Orals: Tue, 5 May, 08:30–12:30 | Room 0.14
Temperate glaciers have traditionally been viewed as unsuitable archives for paleoclimate and environmental reconstruction due to pervasive meltwater percolation and the consequent alteration or disruption of primary atmospheric signals. Yet, in the context of ongoing climate warming, many formerly cold accumulation glacier basins, traditionally targeted for ice-core drilling, are transitioning toward temperate conditions. Exploiting glaciers as sources of past environmental information will therefore increasingly require consideration of temperate glaciers worldwide.
We synthesize more than seven decades of temperate glacier ice-core research, from pioneering efforts in the 1950s to the recent developments. We discuss the physical and chemical mechanisms by which meltwater impacts ice stratigraphy and proxy records, including impurity elution, recrystallization, liquid water redistribution, and the fractionation of water stable isotopes. Through inter-site comparison across climatic regimes (tropical, mid-latitude and high-altitude temperate glaciers), we identify which proxies are most resilient to post-depositional modification and under which conditions meaningful environmental signals can be recovered.
Our results highlight that, while ice cores from temperate glaciers often lack the pristine stratigraphy of cold ice, they can still provide valuable records of climatic and environmental variability, particularly when interpreted in combination with meteorological observations, reanalysis products, and glaciological data.
With cold glaciers becoming increasingly scarce, in particular at low- and mid-latitudes, progress in ice-core science requires a better understanding of temperate ice processes. This contribution provides a reference framework from which future studies can build.
How to cite: Baccolo, G., Eichler, A., Jenk, T., Camara-Brugger, S., Worek, M., Burgay, F., Delmonte, B., Mangili, C., Maggi, V., Di Stefano, E., Bohleber, P., and Schwikowski, M.: Ice-cores from temperate glaciers as paleoclimate archives in a warming world: what we know and what we need to know, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13352, https://doi.org/10.5194/egusphere-egu26-13352, 2026.
In the wake of a warming global climate, prolonged periods of negative mass balance affect even high-altitude Alpine glaciers. For these ideal candidates for paleoclimate-related ice core studies, this greatly complicates the already challenging task of establishing an age-depth relationship, because both the age at depth and at the surface is unknown. Radiometric ice dating methods are an important key to overcome this challenge. For Alpine glaciers that have already lost significant amounts of surface ice, the combined use of the radiometric tracers 39Ar and 14C has proven to be particularly effective (Legrand et al., 2025, Hou et al., 2025, Wachs et al., 2026).
Among other applications, we will present a recently published (Wachs et al., 2026) study on the age-depth profile of the summit glacier of Weißseespitze (WSS, 3500 m a.s.l.) in the Austrian Alps. All 39Ar samples were measured using atom trap trace analysis (ATTA), while 14C data from an earlier publication (Bohleber et al., 2020) complete the record. Constrained by the measurements, age modeling using least squares fitting and Monte Carlo sampling was performed to find a suitable glaciological model and to establish a continuous age-depth relationship.
The results show that the surface ice at WSS dates back approximately 400 years, emphasizing the extent of recent ice loss. At the same time, the continuous age-depth relationship shows no evidence of prolonged periods of mass loss at WSS within the 6000 years glaciation history prior to the present. The resulting age–depth relationship thus forms the basis for the historical interpretation of chemical records from WSS, such as recently published by Spagnesi et al., 2026, and their intercomparison with other paleoclimate archives.
Beyond WSS, the combined 39Ar-14C dating approach is readily transferable to other vulnerable Alpine ice archives. We will discuss ongoing work at sites such as Jamtalferner and others and illustrate its potential to establish robust chronologies across a range of Alpine glacial settings.
