Anthropogenic climate change is driving a widespread retreat of glaciers, which has accelerated in recent decades. By 2100, projections indicate that between 25% and 50% of global glacier mass will be lost, depending on the emission scenario [1]. This rapid decline endangers the climatic information preserved in ice layers. The international Ice Memory project aims to safeguard this natural archive by collecting paired ice cores from mid- and high-latitude glaciers [2]. One core is analysed using present-day techniques, while the second is stored in a cave at Dome C, in Antarctica, ensuring long-term access to this climatic information for future generation of scientists.

The Italian Ice Memory team focused on mid-latitude and Arctic glaciers through six dedicated expeditions. Four expeditions target high-elevation Alpine sites above 4,000 m a.s.l.: Grand Combin (attempted in 2020 and successfully in 2025, Switzerland/Italy), Monte Rosa (2021, Italy/Switzerland), and Colle del Lys (2023, Italy/Switzerland). One expedition was carried out in the Apennines at about 2,700 m a.s.l. on the Calderone Glacier (2022, Italy), and another at Svalbard on the Holthedlafonna Glacier (2023, Norway). Drilling operations were performed using an electromechanical drilling system, and a thermal drill was tested for the first time during the 2025 Grand Combin expedition. The main unexpected challenge encountered at both high- and mid- latitude glaciers was the presence of aquifers located tens of meters below the surface. The occurrence of liquid water layers reflects the polythermal feature of these glaciers, which are increasingly suffering the rising of temperatures.

The recovered ice cores will be analysed in the coming months with the novel Continuous Flow Analysis (CFA) system designed at Ca’ Foscari University, in collaboration with the Institute of Polar Science (CNR-ISP). The analyses include measurements of insoluble dust particles, organic, inorganic and emerging compounds, biochemical markers, and stable water isotopes. In addition, ²¹⁰Pb- based dating and palynological indicators will be analysed using discrete methods. Together, these results will allow the reconstruction of past climate variability and atmospheric circulation patterns.

Future Italian expeditions will focus on Asia, particularly on the Karakorum (Pakistan) and the Himalaya (Nepal).

[1] Zekollari, H. (2024), Cryosphere 18, https://doi.org/10.5194/tc-18-5045-2024

[2] Ice Memory Foundation, https://www.ice‑memory.org

How to cite: Petteni, A., De Blasi, F., Zannoni, D., Spolaor, A., Cozzi, G., Vitale, G., Spagnesi, A., Barbante, C., and Gabrieli, J.: Preserving glacier climate archives in a warming world: the Ice Memory project and the Italian contribution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5517, https://doi.org/10.5194/egusphere-egu26-5517, 2026.

Ice cores represent valuable archives of past climatic, chemical, and biological conditions. Beyond their role in paleoclimate reconstruction, alpine ice cores enable the investigation of microbial biodiversity in extreme frozen environments and natural baselines of antibiotic resistance. This study analyses an alpine ice core from Weißseespitze (Ötztal Alps, Tyrol, Austria) (46°50’46.61393"N, 10°43’00.42181"E) to assess depth-dependent changes in bacterial and fungal communities and antibiotic resistance traits of bacteria.

The ice core was extracted in June 2025 using thermal drilling. It was 5.42 m long and covers a period from ~450–480 years before present at the surface to ~6000 years before present at the base. As a cold-based ice cap, the Weißseespitze is a suitable and well established study site in the Eastern Alps for ice core research. Until now, research has focused on gathering physical and chemical data; therefore, this study aims to provide the first biological information.

The biodiversity of bacteria is evaluated via 16S rRNA gene sequencing using the primers 16S-V3/4 and full-length 16S, while fungal biodiversity is evaluated with ITS regions using the ITS_Fung primer. Nanopore sequencing is used for both assessments. Antibiotic resistance is investigated using a cultivation-based strategy with a disk diffusion test at 20°C and 4°C. The antibiotics tested are of natural, semi-synthetic, and synthetic origin. Subsequently, selected resistant isolates are analysed genetically. 

First results of this study showed a low amount of DNA in the samples. It has also already been demonstrated that bacterial cell abundance varies along the depth profile, as do dissolved organic carbon (DOC) concentrations. In general, we hypothesize that microbial community composition and antibiotic resistance traits vary with depth in response to changes in ice structure, depositional processes, and climatic conditions, while upper layers may additionally reflect anthropogenic influence. This study contributes to a better understanding of microbial persistence in cryospheric environments, natural reservoirs of antibiotic resistance, and potential implications for downstream ecosystems and astrobiological research.

How to cite: Conzelmann, S., Sattler, B., Hartl, L., Fischer, A., Gattinger, D., Summerer, M., Cuzzeri, A. S., Stocker-Waldhuber, M., Seiser, B., Hartig, A., Bertolotti, G., and Gschwentner, A.: Microbial Analyses of a Pre-Industrial Ice Core from Weißseespitze, Tyrol, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19939, https://doi.org/10.5194/egusphere-egu26-19939, 2026.

