The Beyond EPICA – Oldest Ice project in East Antarctica marks a groundbreaking milestone in unraveling Earth’s past climate dynamics. Recent findings confirm that the paleoclimatic record extends back at least 1.2 million years, offering unprecedented opportunities to explore glacial-interglacial cycles and the mechanisms driving Earth’s climate system.
To better constrain the long-term response of Earth’s climate system to continuing greenhouse gas emissions, it is essential to turn to the past. A key advance would be to understand the shift in Earth’s climate response to orbital forcing during the 'Mid-Pleistocene transition' [MPT, 900,000 (900 kyr) to 1.2 million years (1.2 Myr) ago], when a dominant 40 kyr cyclicity gave way to the current 100 kyr period. It is critical to understand the role of forcing factors and especially of greenhouse gases in this transition. Unravelling such key linkages between the carbon cycle, ice sheets, atmosphere and ocean behaviour is vital, assisting society to design an effective mitigation and adaptation strategy for climate change. Only ice cores contain direct and quantitative information about past climate forcing and atmospheric responses.
Drilling operations reached the bedrock at a depth of 2800 meters, granting access to ancient ice. High-resolution analyses of hydrogen isotopes (δD) were conducted, with sampling resolutions down to 25 cm, providing unparalleled insights into climate and environmental fluctuations. Concurrently, dielectric profiling (DEP) measurements were employed to identify detailed climatic stratifications within the ice core.
This presentation will highlight the main results achieved so far, emphasizing their implications for understanding the transition of glacial cycles from 40,000 to 100,000 years and the long-term evolution of greenhouse gas concentrations. These findings lay the foundation for subsequent talks in this session, which will delve into isotopic, chemical, and physical analyses of the ice core.
By bridging critical gaps in our knowledge of paleoclimate, this work also establishes a robust basis for modeling future climate scenarios, reinforcing the importance of understanding Earth’s climatic past to inform predictions of its future.
How to cite: Barbante, C. and the Beyond EPICA Team: Beyond EPICA – Oldest Ice Core: Insights from a 1.2-Million-Year-Old Climate Record, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10358, https://doi.org/10.5194/egusphere-egu25-10358, 2025.
The International Partnership on Ice Core Science (IPICS) set the “Oldest Ice” challenge of retrieving an ice core with a continuous palaeoclimatic record covering the past 1 million years. In order to determine good ice core drill sites, flow modelling is required to assess the potential age of the ice. Different age models were applied to the Beyond EPICA drill site on Little Dome C in East Antarctica. During the 2024/2025 Antarctic field season, drilling reached bedrock and the preliminary measurements from the field suggest the age of the oldest ice to be over 1.2 million years.
In this work, we compare age-depth tie points observations to both 1D and 2.5D ice flow models. The comparison shows how different models using different constraining radar surveys performed when compared with observations from the ice core. We also discuss why a simpler model may be more appropriate in the Dome C region. This validation exercise is of special interest to other ice core drilling projects where these modelling techniques have been used and for searching for new potential “Oldest Ice” drill sites.
How to cite: Chung, A. and the Beyond EPICA community: How accurate was the age modelling for the Beyond EPICA ice core?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17165, https://doi.org/10.5194/egusphere-egu25-17165, 2025.
The Beyond EPICA project aims to collect ice of more than one million years of age. This ice is found approx. 200m above bedrock, the basal unit remained a mystery before drilling. We present the first results from the basal unit, i.e. the section identified from radio-stratigraphy, which seemed to be unstratified and, based on modeling results, also potentially stagnant. Variations in crystal size measured on-site reveal the gradual transition into this basal unit. In the approx. 5 m of basal ice recovered from the core, we find layered bands containing 1-2mm rocks, clogged clays sections of banded dispersed facies, and repetitive transitions of clear ice to debris-rich ice. The mineralogic composition is mainly of granitic and gneiss rocks, mainly in the size fraction of sand. With these new results, we can increase our understanding of ice sheets' formation and evolution, ice flow over the bedrock, and variations in rheology due to ice crystals.
