Orals: Mon, 4 May, 08:30–12:25 | Room F1
Polar ice cores provide valuable insights into past environmental and climatic variability. The recently drilled Beyond EPICA ice core is believed to preserve the climate history of the past 1.5 million years (Ma). To effectively interpret the climatic information retrieved from this ice core, it is imperative to establish a precise chronology, assigning an age to each individual depth level. Dating old ice strongly relies on orbital tuning of the isotopic and elemental composition of atmospheric oxygen and nitrogen, extracted from air bubbles enclosed within the ice to variations in solar insolation. However, extensive layer thinning and enhanced vertical gas diffusion in the deep section of an ice core can substantially impact the signal preservation of these dating tools. Recently obtained data of δ18O of atmospheric O2 (δ18Oatm) from the deepest 100 metres, possibly spanning from ~0.7 to 1.5 Ma, reveal a significant attenuation of the orbital signal amplitude prior to 1.1 Ma, challenging precise orbital dating. Diffusion effects however does not impede reconstruction of the long-term trend in O2 atmospheric concentration and isotopic composition. While δ18Oatm remains stable throughout this period, the relative concentration of atmospheric O2 distinctly decreases around 0.9 Ma. Although this long-term trend with time aligns with previous observations during more recent periods, the natural variation of O2 concentration in the atmosphere potentially poses an additional difficulty for orbital dating accuracy in which the δ(O2/N2) orbital signal is driven by local insolation. We propose using δ(Ar/N2) as a supplementary dating tool, as this ratio exhibits a similar relationship with local insolation while being independent of oxygen. Further, the new deep Beyond EPICA δ(Ar/N2) record reveals a higher signal amplitude in the deepest section compared to δ(O2/N2) because Ar is expected to diffuse less than O2, thereby enhancing the potential for orbital dating. Thus, integrating atmospheric δ18O, δ(O2/N2), and δ(Ar/N2) can facilitate to establish a chronology for the Beyond EPICA ice core, provided that high-precision and high-resolution data are ensured.
How to cite: Klüssendorf, A., Brückner, L., Casado, M., Brugère, E., Baubant, L., Prié, F., Fourré, E., Combacal, T., and Landais, A. and the Beyond EPICA Community: Evaluating Signal Attenuation and Gas Diffusion Impacts on Orbital Dating and Atmospheric Evolution of O2 Concentration in the Beyond EPICA Ice Core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5532, https://doi.org/10.5194/egusphere-egu26-5532, 2026.
The new Beyond EPICA Antarctic ice core plays a crucial role in deciphering the contribution and behaviour of atmospheric proxies before and during the Mid-Pleistocene transition. In order to fully understand and correctly interpret the connection between different proxies both from the ice and gas phase of the ice core, as well as from other climactic archives, an accurate chronology of the entire ice core is needed. This can be achieved with orbital dating, exploiting the unique relationship between insolation and some of the isotopic and elemental ratios of atmospheric constituents such as nitrogen, oxygen, and argon of the air bubbles trapped in the ice. Using new atmospheric δ18O of O2, δ(O2/N2), and δ(Ar/N2) data in the depth range between 2400-2507 m from the Beyond EPICA ice core, we propose new chronological tie points, which are independent of alignment to marine archives, for the construction of a gas and ice chronology of the Beyond EPICA ice core before 800,000 years before present.
Additionally, δ15N of N2 measurements provide a way to quantify variations in the lock-in depth and the age difference between the ice and the gas phase (Δage) over the entire time period covered by the Beyond EPICA ice core. The new δ15N dataset provided here is key for the coherence between the ice and gas timescale. Moreover, we use the expected depth difference (Δdepth) between the same event recorded in the ice phase (through δD or δ18O of the ice) and in the gas phase (through δ15N of N2) as a test for the integrity of the stratigraphy: a concomitant change in δD or δ18O of the ice and δ15N of N2 may be the signature of an ice hiatus or folding event.
How to cite: Brückner, L., Klüssendorf, A., Baubant, L., Brugère, E., Prié, F., Parrenin, F., Capron, E., Minster, B., Fourré, E., Combacal, T., Nomade, S., Bassinot, F., and Landais, A. and the Beyond EPICA water isotope team: Orbital Dating of the Beyond EPICA Ice Core and Identification of Possible Stratigraphic Disturbances, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7309, https://doi.org/10.5194/egusphere-egu26-7309, 2026.
The Beyond EPICA Oldest Ice (BE-OI) ice core provides a unique opportunity to investigate geomagnetic and solar variability across the Mid-Pleistocene Transition (MPT) using cosmogenic nuclides. We present a new high-resolution (15 cm) 10Be concentration profile measured continuously between 2412 and 2502 m depth, representing the oldest and longest cosmogenic nuclide records obtained from an ice core.
Preliminary results reveal an exceptionally well-preserved signal of the Brunhes-Matuyama reversal, the last reversal, that occurred approximately 780 k years ago. The 10Be BE-OI profile across the Brunhes-Matuyama reversal demonstrates a significantly improved signal-to-noise ratio compared with the EPICA Dome C (EDC) ice core which exhibited sporadic 10Be spikes disturbing the geomagnetic record.
The continuous 10Be record allows us to provide valuable dating horizons by identifying geomagnetic reversals and excursions and by direct comparison with authigenic marine 10Be records. Ongoing work focuses on exploiting this record to reconstruct variations in geomagnetic field intensity and to evaluate its consistency with existing marine relative paleointensity (RPI) and authigenic 10Be stacks.
In parallel, we investigate the potential contribution of solar modulation to the 10Be signal based on the differences between RPI and BE-OI 10Be records. We discuss the perspectives offered by the BE-OI record for disentangling, for the first time, geomagnetic and solar influences on cosmogenic nuclide production across the MPT. These results will provide valuable information on geomagnetic field intensity and solar modulation during a key transition in Earth's climate system.
How to cite: Lamothe, A., Baroni, M., Auriol, E., Guillou, V., Aster, T., Bard, E., Rittberger, R., Adolphi, F., Muscheler, R., and Community, B. E.: The Oldest Antarctic 10Be Ice Core Record: New Insights Into Geomagnetic and Solar Variability Across the MPT, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13238, https://doi.org/10.5194/egusphere-egu26-13238, 2026.
Particulate mineral dust is a critical part of the Earth’s climate system, modulating radiative balance and providing a crucial source of micronutrients to surface oceans. In ice cores, mineral dust also serves as a key proxy for past atmospheric dynamics - controlling dust mobilization and transport - as well as hydroclimate variability, which affects the atmospheric residence time of dust in addition to emission strength in the source regions. Previous studies, including those from the 800,000-year EPICA Dome C ice core, have demonstrated a close coupling between dust particle number concentrations in ice cores and glacial-interglacial climate variability, with consistently higher dust concentrations during cold glacial periods. The new Beyond EPICA-Oldest Ice Core (BE-OIC: 75º 18’ S, 122º 27’ W) extends the existing ice core particulate dust record back through the Mid-Pleistocene Transition (MPT), providing new constraints on this enigmatic period in Earth’s climate history.
We present the first continuous record of particulate mineral dust particle size and particle number distributions from the new BE-OIC, spanning from 700,000 years BP through the Mid-Pleistocene Transition. Physical characteristics of individual dust grains were measured online by the University of Bern during the Continuous Flow Analysis measurement campaign at the British Antarctic Survey using dual Classizer One Single Particle Extinction and Scattering instruments (EOS) and an Abakus laser particle sensor (Klotz GmbH), enabling characterization of particle concentration, dust size but also its refractive index over a wide range of diameters (0.2–10 µm). The latter is crucial as it allows us for the first time to resolve the submicrometer mode in the number size distribution.
Consistent with earlier work on the EDC ice core, the new BE-OIC record shows elevated dust concentrations during glacial periods both before, during and post MPT. However, the amplitude of glacial-interglacial variability is reduced relative to the past 800,000 years. In addition, modal particle diameters in the number size distribution are smaller during glacials compared to interglacials, indicating enhanced contributions from long-distance dust transport during the colder climate states. We investigate the processes that lead to dust size and number changes, including how reduced glacial intensity pre-MPT may have impacted dust source regions and the atmospheric lifetimes of dust particles. Together, these observations indicate changes in dust source-to-sink dynamics that have implications for biogeochemical cycles in the Southern Ocean and atmospheric dynamics during the MPT.
How to cite: Jackson, S., Fischer, H., Lee, G., Spelsberg, S., Delmonte, B., Humby, J., Tetzner, D., Thomas, E., and Wolff, E.: A continuous record of particulate mineral dust from the new Beyond EPICA Oldest Ice Core: paleoclimatic implications of variability in dust physical and optical properties, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9326, https://doi.org/10.5194/egusphere-egu26-9326, 2026.
Mineral dust concentration and grain size preserved in polar ice cores serve as critical paleoclimate proxies spanning the Holocene and Pleistocene epochs. These parameters yield valuable information about past environmental conditions in dust source regions, atmospheric dust loading and transport dynamics, exhibiting pronounced variability across glacial–interglacial cycles. The Antarctic dust deposition record derived from the ∼800.000 years old EPICA Dome C (EDC) ice core has now been extended further back into the Early Pleistocene through analysis of the Beyond EPICA-Oldest Ice Core (BEOIC). Here we present the preliminary Coulter Counter-derived dust concentration (0.6-18 μm range) and volume-size data from BEOIC for the period predating the EDC record, and compare them with available marine dust records. Dust concentration and grain size variability in the oldest ice enable the identification of glacial and interglacial periods, with characteristic size distributions showing relatively coarser particles during interglacials and finer particles during glacials.
The use of aeolian dust as a paleoclimatic proxy in ice cores assumes that englacial processes preserve the original physical and chemical signals. However, this paradigm has been partially challenged by evidence of in situ alteration processes that induce physical and geochemical (including mineralogical) modifications within the ice. The extent and nature of these processes in the BEOIC are currently under investigation. Preliminary observations are presented and compared with findings from other Antarctic ice cores (TALDICE, RICE) to evaluate the reliability of paleoclimatic signal preservation in the oldest ice sections.
How to cite: Delmonte, B., Di Stefano, E., Fischer, H., Jackson, S., Lanci, L., Lee, G., and Rabassi, M.: Dust Concentration and grain size record from the Beyond EPICA oldest ice: implications for dust preservation in the oldest sections of the core., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4244, https://doi.org/10.5194/egusphere-egu26-4244, 2026.
The Beyond EPICA–Oldest Ice Core (BE-OIC) project successfully recovered the oldest continuous Antarctic ice core, extending back to at least 1.2 million years. This landmark achievement provides an unprecedented opportunity to address long-standing questions regarding the mechanisms underlying the Mid-Pleistocene Transition (MPT) (Barbante & Beyond EPICA Team, 2025). Among others, this core could be used to study past changes in atmospheric aerosol composition and here, in particular the geochemical composition of mineral dust.
