the ice core science community develops new methods and competencies to extract information from temperate ice addressing meltwater disturbances. To this aim, a 223 m long ice core was drilled in 2021 at the Adamello glacier, in the Italian Alps. At the drilling site (3100 m a.s.l.) the glacier has a negative mass balance and a temperate regime. Thus, the site is ideal to test to what extent temperate ice can be used as a paleoclimatic archive. To this aim, a set of paleoclimatic proxies has been investigated in the upper part of the ice core. We present here preliminary results. They show that while most of the analytes are significantly affected by meltwater percolation and regelation, some of them, in particular the less soluble ones, still exhibit a detectable seasonality. This has allowed to develop a chronology, estimate the age of surface ice and identify what proxies are best preserved in temperate ice.

Paleoclimate and paleoenvironmental stratigraphic reconstructions from temperate glaciers are hindered by surface melting and ice metamorphism, which cause mobilization and concentration of impurities, as well as their interaction through englacial reactions. Despite meltwater intrusions, other impurities such as pollen grains and other palynomorphs remain to their original depth of deposition thanks to their large grain-size. Temperate glaciers close to vegetated areas, therefore, can include palynomorphs of different types that i) can be reliable annual markers for ice-core dating and, ii) allow reconstructing paleoenvironmental changes through time. The Adamello Glacier (Central Alps, Italy) is a temperate glacier that extends over ca 14.35 km2 (2020) at elevations ranging between 2560 and 3420 m a.s.l. In the framework of the CLIMADA Project, a 224 m long ice core (ADA 270) was recovered in 2021 from Pian di Neve, the summit plateau at about 3200 m a.s.l. in the accumulation area of the glacier. Preliminary estimates date the surface ice of the glacier to the 1980s while the bottom of the core might be Medieval in age. Radionuclide-based dating (3H, 14C, 137Cs, 210Pb) is in progress. The multiproxy approach adopted in this study includes black carbon, dust grain size and mineralogy, oxygen and hydrogen stable isotopes and palynomorphs, these last being the main object of this work. Given the site location, the palaeoecological signal is believed to be of regional significance. Despite the stratigraphy may not be preserved for some soluble chemical species, the core contains a high variety of palynomorphs, which allow the reconstruction of palaeoenvironmental and paleoclimatic variations at subannual resolution. The mean ice accumulation rate is about 0.9 m w.eq. yr-1. Consequently, the mean sampling resolution adopted for the palynomorph study is 0.1 m, increased to 0.01 m in specific intervals. Palynomorphs are mainly found in layers representing the spring-summer deposition while their concentration is very low during other periods of the year. Pollen grains, spores, diatom frustules, phytoliths and charcoals characterize the spring-summer layers; glass shards of volcanic origin and green algae have been observed in few intervals. Sporadic but massive Saharan dust events, carrying characteristic dust particles and pollen of African provenance, were identified throughout the core. The comparison between these intervals and the historical “red rain” events in Northern Italy will help better constraining the ice core dating. At ca 66 m depth, an ice interval characterized by a high impurity content has been investigated at 0.01 m resolution. Different palynomorphs are recorded in this interval, implying a quasi-continuous presence of humans and animals on the glacier for few years. Preliminary results link these layers to World War I, intensively fought between Italians and Austro-Hungarians on the slopes surrounding the Pian di Neve. The comparison between historical, archeological and ice core data allow delineating, at subannual resolution, the climate and environmental changes that characterized those years.