Bohleber et al., New glacier evidence for ice-free summits during the life of the Tyrolean Iceman, Scientific Reports, 2020
Hou et al., A radiometric timescale challenges the chronology of the iconic 1992 Guliya ice core, Science Advances, 2025
Legrand et al., Alpine ice core record of large changes in dust, sea-salt, and biogenic aerosol over Europe during deglaciation, PNAS Nexus, 2025
Spagnesi et al., New chemical signatures from Weißseespitze ice cores (Eastern Alps): pre-industrial pollution traces from Roman Empire to Early Modern Period, Frontiers in Earth Science, 2026
Wachs et al., A continuous 6000 year age depth relationship for the remainder of the Weißseespitze summit glacier based on 39Ar and 14C dating, Climate of the Past, 2026
How to cite: Wachs, D., Spagnesi, A., Bohleber, P., Fischer, A., Stocker-Waldhuber, M., Junkermann, A., Mandaric, N., Meienburg, F., Jenk, T., Oberthaler, M., and Aeschbach, W.: 39Ar and 14C on ice - Dating the remainders of Alpine glaciers amid rapid mass loss, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19191, https://doi.org/10.5194/egusphere-egu26-19191, 2026.
Ice cores are one of the best palaeoarchives for the most recent geological record. Their resolution is unmatched as it is possible to retrieve seasonal information of thousands of years of climatic archive. Therefore, dating is fundamental to interpreting these archives. Polar and temperate ice cores are well studied and have provided valuable records for paleoclimate interpretation. However, tropical ice cores remain under- studied because of many technical difficulties inherent to it, even though they have precious information on tropical climate dynamics. One of the biggest challenges is dating tropical ice cores. The relationship between ice depth and age is rarely straightforward and typically requires a multi-proxy approach - specially in tropical records, as they are not submitted to the typical polar and high-latitude climatic dynamic, due to its complex ice flow patterns, post-depositional processes like melting, and high background noise for chemical markers. Here we present results of a 128.3 m long ice core, collected from the Quelccaya Ice Cap, Peru (at 13°55’46,099”S, 70°49’21,557”W, 5.674 m above the sea level) during the austral winter of 2022. . In this study, we used refractory black carbon (rBC), ion concentration depth profiles and a series of frequency analysis to perform annual layer counting (manual and automated) based on seasonal variations. We try to assign to the dating reference horizons using volcanic signatures from historically known events and the El Niño Southern Oscillation (ENSO) index as tie points. The very low mobility of black carbon in ice and snowpack causes it to remain effectively locked in place after deposition, thereby creating a clear and consistent seasonal archive in the ice core data, with pronounced seasonality marked by peaks during the dry season (June – August). Ionic signal is less seasonal and presents intense remobilization indicating that the ice pack is rapidly losing part of its climatic signal that is so important for the understanding of tropical paleoclimate dynamics.
Keywords: ice core, Amazon, black carbon, paleoclimate
How to cite: Brum Poitevin Portella, M., Ilha, J., Barbaro, E., Kaspari, S., Barbante, C., Simões, J., and Mayewski, P.: Dating an Amazonic ice core:disentangling a complex chemical record, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12002, https://doi.org/10.5194/egusphere-egu26-12002, 2026.
From late March to late May 2025, a collaboration between Canada and Denmark drilled a 613-meter ice core through the Müller Ice Cap in the Canadian high Arctic. It is the deepest ice core in the Americas to date. The ice cap is in close proximity to the Arctic Ocean, supporting the primary goal of understanding the evolution of Arctic sea ice over the 10,000+ year record contained within the ice.
For the drilling, we utilized a newly designed intermediate winch and control system, combined with a previously existing tower, and the Danish deep drill system featuring 2.2 m core barrels. The newly designed winch is staged on a movable platform, resulting in a fixed level wind and a short distance to the tower.
Furthermore, we tested an inflatable tent to host the drilling and core processing. This worked well and withstood multiple days with strong winds and gusts above 40kt. The tent was a fraction of the weight of a traditional steel-framed tent.
Drilling concluded after 30 drilling days with 10m of debris-rich, silty ice by hitting bedrock at 612.98m depth. We drilled through numerous sandstones using carbide inserts on the ice core drill, and we recovered samples for optically stimulated luminescence dating.
The first results from the stable water isotopes (δ18O) and electric conductivity measurements (ECM) provide a profile over the full Holocene, as well as the transition from the Younger Dryas and Bølling-Allerød.