How to cite: Westhoff, J. and the Beyond EPICA Community: Basal section of the Beyond EPICA Little Dome C ice core, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17368, https://doi.org/10.5194/egusphere-egu25-17368, 2025.
Antarctica’s ice cores provide seminal records of past climates and calibration points for ice-sheet modelling, but are, by definition, limited to single locations. However, spatially-widespread radar-imaged internal-reflecting horizons, tied to ice-core age-depth profiles, can be treated as isochrones that may link between ice-core sites, and record a 3D age-depth structure across the Antarctic ice sheets. In 2018, the Scientific Committee for Antarctic Research programme formed the AntArchitecture consortium, which has progressively been tracing radiostratigraphy across the Antarctic ice sheets to form a baseline dataset for multiple scientific applications, for example the search for Antarctica’s oldest ice and to reconstruct past mass balance. In this presentation we focus on the use of radiostratigraphy to connect between deep ice-core sites and, in so doing, to calibrate ice-core dating profiles and extend the age-depth profiles into three dimensions and extend knowledge of the age of the ice towards the ice-sheet margins and potential future ice-coring sites. We present our best attempts at radiostratigraphic connections across both the East and West Antarctic ice sheets, and the current state of the art in connecting age-depth profiles between the two ice sheets, calibrated by Antarctica’s main ice cores. We demonstrate that radiostratigraphy is a potent companion to ice cores in the quest to reconstruct past climate and hence reduce uncertainties in projecting future ice-sheet behaviour.
How to cite: Bingham, R. and the AntArchitecture Collaboration: Towards radiostratigraphic connectivity between Antarctica’s deep ice cores and ice-sheet margins, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10469, https://doi.org/10.5194/egusphere-egu25-10469, 2025.
The North-East Greenland Ice Stream (NEGIS) is a major contributor to ice loss experienced by the Greenland Ice Sheet. Our current understanding of the mechanics of this highly dynamic feature is limited compared to the surrounding slowly deforming ice sheet, but significant for enhancing ice flow models and attaining more accurate sea-level rise projections. Especially the shear margins of an ice stream are the regions where, in addition to the ice stream bed, a large part of the deformation occurs. To study the deformation processes that are active in the shear margins on the basis of sub-surface ice samples will contribute to our understanding of how fast flow in ice streams is enabled. The East Greenland Ice-core Project drilled the first deep ice core in such a fast-flowing regime at the onset of NEGIS, reaching bedrock at approximately 2670 m. The EGRIP ice core data provide a comprehensive record of the crystal-preferred orientation (CPO) throughout the core. Additionally, short cores of approximately 100 m length (S5, ExS5-1, ExS5-2) were drilled in 2019 and 2022 in the shear margin south-east of the main core drilling site.
We present results from CPO analysis of these three cores, supported by density data and temperature profiles from the boreholes. Comparing our results with those from the main core reveals the effect of shear localisation in the margin on the physical properties of the ice, and highlights the significant lateral variation between the three locations set in the shear margin within distances of 2-3 km.
How to cite: Kerch, J., Wichartz, A., Streng, K., Stoll, N., Jansen, D., Freitag, J., Ullrich, H., Kipfstuhl, S., Dahl-Jensen, D., and Weikusat, I.: Physical properties in the shear margin of the Northeast Greenland Ice Stream, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18382, https://doi.org/10.5194/egusphere-egu25-18382, 2025.
High-altitude glaciers in the western European Alps have preserved long-term records of anthropogenic air pollution, as shown by numerous ice core studies over the past three decades. These records reveal a significant increase in pollutants over the last two centuries, closely linked to industrialization, with pollutants transported from nearby regions. In contrast, long-term studies in the eastern Alps remain limited, as these glaciers were considered unsuitable for undisturbed ice core preservation due to their lower elevations and temperate basal conditions. However, recent findings suggest that, under specific circumstances, cold ice frozen to bedrock can exist below 4000 m, as demonstrated by the Weißseespitze (WSS) summit ice cap in the Eastern Alps (3499 m a.s.l.), which preserves a 6000-year-old record within ~10 m of depth, despite ongoing surface mass loss.
