Black carbon (BC), a short-lived aerosol produced by incomplete combustion of biomass and fossil fuels, exerts profound influences on local, regional, and global cryosphere through snow albedo feedback mechanisms. Accurately estimating BC concentration in the cryosphere using satellite surface reflectance is a pivotal objective of snow optical remote sensing. Over the past two decades, numerous endeavors have developed various retrieval algorithms for cryosphere's BC and conducted small-scale validations to prove their feasibility. However, few studies have focused on evaluating how these algorithms address the enormous challenges of global BC concentration quantification, which has led to the community's limited knowledge of BC loading in snow globally. Considering the mounting obstacles to achieving carbon neutrality goals and the increasing prevalence of global wildfires, it is imperative to extend state-of-the-art black carbon retrieval algorithms to the global scale to achieve more refined quantitative mapping of snow pollutants with enhanced generalizability. To bridge this gap, this work employs six advanced cryospheric snow BC remote sensing algorithms rooted in analytical asymptotic radiative transfer theory to retrieve global BC abundance. The study comprehensively optimized the covariates used by the six commonly adopted BC direct retrieval algorithms from three aspects: inherent optical properties of ice crystals and BC, snow microstructure and scattering characteristics, and BC's intrinsic physical properties. This research quantified uncertainties using over 20,000 high-quality BC concentration measurements (including thermal, optical, and thermo-optical methods) from the global cryosphere (including Asia, Europe, America, and the Polar Regions) and further analyzed the optimal configuration for remote sensing retrieval of BC. Overall, through large-scale critical evaluation of the current state-of-the-art snow BC concentration remote sensing retrieval scheme, this work revealed the tremendous potential of using satellites to quantify BC abundance in the cryosphere, providing a new perspective for estimating the carbon sequestration capacity of the cryosphere.

How to cite: Ji, W., Hao, X., and Shao, D.: Quantifying Black Carbon Retrieval in Snow Surface: Remote Sensing, Modeling, and Observations Perspectives, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5541, https://doi.org/10.5194/egusphere-egu25-5541, 2025.

Iron (Fe) as a limiting nutrient has profound impacts on ecosystems and the global biogeochemical cycle. Field observations were made at the atmosphere—snowpack interface in various glaciers of the Tibetan Plateau. The formand chemical properties of the Fe detected were investigated in laboratory using TEM‐EDX measurements, to obtain insights in the content and sources of Fe in aerosol pollutants in glaciers, as well as micro‐structure changes and their environmental effects, as well as interface transformation dynamics. We find that Fe occurs in forms of aggregated and single particulates with diameter d < 5 μm. The Fe particulates collected from different locations show clear spatial heterogeneity, with fly ash and soot constituting the major components of anthropogenic Fe. The concentration of Fe aggregates with pollutants (e.g., sulfate and nitrate) is dominant in regions close to the areas of human activity. Moreover, in the remote areas of the interior plateau, an increased concentration of mineral Fe particles is found in the aggregates. These observations are crucial to elucidate the evolution processes of pollutant‐Fe mixing, from generation or emission through anthropogenic activities to accumulation in remote areas and modification of Fe occurrence form during transportation. Our results also show that, during interface deposition, soluble Fe particle concentration increased by 13.8% on average, as Fe solutes with sulfate‐coating enhances of the dissolution of Fe in fly ash‐soot and minerals—a process that produces large quantities of ultrafine Fe particle under reductive dissolution in snowpack. Overall, these changes significantly contribute to enhancing the bioavailable iron content in the study areas affecting thereby the glacier ecosystem.

How to cite: Dong, Z.: Iron Variability Reveals the Interface Effects of Aerosol‐Pollutant Interactions on the Glacier Surface of Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1457, https://doi.org/10.5194/egusphere-egu25-1457, 2025.

Dust storms are significant atmospheric events that play a crucial role in altering the regional and global climate system. In this study, we investigate the characteristics and impacts of pre-monsoonal dust loading events over the Indian Himalayas using a combination of satellite observations and in situ aerosol measurements conducted at Mukteshwar, a representative high-altitude site. Ten prominent dust events were identified through satellite-derived aerosol optical depth (AOD) and corroborated with ground-based observations. These events were further classified into two categories based on air mass back-trajectory analysis: Mineral Dust Events (MDEs) and Polluted Dust Events (PDEs). MDEs are characterized by long-range transported dust plumes, primarily from arid regions such as the Thar Desert and the Middle East, traversing the lower troposphere before reaching the Himalayas. Conversely, PDEs are linked to short-range transported dust plumes that originate from the arid western Indian subcontinent but travel through the highly polluted Indo-Gangetic Plain (IGP) boundary layer before reaching the Himalayan foothills.