However, deep ice is increasingly recognized as a “geochemical reactor”, in which primary mineral impurities undergo post-depositional transformations into secondary phases such as jarosite (Baccolo et al., 2021; Lanci et al., 2025). These alterations pose a major challenge for extracting reliable paleoclimate signals from the analysis of mineral dust trapped into old ice. As such, to avoid misinterpretation of dust-related proxy records, we need to better constrain the nature and extent of deep-ice geochemical processes.
Here, we investigate post-depositional geochemical alterations in the EPICA Dome C (EDC) ice core through elemental analysis of ten sections (55 or 110 cm long) spanning the depth of 282 to 3137 m. For the first time, we apply single-particle inductively coupled plasma time-of-flight mass spectrometry (sp-ICP-TOFMS) coupled to the Bern continuous flow analysis (CFA) system to EDC ice core analysis. This approach allows the separate quantification of dissolved and particulate elemental fractions and enables the characterization of the chemical composition of individual particles. Our results reveal extensive dissolution of primary minerals (e.g. hornblende-like phases), accompanied by the precipitation of secondary insoluble and soluble sulfates (e.g. jarosite, alunite), and possibly other Fe-oxide phases. These transformations are likely driven by localized acidic and oxidative microenvironments that develop during the metamorphism of deep ice, depending, to first order, on the growth of ice grains.
Our findings provide new insights into post-depositional geochemical processes in deep Antarctic ice and are crucial for ensuring robust paleoclimate reconstructions from dust records in the oldest ice cores, including BE-OIC. Notably, significant geochemical alteration is observed in EDC sections at temperatures of approximately −15 °C and above, indicating that, at the conditions encountered at EDC, these changes emerge at around −15 °C and intensify under warmer conditions. Given that BE-OIC ice of comparable age to EDC is colder while exhibiting similar dust concentration, the BE-OIC ice core may preserve a less geochemically altered, and therefore higher-quality, dust archive for periods already covered by the EDC record (<800 ka). On the other hand, portions of the BE-OIC stratigraphy extend to substantially greater ages, implying longer residence times in ice and a higher potential for post-depositional alterations.
How to cite: Lee, G., Erhardt, T., Larkman, P., Zeppenfeld, C., Jackson, S., Delmonte, B., Baccolo, G., Bohleber, P., and Fischer, H.: Post-depositional geochemical processes in EPICA Dome C ice: implications for BE-OIC dust analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7071, https://doi.org/10.5194/egusphere-egu26-7071, 2026.
Which parts of the oldest ice-core water-isotope record can be trusted as a climate archive, and at what temporal resolution is the climatic information preserved?
The water-isotope record from the Beyond EPICA ice core represents the oldest continuous Antarctic ice-core climate archive, extending back to ~1.5 million years and uniquely covering the Mid-Pleistocene Transition. However, the deepest sections of ice cores are commonly affected by ice-flow-induced deformation that can distort the original stratigraphy. In addition, local depositional and post-depositional processes, as well as isotopic diffusion, progressively alter and smooth the climatic signal preserved in water isotopes.
Here, we assess the integrity and effective resolution of the Beyond EPICA water-isotope record by analysing its variability and comparing statistical properties of the measured signal with expectations derived from younger interglacials, other paleoclimate archives, and theoretical estimates of isotopic diffusion. This analysis is complemented by Dielectric Profiling (DEP) and optical line-scan data, which provide independent constraints on stratigraphic continuity and ice-core integrity. Together, these approaches allow us to begin assessing which parts of the Beyond EPICA record between 1.0 and 1.5 million years retain coherent climatic information, and to place first-order constraints on its temporal resolution.
How to cite: Laepple, T., Hörhold, M., Jansen, D., Weikusat, I., Freitag, J., Wilhelms, F., Behrens, M., Meyer, H., Steen-Larsen, H. C., Landais, A., and Shaw, F. and the Beyond-EPICA isotope consortium: Integrity and Interpretation of the Beyond-EPICA Oldest Ice core isotope record between 1 and 1.5 Mio years, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20176, https://doi.org/10.5194/egusphere-egu26-20176, 2026.
Halogens (Br, I) and their enrichment relative to seawater abundance preserved in polar ice cores are powerful tracers for reconstructing past sea-ice dynamics and marine primary productivity. Within the framework of the Beyond EPICA Oldest Ice (BEOI) project, we present a new halogen concentration record derived from discrete ice core samples. Analytical measurements were performed in Italy (ISP-CNR, Ca’ Foscari University), focusing on the relatively stable climatic conditions of the Holocene and on the Mid-Pleistocene Transition (MPT).
The Holocene record, combined with previously published datasets, provides a critical baseline for understanding the environmental processes and transport mechanisms controlling halogen deposition on the central Antarctic plateau. To validate the halogen signal, we investigate the behaviour of bromine and iodine measured in the Younger Ice section of the BEOI ice core during the Holocene, comparing these records with independent paleoclimatic parameters from earlier studies, including temperature reconstructions (ΔT), stable water isotopes (δD), and sea surface temperatures (SST). These comparisons support the interpretation of halogen variability as a proxy for changes in sea-ice conditions.
While the Holocene analysis aims to constrain the halogen signal using well-established climatic parameters, the primary objective of the Beyond EPICA mission is to extend this approach back to 1.5 million years. As drilling reaches the deepest sections of the BEOI ice core, halogen records offer a unique opportunity to investigate changes in sea-ice dynamics across the MPT, when Earth’s climate system transitioned from a dominant 41-kyr to a 100-kyr glacial cyclicity. Ongoing chemical analyses of the oldest ice will help assess whether sea-ice feedbacks played a causal role in the emergence of the 100-kyr cycles or primarily acted as an amplifier of late-Pleistocene glacial intensification.
How to cite: Chelli, G., Bruschi, F., Cappelletti, D., Severi, M., Traversi, R., Di Stefano, E., Spagnesi, A., Raspagni, V., Stenni, B., Barbaro, E., Roman, M., Venier, C., Cairns, W., Delmonte, B., Barbante, C., Petroselli, C., and Spolaor, A.: Halogen Records from the Beyond EPICA Ice Core: Insights from the Holocene to the Mid-Pleistocene Transition, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19245, https://doi.org/10.5194/egusphere-egu26-19245, 2026.
Oxidation products of biogenic volatile organic compounds, such as monoterpenes and isoprene, are widely used to investigate variability in biogenic emissions and atmospheric transformation processes. Quantifying such tracers in ice-core matrices remains challenging because concentrations are ultralow and results can be affected by matrix effects and contamination. Here, we developed a targeted ultratrace LC–MS³ method using a SCIEX QTRAP 5500+ to enhance sensitivity and selectivity for five established SOA markers: cis-pinonic acid, pinic acid, keto-pinic acid, 3-methyl-1,2,3-butanetricarboxylic acid (3-MBTCA), and 2-methylerythritol (2-ME). Method performance was evaluated using procedural blanks and spike-recovery experiments, yielding compound-specific reporting limits of 0.01–0.05 ppt (limits of detection, LOD) and 0.1–0.25 ppt (limits of quantification, LOQ); instrument repeatability based on batch quality-control injections was 5–8% RSD.
The method was applied to meltwater fractions from the oldest section (>700,000 years ago) of the Beyond EPICA ice-core collected sequentially within each core section, resulting in 878 analysed fractions from 183 sections spanning 2399.0–2581.8 m (≈0.66 to ≥1.47 Ma BP, modelled). Concentrations are reported as ppt in meltwater following direct analysis (no preconcentration). Pinic acid was detected above the LOD in 87% of analysed fractions and quantified above the LOQ in 62%, with concentrations ranging from 0.87 to 5.83 ppt (mean 2.19 ppt). 3-MBTCA was detected in 70% of fractions and quantified in 66%, with concentrations of 0.103–0.612 ppt (mean 0.196 ppt). In contrast, cis-pinonic acid and 2-ME were below the LOQ, 0.1 ppt, while keto-pinic acid was not detected in the analysed ice-core samples.
These first measurements, placed within a preliminary age framework, demonstrate quantification of biogenic SOA tracers in Beyond EPICA ice-core at ultratrace levels. Ongoing work will integrate these data with co-measured glaciochemical tracers to evaluate transport, deposition and post-depositional effects, and to assess the potential of these compounds as proxies for past biogenic emissions and atmospheric oxidative processing.
How to cite: Kolawole, T. and the Beyond EPICA: Temporal variability of ultratrace biogenic secondary organic aerosol markers in the oldest ice from Beyond EPICA, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21228, https://doi.org/10.5194/egusphere-egu26-21228, 2026.
Marine productivity in the Southern Ocean is thought to exert a key control on atmospheric CO2 concentrations in the past, present, and likely into the future. However, understanding how marine productivity responds to changes in ice sheet size and sea ice extent is challenging due to the limits of the observational record and the sensitivity of marine sediment core paleo-productivity records to the frontal shifts which accompany major climate changes. Sulfur isotopes in Antarctic ice cores provide a valuable new means of reconstructing past changes in Southern Ocean productivity as they enable the quantification of the contribution of different sulfate sources through isotope mass balance. Marine biological productivity is the major source of sulfate to the Antarctic ice sheet, and quantifying how that source has varied through time allows for a regionally integrated record of Southern Ocean primary productivity. Here we apply this method over the Super-Interglacial MIS31 and contrast it with more recent interglacials to investigate the response of Southern Ocean primary productivity to higher temperatures and a collapsed West Antarctic Ice Sheet.
How to cite: Burke, A., Sun, Y.-J., Prabhat, P., Rhodes, R., Hansson, M., Yang, M., Sugden, P., Innes, H., Pryer, H., Savarino, J., Fischer, H., Wolff, E., and Thomas, L. and the Beyond EPICA Oldest Ice Core Impurities CFA Team: Southern Ocean Marine Productivity across the Super-Interglacial MIS31 Reconstructed from Sulfur Isotopes from the Beyond EPICA Ice Core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20717, https://doi.org/10.5194/egusphere-egu26-20717, 2026.
The Mid-Pleistocene Transition (MPT; 1.25 – 0.8 Myr) marks a transition from the “41-kyr world”, in which the Earth alternated between cold and warm periods about every 41,000 years, to the “100-kyr world” in which the Earth remained predominantly under glacial conditions but was punctuated every 80,000 to 120,000 years by interglacial periods. Variations in orbital forcing, the “pacemaker of the ice ages”, are stable across the MPT and thus cannot be invoked as a driver of this transition. Thus, most hypotheses call upon a forcing that drives a secular change, a feedback in the Earth system that changes/emerges, or a combination of the two.