How to cite: Westhoff, J., Criscitiello, A., Vinter, B., Boeckmann, G., and Dahl-Jensen, D. and the the field, logistics, and ice core processing teams: Drilling 613 m through Müller Ice Cap, Nunavut, Canada – Advances in drill equipment, innovations in camp infrastructure, first results from the ice core, and insights into the basal material beneath the ice, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16803, https://doi.org/10.5194/egusphere-egu26-16803, 2026.
This study provides an overview of the layered structure of Antarctic ice sheets, focusing on the crystalline textural properties and deformational regimes in the Dome Fuji ice core. Polar ice sheets consist of layers with diverse rheological characteristics, shaped by depositional processes such as atmospheric aerosol deposition. Layer thickness varies from millimeters (annual layers) to thicknesses spanning glacial-interglacial periods, with the initial ice fabric forming during firnification.
Key factors influencing the rheology of ice include ion content (e.g., Cl−, F−, NH4+) and insoluble particles such as salts and dust. Ions can substitute within the ice crystal lattice, affecting dislocation density, viscosity, and deformation behavior. These influences persist from firnification to the basal layers of the ice sheet. Notably, salt inclusions have larger volume fractions than dust particles, significantly impacting microstructure evolution.
The ice sheet’s deformation can be divided into two regimes: the upper 80% of the ice sheet, characterized by lower strain and temperature gradients, and the lower 20%, where higher temperatures and strain induce complex recrystallization processes. Four primary factors drive the evolution of crystal orientation fabrics and microstructures: (i) temperature conditions, (ii) strain configurations, (iii) insoluble particle effects, and (iv) dynamic recrystallization, including grain boundary migration and the formation of new grains. These processes result in a deformational history unique to each layer, spanning up to one million years.
Understanding these layered structures has significant implications. For ice sheet modeling, they provide constraints on strain values and inform models of vertical thinning. For ice core sciences, the layered structure highlights the importance of drilling sites. Dome summit sites preserve continuous, undisturbed records of ancient ice, while locations away from domes risk basal disturbances, including folding, faulting, and layer mixing.
This research enhances our understanding of ice sheet dynamics and supports the development of improved dating models, contributing to studies of Earth's climate history over millennia.
How to cite: Fujita, S., Saruya, T., Miyamoto, A., Goto-Azuma, K., Hirabayashi, M., Hori, A., Iizuka, Y., Kameda, T., Ohno, H., Shigeyama, W., and Tsutaki, S.: An overview of the layered structure of the polar ice sheet based on crystalline textural properties of the Dome Fuji summit ice core, Antarctica, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21792, https://doi.org/10.5194/egusphere-egu26-21792, 2026.
Ice cores are exceptional archives of past climate variability, preserving forcing factors and proxies of the climate system’s response. Volcanic eruptions, when recorded as englacial tephra layers, provide insights into explosive volcanism, volcano–climate interactions, and enable long-range synchronization of paleoclimate records, provided the eruptive source is identified. Source attribution of far-travelled tephras requires geochemical characterisation of volcanic glass and comparison with known reference compositions. This task is complicated by the broad range of potential sources and the geochemical similarity of eruptive products. In this context, volcanic minerals, though less commonly used than glass, offer a valuable complementary tool for fingerprinting their source rocks.
More broadly, most analytical protocols rely on melting ice cores, compromising the preservation and future reuse of this important natural archive. As climate change poses increasing threat to global ice reserves, developing an innovative approach is critically needed.
Here, we present a novel, non-destructive Raman spectroscopy–based approach to analyse the mineralogy of visible tephra layers in ice cores. A tephra from Campbell Glacier, Antarctica (74°16′59″ S 164°10′52″ E), has been used to demonstrate advantages and pitfalls of this approach. The observed mineral assemblage is consistent with a strongly alkaline source and with its geochemical signature. This mineralogical dataset enables tephrochronological reconstructions and improves the precision and reliability of established analytical approaches for volcanic source fingerprinting.
How to cite: Rabassi, M., Andò, S., Delmonte, B., Artoni, C., Fiorini, D., Malinverno, E., and Maggi, V.: Raman non-destructive analysis of visible tephra layers in ice cores, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12832, https://doi.org/10.5194/egusphere-egu26-12832, 2026.