The study reveals substantial enhancements in aerosol loading and optical properties during these dust events. During both MDEs and PDEs, the mass concentration of coarse particles (2.5-10 µm) increased by approximately 400% (from 24±15 µg/m³ to 98±40 µg/m³), while the extinction coefficient increased by 175% (from 89±57 Mm⁻¹ to 156±79 Mm⁻¹) compared to background conditions. However, there were significant differences in aerosol optical properties between MDEs and PDEs. Single Scattering Albedo (SSA) and Absorption Ångström Exponent (AAE) showed contrasting trends: SSA and AAE increased during MDEs, indicating dominance of mineral dust particles with relatively low light absorption properties, while they decreased during PDEs, highlighting a more substantial contribution from light-absorbing aerosols such as black carbon (BC).

Notably, black carbon concentrations and aerosol absorption coefficients exhibited a twofold increase during PDEs compared to background levels, whereas minimal changes were observed during MDEs. These contrasting aerosol characteristics critically impact snow albedo reduction (SAR) over the Himalayas. SAR during PDEs was nearly double that of background conditions, driven primarily by the enhanced absorption of solar radiation by black carbon and other light-absorbing aerosols. Although SAR also increased during MDEs, the magnitude of change was comparatively lower.

Our findings highlight the dual nature of dust storms impacting the Indian Himalayas: long-range transported MDEs dominated by mineral dust and short-range transported PDEs enriched with black carbon and anthropogenic pollutants. Both categories significantly alter the aerosol optical properties and have distinct yet substantial effects on snow albedo and subsequent glacier melting processes. These findings highlight the necessity of thorough modeling and observational research to more accurately estimate the long-term effects of dust-induced snow albedo reduction on the Himalayan region.

How to cite: Chandel, A. S., Sarangi, C., Rittger, K., Hooda, R. K., and Hyvärinen, A.-P.: Characterization and Impacts of Pre-Monsoonal Dust Events on Aerosol Optical Properties and Snow Albedo in the Indian Himalayas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2034, https://doi.org/10.5194/egusphere-egu25-2034, 2025.

Asian dust has significant impacts on atmospheric systems and global biogeochemical cycles. In this study, we applied the U isotopic method to trace sediments based on their comminuting age, analyzing the uranium isotopes of cryoconite samples from various glaciers in western China, including the Tibetan Plateau (TP) and Tianshan Mountains. We aimed to explore the spatial variability of the ( 234U/ 238U) activity ratio and residence time, as well as the transport mechanism of the dust cycle in the region. Additionally, we used Nd-Sr isotopes data from our previous work to jointly determine the provenance. Our results indicate that the average ( 234U/ 238U) activity ratios in southern TP glaciers are higher, with mean range of 0.981–0.993, while those in northeastern TP locations are lower, with mean of 0.974. This suggests a decreasing trend from south to north. In the Tianshan region, the ( 234U/ 238U) activity ratio is higher in central areas compared to eastern areas, with a mean range of 0.984–0.996, indicating a decreasing trend from west to east. U-Sr-Nd isotopes analysis showed that dust provenance is from multiple sources, including long-range transported and local dust inputs from the glacier basins, mainly originating from the TP surface and central Asian arid regions. Using the end-member mixing model analysis and meteorological data, we interpret that the cryoconite dust in eastern Tianshan and Qilian Mountains comes from a complex mixture of the southern Gobi, northern TP surface dust, and Taklimakan and Alxa arid deserts. In contrast, the glacial dust in southern TP locations originates mainly from the plateau surface dust. Our findings suggest that the uranium isotopes in high-altitude glaciers are primarily influenced by the origins of dust, which are affected by related atmospheric circulation. We also developed a conceptual model to illustrate the complete process of U isotopic fragmentation and migration changes during dust production, transport, and deposition in the TP region.

How to cite: Jiao, X.: Provenance of Aeolian Dust Revealed by ( 234U/ 238U) ActivityRatios in Cryoconites From High-Altitude Glaciers in WesternChina and Its Transport and Settlement Mechanisms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1464, https://doi.org/10.5194/egusphere-egu25-1464, 2025.

Zinc (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 dataset 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.

How to cite: Rui, W.: Zn Isotope Tracing Unveils Primary Anthropogenic Zn Sources in Glacial Cryoconite of the High Asian Mountains, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1472, https://doi.org/10.5194/egusphere-egu25-1472, 2025.