Ice cores retrieved over the past 50 years from the Greenland Ice Sheet archive invaluable clues about the response of large ice caps to global climate dynamics. Evidence indicates that during past warm interglacial periods, the Greenland Ice Sheet likely experienced significant retreat and may even have collapsed entirely. However, the factors controlling the stability of the Greenland Ice Sheet, its origin, and the environmental implications of its demise are still scarcely understood.

Basal ice, namely debris-rich ice found at the base of the ice mass near the substrate, has the highest potential to preserve information that may help constrain climate conditions conducive to the demise of an ice sheet. To contribute to unfolding these precious archives, we aim to develop and apply innovative organic geochemical techniques targeting fossil organic molecules that can be used as biological markers (in short, biomarkers) for the ecosystems that could have been entrained at the base of the Greenland Ice Sheet during its formation.

Here, we show preliminary results on the methodology developed, including tests on artificial and natural basal ice samples. We also performed geochemical analyses on material (river sediments and permafrost soils) collected from a modern periglacial environment during an expedition to the western margin of the Greenland Ice Sheet. The comparison with the organic geochemical fingerprint preserved in basal material retrieved in deep ice core drilling will help us to reconstruct past ecosystems and ultimately gain insights into the climate and environmental conditions that existed prior to the buildup of the Greenland Ice Sheet.

How to cite: Sabino, M., Martínez-García, A., Rubach, F., Schmitt, M., Vinšová, P., Fouillé, A. F. T., Prud’Homme, C., Stibal, M., Opfergelt, S., Svensson, A., Dahl-Jensen, D., Blard, P.-H., Tison, J.-L., and Fripiat, F.: Unfolding reasons and consequences for the demise of the Greenland Ice Sheet: Perspective from biomarkers stored into basal ice, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17427, https://doi.org/10.5194/egusphere-egu26-17427, 2026.

Runoff waters at the margin of the Greenland Ice Sheet export CH₄-supersaturated waters originating from the ice-sheet bed, contributing to the global atmospheric CH₄ budget [1, 2]. This methane is of microbial origin, likely produced from a mixture of inorganic and ancient organic carbon buried beneath the ice sheet [1, 2, 3].

Debris-rich basal ice layers provide a unique opportunity to investigate the sources and sink of methane at the ice/bedrock interface. Previous studies have shown that Greenland debris-rich basal ice preserves large methane accumulations [4, 5, 6] and may represent a potential endmember contributing to CH₄-rich meltwaters released during the melting season. At Camp Century, CH₄ mixing ratios increase sharply from ~200 ppm to up to 30 000 ppm within 1 m above the ice/bed material transition [6]. Prokaryotic DNA analyses support the microbial origin, and indicate the presence of in situ methanotrophic communities, suggesting active CH₄ consumption and oxidation to CO₂ within the debris-rich ice [6].

Here, we present methane stable isotope measurements (δ¹³C-CH₄ and δD-CH₄) from 7 samples spanning this transition zone. Despite the large methane accumulation, debris-rich ice is strongly gas-depleted, and the limited sample size combined with high CH₄ variability makes isotopic analyses technically challenging. CH₄ was extracted using a melting-freeze extraction coupled to a cold-trap finger filled with HayeSep Q at Université Libre de Buxelles (ULB, Belgium) laboratory, allowing gases to be sealed in glass tubes to prevent atmospheric contamination. CH₄ isotope analyses were performed at the Institute for Marine and Atmospheric Research Utrecht (IMAU, Netherlands) using a Thermo Delta Plus XP (δ¹³C and δD) [7].

The overall isotopic signature supports a microbial origin of CH₄ via methanogenesis, consistent with GRIP values [4]. Despite substantial scatter in δ¹³C-CH₄, a negative correlation is reported between CH₄ concentration and both δ¹³C-CH4 and δD-CH₄, consistent with preferential oxidation of lighter isotopes during methanotrophy. However, the observed relationship suggests a relatively low apparent fractionation factor compared to literature estimates. This could result from under-expression of the true isotope effect due to superimposed processes such as mixing or diffusion, or because the fractionation is intrinsically smaller under low-temperature conditions.

[1] Lamarche-Gagnon et al., 2019, Nature, 565(7737), 73-77. [2] Christiansen et al., 2021, Journal of Geophysical Research: Biogeosciences, 126(11), e2021JG006308. [3] Adnew et al., 2023, Geochimica et Cosmochimica Acta, 389, 249-264. [4] Souchez et al., 2006, Geophys. Res. Lett., 33, L24503. [5] Verbeke et al., 2002, Annals of Glaciology 35, 231-236. [6] Ardoin et al., submitted, The Cryosphere. [7] Menoud et al., 2020, Tellus B: Chemical and Physical Meteorology, 72(1), 1-20.

How to cite: Ardoin, L., Van der Veen, C., El Amari, S., Dahl-Jensen, D., Steffensen, J. P., Tison, J.-L., Röckmann, T., and Fripiat, F.: Investigating the CH4 isotopic signature of debris rich basal ice: insight from Camp Century ice core. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9799, https://doi.org/10.5194/egusphere-egu26-9799, 2026.