Building on earlier work, this study provides further insights into the WSS glacier through expanded chemical analyses of an 8.5 m deep ice core drilled in 2019, complementing previously reported data on major ions and levoglucosan. The extended dataset includes detailed profiles of 22 trace elements (Ag, As, Ba, Be, Bi, Cd, Co, Cr, Cu, Ga, In, Li, Mn, Ni, Pb, Rb, Se, Sr, Tl, U, V, Zn), carboxylic and dicarboxylic acids, obtained from discrete samples collected alongside the 2022 melting campaign performed at Ca’ Foscari University.
A Positive Matrix Factorization (PMF) analysis of the recorded impurities revealed significant anthropogenic contributions to the trace element profiles. This was supported by a Lagrangian particle dispersion model, showing that ~50% of the air masses over the WSS glacier originated in Central Europe, with a notable contribution from the Po Valley, emphasizing its historical role in pollution transport.
To refine the glacier's age-depth relationship and contextualize these findings, age constraints were obtained from micro-14C dating and 39Ar dating using atom trap trace analysis (ATTA) from a parallel ice core and additional shallow cores, integrated with the chemical dataset. This analysis determined that the glacier surface formed approximately 356 +19 -23 years prior to 2019. Additionally, the dating established a precise timeline for a significant levoglucosan and chemical peak at a depth of 6.4 meters, placing it roughly 779 +53 -63 years before 2019. The radiometric age data were combined with an age model using the Raymond model, suitable for ice cap conditions like WSS.
Building on these insights, the regional significance of the prominent horizon at 6.4 m depth in the 2019 Weißseespitze ice core was explored by comparing the levoglucosan record with micro-charcoal data from the Schwarzboden mire in the Maneid valley, a few kilometers southeast of the glacier. This comparison revealed a striking correspondence, offering new insights into the region’s environmental history.
This study highlights the WSS glacier’s exceptional value as a long-term archive of pre-industrial pollution. However, with the industrial period already erased by ice mass loss, this archive is critically endangered. Projections suggest that 30% of the Ötztal glaciers could vanish by 2030, emphasizing the untapped potential of Eastern Alpine glaciers in reconstructing past environmental changes before they disappear.
How to cite: Spagnesi, A., Bohleber, P., Wachs, D., Barbaro, E., Feltracco, M., Festi, D., Gabrieli, J., Langenbacher, L., Aeschbach, W., Oberthaler, M., Stocker-Waldhuber, M., Gambaro, A., Barbante, C., and Fischer, A.: New chemical signatures and 39Ar dating from Weißseespitze ice cores (Eastern Alps): Tracing anthropogenic pollution from the Late Medieval to Early Modern Period , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11519, https://doi.org/10.5194/egusphere-egu25-11519, 2025.