One hypothesis for the MPT suggests that a long-term decline in (glacial) atmospheric CO2 levels led to a cooling, facilitating the formation of extensive ice sheets in North America and a sea-level drop of approximately 70 m (Bintanja & van de Wal, 2008). Accordingly, decreasing atmospheric CO2 concentration may have played a central role in driving this global cooling. Despite recent advances in marine and ice core CO₂ reconstructions (Nuber et al., 2025; Marks Peterson et al., 2025) the change of greenhouse gas forcing across the MPT remains uncertain for CO2.
In order to investigate the role of atmospheric CO2 across the MPT, greenhouse gases and the stable carbon isotopic composition of CO2 (δ13C-CO2) were measured on discrete ice core samples from the Beyond EPICA ice core. For this purpose, a coupled Laser induced sublimation extraction – Quantum Cascade laser Absorption Spectrometer (LISE-QCLAS) was used, allowing the simultaneous and semi-continuous extraction and measurement of CO2, CH4 and N2O as well as δ13C-CO2 on air samples of only 1 – 2 mL, corresponding to 10 – 15 g of ice.
This talk will present the first ice core data capable of capturing glacial–interglacial variations in atmospheric CO₂ across the MPT. Additionally, we will present the first unconditionally pristine measurements of δ13C-CO2 during the 41-kyr world. These data will allow us to explore the underlying biogeochemical processes that may be responsible for the new modes of atmospheric CO2 variability we have observed.
How to cite: Krauss, F., Schmitt, J., Bauska, T., Capron, E., Grilli, R., Heiserer, R., Silva, L., Stocker, T., Fischer, H., and Beyond EPICA community, T. E.: The first coarse-resolution Beyond EPICA CO2 record covering the Mid-Pleistocene Transition: Insights from long-term carbon-cycle dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13891, https://doi.org/10.5194/egusphere-egu26-13891, 2026.
Understanding the drivers of the Mid-Pleistocene Transition (MPT) remains one of the most challenging problems in palaeoclimate. One unfulfilled prerequisite for tackling this problem is a comprehensive view of greenhouses gases (GHGs) across the MPT. The Beyond EPICA Oldest Ice project and other ice core efforts are now focused on extending the ice core record of GHGs through the MPT. As the new data emerges, it is useful to define a set of testable hypotheses - in this case, using predictions of GHGs across the MPT.
Most work on extending GHGs beyond the current ice core record have focused solely on predicting atmospheric CO2, although it is recognized that the combined radiative impact of CH4 and N2O could be of overlooked importance. The methods vary in complexity from statistical approaches using ocean sediment data - to box modelling efforts with prescribed forcings - to inversion methods targeting proxy data with a hierarchy of models - to earth system modelling with minimal (but none-the-less important) assumptions about external forcings.
Here we will build up an objective overview of these predictions. First, we review previous work from the literature. Second, we explore some new statistical models for all three GHGs, with a particular focus on utilizing high-resolution sediment records that capture millennial- and orbital-scale variability (Hodell et al., 2023) as well as highlighting the implications of new estimates of global surface temperature and ice volume (Clark et al., 2024). Finally, we provide novel histories using a combination of box model and published climate model data (Yun et al., 2023) that also go beyond predicting just CO2 and allow us to discuss coeval changes in CH4, N2O and δ13C-CO2.
This synthesis will provide one possible template for interpreting the new datasets that will be presented elsewhere. In particular, we will breakdown the various hypotheses in terms of changes in the mean and range of variability over the past 1.5 million years (i.e. the changes in overall mean, the glacial minima, and interglacial maxima). Furthermore, we will investigate how covariations of greenhouse gases concentration and isotopic composition can constrain the nature of biogeochemical feedbacks operating in the earth system across the MPT.
References
Clark, P.U, et al. (2025) Global mean sea level over the past 4.5 million years. Science 390, eadv8389, DOI:10.1126/science.adv8389
Hodell, D. A.,et al. (2023) A 1.5-million-year record of orbital and millennial climate variability in the North Atlantic, Clim. Past, 19, 607–636, https://doi.org/10.5194/cp-19-607-2023.
Yun, K.-S.,et al. (2023) A transient coupled general circulation model (CGCM) simulation of the past 3 million years, Clim. Past, 19, 1951–1974, https://doi.org/10.5194/cp-19-1951-2023
How to cite: Bauska, T., Krauss, F., Mühl, M., Soussaintjean, L., Silva, L., Heiserer, R., Fischer, H., Schmitt, J., Stocker, T., Capron, E., Fain, X., Grilli, R., Rhodes, R., and Blunier, T.: A challenge for Beyond EPICA Oldest Ice: Predictions of greenhouse gases across the MPT, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18402, https://doi.org/10.5194/egusphere-egu26-18402, 2026.
Under the auspices of the NSF Center for Oldest Ice Exploration and previous projects, multiple seasons of shallow ice core drilling in the Allan Hills Blue Ice Area have yielded ice samples as old as 6.7 Ma, and numerous younger samples beyond the current 800 ka limit of the traditional ice core record. The complex stratigraphy of the existing cores does not allow continuous time series. Instead, “snapshots” have been created by dating over 300 individual samples (with more coming) using the deficit in 40Ar compared to modern air, and analyzing those samples for a range of environmental parameters. Parallel efforts are using continuous flow analysis, continuous electrical conductivity measurements, geophysical observations and surface transects to further understand the preservation and stratigraphy of environmental records in this unique region. This presentation will review recent results including evolving data sets from ice cores collected in the last two years. Primary observations include 1) long term Antarctic cooling of up to ~12 ˚C over the last 6 Ma based on the stable isotopic composition of the ice; 2) long-term mean ocean cooling over the last 3 Ma based on atmospheric noble gas ratios, with a prominent period of cooling coincident with the Plio-Pleistocene transition (~2.7 Ma) and steady temperatures across the mid-Pleistocene transition (1.2-0.8 Ma); 3) atmospheric CO2 concentrations of less than 300 ppm in pristine ice back to 2.7 Ma, corroborated by similar levels reconstructed from ice samples affected by respiration near the glacier bed based on corrections using carbon isotopes or independent constraints based on mass independent fractionation of isotopes in O2; 4) moderate atmospheric methane levels back to 3 Ma (generally less than 600 ppb) with evidence for biologically produced methane in samples near the glacier bed; 5) age reversals and inclined layering from 3 dimensional electrical and chemical measurements, and evidence for both pristine glacial ice and interactions with the glacier bed that alter the ice chemistry. These emerging new Antarctic ice core records are enhancing scientific understanding of Plio-Pleistocene climate and planetary evolution. Ongoing efforts in method development, ice coring, and geochemical analysis will continue to provide new insights from this enigmatic and challenging ice archive.
How to cite: Brook, E. and the NSF Center for Oldest Ice Exploration Ice Coring and Analysis Participants: Pleistocene to late Miocene ice core records of climate and atmospheric composition from Allan Hills, Antarctica, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8430, https://doi.org/10.5194/egusphere-egu26-8430, 2026.
Reconstructing past CO2 concentrations is essential to understanding paleoclimates. However, the CO2 record beyond the 805-ky ice core is insufficient to understand the relationship between CO2 and climate. Results from new ice cores and blue ice samples are highly anticipated. Here, we present the proxy CO2 record from the last 2.6 million years including the Mid-Pleistocene Transition, as determined by the δ13C values of sedimentary leaf waxes at IODP Site U1445, which reflect changes in the C3/C4 vegetation ratio in East Peninsular India. Our results show that interglacial CO2 levels in the early Pleistocene were lower than preindustrial levels. Higher CO2 levels occurred during super-interglacial periods. CO2 covaries with benthic δ18O on the orbital timescale. A strong coupling continued throughout the Pleistocene. Interglacial CO2 variation shows longer cycles averaging ~300 kyr, with several glacial cycles bunched together. A cycle begins with benthic δ18O and δ13C maxima in a glacial period, followed by an abrupt increase and subsequent decrease in interglacial CO2 levels. This suggests that the collapse of large ice sheets triggered the release of accumulated ocean carbon into the atmosphere. The size of the glacial ice sheets and the accumulation of oceanic carbon controlled the extent of deglacial CO2 release.
How to cite: Yamamoto, M., Irino, T., Szarek, R., Seki, O., Abe-Ouchi, A., and Yoshimori, M.: Reconstructed CO2 variability over the entire Pleistocene inferred from sedimentary leaf wax carbon isotopes from the Bay of Bengal, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6220, https://doi.org/10.5194/egusphere-egu26-6220, 2026.
The Mid-Pleistocene Transition (MPT) represents a fundamental shift in the operation of Earth’s climate system, yet the role of CO2 in this transition is uncertain. Prior to the MPT, the climate system was paced by the ~40 kyr obliquity cycle, with available CO2 reconstructions, temperatures, and ice volume all coupled to orbitally-forced changes in solar energy at high latitudes. Following the MPT, this relationship breaks down, with Northern Hemisphere ice sheets persisting through obliquity maxima in a series of “skipped terminations”, leading to longer glacial periods with larger ice sheets. Here we examine the role of CO2 over the MPT, using high resolution boron isotope data from 3 sediment cores, spanning the Atlantic, Pacific, and Indian Oceans. These records show excellent agreement with the ice core record in their younger portions, and striking consistency between sites, supporting the robustness of our reconstruction of atmospheric CO2. We find that CO2 and benthic oxygen isotopes remain largely coupled through the MPT, with limited CO2 rise during the skipped terminations around MIS 36 and 34, notably low CO2 during the deep glaciation of MIS 22 (the “900 ka event”), and notably high CO2 during the “super-interglacial” of MIS31. This underscores the key role of CO2 in glacial and interglacial climate states. In addition, it highlights that the mechanisms governing glacial-interglacial CO2 change, which are thought to be largely centred on the Southern Ocean, are not forced by orbital changes alone, but must be linked to land ice volume, as the only feature of the climate system with the inertia to persist through orbital insolation peaks. This implies the existence of teleconnections between Northern Hemisphere ice volume and Southern Ocean CO2 storage, and we outline potential mechanisms by which this might be achieved.
How to cite: Rae, J., Nuber, S., Chalk, T., Ji, X., Scherrenberg, M., Heaton, T., Zhang, X., Stap, L., Trudgill, M., Block, H., Jian, Z., Xu, C., Kobata, K., Andersen, M., Barker, S., Yu, J., and Foster, G.: Continuous CO2 reconstruction across the MPT from boron isotopes informs mechanisms of glacial CO2 change, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20791, https://doi.org/10.5194/egusphere-egu26-20791, 2026.