Impurities trapped within glacial ice serve as unique archives of past environments. This study presents results from imaging ice core samples collected from Antarctica, Greenland, and the Arctic using the IceSpec (VNIR) hyperspectral imaging (HSI) system. Image processing algorithms, developed with open-source Python libraries (e.g., numpy, photutils, scikit-image, and SPy) enable the quantification of trapped air bubbles, dust content, and other impurities. This work expands parameterization of ice core physicochemical properties.
HSI offers a robust, fast, high resolution and automated method that enhances traditional ice core analyses while introducing new capabilities. A key advantage is its non-destructive nature, which preserves full spectral information for subsequent impurity fingerprinting, chemical characterization and sample archiving.
This work was supported by National Science Foundation (NSF) grants 2149518 and 2149519, and by the Center for Oldest Ice Exploration (COLDEX), an NSF Science and Technology Center funded under grant NSF 2019719. We also acknowledge the logistical support provided by the NSF Antarctic Infrastructure and Logistics Program, the US Ice Drilling Program (supported by NSF Cooperative Agreement 1836328), the NSF Ice Core Facility, and the Antarctic Support Contractor.
How to cite: Kurbatov, A., Rumsey, R., Akiba, S., Beaudoin, H., Schaefer, J., Breton, D., Brook, E., Buizert, C., Fegyveresi, J., Fudge, T., Hargreaves, G., Labombard, C., Nunn, R., Royer, M., and Zhizhin, M.: Developing Hyperspectral Imaging Workflow for Ice Core Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15229, https://doi.org/10.5194/egusphere-egu26-15229, 2026.
Mercury is a contaminant of global concern, but anthropogenic impact on preindustrial mercury cycling in remote locations remained poorly constrained. Here we report a high-resolution record of the mercury concentration and accumulation flux over the Holocene, established by the analysis of the recently retrieved EastGRIP ice core from Greenland. We show that the Holocene ice core mercury record was shaped by a combination of volcanic eruptions, climate excursions, and in recent millennia anthropogenic activity. Our result suggests that human activity started to impinge on Greenlandic mercury cycling since at least 2000 years ago, much earlier than previously thought. We will also discuss the challenges encountered in establishing atmospheric mercury deposition history from the ice core record due to uncertainties associated with potential changes in post-depositional processes over the Holocene.
How to cite: Wang, F., Gao, Z., Oliveira, R., and Dahl-Jensen, D.: EastGRIP ice core mercury record over the Holecene: From the ice accumulation record to atmospheric depositional history , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4630, https://doi.org/10.5194/egusphere-egu26-4630, 2026.
Extending ice core records beyond 800 thousand years (kyr) is a pivotal goal in paleoclimate research. The Allan Hills Blue Ice Area, East Antarctica, provides a unique opportunity to meet this objective, with recent work recovering 6-million-year-old ice. The ice in this area demonstrates several peculiarities—such as strong layer thinning and folding—that warrant an in-depth investigation of its stratigraphy and the climate record it holds. Here, we present a high-resolution multi-measurement continuous flow analysis (CFA) on the upper 69 and 46 m from two shallow ice cores from the Allan Hills to evaluate these complexities.
Our CFA analysis measured methane, water stable isotopes, and particulate dust concentrations and size fractions, allowing us to characterize their variations and to assess the fidelity of the archive, i.e., how well environmental parameters are recorded and preserved in Allan Hills ice. We quantitatively compared the data structures of each climate element to the EPICA Dome C (EDC) climate record by evaluating the correlations and data distributions of each variable. Each climate parameter exhibits a narrower range of values than the EDC core, and distinct data distribution patterns that differed both between the Allan Hills cores and compared to EDC. The data revealed interglacial biases as evidenced by an overrepresentation of warmer climate states when compared to EDC. Discrete 40argon-dated sections from the two Allan Hills ice cores reveal age ranges from ~150-1200 kyr, with substantial age discontinuities and folding highlighting the complex stratigraphy of this ice. Our high-resolution investigation of this ice is a critical step toward better interpreting the discrete records from the Allan Hills, which extend beyond the 800 kyr continuous ice core record into the Pliocene, pushing our ice core records into unique and enigmatic parts of Earth’s climate history.