Anthropogenic nitrogen oxide (NOx = NO + NO2) emissions have increased since the Industrial Revolution as a result of fossil fuel burning, contributing to increasing atmospheric acidity and changes to the oxidative capacity of the atmosphere. Oxidation of NOx leads to the formation of atmospheric nitrate both in the gas phase (HNO3(g)) and aerosol phase (p-NO3–), which may then be removed from the atmosphere via wet and dry deposition. Ice core records of nitrate may thus be used to infer past changes in atmospheric NOx concentrations and atmospheric acidity given high enough accumulation rates to prevent substantial post-depositional photolytic loss from the snowpack. Increasing trends innitrate concentrations over the 20th century have been observed in ice core records throughout the Northern Hemisphere including Greenland and the North Pacific. However, two ice cores (1980 NW Col and 2002 PR Col ice cores) retrieved from the summit plateau (5,334 m a.s.l.) of Mt. Logan, the second tallest mountain in North America located in the glaciated region of the St. Elias Mountains in southwest Yukon, revealed no long-term trend in acid chemistry. This lack of sensitivity to increasing atmospheric acidity was largely attributed to the high elevation of the site within the free troposphere and the efficient scrubbing of atmospheric pollutants during transit across the Pacific. Here, we present a nitrate record from the new 2022 Mt. Logan ice core since 1912 CE (~256 m depth). Reconstructed accumulation at the site is extremely high with an average rate of 2.97 m weq a-1 from 1912 to 2020, implying excellent preservation of volatile species coupled with low average temperatures (-26.9°C). The nitrate record suggests a statistically significant (p < 0.01) increasing trend since 1912 CE, in contrast to both the NW Col and PR Col records. The record agrees with other Northern Hemisphere ice core nitrate records including Summit (Greenland; r = 0.49, p < 0.01, 1912–2006), Begguya (Alaska; r = 0.44, p < 0.01, 1912–2012), and Eclipse (Yukon; r = 0.30, p < 0.01, 1912–2001). These results indicate that the highest elevation regions of the North Pacific, such as Mt. Logan, are indeed sensitive to anthropogenic NOx emissions, with ice cores providing rare insight into mid-tropospheric acid chemistry where preservation is adequate.
How to cite: Holland, K., Criscitiello, A., McConnell, J., Markle, B., Yousif, H., Jensen, B., Wensman, S., Skelton, E., Winski, D., Campbell, S., and Chellman, N.: Nitrate record of the 2022 Mt. Logan ice core suggests highest elevation regions sensitive to atmospheric acidity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15112, https://doi.org/10.5194/egusphere-egu25-15112, 2025.
Black carbon (BC) particles, emitted by incomplete combustion of biomass and fossil fuels, play a crucial role in Earth's radiation budget and climate. Conversely, climate changes can influence BC emissions from biomass burning (BB). Global warming has been linked to the recent increase in large wildfires worldwide, causing significant ecological and societal damage. Increased occurrence of large wildfires in the future could affect Earth’s radiation budget, and change the frequency at which certain regions are exposed to serious hazards. Understanding the long-term changes in BC concentrations and size distributions is essential to assess BC's role in climate dynamics and its response to climate change. At the EGU 2024 General Assembly, we presented an ice core BC record from the EastGRIP site in northeastern Greenland, focusing on temporal variability in BC derived from anthropogenic emissions. In this study, we present a high-resolution BC record from the SIGMA-D ice core in northwestern Greenland, spanning the past 350 years. Using an improved BC measurement technique coupled with a continuous flow analysis (CFA) system, we obtained accurate, high-temporal-resolution data on BC particle size and mass/number concentrations.
Our results reveal that both BC number and mass concentrations began to increase in the 1870s, peaked during the 1910s–1920s due to the inflow of anthropogenic BC, and subsequently decreased to pre-industrial levels or lower. However, BC particle size did not return to pre-industrial values, remaining elevated during the 1960s–2000s. Anthropogenic BC emissions also shifted the annual peak in BC concentrations from summer to winter–early spring, while the peak returned to summer after BC concentrations declined to pre-industrial levels. This suggests that BB has become the dominant source of BC at the SIGMA-D site in recent years. Interestingly, anthropogenic BC emissions made only a minor contribution to summer BC concentrations throughout the past 350 years. By separating winter and summer BC data, we reconstructed temporal variations in BC originating from boreal forest fires, even during periods of significant anthropogenic input. Our findings indicate no increase in boreal forest fire-derived BC until the early 2000s. These results enhance our understanding of the interplay between natural BC emissions, anthropogenic influences, and climate variability since the preindustrial time.