Light-absorbing aerosols, including elemental carbon and mineral dust, reduce the albedo of snow covers after deposition. This enhances melting, reducing the duration of the snow cover. Mineral dust additionally introduces various elements to the deposition area, e.g., Fe and Ca. In thermal-optical analysis, which is frequently applied to snow samples after melting and filtration over quartz fibre filters, these Fe-oxides contained in mineral dust lead to a bias in the classification of elemental and organic carbon [1]. Especially for remote environments like glaciers, the correct quantification of both compounds is of interest.

We quantify organic and elemental carbon (OC and EC) via thermal-optical analysis (TOA) in the snow cover collected at the glaciers surrounding the remote high-altitude Global Atmosphere Watch station Sonnblick Observatory (3106 m a.s.l.), located in the Austrian Alps. Samples were collected between 2016 and 2024 with a resolution of 20 cm, providing a continuous data set covering 9 years. We identify samples, which contain mineral dust, using the temperature dependent change of optical properties as previously described and assess the Fe loading directly from TOA data for the current data set. Up to 44 % of samples in the annually collected snow covers were identified to be affected by mineral dust, which is deposited after long-range transport. To counter the influence of mineral dust on OC and EC data, we evaluate those samples using a linear approach and quantify the changes in OC and EC concentrations in the annual snow covers when considering or neglecting the influence of mineral dust on TOA. We analyse the corrected EC data for trends.

Using elemental data of the snow samples collected at Sonnblick Observatory and approaches from literature, we discuss the possibility to deduce the mineral dust loading directly from TOA data.

[1] Kau, D., et al. (2022). Thermal–optical analysis of quartz fiber filters loaded with snow samples–determination of iron based on interferences caused by mineral dust. Atmospheric Measurement Techniques, 15(18), 5207-5217.

How to cite: Kau, D., Greilinger, M., Vukićević, A., Bielecki, J., Zbiral, J., and Kasper-Giebl, A.: Concentrations of organic carbon, elemental carbon and mineral dust in the snow cover between 2016 and 2024 at Sonnblick Observatory, Austria, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16660, https://doi.org/10.5194/egusphere-egu25-16660, 2025.

In the current context of climate change, the study of cryospheric environments is becoming increasingly important. While it was originally believed that these natural systems were unable to support life, it is now well known that they represent microbial biodiversity hot spots. To better understand the dynamics and drivers that regulate the cryospheric microbial communities inhabiting cryoconite holes throughout the melting season, 60 samples were collected from an alpine glacier (Jamtalferner, Austrian Alps), consisting of sediment and supernatant water from June to September 2022. The present study harnesses the power of long-read Nanopore 16S rRNA sequencing, flow cytometry for cell counting in supra-glacial water, and a technique for estimating bacterial productivity of cryoconite sediment based on ³H-Leucine incorporation.

The results of bacterial abundance and productivity showed numbers ranging from 64.000 (early July) to 300.000 cells/mL (early August). Levels of bacterial productivity were shown peaking in early June and early August (ranging from 10^-8 - 10^-5 gC/g ww·h), especially at the beginning of the season and during late July - early August, but, unlike the community structure, they suggest no distinctive trends. On the other hand, the significance of the observed trends in microbial ecology was investigated by means of Generalized Linear (Mixed) Models. It revealed a globally increasing diversity along the season for all alpha diversity indices, and a strong presence of cyanobacteria, mainly belonging to the family Leptolyngbyales, which decreased along the season in favor of Proteobacteria (Polaromonas sp.) and Bacteroidetes (fam. Chitinophagaceae). This highlights a fully-fledged ecological succession despite the harsh environmental conditions and the relatively short intra-seasonal time frame.

The ongoing climate change scenario represents a clear threat to the communities inhabiting the supraglacial environments due to the faster ice melting rates observed on low altitude glacial tongues. While the long-term repercussions are somewhat difficult to envision and quantify, what we currently know is that the (deriving) functional losses encompass different aspects, such as carbon fixation by cyanobacteria (estimated in the tens of thousands of tons worldwide for non-Antarctic cryoconites alone). Also, bacteria are able to degrade persistent organic pollutants from agricultural use like pesticides, or, more generally, to handle a variety of compounds as growing substrates, due to the otherwise environmental scarcity they are subjected to. In this sense, along with the ice, a plethora of filter ecosystems are quickly disappearing. The natural continuation of our study is to directly analyze the expressed activities compared to the genomic potential shown by these communities (genomics versus transcriptomics), extending the field of application to extreme latitudes (East Antarctica). Finally, to pinpoint the provenance of the various components of the aforementioned communities, sampling the bioaerosols insisting on these glacial areas and backtracking the air masses’ trajectories will provide us with the last piece of the puzzle, to understand the assembly processes that lead to the observed ecological configurations.