How to cite: Hudak, A., Banerjee, A., Buizert, C., Brook, E., Kalk, M., Steig, E., Davidge, L., Schauer, A., Brown, N., Kirkpatrick, L., Chalif, J., Osterberg, E., Miranda, M., Saltzman, E., Hishamunda, V., and Higgins, J.: Fidelity and stratigraphy of the Antarctic Allan Hills old ice archive from Continuous Flow Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8410, https://doi.org/10.5194/egusphere-egu26-8410, 2026.
The Antarctic ice sample record, collected since the 1960s, covers the past 1.2 million years continuously, and contains discontinuous “snapshots” up to 6 million years. Over 40 Antarctic ice cores have vastly advanced the understanding of past climate variations and will continue to tackle key paleoclimate question in the coming decades.
To obtain and further refine the discontinuous record older than 1.2 million years, ongoing efforts are targeting so-called blue ice areas. In these areas, complex ice flow patterns can trap extremely old ice, as demonstrated in the Allan Hills region (Transantarctic mountains). However, these complex flow patterns pose challenges in the search for and interpretation of ancient ice. To overcome these challenges and further unlock this paleoclimatic archive, blue ice research advances with: (i) systematic surface dating as a preliminary step to drilling; (ii) improving the understanding of age relationships between ice, dust, and meteorites; (iii) developing models that account for the specific physical properties of blue ice to identify and characterize the oldest trapped ice; and (iv) methods for the reconstruction of the paleoclimate signals preserved within this archive. In this perspective, we discuss past and current blue ice projects and contextualize the findings in the Antarctic paleoclimate record.
How to cite: Tollenaar, V. and Legrain, E.: A perspective on ancient Antarctic (blue) ice, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5512, https://doi.org/10.5194/egusphere-egu26-5512, 2026.
Blue ice areas have attracted growing interest over the past decade, notably following the recovery of ice older than the current record of deep ice core drilling, in the Allan Hills region of Antarctica (snapshots up to 6 million of years). In this study, we assess the suitability of flowline modelling for surface age prediction in blue ice environments. To this end, we perform 10,000 theoretical experiments covering a wide range of site conditions, using an ice-dynamical flowline model, to determine which factors most strongly favor the preservation of old ice at the surface. Our results show that a strong negative surface mass balance (i.e. high ablation) and slow surface velocities along the flowline are the primary controls on the emergence of old ice at the surface, whereas ice thickness and distance from the upstream accumulation zone play only secondary roles. Moreover, based on statistical and machine learning analyses, we illustrate that the occurrence of very old ice at the surface appears to be mostly correlated with exceptionally low surface velocities, with high ablation rates being insufficient on their own. We compare these findings with recently measured surface mass balance and surface velocities in the Sør Rondane Mountains blue ice areas (Dronning Maud Land, East Antarctica) to inform the selection of future ice core drilling site in the region.
How to cite: Legrain, E., Tollenaar, V., Pattyn, F., Izeboud, M., Ardoin, L., Fripiat, F., and Zekollari, H.: Identifying optimal drilling sites in Antarctic Blue Ice Areas using a flowline model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5661, https://doi.org/10.5194/egusphere-egu26-5661, 2026.
We present evidence of greenhouse gases produced in-situ via photochemical reactions in Antarctic blue ice. Within near-surface layers (< 4.6 m), the air in bubbles exhibit markedly elevated concentrations of CO₂, CH₄, and N₂O. Considering the upward advection of the ice strata, these excess gas species are inferred to have originated within recent decades or the past century. Analytical evidences indicate that these excess greenhouse gases are products of photochemical reactions. The isotopic signatures of CO₂ and CH₄ elucidate that the carbon precursors are both organic and inorganic constituents embedded in the ice matrix.
To elucidate the kinetic pathways, we plan to perform laboratory simulations involving UV irradiation of ice samples, followed by rigorous analyses of the generated gas phases. Additionally, synthetic bubbly ice with precise gas compositions and specific ionic dopants, is being utilized to isolate the variables governing these reactions. We contend that occluded gas bubbles act as receptive vessels that preserve photochemical derivatives, thereby amplifying the detectability of minute chemical alterations. Our near future investigations will also address the isotopic fractionation dynamics occurring between the parent substrates and the resultant greenhouse gases.