How to cite: Goto-Azuma, K., Ogawa-Tsukagawa, Y., Fukuda, K., Fujita, K., Hirabayashi, M., Dallmayr, R., Ogata, J., Moteki, N., Mori, T., Ohata, S., Kondo, Y., Koike, M., Matoba, S., Kadota, M., Tsushima, A., Nagatsuka, N., and Aoki, T.: Biomass burning over the past 350 years: insights from high-resolution analysis of black carbon particles in a northwestern Greenland ice core, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4894, https://doi.org/10.5194/egusphere-egu25-4894, 2025.
How to cite: Tetzner, D., Thomas, E., and Allen, C.: Sea ice diatoms in ice cores, a novel proxy for reconstructing past Antarctic sea ice changes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21557, https://doi.org/10.5194/egusphere-egu25-21557, 2025.
Ice core derived records of the past atmospheric methane concentration ([CH4]) allow us to reconstruct its past variability and its link to changes in the climate system. During the last glacial cycle [CH4] showed pronounced increases from glacial to interglacial conditions, but [CH4] also closely followed large and rapid millennial-scale warming events in the Northern Hemisphere associated with Dansgaard-Oeschger (DO) events, indicating a strong sensitivity of NH low-latitude CH4 sources to the position of the Inter-Tropical Convergence Zone.
Past [CH4] are well recorded by the measurements of Antarctic and Greenland ice cores, however, large parts of existing Greenland records over the last glacial period suffered from excess methane production during analysis (Mühl et al., 2023). The individual contributions of various sources and sinks to the global methane budget are still a matter of debate and a quantitative assessment is still missing for many time periods in the past. Synchronized ice core records from both polar regions allow to derive the Inter-Polar Difference (IPD) in [CH4] reflecting latitudinal emission variability and are used to distinguish low and high latitude CH4 sources. Another powerful tool to separate emissions from different sources are measurements of the stable hydrogen and carbon isotopic signature of CH4 (δ2H-CH4, δ13C-CH4) as CH4 released by the various sources are associated with characteristic isotopic signatures and different sinks are connected to systematic isotope fractionations, providing additional constraints on past CH4 source variability and top-down quantifications of the CH4 budget.
In this study we present the first complete δ2H-CH4 record over the last glacial cycle complementing our existing δ13C-CH4 record (Möller et al., 2013). The record shows only relatively small variations in δ2H-CH4 over the last glacial cycle, while δ13C-CH4 showed pronounced millennial variability, which are correlated to concurrent CO2 changes but not to stadial/interstadial climate variability. With additional measurements of Greenland ice core samples (GRIP) in the time interval 73-105 kyr, we can derive for the first time an IPD in both the methane concentration and the methane dual-isotopic signature during glacial times. We concentrate our CH4 budget reconstruction on selected time intervals during Heinrich Stadials 7b and 9, and DO events 21-23, where excess CH4 production does not affect our results.
How to cite: Mühl, M., Fischer, H., Schmitt, J., and Seth, B.: Improving the past methane budget using dual-isotope methane records over the last glacial cycle, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5912, https://doi.org/10.5194/egusphere-egu25-5912, 2025.
Past climate and environmental changes can be reconstructed from palaeoclimate archives, including marine sediment and polar ice cores. Understanding mechanisms associated with major climate changes requires an accurate and precise chronology for each archive and the synchronisation of these individual chronologies to a common multi-proxy timescale. Discrepancies between the individual chronologies can lead to misinterpretation of the phase relationships and the climate dynamics. For old terminations that occurred more than 700,000 years ago, when using original chronologies, ice core data suggest that the increase in atmospheric CO2 concentration lags behind the sea level rise recorded in marine sediment cores. This finding strongly contradicts the established understanding of the climate mechanisms during deglaciations based on observations over the seven most recent terminations, suggesting a mismatch between the site-specific chronologies. Deep ice core age scales are generally developed based on orbital dating correlating gas orbital tracers with insolation variations. However, in the deepest and oldest section of an ice core, thermally enhanced gas diffusion and extensive annual layer thinning significantly mute the proxy records, hampering precise orbital dating.