How to cite: Cuzzeri, A. and Sattler, B.: Intra-seasonal trends of cryoconite bacterial communities on an Alpine Glacier , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9461, https://doi.org/10.5194/egusphere-egu25-9461, 2025.

Svalbard is one of the hot spots of Arctic Amplification, i.e., fastest warming places on Earth. Most often dust and black carbon (BC, soot) investigations in Svalbard have been carried out in clean remote areas and investigations close to the settlement and coal mines are rare. Therefore, our investigation focused on the vicinity of Mine 5 and Mine 7 (coal mining) and on the Longyearbyen settlement surroundings, as well as on samples collected from a nearby glacier. Dust storms have been observed in Svalbard (e.g., 11 September 2024).

During 22-28 April 2024, the Faculty of Environmental Sciences - Czech University of Life Sciences Prague and University of Arctic (UA) Thematic Network on Nordic Snow Network (established from Nordic Snow Network project funded by the Nordic Council of Ministers) organized an educational Polar Winter School (PWS) in Svalbard. Several research and educational activities were carried out. Here we present our work related to dust and black carbon and results from the samples that we collected during the PWS. In the field, the snow surface was often observed visually dark, either due to soot (black) or dust (tones of grey and brown), depending on the location. Dark impurity layers (with ice) were observed and sampled from a deep snowpack nearby the Mine 7. The glacier samples appeared visually clean.

The samples were transported from Svalbard to the laboratory of the Finnish Meteorological Institute (FMI), Helsinki, Finland, mainly as snow and ice. In Finland, these samples were melted and filtered. Thereafter, the particle and filter samples were investigated with multiple methods for their dust and BC (soot particle) properties at FMI and at the University of Chemistry and Technology (UCT), Department of Inorganic Chemistry, Prague, Czech Republic. For example, our soot samples (loose particle sample no. 7, and quartz filter sample no. 7 from a dirty ice layer close to the Mine 7) particle volume size distributions had a peak at 200 µm, and rectangular, non-spherical shapes (observed using scanning electron microscopy). The presence of C (74.6 Wt%), O (13.2 Wt%), Zr (4.5 Wt%) Fe (4.4 Wt%) and <1 Wt% of Si, S, Al, Ca, Mg, Na and K were detected using SEM/EDS by UCT. In addition to dust and BC results, we demonstrate how to utilize remote sensing observations to better understand our field work environment and our data.

We gratefully acknowledge all the PWS participants, as well as Faculty of Environmental Sciences - Czech University of Life Sciences Prague, Faculty of Science -  University of South Bohemia, České Budějovice, UArctic Thematic Networks on High Latitude Dust (HLD) and Nordic Snow Network, Norway grants within EEA funds, Czech Arctic Research Station and Summit Trade.

How to cite: Meinander, O., Dagsson-Waldhauserova, P., Fathi, J., Kosmale, M., Leppänen, L., Juras, R., Kavan, J., Jankovsky, O., Moravec, V., and Nadir Arslan, A.: High Arctic snow, ice, and particle samples to investigate dust and black carbon occurrence close to Longyearbyen, Svalbard , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3234, https://doi.org/10.5194/egusphere-egu25-3234, 2025.

The Arctic is warming as much as four times the global rate, with warming particularly pronounced on Svalbard. This warming is leading to reductions in snow, glaciers and sea ice and a potential increase of local dust emissions. In addition to climate warming, another factor that can contribute to snow and ice melt is the deposition of light absorbing particles (LAP). LAP include black carbon, dust and biogenic impurities.  When deposited on snow and ice surfaces, LAP reduce albedo, increase energy absorption, and can accelerate snow and ice melt.  Numerous studies have investigated black carbon in snow and ice cores from Svalbard, but less work has been done on dust, and measurements of snow dust concentrations and dust deposition rates are sparse.  Recent studies have called for an assessment of the impacts of climate change on dust emissions and the cryosphere in the Arctic, as decreases in seasonal snow cover and duration, glacier retreat, and warming temperatures are all hypothesized to lead to an increase in dust sources and emissions, and subsequent deposition of dust on snow and ice surfaces.