How to cite: Ahn, J., Lee, G., Han, J., Lee, S., Azharuddin, S., Oyabu, I., Peterson, J., Han, C., Hirabayashi, M., Brook, E., and Kawamura, K.: Photochemical Modification of Greenhouse Gas Concentrations in Antarctic Blue Ice, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15278, https://doi.org/10.5194/egusphere-egu26-15278, 2026.
81Kr (t1/2 = 229 ka) is a valuable isotope for radiometric dating of water and ice with a dating range from thirty thousand to over one million years. Based on laser cooling and trapping, the detection method Atom Trap Trace Analysis (ATTA) has enabled 81Kr analysis at extremely low isotopic abundance levels in the environment. Here, we present the realization of a new-generation ATTA system that overcomes previous large sample-size requirements, making it possible to date polar ice-core samples of ~1 kg with ages up to 1.5 Ma.
We demonstrate the field applicability of this system through successful 81Kr dating of two dated 1-kg ice-core samples from Taylor Glacier, Antarctica. Based on this validation, we apply 81Kr dating to ancient ice samples with unknown ages from both polar regions. In Antarctica, we dated basal ice from the RICE core providing constraints for the existence of the Ross Ice Shelf through the Last Interglacial. In Greenland, we dated basal ice from the GISP2 ice core, obtaining 81Kr ages which implies that the central Greenland Ice Sheet persisted through the prolonged warm period of Marine Isotope Stage 11. To further reconstruct history and extent of the Greenland ice sheet, dating of ice core samples from other drill sites in Greenland is currently ongoing.
These examples demonstrate that the presented sample size reduction for 81Kr dating enables absolute age determination for stratigraphically disturbed basal ice, providing valuable information on the history of polar ice sheets.
How to cite: Feng, X., Brook, E. J., Ritterbusch, F., Yang, G.-M., Severinghaus, J. P., Wang, J. S., Higgins, J. A., Zhao, L., Sun, L.-T., Harris, M., Bender, M. L., Bertler, N. A. N., Lin, Q.-S., Shackleton, S., Ferrick, T., Jiang, W., Jia, Z.-H., and Lu, Z.-T.: 81Kr Dating of 1 kg Polar Ice, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15595, https://doi.org/10.5194/egusphere-egu26-15595, 2026.
Earth’s energy imbalance (EEI) determines whether the planet experiences a net gain or loss of energy. The ongoing surge in atmospheric greenhouse-gas concentrations, caused by burning fossil fuels and land-use change, causes a positive EEI, which ultimately drives global warming. Today, most of this excess heat is taken up by the largest, fast-responding energy reservoir that is the surface ocean. On millennial to orbital timescales, by contrast, energy partitions between two considerably larger but slower-responding reservoirs: the global (deep, intermediate, and surface) ocean and the latent heat involved in growing and melting continental ice sheets. Ocean heat content (OHC) and global sea level, which mirrors ice sheet volume, are thus key metrics to assess the global energy balance during the Quaternary.
Past OHC can be reconstructed by analyzing noble-gas ratios in polar ice-core samples. This method makes use of the temperature-dependent and species-specific solubility of noble gases in seawater, as well as their inertness, due to which the total amount of noble gases in the ocean‐atmosphere system is conserved. Earlier studies mostly focused on the last glacial Termination and other periods of interest across the last glacial cycle. Here, we present data for an entire glacial cycle (MIS 9–7) together with data over the last four glacial terminations in millennial resolution.
By combining our OHC record with past sea-level reconstructions we obtain an EEI record spanning an entire glacial cycle. This EEI record shows the expected orbital-scale variability in response to the albedo and greenhouse gas feedback, with energy fluxes partitioning approximately equally between the ocean and ice sheet reservoirs. The EEI record also manifests strong millennial power. These millennial-scale EEI features are mirrored in the OHC record, whereas the ice sheet response is delayed and subdued, indicating that the ocean is the dominant millennial-scale energy reservoir. Millennial-scale EEI and OHC variability is closely linked with changes in AMOC strength, suggesting that ocean circulation modulates EEI and OHC across different climate states. Potential AMOC weakening under future global warming may thus add to the EEI anomaly for centuries to come.