The BURNice project aims to quantify global fire emissions during important climate events from the Holocene to the last interglacial termination using ethane in polar ice cores. The project aims to combine analytical measurements and model simulations to explore the fate of ethane (C₂H₆) in the atmosphere in the past. Ethane is a short-lived non-methane hydrocarbon with a simple atmospheric budget. Ethane is primarily emitted into the atmosphere by fire and is removed via reaction with OH and Cl radicals, resulting in a lifetime of ~2 months.

Measurements of ethane in ice cores are conducted using continuous sublimation extraction (CSE) method in tandem with GC-IRMS for parallel quantification of ethane, methane (CH₄), methane isotopes (δ¹³CH₄), and other trace gases. We perform simulations using the Community Earth System Model (CESM) with an improved representation of halogen chemistry to investigate the spatio-temporal dynamics of ethane in the paleo-atmosphere. Preliminary results focus on the effect of the Cl-sink on ethane in modern-day, which is poorly constrained.

This study presents 1) advancements in measurements of ethane in NH and SH ice cores using CSE-GC-IRMS, and 2) results of sink-varied modern-day simulations of ethane in the atmosphere using CESM.

How to cite: Campos Ayala, J., Grimmer, M., Seth, B., Krauss, F., Schmitt, J., Raible, C. C., Meidan, D., Saiz-Lopez, A., and Fischer, H.: BURNice: Global biomass burning reconstruction using ethane in polar ice cores, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19279, https://doi.org/10.5194/egusphere-egu26-19279, 2026.

Ice cores provide the only direct archive of past atmospheric greenhouse gases (GHG). However, physical and chemical processes occurring before, during, and after bubble enclosure can alter the atmospheric signal recorded in ice. In particular, gas diffusion within the bubble-clathrate transition zone (BCTZ) has been shown to generate centimeter-scale, non-atmospheric variability, which we refer to as the “Lüthi effect” (Lüthi et al., 2010). Below the BCTZ, diffusive smoothing dampens these non-atmospheric signals but also atmospheric variability. While the Lüthi effect and diffusive smoothing have been documented for CO₂ and the δO₂/N₂ ratio, their impact on N₂O and CH₄ remains poorly constrained. In addition, chemical reactions within the ice can alter atmospheric signals, particularly for N₂O, which has been shown to be produced in situ by nitrate reduction in dust-rich Antarctic ice during glacial periods.

Here we investigate diffusion and in situ production processes potentially affecting CO₂, CH₄, and N₂O by analyzing five samples from the BCTZ of the Talos Dome ice core (TALDICE). GHG concentrations were measured at centimeter-scale resolution using a novel laser sublimation extraction system coupled to a quantum cascade laser absorption spectrometer (Mächler et al., 2023). δO₂/N₂ ratios were analyzed by isotope ratio mass spectrometry following the recapture of the same samples after GHG measurements with the laser spectrometer.

Our results show for the first time that N₂O and CH₄ are also affected by the Lüthi effect in the BCTZ. The strong 1:1 correlation between CO₂ and N₂O variability suggests similar diffusion coefficients for these gases. These findings provide new constraints on N₂O diffusion, relevant for modeling diffusive smoothing in deep and old ice such as the recently drilled Beyond EPICA ice core. Consistent with previous studies, our results indicate that the N₂O record in TALDICE is not significantly affected by the aforementioned in situ production during glacial periods. The atmospheric N₂O signal can therefore be retrieved when measurements are either spatially averaged to smooth the centimeter-scale variability induced by the Lüthi effect, obtained above the BCTZ, or taken well below the BCTZ where diffusive smoothing has attenuated this variability.

References

Lüthi, D., Bereiter, B., Stauffer, B., Winkler, R., Schwander, J., Kindler, P., Leuenberger, M., Kipfstuhl, S., Capron, E., Landais, A., Fischer, H., and Stocker, T. F.: CO₂ and O₂/N₂ variations in and just below the bubble–clathrate transformation zone of Antarctic ice cores, Earth and Planetary Science Letters, 297, 226–233, https://doi.org/10.1016/j.epsl.2010.06.023, 2010.

Mächler, L., Baggenstos, D., Krauss, F., Schmitt, J., Bereiter, B., Walther, R., Reinhard, C., Tuzson, B., Emmenegger, L., and Fischer, H.: Laser-induced sublimation extraction for centimeter-resolution multi-species greenhouse gas analysis on ice cores, Atmos. Meas. Tech., 16, 355–372, https://doi.org/10.5194/amt-16-355-2023, 2023.

How to cite: Soussaintjean, L., Krauss, F., Schmitt, J., Traeger, H., Bauska, T., and Fischer, H.: Centimeter-scale diffusion and in situ production effects on greenhouse gas records in the TALDICE ice core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12071, https://doi.org/10.5194/egusphere-egu26-12071, 2026.

Ice cores serve as valuable archives for past atmospheric conditions. They can provide direct records of past atmospheric CO₂ concentrations, but measurements from very old or stratigraphically disturbed ice are often limited by sample size and analytical precision. This study presents a custom-built multiport CO₂ extraction and crushing system designed to enable accurate and precise CO₂ concentration measurements from small ice samples (~10 g) with faster throughput than previous systems at OSU. The system allows sequential extraction of multiple samples under identical analytical conditions, improving throughput while minimizing contamination and analytical drift with ultimate throughput of 8-12 samples per day. 