The climate evolution over the Pleistocene (last 2.6 Myr) is characterised by a sequence of cold glacials that are interrupted by warmer interglacial phases. These glacial-interglacial cycles are expressed in changes in global ice volume, ocean temperature, and other parameters that serve as proxies to infer land and ocean processes or to provide information about radiative forcing changes.
The Mid-Pleistocene Transition (MPT; 1.2-0.9 Myr) is characterised by the transition from 41 kyr cycles to about 100 kyr cycles and likely a trend toward colder glacial periods. The Mid Brunhes (MB) marks a climate transition at about 450 kyr after which the interglacial intensity (e.g. temperatures and greenhouse gas concentrations) increased. Consolidated explanations of the causes of both the MPT and the MB are lacking. Internal climate dynamics or feedback mechanisms are required since frequencies and the power of orbital parameters did not systematically change over the last 1.2 Myr.
For the MPT, two main classes of explanations have been put forward to account for the advent of the 100-kyr cycles. One argues that the ice sheets grew larger because the glacial climate became colder, driven by a long-term decline in glacial CO2 (GHG forcing). The other argues that NH ice sheets survived the next potential termination because land-surface properties (e.g. regolith, routing of ice sheets) made them less sensitive to meltdown.
Here, we present a record of CF4 measured on ice core samples from the EPICA and Beyond EPICA ice cores, as well as some even older samples from the Alan Hills blue ice area that may shed additional light on the potential reasons for the MB and MPT. CF4 is a natural gas with a very long lifetime (on the order of 100 kyr) occurring predominantly in granitic rocks and other acidic plutonites and is released during chemical weathering and erosion of these rocks. Granites are globally distributed but have a bias towards high northern latitudes (Laurentide region, Scandinavia). Accordingly, some connection of CF4 release to ice sheet extent is to be expected. Over the Pleistocene, the surfaces of these high northern areas have been intensively eroded, and we would expect that a removal of this regolith layer would have left a sizable imprint in our CF4 record. However, our CF4 record shows a rather gradual decline from 2.6 Myr BP toward its local minimum reached shortly before the MB. In contrast, our CF4 record is consistent with the view that the CF4 release is most sensitive to chemical weathering and thus to temperature and the hydrologic regime. While we observe moderate changes in the average long-term CF4 emission flux (several glacial-interglacial cycles), the dominant variability is between glacials and interglacials, with the interglacials exhibiting about 40% higher emissions than colder times. The post-MB increase in CF4 is thus most easily understood through increased weathering during the warmer post-MB interglacials.
Our work provides new constraints on the regolith hypothesis for the MPT, and the first record of Pleistocene granite weathering/erosion trends.
How to cite: Schmitt, J., Seth, B., Grimmer, M., Krauss, F., Higgins, J., Hishamunda, V., Brook, E., Buizert, C., Willenbring, J., Köhler, P., and Fischer, H.: No abrupt changes in CF4 emissions by granite weathering and erosion over the Mid-Pleistocene Transition , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13085, https://doi.org/10.5194/egusphere-egu26-13085, 2026.
As nearly all the mass, heat capacity, and carbon in the ocean-atmosphere system resides in the deep sea, ice cores must be correlated and integrated with marine sediment cores to provide a comprehensive, dynamic understanding of Earth's past climate. The SW Iberian Margin (SWIM) is a well-known location where sediments accumulate at high rates and can be correlated precisely to the polar ice cores. With new drilling during IODP Expedition 397, we filled a 30-kyr hiatus in the previous record of Site U1385 across the MIS 12/11 transition (Termination V) and extended the record to MIS 53, which we call SWIM1500. For the last 800 kyrs, we demonstrate that CH4 and δD in the EPICA ice core can be precisely correlated on millennial time scales to the planktic and benthic δ18O proxies, respectively, using a new Bayesian algorithm for automated synchronization of proxy timeseries (e.g. Muschitiello and Aquino-Lopez, 2024) that factors in prior knowledge on accumulation rates.
We suggest that SWIM1500 can serve as a predictive tool for isotopic and CH4 variations for the new BE-OI core beyond 800 ka and will aid in evaluating disturbance and/or diffusion in the oldest ice. We focus on the period older than 1.2 Ma because the stratigraphy and chronology of the BE-OI core is less certain in this interval. The unique shapes of the glacial-interglacial cycles (related to the phasing of obliquity and precession) and nested glacial millennial variability offer a template for correlating and interpreting the BE-OI and Site U1385 records. These correlations will be particularly important for evaluating the climate background state in the "41-kyr world" before the beginning of the Middle Pleistocene Transition at 1.2 Ma.
Muschitiello, F. and Aquino-Lopez, M. A.: Continuous synchronization of the Greenland ice-core and U–Th timescales using probabilistic inversion, Clim. Past, 20, 1415–1435, https://doi.org/10.5194/cp-20-1415-2024, 2024.
How to cite: Hodell, D., Rhodes, R., Wolff, E., and Muschitiello, F.: SW Iberian Margin 1500 ka (SWIM1500): A benchmark record for comparison with the Beyond EPICA-Oldest Ice (BE-OI) Core , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7431, https://doi.org/10.5194/egusphere-egu26-7431, 2026.
The duration and magnitude of Earth’s glaciation cycles increased substantially during the course of the Pleistocene without an obvious shift in external forcing. Changes in ocean circulation have been posited as one potential influence on this mid-Pleistocene transition (MPT). New drilling of a depth transect of sites on the Iberian margin during IODP Expedition 397 offers the opportunity to examine the record of deep-ocean circulation changes in the eastern north Atlantic over a range of bottom depths and water masses. Benthic carbon isotopes (d13C) and sedimentary characteristics that reflect bottom water conditions at Site U1587 (37°35′N, 10°22′W, 3.5 km) reveal persistent glacial-interglacial changes throughout the Pleistocene, with a shift toward larger and longer glacial cycles evident in benthic oxygen isotopes (d18O) across the MPT. A comparison with shallower Site U1385 (37°34′N 10°08′W 2.6 km) indicates that the vertical carbon-isotope gradient over this water depth also increased across the transition, particularly within glacial intervals, with far more negative d 13C at the deeper Site U1587. Uranium and thorium isotope analyses also indicate intervals of reduced dissolved oxygen and the deposition of authigenic uranium at greater depth. These observations suggest greater stratification and carbon storage in the deep eastern north Atlantic after the MPT, and support a likely role for ocean circulation in this important climate transition.
How to cite: McManus, J., Pallone, C., Arellano, A., Mathews, M., Kenna, T., Alonso-García, M., Lasluisa Molina, E. R., Kinney, Y., Kim, E., Harrison, B., Plower, I., Sturley, A., and Pryor, A.: Changes in Deep Circulation and Carbon Storage in the Eastern North Atlantic Ocean Across the Mid-Pleistocene Transition, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14053, https://doi.org/10.5194/egusphere-egu26-14053, 2026.
The basal section of the 2,800-m-long Beyond EPICA ice core (the lowermost 316 m) is of particular interest, not only because it potentially represents the oldest part of the core, but also because it contains important clues about past and present ice-sheet dynamics. We present here field observations and ongoing analyses aimed at characterizing the different ice units above the basal interface. Below the bottom of the “stratified ice” at 2,506 m, electrical conductivity, water-isotope composition, and crystal size allow the identification of a thinned and distorted zone extending down to 2,583 m, with no clear evidence of preserved climatic cycles. Below 2,583 m, the conductivity signal shows a sharp increase that persists over more than 200 m, although with some variability, and is associated with a marked increase in ice crystal size, reaching more than 10 cm.
The first occurrence of basal rock debris is observed at 2,795 m, where sand-sized and finer particles are embedded within the ice matrix, together with a few angular centimettric pebbles. This debris-rich section exhibits a heterogeneous composition, with decameter-scale alternations of banded, dispersed facies and clear-ice intervals. Density estimates of these basal units indicate that debris generally accounts for less than 1% of the mass, although it may locally reach a few percent. Two angular pebbles with volumes of several cubic centimeters are currently being processed for luminescence dating. Mineralogical observations suggest multiple source lithologies, supporting the hypothesis that the debris result from lateral transport and that the core did not reach the underlying bedrock. Scanning electron microscopy (SEM) observations of grain textures, together with geochemical analyses (Sr and Nd isotopes) and gas content will add additional constraints and help refine this interpretation and look for possible evidences of past deglaciation events. In addition, clay minerals and large (by XRD) will be analyzed to identify partially melted basal conditions in the past or weathering during ice free conditions.
How to cite: Blard, P.-H., Westhoff, J., Crinella, L., Fripiat, F., Wilhelms, F., and Ardoin, L. and the Beyond EPICA community: New insights from the basal section of the Beyond EPICA ice core (Little Dome C) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15296, https://doi.org/10.5194/egusphere-egu26-15296, 2026.
We present an optimised impurities continuous-flow analysis (CFA) method specifically developed to analyse the Beyond EPICA Oldest Ice Core (BE-OIC; >700 ky bp). Hosted at the British Antarctic Survey (BAS1) and operated collaboratively with our BE-OI partners2-12, the new CFA method was designed to operate at a melt rate of 1.5 cm min-1. The system included the continuous analyses of trace elements (triple quadrupole inductively-coupled plasma mass spectrometry, Agilent 8900 ICP-QQQ-MS/MS & inductively-coupled plasma optical emission spectroscopy, Agilent 5900 ICP-OES; BAS1); major anions (Cl-, SO42-, NO3- and MSA, Dionex fast ion chromatography, FIC; BAS1); NH4+ (fluorometry; BAS1); electrolytic conductivity (Dionex CDM-1 & Amber Science ECM 3201; BAS1); insoluble particulate size distribution (Abakus Klotz laser diffraction spectrometry, and EOS Single Particle Extinction Scattering, SPES2; U. Bern2); and stable water isotopes (δ18O, δ2H; Picarro cavity ring-down spectrometry, CRDS; U. Bern2, BE-OI Isotope Consortium7-10,12). For the first time, we present sections of BE-OIC chemistry data, focusing on trace elements (ICP-QQQ-MS & ICP-OES) and major anions (FIC).
In addition, the CFA campaign provided discrete liquid samples for single-particle trace elemental analysis (U. Bern2), organic analysis (U. Cambridge3, Ca’ Foscari U. Venice9&CNR-ISP10), δ34S (U. St. Andrews5), diatoms (BAS1), halogens (Ca’ Foscari U. Venice9 & CNR-ISP10), and tephra (BAS1, U. St. Andrews5 & Swansea U.6). Furthermore, discrete gas samples were collected for 81Kr dating (Heidelberg U.11).