In this study, we evaluate the diffusion effect on the frequencies of the gas records critical for orbital dating and explore the incoherence within and between the AICC2023 ice core chronology and modelled LR04 age scale for the marine sediment cores for the period between 600,000 to 800,000 years ago utilising new high-resolution data (~700 years on average instead of >1000 years on average in the previous chronology reconstruction) from the deepest 200 metres of the EPICA Dome C (EDC) ice core. Spectral analyses of CH4, δ18O of O2, and δ(O2/N2) confirm that diffusion does not significantly affect the orbital-scale variability, which enables us to revise the existing depth-age relationship for EDC on its deepest section. Integrating chronological information from the ice core and a continuous high-resolution stable oxygen isotope record of benthic foraminifera using the statistical dating tool Paleochrono-1.1, we link the ice core chronology to marine sediment cores and propose an improved and coherent timescale to reconceive the CO2 and sea level scenario over old terminations.
How to cite: Klüssendorf, A., Auriol, E., Bouchet, M., Casado, M., Guilluy, H., Parrenin, F., Capron, É., Michel, E., Prié, F., Brugère, E., Teste, G., Salaün, S., and Landais, A.: Reliable Orbital Dating in Deep Ice Core Provides Accurate Marine-Ice Sequences over Old Terminations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11255, https://doi.org/10.5194/egusphere-egu25-11255, 2025.
Cosmogenic nuclides such as beryllium-10 (10Be) and chlorine-36 (36Cl) are valuable tools for dating deep ice cores and reconstructing paleomagnetic events. These nuclides are formed through interactions of target atoms in the atmosphere with galactic cosmic rays and deposited on ice sheets in aerosol form only and aerosol and gaseous forms for 10Be and 36Cl, respectively. However, questions persist regarding the preservation of their production signals in deep ice cores. In particular, low snow accumulation rates favour H36Cl migration and outgassing from the snowpack (Delmas et al., 2004; Pivot et al., 2019).
Here, we present new measurements of 10Be and 36Cl in the Talos Dome ice core, focusing on periods older than 170 ka BP. When corrected from the radioactive decay of 36Cl and 10Be, a 36Cl/10Be ratio of 0.125 is observed, consistent with ratios observed during the last 700 years in the Talos Dome ice core. The 36Cl/10Be ratio generally overestimate the reconstructed age compared to those expected from AICC2023 chronology (Bouchet et al., 2023). Thus, the consideration of climatic and chemical concentrations is necessary to correctly apply the 36Cl/10Be ratio as a dating tool.
Additionally, 10Be and 36Cl fluxes record past Earth magnetic field variations. We identify the Iceland Basin geomagnetic excursion around 190 ka as a clear stratigraphic marker, associated with a near doubling of the 10Be and 36Cl fluxes compared to background levels. By contrast, evidence for the Pringle Falls excursion(s) is less apparent. This different observation suggests that only the most intense excursions can be recorded in East Antarctic ice cores. This conclusion is of importance for future consideration of Beyond EPICA ice samples for investigating excursions and inversions after 800 ka.
Overall, our findings underscore the good preservation of atmospheric cosmogenic nuclide signals in the Talos Dome ice core, reinforcing their utility for dating deep ice and investigating paleomagnetic events.
How to cite: Lamothe, A., Baroni, M., Auriol, E., Severi, M., Team, A., and Bard, E.: Measurements of the 36Cl/10Be ratio in the deep ice of Talos Dome (East Antarctic): applications to paleomagnetism and ice dating., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14925, https://doi.org/10.5194/egusphere-egu25-14925, 2025.