We evaluate the performance of the multiport system through repeated analyses of ice standards and replicate small-sample measurements, assessing reproducibility, extraction efficiency, and measurement precision. CO₂ concentrations measured using this system demonstrate consistent reproducibility across ports, with precision comparable to previous methods at OSU. This method enables faster higher spatial resolution sampling and provides a foundation for improving CO₂ measurements in ancient ice where sample availability and potential respiratory inputs are key challenges.

How to cite: Byland, T., Brook, E., and Kalk, M.: A Multiport CO₂ Extraction System for Accurate and Precise Measurements from Small Ice Core Samples, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15040, https://doi.org/10.5194/egusphere-egu26-15040, 2026.

The Beyond EPICA oldest ice is a unique climate archive, continuously reaching back to possibly 1.5 Ma. The continuity of the signals in the ice core likely allows for developing a continuous timescale, mostly based on orbital tuning with O₂/N₂ and δ¹⁸O_atm. The obtained timescale can then be checked for consistency with marine records, ³⁶Cl/¹⁰Be dating and possibly with magnetic tie points from cosmogenic isotopes. Since these consistency checks have caveats, additional absolute age constraints may prove useful.

The noble gas radioisotope ⁸¹Kr ( t_1/2 = 229 ka ) with a dating range from 30 ka to 1.5 Ma can provide robust absolute age constraints in ice cores. Especially due to its gaseous and inert properties, its isotopic ratio is not altered by geochemical processes so that it preserves the pristine age information. ⁸¹Kr dating could provide additional absolute age constraints for the Beyond EPICA oldest ice. However, due to the high ice demand for numerous analyses on the core, there is no ice available for ⁸¹Kr analysis on discrete ice samples.

We present gas extraction from the Continuous Flow Analysis (CFA) of the Beyond EPICA oldest ice for ⁸¹Kr dating. The gas has been passively collected from the overflow of the debubbler into multi-layer aluminium-foil bags, which are routinely employed for ⁸¹Kr dating of groundwater. From the continuous melting of ~3 m long core, discrete ~100 mL STP gas samples have been extracted, and subsequently analyzed offline for ⁸⁵Kr and ⁸¹Kr. Modern air contamination, likely from diffusion through the gas bags during storage, has been quantified with the anthropogenic ⁸⁵Kr. The contamination can be avoided by transfer of the sampled gas from bag to metal container after collection. The ⁸¹Kr age constraints that could be obtained are consistent with preliminary timescales. The presented gas extraction method is non-invasive and requires minimum equipment, potentially providing a base for usage also in future CFA campaigns.

How to cite: Ritterbusch, F., Wöhrl, J., Baumbusch, C., Wachs, D., Tetzner, D., Humby, J. D., Miller, S., Thomas, E. R., Feng, X., Wang, J., Jiang, W., Lu, Z.-T., Yang, G.-M., Urbach, K., Dallmayr, R., Hörhold, M., Freitag, J., Wilhelms, F., Aeschbach, W., and Bohleber, P.: Gas extraction from CFA for 81Kr dating of the Beyond EPICA oldest ice, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9377, https://doi.org/10.5194/egusphere-egu26-9377, 2026.

Over the last 15 years, studies of non-polar ice core archives have successfully demonstrated the usefulness of ice core dating via ¹⁴C in particular organic carbon (PO¹⁴C). It excels especially in deeper layers, where stratigraphic dating methods cannot be applied.
This presentation focuses on improvements made to the PO¹⁴C inline filtration-oxidation unit (REFILOX) system developed by Hoffmann et al. (2017, Radiocarbon, doi:10.1017/RDC.2017.99), which has been successfully applied in several Alpine ice core studies (e.g. Legrand et al. 2025, PNAS Nexus, doi:10.1093/pnasnexus/pgaf186).
The device was redesigned to allow an easier handling by avoiding the fragile, difficult to obtain and expensive quartz glass to stainless steel passages of the device. In addition, the material of the combustion chamber was changed to borosilicate glass, which is much easier to handle compared to quartz glass. Combined, these changes allow a faster and more thorough cleaning and assembly process. We introduce the new key characteristics of the modified setup, which already showed that the process blank could be maintained in the sub-microgram range. Beside blank characteristics and precision compared to standard material, a first application of the improved system is presented demonstrating its potential for radiocarbon dating of real glacier ice samples.

How to cite: Wörner, J., Preunkert, S., and Aeschbach, W.: PO14C dating of glacier ice – recent improvements for an easier device handling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13148, https://doi.org/10.5194/egusphere-egu26-13148, 2026.