How to cite: Humby, J. and Thomas, E. and the Beyond EPICA Oldest Ice Core Impurities CFA Team: The Beyond EPICA Oldest Ice Impurities Continuous Flow Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5685, https://doi.org/10.5194/egusphere-egu26-5685, 2026.
The Beyond EPICA project has extended our continuous ice core archive to 1.2—potentially 1.5—million years before present, covering the Mid-Pleistocene Transition (MPT). Ice older than that of the original EPICA core, spanning up to 800 kyr, is preserved in approximately only 100 meters of core.
To analyse this invaluable ice, European laboratories will converge in Copenhagen in February–March 2026 with their equipment to conduct simultaneous measurements of as many gas components as possible. Planned analyses include CH₄, CO, N₂O, and isotopes of O₂, N₂, and Ar. Since a methane record is a specific deliverable of the Beyond EPICA project, the campaign is designed to achieve the highest-resolution methane data possible.
The method involves melting a 3.5 × 3.5 cm ice stick on a specialised melt head. The inner, clean portion of the meltwater is then directed through a membrane system that separates the ancient air from the water. The meltwater itself is analysed for conductivity and dust content to synchronise the gas record with detailed chemical measurements of the core. The liberated air is analysed in real time using a suite of instruments. For the full set of gases, we combine two mass spectrometers with three laser spectrometers.
We will report on the outcome of the measurement campaign and present the first results.
How to cite: Blunier, T. and the Beyond EPICA fastCFA Team: Multi-gas component measurements of Beyond EPICA ice older than 700 kyr, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13905, https://doi.org/10.5194/egusphere-egu26-13905, 2026.
We present a quasi-non-destructive technique for measuring water isotopes in ice cores using a femtosecond infrared laser ablation system. Our cold-ablation approach enables a direct solid-to-vapour transition with sub-millimetre resolution and negligible sample consumption. Experiments conducted on synthetic ice demonstrate reproducible crater formation. Utilising a pulse energy of 35 μJ and a total ablation time of 16 s, repeatable craters with a typical diameter of ∼120 μm are produced. The ablation is performed at atmospheric pressure and requires only compressed dry air.
We demonstrate a sequence of 530 craters along a 27 cm long standard CFA ice section (30 × 30 mm), with the capability to extend to a full 55 cm ice-core bag and to accommodate a complete 4″ round core. The crater spacing is 0.5 mm and a full ablation run takes approximately 30 min and is largely unattended. Finally, we present preliminary results on coupling a cavity ring-down spectroscopy (CRDS) instrument to the ablation system.
This development is relevant for very old and deep ice core samples, such as those targeted by the BEOIC project and other >1 Myr ice cores, where sample preservation and spatial resolution are crucial.
How to cite: Bertsia Kanatouri, I., Nielsen, R. V., and Gkinis, V.: Quasi-non-destructive water isotope measurements in ice cores using femtosecond laser ablation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7227, https://doi.org/10.5194/egusphere-egu26-7227, 2026.
Deep Antarctic ice cores can contain thousands of years of past climate history stored in a meter of ice. This limited sample availability demands experimental setups to extract the maximum amount of information while using the minimum amount of sample. Here we present the BigCIM (Big Centrifugal Ice Microtome), a novel system for discrete ice core measurements of atmospheric CO2, d13C-CO2, CH4 and N2O. Combining the fast dry extraction principle from the Centrifugal Ice Microtome (CIM; Bereiter et al., 2013), and the analytical capabilities of the Quantum Cascade Laser-based Absorption Spectrometer (QCLAS; Bereiter et al., 2020), the BigCIM requires 16-g cuboid samples and throughputs 5 samples/day. Blank measurements using standard gas over gas-free ice achieve precisions (1s) of 0.3 ppm for CO2, 0.06 permil for d13C-CO2, 2 ppb for CH4 and 1 ppb for N2O, comparable to other dry-extraction methods (Mächler et al., 2023). Preliminary results from the EDC ice core shows general agreement with previously published data. The ability to measure multiple gas species simultaneously on small samples at a relatively quick pace makes the BigCIM a suitable instrument for measuring late Pleistocene greenhouse gas records on BE-OI ice core.
REFERENCES
Bereiter, B., Stocker, T. F., and Fischer, H., A centrifugal ice microtome for measurements of atmospheric CO2 on air trapped in polar ice cores. Atmos. Meas. Tech., 6, 251-262 (2013).
Bereiter, B. et al., High precision laser spectrometer for multiple greenhouse gas analysis in 1 mL air from ice core samples. Atmos. Meas. Tech., 13, 6391–6406 (2020).
Mächler, L. et al., Laser-induced sublimation extraction for centimeter-resolution multi-species greenhouse gas analysis on ice cores. Atmos. Meas. Tech., 16, 355–372 (2023).
How to cite: Silva, L., Heiserer, R., Krauss, F., Walther, R., Marending, S., Reinhard, C., Schmitt, J., Fischer, H., and Stocker, T.: Multi-GHG analysis with the BigCIM: a novel system for fast and discrete ice core reconstructions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11375, https://doi.org/10.5194/egusphere-egu26-11375, 2026.
The "Beyond EPICA Oldest Ice Core" (BE-OIC) collaboration has successfully recovered the Antarctic ice core BELDC (Beyond EPICA Little Dome C) reaching back at least 1.2 million years (Stenni et al., 2025). This record is expected to provide a crucial missing link for understanding the cause of the Mid-Pleistocene Transition. However, the extreme thinning of the deepest ice layers compresses more than 20k years in one meter, and thus calls for analysis at high spatial resolution going hand-in-hand with a rigorous assessment of stratigraphic integrity. For aerosol-related chemical impurities, post-depositional processes, such as diffusion, grain growth displacement, and geochemical reactions, are known to pose significant challenges for record preservation in deep ice.
Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) offers decisive advantages in this context by analysing the surface of solid ice samples at the micrometer scale (in the order of 1−100 μm). To fully exploit its potential for the BE-OIC project and to coordinate the LA-ICP-MS analysis of the BELDC deep sections, a dedicated "Laser Ablation Focus Group" has been established with members of AWI Bremerhaven and the Universities of Frankfurt, Venice and Cambrige. Here we present the first results of an ongoing "round robin" experiment designed to integrate the strengths of our different analytical systems. This intercomparison study utilizes shallow BELDC sections, covering both glacial and interglacial ice, which are currently analysed by two newly established systems: a broadband 2D mapping setup (AWI Bremerhaven; Bohleber et al., 2025) recently upgraded with a 33 cm cryogenic chamber for high throughput, and a dual-wavelength (157 & 193 nm) system optimized for high ablation efficiency of ice including a custom-designed cryo-holder (Uni Frankfurt; Erhardt et al. 2025).
By extending this inter-laboratory comparison to further LA-ICP-MS facilities of the focus group, we aim to establish a standardized framework for the BELDC deep-ice analysis and possibly also other future ice core projects. At the same time, our results provide the first LA-ICP-MS datasets for the BELDC core and indicate how these high resolution impurity datasets can be integrated with other methods, such as Continuous Flow Analysis (CFA). Ultimately, this collaborative effort aims to maximize the scientific output of LA-ICP-MS for the BE-OIC project by contributing to the most robust interpretation of this unique paleoclimate archive.
References
Bohleber, P., Stoll, N., Larkman, P., Rhodes, R. H., & Clases, D. (2025). New evidence on the microstructural localization of sulfur and chlorine in polar ice cores with implications for impurity diffusion. The Cryosphere, 19(11), 5485-5498. https://doi.org/10.5194/tc-19-5485-2025
Erhardt, T., Norris, C. A., Rittberger, R., Shelley, M., Kutzschbach, M., Marko, L., ... & Müller, W. (2025). Rationale, design and initial performance of a dual-wavelength (157 & 193 nm) cryo-LA-ICP-MS/MS system. Journal of Analytical Atomic Spectrometry, 40(10), 2857-2869. https://doi.org/10.1039/D5JA00090D
Stenni, B., Wilhelms, F., Westhoff, J., Alemany, O., Hansen, S., Dahl-Jensen, D., ... & Zannoni, D. (2025). The Beyond EPICA–Oldest Ice Core Project. European Association of Geochemistry. Goldschmidt 2025 Abstract. https://doi.org/10.7185/gold2025.29931
How to cite: Bohleber, P., Erhardt, T., Barbante, C., Dallmayr, R., Larkman, P., Rhodes, R., Roman, M., Roy, T., Stoll, N., and Müller, W.: Coordinating Analytical Strengths for LA-ICP-MS Analysis of the Beyond EPICA Core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12940, https://doi.org/10.5194/egusphere-egu26-12940, 2026.
The Southern Hemisphere Westerly Winds play a crucial role in the Earth's climate system and may have influenced the physical and biological processes that drove CO2 exchange in the Southern Ocean during the Mid-Pleistocene Transition (MPT). Numerous paleoclimate archives have been utilised to reconstruct past westerly winds over different timescales; however, many are limited by their reliance on precipitation or temperature proxies to infer SHWW changes. Marine diatoms found in Antarctic ice core layers have recently established as a reliable proxy for directly reconstructing historical changes in wind strength and atmospheric circulation within the Southern Hemisphere Westerly Wind belt.
In this study, we present diatom records preserved in two snow pits from Little Dome C and in Holocene samples from the EPICA Dome C ice core. The annual abundance of diatoms preserved in Little Dome C snow layers strongly correlates with wind strength over South America and the South Atlantic sector of the Southern Ocean. Backward trajectory analyses enable us to trace the pathways of air masses before reaching the Little Dome C site, aiming to identify potential primary source regions for the Little Dome C diatoms. The strong positive correlation between Little Dome C diatoms and wind strength in South America and the South Atlantic highlights the potential to use diatoms preserved in the BE-OI as a proxy for reconstructing past changes in mid-latitude winds. This study lays the groundwork for further exploration of diatom records preserved in excess meltwater collected during the BE-OI slow CFA campaign.
How to cite: Tetzner, D., Allen, C., Segato, D., Veale, J., Harris-Stuart, R., and Westhoff, J.: Windblown diatoms at Little Dome C and their potential for reconstructing Southern Hemisphere Westerly Winds during the MPT , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22482, https://doi.org/10.5194/egusphere-egu26-22482, 2026.