The RICE ice core was drilled on the NE edge of the Ross Ice Shelf, at the summit of Roosevelt Island (79.364°S, 161.706°W, 550 m a.s.l.), an ice rise 764 m thick, locally-grounded 214 m below sea level (Bertler et al., 2018). The climate record documented in the ice core covers the last 83 ka, providing rich insights on the coastal Antarctic climate. Insoluble impurities in the RICE ice core mainly consist of mineral dust particles. Direct SEM and X-Ray diffraction analyses on single-grains from discrete dust samples extracted from RICE sections show evidence of extensive englacial diagenesis, in particular below ca. 650 m depth. Within the upper part of the core, dust particles are mostly volcanic or aeolian. In the deepest part of the core, conversely, aeolian dust particles show authigenic, eudral crystals grown on their surface. Also, individual crystals not showing signs of atmospheric transport both possibly resulting from in situ mineralization have been observed. Mineral neoformation likely results from the interaction between dust and fluids concentrating in ice crystal boundaries and triple junctions. Newly-formed minerals include Fe-bearing compounds such as Jarosite, Goethite, Magnetite and Hematite. These results are in line with the ice-weathering model proposed for ice deeper than about 1500 meters at Talos Dome (Baccolo et al., 2021a, 2021b), although in the case of RICE the depth of englacial mineralization is much shallower. Our results corroborate the finding that weathering and englacial diagenesis is a common process at depth inside thick ice sheet, potentially affecting the climatic interpretation of dust records in deep ice cores. Considering the different depth at which such processes have been found in RICE and Talos Dome ice cores, it remains to be understood which are the limiting factors controlling the initiation of such englacial reactions.Bertler, Nancy AN, et al. "The Ross Sea Dipole–temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years." Climate of the Past 14.2 (2018): 193-214.Baccolo, G., Delmonte, B., Niles, P.B., ... Snead, C., Frezzotti, M. Jarosite formation in deep Antarctic ice provides a window into acidic, water-limited weathering on Mars, Nature Communications, 2021, 12(1), 436Baccolo, G., Delmonte, B., Di Stefano, E., ... Marcelli, A., Maggi, V. Deep ice as a geochemical reactor: Insights from iron speciation and mineralogy of dust in the Talos Dome ice core (East Antarctica), Cryosphere, 2021, 15(10), pp. 4807–4822

High Purity Germanium (HPGe) detectors are powerful detectors for gamma-ray spectroscopy. The sensitivity to low-intensity gamma-ray peaks is often hindered by the presence of Compton continuum distributions, originated by gamma-rays emitted at higher energies. This study explores novel, pulse shape-based, machine learning-assisted techniques to enhance Compton background discrimination in Broad Energy Germanium (BEGe TM) detectors. We introduce two machine learning models: an autoencoder-MLP (Multilayer Perceptron) and a Gaussian Mixture Model (GMM). These models differentiate single-site events (SSEs) from multi-site events (MSEs) and train on signal waveforms produced in the detector. The GMM method differs from previous machine learning efforts in that it is fully unsupervised, hence not requiring specific data labelling during the training phase. Being both label-free and simulation-agnostic makes the unsupervised approach particularly advantageous for tasks where realistic, high-fidelity labeling is challenging or where biases introduced by simulated data must be avoided. In our analysis, the full-energy Peak-to-Compton ratio of the 137-Cs, a radionuclide contained in a cryoconite sample, exhibits an improvement from 0.238 in the original spectrum to 0.547 after the ACM data filtering and 0.414 after the GMM data filtering, demonstrating the effectiveness of these methods. The results also showcase an enhancement in the signal-to-background ratio across many regions of interest, enabling the detection of lower concentrations of radionuclides.

The dark sediment on the surface of glaciers, called cryoconite, plays an important role in accumulating various contaminants during glacier melting. One of the high-risk is anthropogenic fallout radioisotopes, which have been accumulating since 1945. The melting of alpine glaciers is accelerating, rapidly releasing stored pollutants, and becoming secondary sources of radioisotopes for nearby ecosystems. This study indicates the potential sources of radioisotopes based on their signatures with global and local signals using wide sampling covering eight glaciers in distinct regions of the Alps. For this purpose, the activity ratios of anthropogenic radionuclides (238Pu/239+240Pu, 239+240Pu/137Cs, 241Am/239+240Pu) and mass ratios (240Pu/239Pu) were determined. The activity ratio of 238Pu/239+240Pu in Alpine glaciers shows that plutonium-related radioactivity is mostly from global fallout, with an additional contribution from the atmospheric re-entry of the SNAP 9A satellite. 240Pu/239Pu atomic ratio suggests the heterogeneous contribution of low- and high-yielded nuclear detonations. The activity ratios of 241Am/239+240Pu are partly comparable to the reference isotopic ratio for global fallout, but the impact of unknown local radioactive contamination source(s) is also considered. The post-Chernobyl and global fallout account of 137Cs in the examined glacial area of the Alps. The results confirm the ability of cryoconite to accumulate artificial radioisotopes while recording the influence of multiple regional and global sources. Cryoconite is confirmed as an extremely valuable environmental matrix for studying radioactive contamination in glacial environments.