Absolute dating methods are required to provide accurate age estimates of extremely thinned and folded layers in the deepest sections of ice cores. The ³⁶Cl / ¹⁰Be chronometer works on the principle that the ratio of ³⁶Cl (half-life; 301 kyr) will decrease relative to ¹⁰Be (half-life; 1.4 Myr) with increasing age of ice. This method is especially desirable because it generally requires less ice for analysis than other absolute dating techniques such as ⁸¹Kr. However, both ³⁶Cl and ¹⁰Be are affected by processes that complicate their reliability as geochronological tools. For instance, at low accumulation sites, the ³⁶Cl inventory can be depleted through hydrogen chloride outgassing, however ³⁶Cl is largely preserved in glacial periods due to increased buffering from alkaline species associated with increased dust content. Conversely, increased dust content during glacial periods can complicate the ¹⁰Be inventory due to adsorption of  ¹⁰Be onto dust. In deep ice, such ¹⁰Be migration has resulted in observations of the ¹⁰Be concentration decreasing faster than expected from physical decay alone (Kappelt et al., 2025), which can lead to potential age underestimates when using the ³⁶Cl / ¹⁰Be chronometer.

Here we focus on the issue of ¹⁰Be migration in deep ice by using a 0.45μm filter to separate the ¹⁰Be inventory attached to dust particles and in ice prior to ¹⁰Be measurement. We present preliminary results using our filtration method on Holocene, LGM and MIS-4 samples from the Dye-3 ice core from southern Greenland. Our results confirm that the impact of dust on the ¹⁰Be budget is more pronounced during glacial periods. Additionally, we use our filtration technique to test its potential to resolve the depletion of ¹⁰Be observed in the deeper sections of ice cores, by working on deep core sections that are independently dated by ⁸¹Kr. To make progress on better constraining the ¹⁰Be signal, we also present a modified sequential leaching technique, previously applied to ocean and river sediments. By performing sequential leaching on the filtered dust, we aim to separate the labile meteoric ¹⁰Be fraction (adsorbed from the ice) from the meteoric ¹⁰Be fraction that was already present at the dust surface prior to the incorporation of the dust into the ice. In better constraining the impact of ¹⁰Be migration onto dust on the total ¹⁰Be inventory in deep ice cores we hope to improve the accuracy of the paired ³⁶Cl / ¹⁰Be chronometer for small-sample (< 1 kg) ice core analyses.

How to cite: Adams, J., Protin, M., Muscheler, R., Fourre, E., Combacal, T., Dahl-Jensen, D., Steffensen, J. P., Svensson, A., Fripiat, F., Team, A., Team, E. T. H. Z., and Blard, P.-H.: A Filtered View of Time: Improving the performance of the 36Cl / 10Be chronometer in Greenland ice cores by separation of the 10Be budget in ice and dust, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17690, https://doi.org/10.5194/egusphere-egu26-17690, 2026.

The folded stratigraphy of the ice between 2432.2 and 2540 m in the Greenland NEEM ice core precludes direct access to climatic information older than 128.5 ka b2k (thousands of years before 2000 CE) (NEEM comm. Members, 2013). The disturbed stratigraphy is particularly unfortunate because this ice’s age corresponds to the Termination II (140–130 ka b2k). The climatic transition from the penultimate glacial period (MIS 6, 190–130 ka b2k) to the last interglacial (MIS 5e, 130–120 ka b2k) has not yet been extracted from Greenlandic ice core records.

In this study, we propose a possible reconstruction of the disturbed NEEM stratigraphy spanning the MIS 6–MIS 5e transition based on the succession of globally well-mixed gas parameters. The NEEM δ¹⁸O_ice chronological sequence is obtained by comparing a new set of δ¹⁸O of atmospheric O₂ and CH₄ measurements from the bottom section of the NEEM core with their counterpart in composite Antarctic records. The proposed stratigraphy is also discussed with respect to three radiometric ages estimated from new ⁸¹Kr measurements from the bottom part of the NEEM core. The new gas measurements suggest that disturbed ice below 2432.2 m in the NEEM ice core contains, stratigraphically intact, but folded ice, with climatic information from MIS 6 and MIS 5e, possibly from the penultimate deglaciation, and that sections of MIS 5e are present twice in the ice. 

How to cite: Bouchet, M., Svensson, A., Landais, A., Fourré, E., Blunier, T., Dahl-Jensen, D., Westhoff, J., Kjær, H. A., Feng, X., Jiang, W., Lin, Q.-S., Lu, Z.-T., Wang, J. S., and Yang, G.-M.: Is the penultimate deglaciation (Termination II) recorded in the folded ice in the deepest part of the Greenland NEEM ice core?  , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9646, https://doi.org/10.5194/egusphere-egu26-9646, 2026.

Over the past few decades, the Greenland Ice Sheet has experienced multiple widespread surface melt events (e.g. 2012 and 2019), affecting nearly its entire surface. While seasonal surface melt occurs regularly at the margins of the Ice Sheet, it is rare in the high-elevation, central-north area and thus an indicator for extreme warm events. However, due to sparse in situ observations, particularly prior to the instrumental period little is known about the historical occurrence of such melt events.

Signatures of surface melt are archived within the firn column of the ice sheet as layers of refrozen melt water (melt layers), visually distinguishable from the surrounding unaffected firn and bubbly ice, due to the higher density and absence of air bubbles. We here analyse 22 firn cores from 15 sites across north-central Greenland, covering the past ~1000 years (until 2018 CE), to identify melt layers using visual inspection and micro-computed tomography. For the first time, we present a derived Greenland melt feature database, comprising over 1000 melt features.