Antarctic ice cores provide exceptional archives of past climates and volcanic activity. Advances in sampling and analytical techniques are now enabling the detection and characterisation of both visible and cryptotephra deposits across increasingly long climate records. The Beyond EPICA Oldest Ice (BE-OI) project recently recovered what is thought to be the longest continuous Antarctic ice core. This core likely reaches back to ca. 1.2 million years, offering a unique opportunity to refine the chronology of glacial–interglacial cycles and the Mid-Pleistocene Transition. Here we present six visible tephra horizons identified within the upper 1850 m of the BE-OI record, thought to be originating from volcanic sources across the Antarctic region and beyond. These tephra deposits have modelled ages of 10.3, 70.3, 89.8, 142, 189 and 200 ka. Within this study, we explore potential correlations to tephras in the EPICA Dome C record.
Grain-size measurements, obtained through Coulter Counter analysis, together with optical microscopy and high-resolution single grain mineralogical data, have established the physical characteristics of the six tephra layers. Major element compositions determined by electron microprobe analysis and trace element data generated by LA-ICP-MS provide geochemical fingerprints for each deposit and point towards volcanic sources such as the South Sandwich Islands and Marie Byrd Land. The combination of these datasets enables robust tephra characterisation and supports correlations with established Antarctic tephra horizons. This work directly contributes to the refinement of the Beyond EPICA Oldest Ice chronology and its integration with the EPICA Dome C record.
How to cite: Thomas, C., Davies, S., Delmonte, B., Rabassi, M., Albert, P., Hutchison, W., Andò, S., and Watts, E.: Characterisation and Correlation of Visible Tephra Horizons in the Beyond EPICA Oldest Ice Core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15092, https://doi.org/10.5194/egusphere-egu26-15092, 2026.
During the main BEOIC processing campaign in 2025 at AWI, linescan images of double-sided polished ice slabs were routinely recorded. The linescanner is a well-established optical system in ice-core analysis that operates in darkfield mode, capturing scattered light from internal reflection surfaces and nuclei that are mostly associated with dust particles within the ice. The spatial resolution of the images is in the sub-millimetre range. As the measurement method produces almost no signal dispersion, it enables an exceptionally detailed view of small-scale layering.
In this contribution, we present images and grey-value records of the oldest-ice section between 2400 m and 2580 m depth and provide a preliminary interpretation of the observed features. Owing to the expected strong thinning—where more than 10,000 years may be compressed into a single metre of ice—these data offer a first indication of the limits of temporal resolution that can be achieved with other proxy parameters. Further image analysis addresses ice deformation as well as questions of stratigraphic integrity and continuity at the BEOIC site. We focus on selected depth intervals and present an initial overview of the evolution of lateral stability in the layered structures observed in the data.
How to cite: Freitag, J., Jansen, D., Weikusat, I., Stoll, N., Westhoff, J., Hörhold, M., Behrens, M., and Wilhelms, F.: Visual stratigraphy of the BEOIC oldest-ice section – preliminary results from linescan images, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21616, https://doi.org/10.5194/egusphere-egu26-21616, 2026.
Water stable isotope records from Antarctic ice cores provide exceptional paleoclimatic information, currently spanning the last 800,000 years from the EPICA Dome C ice core (EDC). The recently retrieved Beyond EPICA Little Dome C (BELDC) ice cores should enable us to extend continuous Antarctica paleoclimate records back to at least 1.2 or even 1.5 million years ago, document past Antarctic climate and water cycle variability, and compare these new records with information extracted from other paleoclimatic archives.
The quantification of reliable past climate information based on high resolution water isotope records in deep Antarctic ice cores requires to characterize post-deposition processes which alter the initial precipitation isotopic composition. The isotopic composition of surface snow is affected by processes such as sublimation, hoar formation and snow redeposition. Then, diffusion smoothes isotopic profiles both in the firn and in the ice. Such processes can be particularly important in very low accumulation sites such as Little Dome C, and for very old ice.
For this purpose, we explore insights from new high-resolution measurements of δ18O of water from recent Little Dome C (LDC) firn cores and BELDC ice core, with a focus on three specific time slices.
First, we present the δ18O continuous flow analysis over the top 84 m of the LDC firn, spanning the past 2154 years based on volcanic age markers. This allows to estimate the LDC accumulation rate at approximately 24 mmwe.yr-1. Our record is confronted to series generated by a virtual firn core model. Surface mixing plays an important role in reshaping the recorded signal within the first 3 m, with a best agreement obtained with an 8 cm mixing layer. Our results highlight that the diffusion is overestimated based on classical diffusion modelling.
We then focus on the last interglacial period, MIS5, and compare 2.5 and 10 cm dD resolution measurements from BELDC with earlier 11 cm records from EPICA Dome C, where the highest δD anomaly of the last 800 ka is observed.
Finally, we present 2.5 cm resolution δD records from BELDC spanning the time period prior to the EPICA Dome C record, from MIS23 (around 900 ka) to warm MIS31(around 1.08 to 1 Ma).
How to cite: Minster, B., Samin, E., Landais, A., Fourré, E., Casado, M., Ooms, A., Dutrievoz, N., Agosta, C., Masson-Delmotte, V., Combacal, T., Stenni, B., Salvini, M., Hörhold, M., Wilhelms, F., Behrens, M., Freigtag, J., Jansen, D., Weikusat, I., Steen-Larsen, H. C., and Gkinis, V. and the The Beyond Epica water isotopes consortium: High resolution water isotopic records on the Little Dome C firn cores and Beyond EPICA ice core for past climate and atmospheric water cycle reconstructions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5446, https://doi.org/10.5194/egusphere-egu26-5446, 2026.
Deep ice cores from the East Antarctic plateau provide unique continuous records for paleoclimate. While some proxies are recorded in the ice phase, others are recorded in the gas phase. Air enclosure occurs at several dozens of meters below the snow surface which leads to gas being always younger than the surrounding ice. Presenting the records measured on the gas and ice phases on the same chronology relies on the determination of the lock-in depth (LID) where air is isolated from the atmosphere. Two different methods can be used to determine past LID in ice core. On the one hand, firn densification models have been developed over the past 45 years to model progressive evolution densification from surface snow to ice over the top 60 -120 m and empirical determinations permit to link firn density to the lock in process. On the other hand, measurements of d15N of N2 in trapped air in ice cores provide information on the past evolution of the LID through the gravitationnal fractionation which leads to a linear relationship between d15N of N2 and firn diffusive height, itself directly linked to LID in the absence of any surface convective zone.
Here, we present independent estimate of the LID at two neighboring central sites in East Antarctica, Dome C (DC) and Little Dome C (LDC) where the EDC and BELDC deep ice cores have been drilled. We present results from different firn densification models and measurements of d15N of N2 both in the open porosity in the upper snow and in bubbles trapped in ice over the penultimate deglaciation and last interglacial period. For both studies, the measurementsshow a coherent 10% shallower LID at LDC than at DC which is relatively large given the similar climatic conditions on these neighboring sites. The firn densification models used in this study are not able to reproduce both the LID difference of about 10% between the two sites and the LID increase over the glacial -interglacial transitions. Missing processes in the firn densification model might be related with variations in the physical properties of the surface snow and surface snow metamorphism. To explore this hypothesis, our study hence also includes high resolution profile of density and specific surface area measurements at both sites.
How to cite: Landais, A., Stucki, C.-M., Harris-Stuart, R., Freitag, J., Arnaud, L., Picard, G., Jacob, R., Brückner, L., Parrenin, F., Bouchet, M., and Orsi, A. and the Beyond EPICA team: Firn densification in East Antarctica – a detailed model-data comparison at Dome C and Little Dome CFirn densification in East Antarctica – a detailed model-data comparison at Dome C and Little Dome C, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5800, https://doi.org/10.5194/egusphere-egu26-5800, 2026.
A new deep ice-core record from the East Antarctic Plateau reaching at least 1.2 million years is now available through the Beyond EPICA Oldest Ice Core project (BEOIC). This record spans the Mid-Pleistocene Transition (MPT), when glacial-cycle pacing shifted from ~40 kyr to ~100 kyr, and therefore offers key constraints when combined water-isotope and greenhouse-gas measurements are interpreted together.
Recovering an accurate water-isotope signal from the deepest and oldest ice is challenging because diffusion in solid ice attenuates high-frequency variability. High-precision, high-resolution measurements combined with physically based estimates of isotope diffusion can be used to quantify signal attenuation and assess the feasibility of signal deconvolution.
Here, we present a combined modelling and data study that quantifies diffusion-driven attenuation of the water isotope signal along the BEOIC using updated age–depth information and borehole temperature constraints. We apply the resulting transfer functions to high-resolution isotope sections from multiple depths to evaluate the recoverable bandwidth and to test spectral/Wiener restoration approaches, including the impact of measurement noise and sampling resolution on the reconstruction.
How to cite: Juelsholt, C., Vinther, B. M., Hörhold, M., Behrens, M., Wilhelms, F., Freitag, J., Weikusat, I., Jansen, D., Laepple, T., Minster, B., Landais, A., Steen-Larsen, H. C., Phumchat, N., Stenni, B., Salvini, M., Barbante, C., Parrenin, F., Samin, E., Scoto, F., and Gkinis, V.: Assessing the issue of the water isotope signal loss in the BEOIC ice core. A model and high-resolution data perspective., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9284, https://doi.org/10.5194/egusphere-egu26-9284, 2026.
The Beyond EPICA project (BE-OI) has extended the oldest continuous ice core climate record, capturing at least 1.2 million years. The 2,800-meter-long core was drilled at Little Dome C (LDC) in the East Antarctic Plateau, 35 km south-east of Dome C (DC). BE-OI seeks to disentangle the Mid-Pleistocene Transition (0.9-1.2 Myr BP), a crucial period of Earth’s climate history when the shorter 41 kyr glacial cycles shifted to a dominant 100 kyr regime.
Paleotemperature reconstructions obtained from ice cores mainly rely on water stable isotopes (ẟ18O and ẟ2H). Variations in isotope ratios reflect changes in local temperature with less negative values characterizing warmer periods and more negative values associated with colder conditions. Past interglacial periods characterized by higher temperatures, higher sea levels, and reduced ice sheets provide valuable insights for investigating how different orbital configurations affect the climate system without the influence of northern hemisphere glacial ice sheets.
Within this framework, a preliminary comparative analysis was carried out between EPICA Dome C (EDC) and Beyond EPICA isotope records, with a focus on the climate variability between 700 and 800 kyr BP. This period covers two interglacials corresponding to the bottom part (3082-3189 m) of the EDC ice core including MIS 19 which represents the period with the closest orbital configuration parameters to the Holocene. In this study, high-resolution measurements of ẟ2H and ẟ18O were performed by means of Cavity Ring-Down Spectroscopy. Sample analyses were conducted with a sampling resolution of 2.5 cm using internal standards intercalibrated within the laboratories of the Beyond EPICA water isotope consortium. This high-resolution record is in good agreement with the low-resolution isotopic measurements performed in the field. The captured climate variability has been compared with the EPICA record to assess the onset of potential new climatic information captured by water stable isotopes. To account for the differences between the two coring locations, the stable isotope composition of surface snow collected along an initial traverse between DC and LDC during the 2023–2024 field season will be considered, together with snow trench samples from both sites.