We present LAP results from snow and firn core samples that were collected from spatially distributed Svalbard glaciers between 2021-2025. The samples were analyzed for black carbon using a Single Particle Soot Photometer (SP2), dust concentrations via gravimetric filtration and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), dust spectral reflectance using a spectroradiometer, and dust composition and mineralogy via X-Ray diffraction (XRD) and a scanning electron microscope with a Back Scatter Electron (BSE) detector.  Results indicate that dust concentrations vary seasonally with low concentrations during the winter and higher concentrations during the summer-fall, and there are spatial variations in dust concentrations and dust optical properties that are likely associated with variations in local dust sources. Modeled albedo reductions indicate that LAP albedo reductions are dominated by dust, with smaller albedo reductions from black carbon. Changes in dust emissions and dust deposition spatially and temporally in response to a changing climate on Svalbard are also considered.

How to cite: Kaspari, S., Isaksson, E., Gallet, J.-C., Kohler, J., Hodson, A., Hartz, W., Orme, O., Spoloar, A., Scoto, F., Di Mauro, B., and Moholdt, G.: The Role of Light Absorbing Particles in Snow and Ice on Svalbard: A Focus on Dust, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6410, https://doi.org/10.5194/egusphere-egu25-6410, 2025.

In August 2023, the HEFEX II (HinterEisFerner-EXperiment) campaign was conducted in the Austrian Alps to investigate multi-scale exchanges between the atmosphere and glaciers. The campaign combined data from numerous automatic weather stations (AWS) and Eddy-Covariance (EC) stations operating over four weeks and an intensive three-day observation utilizing unmanned aerial vehicles (UAVs) and LIDAR technology. These measurements provided detailed insights into various atmospheric parameters, including temperature, humidity, wind information, and heat fluxes, across spatial and temporal scales.

The collected data serves as a valuable resource for validating high-resolution ICON-LES (Large Eddy Simulation) models with a horizontal resolution of 51 meters. This validation is performed both qualitatively and quantitatively, focusing on capturing the spatio-temporal variability of the measured atmospheric parameters. Through this process, the campaign aims to refine model parameterization to enhance simulation accuracy, particularly for the complex and dynamic processes governing atmosphere-glacier interactions.

Preliminary results confirm that ICON-LES simulations exhibit strong agreement with observed data. These findings support the potential of ICON-LES as a reliable tool for modeling atmosphere-glacier interactions, paving the way for climate impact studies in alpine regions. This study highlights the synergy between advanced observational techniques and high-resolution modeling, advancing our understanding of atmosphere-glacier dynamics and their broader climatic implications.

The HEFEX campaign demonstrated the effective application of UAVs in atmospheric research. These platforms demonstrated their capability to collect high-resolution, flexible, and precise data in challenging high-elevation environments. By integrating UAV observations with traditional measurement methods, the campaign underscores their growing importance in complementing and extending stationary observations.

Overall, the HEFEX campaign contributes to advancing understanding of atmosphere-glacier processes, improving numerical weather prediction models, and showcasing innovative observational techniques in atmospheric science.

How to cite: Georgi, A. and Sauter, T.: Validation of ICON-LES from HEFEXII field campaign observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20381, https://doi.org/10.5194/egusphere-egu25-20381, 2025.

Near-surface air temperature (Ta) is crucial for glacio-hydrological modeling, yet measuring
and modeling it in glacierized regions is challenging due to spatial variability. On-glacier Ta
data is scarce in the Himalaya, and in these regions, katabatic winds significantly influence
Ta, and linear extrapolation of Ta from off-glacier does not perform well. This study focuses
on the Chhota Shigri Glacier in the Western Himalaya, examining how local wind systems,
particularly katabatic and valley winds, influence Ta and glacier mass balance (MBs). Using
data from nine on-glacier and three off-glacier weather stations during the summer of 2022,
the study highlights interactions between winds and Ta variability across the glacier surface.
Katabatic winds, which accounted for 89% of the observed data, cooled near-surface Ta by
up to 2°C compared to temperatures extrapolated using linear lapse rates (LRs). This cooling
effect, most pronounced during midday, significantly influenced the glacier's thermal regime
and highlighted the limitations of linear LRs in capturing Ta variability. The piecewise linear
regression approach (SM10 model), incorporating katabatic wind effects, was applied to
extrapolate on-glacier Ta. Modeled Ta (SM10) and extrapolated Ta (using LRs) were used in
a temperature index model to simulate point mass balance (MBs) and compare with in-situ
MB observations (using stake data). When validated against in-situ measurements, LR-based
models overestimated point MBs by up to 92%, while the SM10 model reduced the errors to
just 8%.
These results highlight the crucial role of local winds in regulating glacier surface
temperatures and emphasize the need to account for the katabatic wind effect in MBs
modeling. This study enhances the integration of observed Ta into glacio-hydrological
models by analyzing the “glacier cooling effect,” advancing the understanding of glacier-
atmosphere complex interactions in the Himalayan terrain and improving the accuracy of
melt and mass balance studies.