Interpreting the melt features as a proxy for past extreme warm events allows to reconstruct the spatial extent and frequency of past melt events. Initial analyses indicate that both, elevation and geographic location strongly influence melt occurrence: lower-elevation sites experience more melt than higher-elevation sites, and the north-eastern basin shows more frequent surface melt than the north-western basin. This new dataset also places recent surface-melt events into a long-term context, demonstrating that the 2012 melt event was the most intense event in north-central Greenland over the last millennium.

How to cite: Zander, S., Hörhold, M., Freitag, J., Sasgen, I., Kipfstuhl, S., Koldtoft, I., Kjaer, H. A., Zeppenfeld, C., Vinther, B., and Laepple, T.: Past and Recent Extreme Warm Events in Greenland derived from Firn Core Melt Layers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17244, https://doi.org/10.5194/egusphere-egu26-17244, 2026.

Polar ice cores are archives of past climate conditions and atmospheric composition. Atmospheric aerosols deposited on the ice sheets and subsequently preserved in the ice provide detailed records of past atmospheric conditions. Analyses of these impurities therefore offer valuable insights into environmental changes in the past.

Here we present high-resolution impurity records from the East Greenland Ice Core Project (EGRIP) ice core measured with the University of Bern continuous flow analysis (CFA) set-up. Continuous melting and the analysis of only the inner part of the ice stick allows for high resolution while minimizing contamination. The analyzed components include water-insoluble dust particles as well as the dissolved impurities calcium, ammonium, and nitrate. For the dust record, we focus on the previously not studied changes in the main mode of the dust number concentration (<1 µm) and the dust refractive index. The dissolved species act as proxies for aridity (calcium) as well as vegetation cover and biomass burning (ammonium). Additionally, volcanic eruptions are imprinted in the electrolytic conductivity record of the meltwater.

The records span the period from 30k to 15k years BP, covering the Last Glacial Maximum (LGM). In Greenland ice cores, the LGM is characterized by high impurity content including dust, calcium, and nitrate. In contrast, ammonium concentrations are consistently low, reflecting extensive northern hemisphere ice sheets during this period. We observe dust concentrations up to 60 times higher than during the Holocene for particles in the 0.2-2 µm size range. Although dust concentrations remain high throughout the studied period, they exhibit pronounced variability. While the refractive index stays largely constant, the dust size distribution varies, but not in parallel with the concentration. Since the preserved size distribution is primarily controlled by atmospheric transport time, we hypothesize that dust source region contributions to Greenland changed during the LGM.

How to cite: Zeppenfeld, C., Jackson, S., Lee, G., Erhardt, T., Kjær, H. A., Jensen, C. M., and Fischer, H.: Aerosol data from the EGRIP ice core covering the Last Glacial Maximum, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18172, https://doi.org/10.5194/egusphere-egu26-18172, 2026.

To investigate millennial-scale variations in mineral dust and its provenance during the last glacial period, we analyzed the Dome Fuji deep ice core using a Continuous Flow Analysis (CFA) system. We measured microparticles, eight elements (Na, Mg, Al, Si, K, Ca, Fe, and S), and stable water isotopes over the depth interval from 730 to 930 m. This interval corresponds to approximately 35–53 kyr BP, encompassing Antarctic Isotope Maxima (AIM) 8 to AIM 13 and part of AIM 14. In addition to the CFA measurements, discrete samples were continuously collected at 50 cm intervals and analyzed for particle concentrations and size distributions using a Coulter Multisizer 4e.

Concentrations and fluxes of microparticles—predominantly derived from mineral dust—as well as dust-sourced elements decreased during AIM events and increased during stadial periods, consistent with previous Antarctic ice-core studies. Centennial averages of elemental concentration ratios (Ca/Al, Fe/Al, and Si/Al) exhibit only minor variations throughout this period. This behavior contrasts with the pronounced changes observed during Termination I, suggesting relatively stable dust provenance during 35–53 kyr BP. Microparticle sizes increased during AIM events and decreased during stadials, indicating changes in transport and/or deposition rather than source shifts.

How to cite: Goto-Azuma, K., Hirabayashi, M., Fukuda, K., Ogata, J., Okumura, H., Oyabu, I., Kitamura, K., Nakazawa, F., Fujita, S., Saruya, T., and Kawamura, K.: High-resolution analyses of mineral dust at Dome Fuji, Antarctica during 35-53 kyrBP, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6202, https://doi.org/10.5194/egusphere-egu26-6202, 2026.

In recent years, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been further developed to obtain aerosol-derived impurity records from ice core samples at sub-mm to µm resolution (Müller et al., 2011; Bohleber et al., 2020).

For thinned ice from the lower parts of ice cores, the high spatial resolution of the method in principle promises to resolve climate variability at temporal scales that are unresolvable by other methods such as continuous flow analysis. However, spatially resolved, two-dimensional maps of the impurity distribution in the ice from LA-ICP-MS have revealed the complex interplay between the impurities and the ice’s polycrystalline structure (Della Lunga et al., 2014; Bohleber et al., 2020; Stoll et al., 2023). Some impurities such as sodium, predominantly from sea salt aerosols, show very high localisation along grain boundaries. Other elements that are typically associated with water-insoluble dust aerosols such as iron, aluminium, and calcium, however, often do not show such a strong localisation but are dispersed as particles in the ice matrix.