How to cite: Grimmer, M., Traeger, H., Tinner, P., Baggenstos, D., Schmitt, J., and Fischer, H.: Earth’s energy imbalance across an entire glacial cycle (MIS 9–7) reconstructed from noble-gas ratios in ice cores, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3938, https://doi.org/10.5194/egusphere-egu26-3938, 2026.
Analysis of water isotopes (oxygen and hydrogen) in Antarctic ice cores has enabled reconstruction of Earth’s temperature over the last 800,000 years with the EPICA deep ice core (Dome C) and, soon, over 1.5 million years with the Beyond EPICA deep ice core (Little Dome C). In parallel, differences in fractionation between hydrogen isotopes and oxygen isotopes provided information about the water cycle in the past.
In particular, deuterium excess (dxs = δD − 8 * δ18O) has been developed to track evaporation and transport conditions from oceanic regions to the ice sheet. However, it is quite challenging to deconvolute source-related and transport-related effects. The 17O-excess (17O-excess = ln(δ17O+1) − 0.528×ln(δ18O+1)) is a less known second-order parameter, complementary to dxs, also expected to reflect the conditions encountered by the air mass.
Here we present the first long-term record of 17O-excess (from 41,520 to 800,000 years, with 2,447 data points) based on the analysis of the EPICA deep ice core to better understand the long-term variability of this proxy and its integration into high-latitudes climate variability.
In addition to variations over glacial–interglacial cycles, we observe a significant decrease of the 17O-excess over the Mid-Brunhes transition ~400,000 years ago. This 17O-excess record carrying information on the origin of the moisture precipitating in East Antarctica is compared with long-term reconstructions of sea surface temperature, Antarctic circumpolar current strength, and southern westerly winds to disentangle the effects of source changes and isotopic fractionation along transport pathways.
Measuring the 17O-excess record over such a long period, and compare it with other paleoclimatic records, offers the opportunity of better understanding the variability of this proxy, but also of deepening our understanding of the relationship between climate and water cycle changes at high latitudes.
How to cite: Samin, E., Landais, A., Combacal, T., Grisart, A., Jouzel, J., Masson-Delmotte, V., Minster, B., Prié, F., and Stenni, B.: First interpretation of 17O-excess variability over 800,000 years on the East Antarctic Plateau, based on EPICA Dome C deep ice core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4901, https://doi.org/10.5194/egusphere-egu26-4901, 2026.
Ice core derived records of the past atmospheric methane concentration ([CH4]) and its isotopic composition (δ13C-CH4 and δD-CH4) allow us to reconstruct its past variability and its link to changes in the climate system. During the last glacial cycle, [CH4] showed pronounced increases from glacial to interglacial conditions, but [CH4] also closely followed large and rapid millennial-scale warming events in the Northern Hemisphere associated with Dansgaard-Oeschger (DO) events, indicating the strong sensitivity of terrestrial biogeochemistry to (hydro-) climatic changes.
To better understand the climate-greenhouse gas feedback cycle and what controlled past atmospheric methane variability it is essential to quantify the response of the CH4 budget and terrestrial biogeochemistry to such abrupt climate variations. Such a budget provides a framework to infer the strength and temporal dynamics of individual CH4 sources (e.g. wetlands, biomass burning, geologic emissions). However, for most parts of the last glacial cycle a quantitative source attribution is missing or still a matter of debate.
Synchronized ice core records from both polar regions allow us to derive the Inter-Polar Difference in [CH4] reflecting latitudinal emission difference and are used to distinguish low and high latitude CH4 emissions. Another powerful tool to uncover source contribution to the global CH4 budget is provided by records of methane’s stable isotopic composition (δD-CH4, δ13C-CH4) as CH4 released by the various sources are associated with characteristic isotopic signatures and different sinks are connected to systematic isotope fractionations.