How to cite: Kaushik, H. and Azam, M. F.: The Role of Observed Air Temperature and Local Winds in Glacier Mass BalanceModeling: Chhota Shigri Glacier, Western Himalaya, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1186, https://doi.org/10.5194/egusphere-egu25-1186, 2025.

Saharan dust depositions frequently color alpine glaciers in orange. Along with other light absorbing particles, dust lowers snow albedo, increases the melt rate of snow, and lowers the surface mass balance of glaciers. Since the surface mass balance drives the evolution of alpine glaciers, assessing the impact of impurities helps understanding the current and future evolution of alpine glaciers. Here, we quantify the impact of impurities on glacier surface mass balance taking into account mineral dust. To do so, we used the SURFEX/ISBA-Crocus snow model, that explicitely accounts for the evolution of impurities content within the snowpack and computes their effect on albedo with the TARTES two stream radiative transfer model.  Over the Argentière Glacier (Mont-Blanc area, France), our modeling show that considering the impact of mineral dust leads to a decrease in the glacier-wide annual surface mass balance by around 0.25 m w.e. on average for the period 2019-2021, but it reaches the double during the exceptionnal melt of 2022 (around 0.5 m w.e.) on average over the whole glacier, and up to 1.00 m w.e. locally. This highlights the importance of accounting for the impact of mineral dust when simulating the surface mass balance of mountain glaciers, and the need to understand how this contribution varies at the mountain range scale and for different periods of times.

How to cite: Roussel, L., Dumont, M., Réveillet, M., Six, D., Kneib, M., Nabat, P., Fourteau, K., Monteiro, D., Gascoin, S., Thibert, E., Rabatel, A., Sicart, J.-E., Bonnefoy, M., Piard, L., Laarman, O., Jourdain, B., Lafaysse, M., Vernay, M., and Fructus, M.: Saharan dust impacts on Argentière glacier surface mass balance during the 2022 extreme melt year, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5894, https://doi.org/10.5194/egusphere-egu25-5894, 2025.

Glaciers are retreating worldwide, yet little is known about the influence of these changes on local weather and climate in glacial landscapes. Changes in glacier extent and proglacial lakes alter the thermodynamic forcing in glacier-lake-valley systems that may be of similar or greater importance for future microclimate than direct effects of global warming. To study the impact of these changes, we combine the first set of high-density spatiotemporal observations of a glacier-lake-valley system at Nigardsbreen in western Norway with high-resolution numerical simulations from the Weather Research and Forecasting (WRF) model. The sensitivity of the thermodynamic circulation to glacier extent and proglacial lakes is tested using glacier outlines from 2006 and 2019 as well as varying lake surface temperature. The model represents the evolution of glacier flow and cold air pools well when thermal forcing dominates over large-scale forcing. During a persistent down-glacier flow regime, the glacier-valley circulation is sensitive to lake temperature and glacier extent, with strong impacts on wind speed, convection in the valley, and interaction with mountain waves. However, when the large-scale forcing dominates and the down-glacier flow is weak and shallower, impacts on atmospheric circulation are smaller, especially those related to lake temperature. This high sensitivity to meteorological conditions is related to whether the flow regime promotes thermal coupling between the glacier and the lake. The findings of this study highlight the need for accurate representation of glacier extent and proglacial lakes when evaluating local effects of past and future climate change in glacierized regions.

How to cite: Haualand, K. F., Sauter, T., Abermann, J., de Villiers, S., Georgi, A., Goger, B., Dawson, I., Nerhus, S. D., Robson, B. A., Sjursen, K. H., Thomas, D. J., Thomaser, M., and Yde, J. C.: Meteorological Impact of Glacier Retreat and Proglacial Lake Temperature in Western Norway, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5819, https://doi.org/10.5194/egusphere-egu25-5819, 2025.

Glaciers in mountain valleys create unique local climates consisting of glacier winds, valley winds and slope winds. These local winds together with the synoptic winds mediate the turbulent heat fluxes between the glacier surface and the atmosphere, and contribute up to one-third of the total glacier melt. The knowledge of on-glacier wind speed distribution is required to estimate these fluxes, which can be either obtained through weather stations or climate reanalysis products. Weather station data is sparse on glaciers due to logistic reasons. Large scale climate models on the other hand, fail to capture these local winds entirely due to their coarse resolution. Hence we develop a parameterisation for summertime hourly wind speed at any glacier around the world using freely available large scale climate and topographic data. We calibrate and validate this parameterisation using station data from 25 near-glacier weather stations around the world. Our method reduces the prediction errors of wind speed and turbulent heat fluxes by a factor of 1.6 and 3 respectively, as compared to the state-of-the-art climate data product. This will help improve the glacier- to basin- scale melt and runoff estimates by regional and global models.