How to cite: Salvini, M., Stenni, B., Biscaro, E., Landais, A., Masiol, M., Dreossi, G., Scoto, F., Zannoni, D., Barbante, C., Samin, E., and Parrenin, F. and the Beyond EPICA isotope and processing team: High-resolution ẟ18O and ẟ2H profiles from 700 to 800 kyr BP in the Beyond EPICA ice core: insights from a comparison with EPICA Dome C, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12810, https://doi.org/10.5194/egusphere-egu26-12810, 2026.
While most of the below 700ka section of the Beyond EPICA ice core has been measured for water isotopic composition in 2.5 cm samples, a sub-section (depth 2473-2475 meters) has been cut into 1.25 cm. These ultra-high-resolution samples have been measured side-by-side with the 2.5 cm samples from the same depth, allowing a direct comparison with minimal calibration or instrument drift-induced uncertainty. With great care for optimal measurement quality, we present here a comparison of the samples, with average precisions (+/- 1 STD) of 0.03 o/oo and 0.07 o/oo for ẟ18O and ẟ2H, respectively, and average accuracies of 0.03 o/oo and 0.4 o/oo for ẟ18O and ẟ2H, respectively.
Variations between the 1.25 cm and 2.5 cm samples that cannot be attributed to measurement uncertainty are observed. Our ultra-high-resolution measurements provide critical insights into intra-core variability, and we argue that ice cores, when possible, should be measured at the highest resolution to obtain optimal information about past climate variability.
How to cite: Steen-Larsen, H. C., Phumchat, N., Gkinis, V., Stenni, B., Dreossi, G., Zannoni, D., Hörhold, M., Behrens, M., Wilhelms, F., Freitag, J., Weikusat, I., Jansen, D., Laepple, T., Minster, B., Landais, A., and Isaksson, E.: Ultra-High-resolution ẟ18O and ẟ2H measurements on the Beyond EPICA ice core: new insights into signal preservation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14467, https://doi.org/10.5194/egusphere-egu26-14467, 2026.
Changes in climate variability are as critical to understand as changes in the mean climate, yet remain difficult to quantify from ice cores because single records are strongly affected by local noise arising from depositional, post-depositional, and diffusive processes. As a result, past changes in climate variability cannot be robustly separated from changes in ice-core noise using individual cores alone.
This limitation can be overcome by analysing replicated ice-core records, where the common signal can be interpreted as climate-driven variability. For the first time, such an approach is now feasible for deep Antarctic ice cores through the paired water-isotope records of EPICA Dome C and the new Beyond EPICA Oldest Ice Core (BE-OIC), which together provide a replicated archive extending back 800,000 years.
Here, we present first results from the upper ~ 300 m of the BE-OIC ice core focusing on Holocene variability in stable water isotopes. Using spectral methods, we compare the statistical properties of isotope variability between the two cores to separate common climate variability from local noise and to assess the effective temporal resolution of the preserved signal. These preliminary results provide an initial step towards quantifying multidecadal to millennial-scale climate variability in Antarctic temperature during the Holocene and establish the basis for extending this analysis to earlier interglacial periods with the BE-OIC ice core record.
How to cite: Brocker, K., Laepple, T., Hörhold, M., Meyer, H., Wilhelms, F., Behrens, M., Freitag, J., Jansen, D., Weikusat, I., Steen-Larsen, H.-C., Hirsch, N., and Landais, A. and the Beyond-EPICA isotope consortium: Inferring climate variability from replicated Antarctic ice-core water isotope records, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20885, https://doi.org/10.5194/egusphere-egu26-20885, 2026.
The two major heat reservoirs on the Earth’s surface are oceans and the latent heat required to melt glaciers and ice sheets. Of these, the ocean is the largest and the fluctuations in Ocean Heat Content (OHC) therefore yield insights into Earth’s energy balance through time. We reconstruct OHC fluctuations through Mean Ocean Temperature (MOT) change, in turn reconstructed through the measurement of noble gas ratios in ice cores. Noble gases are inert; on the Earth’s surface they mainly partition between the atmosphere and the oceans depending on the latter’s temperature. From ice core measurements, past atmospheric noble gas ratios can be determined and from these a global, integrated, mean ocean temperature record is obtained. Until recently, MOT reconstructions were mostly focused on glacial Terminations, leaving the sections separating them sparsely covered.
Here, we present a millennial scale resolution MOT reconstruction for the MIS 9 glacial inception. The MIS 9e overshoot (centred around 336 kyrs) sees an intermittent 2°C MOT rise before returning to interglacial values. During the glacial inception itself (~325 – 307 kyrs), the oceans cooled by approximately 2°C, roughly two thirds of the glacial period’s total. This initial MOT drop coincides with a decline in both Southern Ocean and Antarctic plateau temperatures. However, we note a decoupling between decreasing temperatures and CO2 concentration; the latter plateaus for around five millennia after the start of ocean temperature decline. Further MOT measurements are planned on the Beyond EPICA ice core covering the most recent glacial inception (104-126 kyrs). These could lead to additional insights into glacial inceptions.
How to cite: Traeger, H., Grimmer, M., Tinner, P., Schmitt, J., and Fischer, H.: Millennial scale resolution Mean Ocean Temperature over the MIS 9 glacial inception, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4844, https://doi.org/10.5194/egusphere-egu26-4844, 2026.
Within the framework of the Beyond EPICA project, the oldest continuous Antarctic ice core recovered to date provides, for the first time, direct measurements of the atmospheric composition over (at least) the past 1.2 million years (hereafter Ma), through the analysis of the air bubbles trapped in the ice. This interval encompasses the Mid-Pleistocene Transition, marked by a shift in the dominant climatic periodicity from ~40 ka to ~100 . Interestingly, preliminary results show that this time interval also witnesses a long-term decline in the atmospheric dioxygen (O2). Despite being a period of major reorganization of the Quaternary glacial–interglacial climate system, the processes that drove the MPT remain debated. Several hypotheses have been proposed, involving changes in ice-sheet dynamics, ocean circulation or the radiative forcing of atmospheric CO₂. Because atmospheric CO₂ and O₂ are tightly coupled through biogeochemical processes, investigating the evolution of atmospheric O₂ across the MPT may provide additional constraints on the mechanisms underlying this fundamental climatic shift. Here, we focus on the concentration of the triple isotopic composition of O2 (Δ¹⁷O(O₂)), a proxy for global biosphere productivity when interpreted together with CO2 concentration. We present the evolution of Δ¹⁷O(O₂) including the first continuous records from the deepest section of the Beyond EPICA ice core (from 2400 m to 2507 m). This record has been obtained as a by-product measurement when analysing the O2, N2 and Ar elemental and isotopic composition hence without O2 purification. Although characterized by relatively low analytical precision so far, the dataset offers comparatively high temporal resolution. The new Δ¹⁷O(O₂) record also confirms previously reported trends over the last 0.7–0.8 Ma, supporting its robustness for investigating both long-term changes and glacial-interglacial variability. We compare the long-term evolution of Δ¹⁷O (O₂) with the observed decrease in atmospheric O₂, and examine the amplitudes of glacial–interglacial variations in Δ¹⁷O (O₂) relative to those of CO₂ over the past 1.2 Ma. It appears that variations in the Δ¹⁷O (O₂)–CO₂ relationship during specific glacial – interglacial cycles could reflect changes in the biosphere productivity warranting further investigation.
How to cite: Baubant, L., Landais, A., Brückner, L., Klüssendorf, A., Brugere, E., Prié, F., Krauss, F., Schmitt, J., Fischer, H., and Duchamp-Alphonse, S. and the Beyond EPICA Community: First Δ¹⁷O of O₂ Data from Beyond EPICA Ice Core across the Mid-Pleistocene Transition (1.2 to 0.7 million years) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5716, https://doi.org/10.5194/egusphere-egu26-5716, 2026.
The Mid-Pleistocene Transition (MPT) is characterized by a shift from 40 kyr to 100 kyr glacial cycles and increasing glacial ice volume. The reason for this change is still a matter of debate, but a plausible explanation could be a long-term decline of greenhouse gas (GHG) radiative forcing during glacial times across the MPT, which would have allowed global ice sheets to grow over a longer time interval and to greater size.
Although recent developments in marine CO2 proxies (for example Nuber et al., 2025) and CO2 measurements on blue ice samples (Marks Peterson et al., 2025) have led to first results to constrain the atmospheric CO2 over the MPT, an ultimate answer to the question how glacial/interglacial radiative forcing changed over the MPT is still missing. Marine CO2 proxies are limited in terms of precision and accuracy, making it difficult to reconstruct CO2 changes smaller than app. 20 ppm. Blue ice records show stable mean CO2 (and CH4) over the MPT with surprisingly little glacial/interglacial variations. The latter is likely due to glaciological reasons specific for blue that do not impact the continuous Beyond EPICA deep ice core.
Using the novel Laser Sublimation Extraction and multi-beam Quantum Cascade Laser Absorption Spectrometer developed at the University of Bern (in particular for the Beyond EPICA ice core, where availability of ice as old as the MPT is extremely limited due to the glacial thinning) we are able to measure CO2 (and its carbon isotopic composition!), CH4, and N2O concentrations all on the same ice core sample of only 15 g with highest precision and accuracy. We applied this technique to discrete samples from the Beyond EPICA ice core to reconstruct the first multi-millennial record for all three GHG over the MPT, which allows us to quantify changes in the total GHG radiative forcing. The preliminary results confirm minimal secular changes across the MPT, but in contrast to the blue ice record reveals significant glacial/interglacial variations in all three GHG.
This poster will introduce the analytical details of this unique analytical system, present the latest results for the Beyond EPICA greenhouse gas records and discuss the implications and limitations of these results for the interpretation of the MPT.
References
Marks Peterson, J. et al., Ice cores from the Allan Hills, Antarctica, show relatively stable atmospheric CO2 and CH4 levels over the last 3 million years, Research Square preprint under review, https://doi.org/10.21203/rs.3.rs-5610566/v1.
Nuber, S. et al., Mid Pleistocene Transition caused by decline in atmospheric CO2, Research Square Preprint under review, DOI: https://doi.org/10.21203/rs.3.rs-6480074/v1.