Here we present new δD-CH4 data from bi-polar ice cores (EDC, EDML and GRIP ice core samples) covering large parts of the last glacial cycle complementing our existing δ13C-CH4 record (Möller et al., 2013). We use δ13-CH4 and δD-CH4 as quantitative tracers of changes in the CH4 budget and interpret atmospheric signals in a simple CH4 stable isotope-enabled one-box model of the global CH4 cycle concentrating on the prominent DO-21interval between 86 kyr and 76 kyr. We derive quantitative estimates of plausible global CH4 source mix scenarios but also review in this context uncertainties arising from poorly constrained assumptions in the past. Limited knowledge of past isotopic source signatures of biogenic CH₄ sources (wetlands) and their latitudinal distribution introduces substantial uncertainty into reconstructions of the past methane budget. Because drivers of past changes remain poorly understood, uncertainties in these assumptions propagate into estimated CH₄ emissions. For the first time, dual-isotopic CH₄ records enable an evaluation of temporal changes. Building on the new dual-isotopic constraints, we go beyond previous studies and present a new Monte Carlo approach that simulates realistic past isotopic source signatures and assesses their impact on the inferred CH₄ budget.
How to cite: Mühl, M., Schmitt, J., Seth, B., and Fischer, H.: Improving the CH4 budget using new dual-isotope CH4 records over the last glacial cycle, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3718, https://doi.org/10.5194/egusphere-egu26-3718, 2026.
While air bubbles in polar ice cores preserve past atmospheric composition, the quantity of trapped air, known as Total Air Content (TAC), also carries significant paleoclimatic information. First applied to reconstruct past ice sheet elevation, TAC later became an orbital dating tool due to its correlation with local summer insolation. To address knowledge gaps and better understand TAC as an environmental proxy and as an orbital dating tool, we investigate the relationships between surface parameters, pore volume at close-off depth, and TAC changes at spatial and temporal scales.
We present and analyze a new dataset extending the EDC TAC record from 440 to 800 ka, as well as new TAC records from TALDICE and EDML covering the last glacial-interglacial cycle. We combine these new datasets with a compilation of published TAC data from deep and shallow ice cores across Antarctica and Greenland to explore the influence of surface climate parameters controlling the changes in TAC. Our spatial-scale analysis demonstrates that present-day TAC values relate primarily to atmospheric pressure and elevation. When examining pore volume at close-off (i.e. TAC values corrected for ideal gas law effects), we evidence a correlation with local half-year summer insolation for sites located in East Antarctica, suggesting a direct control of local insolation on firn densification in this region. Temporal-scale analyses on TAC records covering at least 45 ka confirm that TAC records contain an orbital-scale signature of local insolation but also show that local summer insolation alone cannot capture the full TAC variability. Multiple linear regression analyses incorporating both local insolation and reconstructed surface temperatures or accumulation better predict the observed TAC temporal changes, particularly during large glacial terminations. Our new EDC high-resolution record also reveals significant millennial-scale TAC changes during these glacial-interglacial transitions, highlighting that in addition to orbital-scale impacts of local summer insolation, millennial-to-multi-millennial-scale changes in surface climate parameters also influence temporal TAC changes. Our findings have implications for the use of TAC as an orbital dating tool as they suggest that performing an orbital tuning between TAC and local insolation without accounting for additional surface climate controls could introduce dating uncertainties of 1–4 ka. Building on these results, we present a new TAC profile measured on the Beyond EPICA Oldest Ice Core (BEOIC) core between 2438 and 2485 m depth and evaluate its potential for providing orbital age constraints on ice older than 800 ka and up to 1.2 million years.
How to cite: Guilluy, H., Capron, É., Parrenin, F., Lipenkov, V., Schmitt, J., Wu, Z., Yin, Q., Klüssendorf, A., Landais, A., Martinerie, P., Seth, B., Fischer, H., Jacob, R., Teste, G., Bauska, T. K., Venkatesh, J., and Raynaud, D.: On the link between Total Air Content (TAC) changes and local surface climate conditions in Greenland and Antarctica, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10076, https://doi.org/10.5194/egusphere-egu26-10076, 2026.
Posters on site: Mon, 4 May, 16:15–18:00 | Hall X5
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 δ18Oatm. 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 ( t1/2 = 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 δ18Oice 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.