This localisation poses the question: At what spatial and thus temporal scale the LA-ICP-MS records are interpretable as climate records? And at which scale the post-depositional processes in the ice masks the climate signal by e.g. by dynamic or static recrystallization. This is especially relevant in the context of the evolution of the ice towards generally larger crystal sizes with increasing depth within the ice sheet accompanied by the thinning of the annual layers.

To investigate the preservation of high-frequency climate variability, we applied our newly developed 157 nm cryo-LA-ICP-MS/MS setup (Erhardt et al., 2025) to ice covering the warming transition into Greenland Interstadial 1 in the EGRIP ice core at 1375 m depth. Here, we present spatially resolved impurity maps at the ~100-µm scale spanning the rapid warming transition. Bulk concentration data from continuous flow analysis of the same ice indicates that this warming transition is exceptionally fast at EGRIP, happening within only a few years. Ice-fabric data shows grain diameters increasing from 1.5 to 1.8 mm across this transition from dustier stadial to cleaner interstadial ice (Stoll et al., 2025). This makes it a good candidate to investigate the imprint of the ice matrix onto rapid climate signals in the ice-core impurity record.

Bohleber, P. et al. (2020) Imaging the impurity distribution in glacier ice cores with LA-ICP-MS. Journal of Analytical Atomic Spectrometry

Della Lunga, D. et al. (2014) Location of cation impurities in NGRIP deep ice revealed by cryo-cell UV-laser-ablation ICPMS. Journal of Glaciology

Erhardt, T. et al. (2025) Rationale, design and initial performance of a dual-wavelength (157 & 193 nm) cryo-LA-ICP-MS/MS system. Journal of Analytical Atomic Spectrometry

Müller, W., Shelley, J.M.G. & Rasmussen, S.O. (2011) Direct chemical analysis of frozen ice cores by UV-laser ablation ICPMS. Journal of Analytical Atomic Spectrometry

Stoll, N. et al. (2023) Chemical and visual characterisation of EGRIP glacial ice and cloudy bands within. The Cryosphere

Stoll, N. et al. (2025) Linking crystallographic orientation and ice stream dynamics: evidence from the EastGRIP ice core. The Cryosphere

How to cite: Erhardt, T., Linda, M., Zeppenfeld, C., Weikusat, I., Fischer, H., and Müller, W.: Investigating the preservation of rapid climate signals in the ice matrix using 2D LA-ICP-MS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8223, https://doi.org/10.5194/egusphere-egu26-8223, 2026.

Ice cores are extremely valuable archives of the past atmospheric composition, extending back more than 1 million years. In such ancient ice, ice layers become extremely thinned, and the spatial resolution of analytical techniques becomes the primary factor limiting the ability to resolve past climate signals, such as the temperature-related variability inferred from the stable isotopic composition of the ice. Laser ablation (LA) is a micro-destructive technique that has recently shown strong potential for coupling to cavity ring-down spectroscopy (CRDS) to retrieve the isotopic composition of ice-core samples with minimal sample loss. In principle, LA–CRDS not only enables substantially higher spatial resolution than conventional methods but has the potential to gain new insights into signal formation processes in shallow ice by mapping the two-dimensional distribution of stable water isotopes within the ice matrix. However, LA–CRDS hyphenation remains challenging due to several factors, including wavelength-dependent suboptimal laser–ice interaction that can induce isotopic fractionation during ablation, and limitations related to the fast detection of transient signals by commercially available CRDS analyzers. To address these challenges, it is necessary to identify and constrain the factors affecting the ablation efficiency and the aerosol transport between the two systems, while remaining within the operational specifications of both instruments. In the context of the Isotope iMAGing for Ice Core Science (IMAGICS) project, we investigate how laser energy density, artificial ice generation (slow and flash freezing), and measurement configuration affect the LA–CRDS efficiency using an ArF excimer laser (Analyte Excite+, Teledyne Photon Machines) coupled to a CRDS water vapor isotope analyzer (L2130-i, Picarro). Artificial ice samples with known isotopic composition were analyzed under varying laser fluence, dosage, and firing duration. The water-vapor-calibrated CRDS analyzer collected aerosol and vapor generated in the LA cell via an Aerosol Rapid Introduction System (ARIS), operated under its default sampling configuration (~40 ml min^-1, 1 Hz). Preliminary results from this study indicate that, although isotopic fractionation effects are observed in the retrieved aerosol and vapor composition, as previously reported in Malegiannaki et al (2024), the high repeatability of water vapor peaks and isotopic plateaus suggests that the LA–CRDS system introduces a systematic, non-random bias. This finding implies that a correction based on tailored calibration experiments to characterize ice–laser sensitivity is feasible. Such an approach would enable reproducible and accurate isotopic analyses of ice samples with reasonable analysis times (e.g., <10 s per mm² of ablated ice surface).