How to cite: Fischer, H., Krauss, F., Schmitt, J., Heiserer, R., Silva, L., Stocker, T., Capron, E., Mühl, M., Fain, X., Grilli, R., Bauska, T., Soussaintjean, L., Rhodes, R., Blunier, T., and Beyond EPICA community, T. E.: The first millennial-resolution triple greenhouse gas record over the MPT using novel sublimation extraction/laser spectrometry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6467, https://doi.org/10.5194/egusphere-egu26-6467, 2026.
Measurements of the total air content (TAC) in ice cores have a long history and were motivated to reconstruct past changes in the altitude of the ice sheet at the drill site, as air pressure is the dominant control on TAC. To allow this, one must know the porosity at bubble closure (pore volume) and correct for temperature. Temporal changes in the porosity are difficult to constrain, limiting its use as an altitude proxy. Orbital changes in the local insolation were found to modulate the TAC signal, allowing this parameter to be used as an additional orbital dating tool without a precise process understanding of the driving mechanism. Recent measurement campaigns on the EPICA Dome C ice core covering the last 450 kyr have increased the temporal resolution and allow about 1 kyr resolution between MIS 9 and MIS 7 (around 350 to 210 kyr). Our high-resolution record corroborated the well-known orbital TAC variations; however, it also showed rapid upward jumps within 2 kyr that were not previously visible. These TAC jumps are especially pronounced in MIS 7 and 9, interglacials characterised by so-called late deglacial overshoots in CO2 and CH4, but are also visible in water isotopes and aerosol records. The characteristic sequence for these overshoot interglacials is as follows:
From a TAC maximum that is reached already before the start of the deglaciation, TAC is slowly dropping to reach a pronounced minimum right at the interglacial temperature maximum. After this minimum, TAC values rapidly increase within 2 kyr, thus less than the age of the firn column. This suggests that the millennial-scale changes in temperature and accumulation at the start of the interglacial lead to a transient disequilibrium in firnification. I.e., during the early interglacial warming, the rise in snow accumulation, hence overburden pressure, on top of a firn column leads to a transient creep-related reduction of porosity, hence to the pronounced TAC minima. Similar millennial-scale TAC features were observed in Greenlandic ice cores (Eicher et al. 2016) during rapid DO events.
With the advent of the Beyond EPICA ice core, we can now examine the characteristics of older interglacials to answer the question which of the interglacials during the MPT exhibit these dynamic TAC features and which resemble interglacials that seem to lack them (e.g. MIS 11). First measurements on the BEOI during the MPT indicate an orbital TAC dynamic similar to those over the last 600 kyr, while pronounced TAC minima characteristic of overshoots have not yet been identified. Moreover, the TAC evolution of MIS 31 seems to resemble the overall characteristics of MIS 11, i.e., it lacks the overshoot characteristics.
How to cite: Seth, B., Schmitt, J., Grimmer, M., Guilluy, H., Capron, E., Parrenin, F., Klussendorf, A. M., Bruckner, L., Landais, A., and Fischer, H.: Millennial-scale jumps in total air content at Dome C and new total air content measurements over the MPT on the Beyond EPICA ice core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10015, https://doi.org/10.5194/egusphere-egu26-10015, 2026.
How to cite: Millot-Weil, J., Valdes, P., and Farnsworth, A.: Exploring orbital-paced forcings impacts on the Mid-Pleistocene Transition using snapshot simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7849, https://doi.org/10.5194/egusphere-egu26-7849, 2026.
Several international projects aim to retrieve million-year-old ice from Antarctica. Most focus on obtaining a continuous climate record. In the about-to-start 5-year project Million-year Ice from Antarctica (MIA), we will conduct an observation-based assessment of the potential of a preserved climate record older than 1.5 Myr in the European flagship ice core, BEOI. MIA will explore the “stagnant” ice zone, a roughly 200 m thick area of presumed stagnant ice that has not yet been characterised. In addition to exploiting its full paleoclimatic potential, MIA will advance our understanding of the ice dynamics of “stagnant" ice. This is highly relevant for ice sheets and glaciers and, thus, their impact on future sea level rise via solid ice discharge into the oceans. To accomplish these ambitious goals, we will apply a holistic approach. We will simultaneously analyse microstructural (e.g., grain size and shape, crystal-preferred orientation) and geochemical properties (e.g., impurity localisation) of solid ice samples using multiple methods. We will combine these measurements with the full-Stokes numerical ice flow model Underworld2, applying derived anisotropy data. We will also compare these results with the deepest sections of BEOI’s counterpart, the Million Year Ice Core (MYIC) project by the Australian Antarctic Division. MYIC is assumed to contain (almost) no “stagnant” ice. To fully exploit our interdisciplinary approach, we will analyse 2 COLDEX blue ice cores from the Allan Hills region, where the so-far-oldest ice on Earth was found. This contribution will outline the next five years of the MIA project and its potential to enhance our understanding of the oldest parts of the Antarctic Ice Sheet.
How to cite: Stoll, N.: Million-year Ice from Antarctica and the “Stagnant” Ice Zone: From Microstructure to Geochemistry (MIA:Mic2Geo) – linking BEOI’s “stagnant” ice, COLDEX’s Allan Hills blue ice, and Million Year Ice Core ice, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13041, https://doi.org/10.5194/egusphere-egu26-13041, 2026.
The Mid-Pleistocene transition (MPT) is marked by a progressive increase of glacial-interglacial cycle amplitude, a shift of the climatic response from a 41-ka cycle dominated to a 100 ka-cycle, a prominent asymmetry in large glacial inceptions and an extension of glaciation. This transition is associated with a cooling of the sea surface temperatures and an increase of the atmospheric CO2 concertation, that could be associated with a change in the ice-sheet volume. One of the hypotheses to explain the MPT transition is the regolith hypothesis, based on the basal erosion of glaciers, resulting in changes in weathering and in ice-sheet volume. Here, we apply clumped isotope thermometer (Δ47) to benthic foraminifera. The Δ47 has also the advantage to be independent of the isotopic composition of the seawater (δ18Osw). As consequence, by combining Δ47 and δ18O from benthic foraminifera, the δ18Osw can be reconstructed. Our data are compared to osmium (Os) isotope measurements to observe potential change in weathering intensity. Thanks to this unique combination of Os isotope and Δ47, we can test the regolith hypothesis. We therefor present a new deep temperature dataset, combined with osmium, over the MPT, from the “Shackleton” site (IODP U1385 from exp. 397) in the North Atlantic Ocean.
The deep-temperatures show an unexpected increase between MIS 30 and MIS 22, associated to an increase of δ18Osw, while the osmium isotope decrease, indicated a decrease of weathering. These results point toward the regolith hypothesis with changes in ice sheet volume and weathering.
How to cite: Peral, M., Müller, I., Nana Yobo, L., Caley, T., Goderis, S., and Claeys, P.: Combined benthic clumped isotope and osmium isotope data over the Mid-Pleistocene transition: towards better constraints on the weathering and seawater temperatures and d18O, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18696, https://doi.org/10.5194/egusphere-egu26-18696, 2026.
Understanding Greenland Ice Sheet (GrIS) variability over million-year timescales is critical for assessing its long-term stability and sensitivity to climate change. This study presents a synthesis of published evidence on past ice-free and ice-covered conditions in Greenland, integrating multiple paleoclimatic methods and datasets to provide a coherent overview of GrIS evolution. This outline highlights key intervals of changes in ice cover, such as warm and interglacial periods that are older than the last interglacial but remain less explored. Special attention is given to the Mid-Pleistocene Transition (MPT), when global glacial cycles shifted from 41 kyr to 100 kyr periodicity, potentially forming the basis for the present-day ice sheet geometry and state. Plausible scenarios for the GrIS respond to these periods will be explored and discussed based on the outline of evidence.
In addition to the synthesis, new age constraints from the Green2Ice project refine the existing picture. Novel krypton-81 dating of deep ice from the GRIP core reveals ice as old as 856 (+35/-33) ka, indicating persistent ice cover in central Greenland for nearly one million years. This finding provides a key point for evaluating model simulations and assessing physically meaningful scenarios for GrIS. Furthermore, these new results help test the hypotheses of significant ice sheet reorganization during the MPT.
By comparing evidence of ice-cover and ice-free conditions across methods and locations, this work explores areas of strong coherence and remaining uncertainties in Greenland’s long-term history. These insights not only improve our understanding of past GrIS behaviour but also inform projections of its future response under ongoing climate change.
How to cite: Kande, J., Svensson, A., Landais, A., Fourré, E., Feng, X., Jiang, W., Lin, Q.-S., Lu, Z.-T., Wang, J. S., Yang, G.-M., and Dahl-Jensen, D.: New Constrains on the History of the Greenland Ice Sheet from Krypton-81 Age Estimates, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18791, https://doi.org/10.5194/egusphere-egu26-18791, 2026.
Posters virtual: Fri, 8 May, 14:00–18:00 | vPoster spot 4
EGU26-8488 | Posters virtual | VPS7
The Million Year Ice Core Project at Dome C NorthFri, 08 May, 15:27–15:30 (CEST) vPoster spot 4
The Million Year Ice Core (MYIC) Project is an Australian Antarctic Program initiative to recover a continuous ice core spanning the mid-Pleistocene Transition (MPT; 700–1,250kyr). MYIC pilot drilling and borehole reaming for casing installation started in the 2024/25 austral summer at Dome C North (DCN, 75.04220S, 123.63120E, ice depth of 3064 m). DCN is 9 km NE of Concordia Station and 45 km NE of the European Beyond EPICA Oldest Ice site at Little Dome C (LDC). In the 2025/26 season, casing was installed and deep drilling commenced using a new AAD deep drill system. Completion of drilling to bedrock is scheduled for the 2028/29 season.
One-dimensional ice modelling, constrained by ice penetrating radar and isochrones traced back to the original EPICA Dome C ice core site, indicate an age above the basal ice at DCN potentially reaching 2 million years (Ma) and a resolution at 1.5 Ma of 10,000 years per metre or better (Chung et al., 2023).
Laboratory capabilities for MYIC are directed at measurements required to test hypotheses on the cause of the MPT. Ice core continuous flow analysis (CFA) for conductivity, particles and soluble ions are underway, with fraction-collected aliquots taken for measurement of cosmogenic 10Be. Gas and water isotope measurements on the returned ice are scheduled to start this year. The new gas laboratory developed for the project combines a small-sample sublimation extraction system coupled to a Quantum Cascade Laser spectrometer and dual inlet mass spectrometry for combined measurement of CO2, δ13C-CO2, CH4, and N2O, as well as the main air isotopes. There are opportunities for measurements of other parameters through national and international collaboration.
How to cite: Pedro, J. B. and the Million Year Ice Core Project Team: The Million Year Ice Core Project at Dome C North, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8488, https://doi.org/10.5194/egusphere-egu26-8488, 2026.