How to cite: Jayan, K., Banerjee, A., Kaushik, H., Azam, M. F., Sarangi, C., and Shankar, R.: Parameterisation of summertime surface winds near mountain glaciers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17274, https://doi.org/10.5194/egusphere-egu25-17274, 2025.

Mountain glaciers are a perfect laboratory to study the interaction between the mountain atmosphere, including the multiscale processes developing within it, and the stably stratified ice surfaces. Due to their setting within mountain valleys, the structure of the glacier boundary layers is a result of a complex interplay between the surface thermal forcing, the thermally and dynamically driven multiscale mountain flows and the larger scale flow aloft. This complex flow structure plays an important role in glacier microclimates and surface energy and mass balance of glaciers. However, few datasets of atmospheric measurements over the whole surface of a glacier are available to probe this complex interaction and spatio-temporal variability. In August and September 2023, the Second Hintereisferner Experiment (HEFEX II), a three-week measurement campaign took place on the Hintereisferner glacier in the Austrian Alps to address these challenges. The glacier was instrumented with 18 surface weather stations, of which 10 were equipped with two or three levels of turbulence measurements.

The data from this extensive dataset is used to characterize the surface atmospheric flow over the glacier and investigate its turbulent properties. Using a clustering method on the vertical profiles from one tower at the upper part of the glacier tongue, we show that different classes of katabatic flows, as well as some perturbed flows related to the impact of synoptic flows during strong synoptic winds periods, and the passage of a cold front take place during the campaign. We also show that these different types of flow show characteristic horizontal wind and temperature structure across the glacier tongue. The results thus suggest that it is possible to recover the type of flow from one multi-level measurement location and extend it consistently to the whole surface of the glacier, meaning that a well-chosen point on the glacier is correctly representing the spatial structure of the flow. The surface measurements are then used to explore the turbulence structure during the different flow regimes, and estimate the surface energy balance over the glacier and calculate the melt rate. The calculated melt rates are consistent with ablation measurements. The results indicated that the different clusters are associated with different melt rates and surface energy balance contributions, with katabatic flows having a large radiative contribution and synoptically perturbed flows having large sensible and latent heat contribution.

How to cite: Nitti, G. and Stiperski, I.: Flow structure and turbulence characteristics on a mid-latitude glacier, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9826, https://doi.org/10.5194/egusphere-egu25-9826, 2025.

Local snow accumulation in alpine terrain is highly influenced by wind-driven redistribution of snow. Accurate knowledge of the small-scale flow field and the interactions between the snow and the atmosphere are therefore necessary to better simulate and understand glacier mass balance. To bridge the gap between an explicit treatment in high-resolution numerical simulations and computational feasibility for (multi-)seasonal assessments, we introduce SNOWstorm (the SNOW drift Sublimation and TranspORt Model), a deep-learning based model to predict high-resolution near-surface winds, snow redistribution and drifting snow sublimation from low-resolution atmospheric input and high-resolution topography. The model has a stacked U-Net shape architecture and is trained with data from large-eddy simulations (dx=50 m) in a semi-idealized environment. The numerical simulations for the training data set are performed with the Weather Research and Forecasting model (WRF) using a coupled drifting snow module. The surface topography and atmospheric conditions used in WRF reflect the variability seen in alpine terrain over a winter season.

Here we present the basic design of the model, possibilities for applications in the future, as well as first assessments of case studies coupling the model to real-world atmospheric input.

How to cite: Saigger, M. and Mölg, T.: SNOWstorm – A new emulator model for near-surface winds and drifting snow in glaciological applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17454, https://doi.org/10.5194/egusphere-egu25-17454, 2025.

Common turbulence parametrization in numerical weather prediction models and traditional boundary layer theory are predominantly designed for horizontally homogeneous flat terrain and only consider vertical transport processes. However, these assumptions fail in valleys, where the horizontal constrictions to the flow as well as prevalent surface heterogeneity mean that horizontal terms in the budget equations (e.g. advection, horizontal flux divergence) become important. Over a mountain glacier, in addition, the acceleration of the katabatic wind downslope, a decrease in wind speed from the centerline towards the margin due to lateral variation in the forcing (glacier ice vs. rocky sides), and horizontal temperature gradients necessitate consideration of horizontal terms in the budgets of mean and turbulent quantities.