Malegiannaki, E., Bohleber, P., Zannoni, D., Stremtan, C., Petteni, A., Stenni, B., Barbante, C., Vinther, B. M., & Gkinis, V. (2024). Towards high-resolution water isotope analysis in ice cores using laser ablation - cavity ring-down spectroscopy. Analyst , 149 (24), 5843–5855. https://doi.org/10.1039/d4an01054j

How to cite: Zannoni, D., Roman, M., Bohleber, P., and Stenni, B.: Optimizing Laser Ablation–CRDS Coupling for Spatially-Resolved Millimetric Isotopic Measurements on Ice Cores, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5609, https://doi.org/10.5194/egusphere-egu26-5609, 2026.

Polar amplification leads to a larger warming in polar regions compared to the global average [1]. While an overall warming is observed in West Antarctica and Antarctic Peninsula, the temperature signal in East Antarctica remains uncertain [2]. In Antarctica, atmospheric weather stations are sparse and mainly located near the coast. While state-of-the-art atmospheric reanalysis are available from 1940, the historical climate variability at the Southern Hemisphere high latitudes are mostly based on the teleconnections with low-latitude regions, as almost no high-latitude observations are available before the satellite era (i.e., 1979). This therefore introduces a discontinuity in around 1980 associated with the incorporation of satellite observations in reanalysis.

To address these limitations, ice core records provide a valuable long-term archive of past climatic conditions through the well-established relationship between water isotopes (δ¹⁸O and δ²H) and local temperature. This relationship – commonly referred to as “paleothermometer” – is widely used for reconstructing past temperature variations.

Within the framework of the East Antarctic International Ice Sheet Traverse (EAIIST, 2019–2020), a set of shallow ice cores was recovered between Concordia Station and the South Pole. Here, we present isotope records from firn cores collected at Paleo (79°38′47″S; 126°08′15″E) that we combine to the water isotopic record obtained on the 85 m firn core at Little Dome C within the Ice CORe Dating project (ICORDA, 2019–2025, see poster by Minster, Samin et al.) providing climatic information at decadal resolution in this region of the interior of the East Antarctic Plateau. By comparing these records with atmospheric reanalyses and temperature reconstructions, we observe a strong spatial contrast between the interior and the coastal region over the past few decades. This dipole pattern is characterized by a surface warming in the interior of the continent and surface cooling along the coast of Adélie Land. To isolate the local signal of anthropogenic warming, we account for the influence of large-scale atmospheric dynamics, such as the Southern Annular Mode. Furthermore, ice core evidences, combined with climate model outputs, provide a context of the current warming over the last two centuries. This permits to assess whether climate models can correctly reproduce the spatial contrast between the interior and the coastal region in terms of surface temperature multi-decadal variability, essential for reliable future projections.

Italian partners received funding from the PNRA through “EAIIST” (PNRA16_00049-B) and “EAIIST-phase2” (PNRA19_00093) projects.

[1] Casado M., et al. (2023), Nat. Clim. Change 13. https://doi.org/10.1038/s41558-023-01791-5

[2] Clem KR., et al. (2020), Nat. Clim. Change 10. https://doi.org/10.1038/s41558-020-0815-z

How to cite: Stenni, B., Petteni, A., Casado, M., Dalaiden, Q., Savarino, J., Spolaor, A., Becagli, S., Ooms, A., Dutrievoz, N., Agosta, C., Gautier, E., Landais, A., Samin, E., Frezzotti, M., Fourré, E., Dreossi, G., Jacob, R., Combacal, T., Orsi, A., and Masiol, M.: Spatial variability of climate change signature in Antarctica revealed by ice cores, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6988, https://doi.org/10.5194/egusphere-egu26-6988, 2026.

The Skytrain Ice Rise ice core adds to the handful of climate records from Antarctica that cover the whole of the last glacial period (here, we consider ~100-10 ka bp). By our count 7 records have been published covering the entire period and a further 6 cover a substantial part of it. Using the synchroneity of signals across the continent (for example in components of dust and in methane) we can tie the records together temporally. The precision of such ties is good enough to allow comparison of the timing and shape of particular events across the continent.

Many of the differences between sites will derive from local changes of elevation that certainly occur at ice rise sites. We first will discuss the glacial water isotope record from Skytrain Ice Rise (in comparison to other sites) in this context.  This will supplement the work we have already done on the Holocene and the last interglacial period using the Skytrain Ice Rise core.

However we primarily focus on a number of events such as the Antarctic Cold Reversal and some of the large Antarctic Isotopic Maxima (eg AIM 12).  We will present records from the different sectors of Antarctica. We will investigate whether any sectors of Antarctica led in such events, and determine the relative amplitude of such events around the continent. This information will offer diagnostic tests to ideas about the causes and process of millennial scale variability across the glacial period.

How to cite: Wolff, E., Rowell, I., Bauska, T., Grieman, M., Hoffmann, H., Humby, J., Mulvaney, R., Nehrbass-Ahles, C., and Rhodes, R.: The expression of climate in the Weddell Sea region in comparison to the rest of Antarctica for events in the last glacial period, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5553, https://doi.org/10.5194/egusphere-egu26-5553, 2026.