Here we investigate the importance of horizontal term in the budgets of momentum, heat, TKE and sensible heat flux, for deep katabatic flows over the Hintereisferner glacier in Austria. The analysis is based on data collected during the three-week Hintereisferner Experiment (HEFEX) field campaign that took place in the summer of 2018, where four turbulence towers were installed in an along- and across-glacier transect, allowing the estimation of horizontal terms in the down-glacier and cross-glacier direction. Towers were equipped with two levels of turbulence sensors, and one level of mean wind and temperature sensors. The focus of the study is on deep flows where both turbulence observational heights were below the potential jet maximum height, so that all the estimated budget terms are located within the same layer.

The results indicate that, for certain selected periods with deep flow, horizontal terms have an important contribution to the budget equations. The largest contribution comes from the horizontal advection terms, and they are shown to enhance TKE destruction by buoyancy and TKE production by advection and shear over Hintereisferner. These results highlight the importance of considering horizontal processes to correctly capture the flow dynamics in complex terrain.

How to cite: Staudinger, I. and Stiperski, I.: Exploring the importance of horizontal transport terms in a katabatic flow over a glacier, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9840, https://doi.org/10.5194/egusphere-egu25-9840, 2025.

Land-terminating ice cliffs are rare features of the cryosphere, displaying unique atmosphere-cryosphere interactions due to their vertical nature. Although the ice cliff surface is small compared to the total glacier surface, the mass balance of the vertical face can play a decisive role in glacier ablation, due to the cliff's altered exposure to radiative fluxes and modulation of turbulent heat fluxes. Understanding the boundary layer fluxes over these vertical ice walls is therefore essential for accurately modeling the melt of the cliff and other related processes. Our research addresses this gap by analyzing turbulence and microclimate data collected from ice cliffs in two distinct climatic regions: northern Greenland and Kilimanjaro.

The dataset from Greenland includes low-frequency temperature and humidity observations from the vertical ice face and its surroundings, allowing us to characterize the microclimate of ice cliffs in polar environments. The Kilimanjaro site was additionally equipped with high-frequency instrumentation. These measurements provide reliable insights into the boundary layer structure and turbulent fluxes of heat and moisture. Therefore, using data from this site, we aim to evaluate whether heat and moisture fluxes calculated from low- and high-frequency measurements are consistent. This allows us to determine whether the low-frequency data is sufficient to calculate turbulent fluxes at sites without high-frequency instrumentation. The insights gained from these analyses can help improve the representation of turbulent fluxes in ice cliff melt models.

In summary, this work contributes to the broader understanding of cryosphere-atmosphere interactions at vertical ice cliffs, offering valuable insights into the boundary layer processes that control their melt under varying climatic conditions.

How to cite: Schroeder, M., Prinz, R., Nicholson, L., Abermann, J., Steiner, J., Winkler, M., and Stiperski, I.: Cryosphere-Atmosphere Interactions on the Edge: The Ice Cliff Boundary Layer, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17840, https://doi.org/10.5194/egusphere-egu25-17840, 2025.

Mountain glaciers are important components of the global climate system, playing a crucial role in regional hydrology, energy balance and atmospheric dynamics. These systems are highly sensitive to climate change, and small-scale processes such as localised thermodynamic adjustments can trigger rapid feedback mechanisms that significantly alter large-scale atmospheric conditions. Observing and directly interpreting these adjustments is challenging due to non-linear and often opaque cause-effect relationships mediated by intermediate steps. This complexity limits the predictability of meteorological and cryospheric phenomena in mountainous regions. Addressing these challenges requires a holistic analysis that does not rely on assumptions of linearity or simple correlations.
To overcome these obstacles, we use high-resolution numerical atmospheric simulations to study the interactions between glacier microclimates and the free atmosphere, as well as the feedbacks that occur across scales. Using transfer entropy, we uncover the causal relationships driving these feedbacks, identify directional influences between mass and energy fluxes, and analyse how localised processes propagate across micro-, meso- and synoptic scales. For example, our analysis shows how changing glacier geometries affect microclimates and regional energy balances, which in turn drive mesoscale atmospheric circulation patterns.
This presentation highlights key insights from these simulations, in particular the role of glacier-atmosphere interactions in shaping elevation-dependent warming and energy flux dynamics. By advancing computational techniques to better analyse scale coupling in complex terrains, this work addresses unresolved questions in climate research. Ultimately, it provides a way to improve the predictability of cryospheric and atmospheric phenomena in high mountain regions.

How to cite: Sauter, T.: Exploring Scale Interactions and Feedback Mechanisms in Glacier-Atmosphere Dynamics in Mountain Regions: Insights from High-Resolution Simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19772, https://doi.org/10.5194/egusphere-egu25-19772, 2025.