Skytrain Ice Rise is a separate ice flow centre at the inland edge of the Ronne Ice Shelf, on the periphery of the West Antarctic Ice Sheet. An ice core drilled through to the base of the ice at 651 m was dated as far as 126 ka before present, which is found at 627 m depth. This ice has been used so far to investigate the climate and the ice sheet stability of the Holocene and the last interglacial. Here we investigate the ice between 627 and 651 m depth. Three methods for dating old ice have been applied to samples within this depth range. Analysis using the ATTA method of 81Kr, with a half-life of 229 kyr, has been carried out on three samples between 635 and 648 m, as well as on one younger sample of known age. 40Ar in the atmosphere is increasing with time, and therefore the deficit compared to modern of the derived quantity 40Aratm can be used to date ice. Two samples of deep ice have been analysed for this measure. Finally the ratio of 36Cl/10Be should be independent of production rate changes, and has an apparent half-life of 384 kyr. Five samples were analysed between 633 and 650 m. We first compare the findings from the three methods to establish their consistency. The combination of data from the three methods suggests that, despite flow disturbances that are apparent around the last interglacial (LIG) ice, the ages are monotonically increasing with depth. Ice just above the bottom is around half a million years old, suggesting that the ice at Skytrain Ice Rise has been present since before Marine Isotope Stage 11. The climate record will be shown, but has to be interpreted very carefully because we can assume that flow disturbances, similar to those in the LIG, have affected ice at the interfaces between cold and warm periods, leading to missing sections of the record.
How to cite: Wolff, E., Feng, X., Jiang, W., Lu, Z.-T., Ritterbusch, F., Wang, J., Yang, G.-M., Landais, A., Fourré, E., Combacal, T., Kappelt, N., Muscheler, R., and Mulvaney, R.: Ice half a million years old at the base of the Skytrain Ice Rise ice core, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6428, https://doi.org/10.5194/egusphere-egu25-6428, 2025.
81Kr (t1/2=229 ka) is a valuable isotope for radiometric dating of water and ice with a dating range from thirty thousand to over one million years. It is produced by cosmic rays in the stratosphere, and uniformly distributed in the atmosphere with an isotopic abundance of 81Kr/Kr ~ 1 ×10-12. Based on laser cooling and trapping, the detection method Atom Trap Trace Analysis (ATTA) has enabled 81Kr analysis at the extremely low isotopic abundance levels in the environment. However, it has been a challenge to apply 81Kr dating on ice cores where sample size is limited. Here, we present the realization of an all-optical ATTA system, reducing cross-sample contamination during 81Kr analysis by two orders of magnitude. As a consequence, the sample size requirement reduces to 1 kg of ice and the upper dating limit is extended to 1.5 million years. Using the all-optical ATTA system, we demonstrate 81Kr dating of 1-kg ice core samples from Taylor Glacier, Antarctica, whose gas ages are precisely known from their stratigraphic alignment. Moreover, we have performed 81Kr analysis on basal ice samples of the GISP2 core, providing constraints on when Greenland Summit was most recently ice-free. The achieved sample size reduction facilitates 81Kr dating of ice-core sections to address open questions in paleoclimatology such as the evolution of glaciers on the Tibetan Plateau or the stability of the West-Antarctic ice sheet.
How to cite: Wang, J., Ritterbusch, F., Feng, X., Shackleton, S., Bender, M., Brook, E., Higgins, J., Jia, Z., Jiang, W., Lu, Z., Severinghaus, J., Sun, L., Yang, G., and Zhao, L.: 81Kr dating of 1 kg polar ice, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2317, https://doi.org/10.5194/egusphere-egu25-2317, 2025.
Ice cores are indispensable archives for preserving terrestrial climate history, yet continuous Antarctic cores are limited to 1–1.5 million years due to basal melting, ice flow dynamics, and layer thinning, with the oldest continuous ice core (the EPICA Dome C core) extending to 800,000 years before present. Recent discoveries of ice as old as 6 million years from shallow cores drilled in the Allan Hills Blue Ice Area (BIA) in Antarctica indicate that it is possible to extend the polar ice core record well beyond what is possible from continuous ice cores. However, developing robust paleoclimate archives from Antarctic BIA ice cores is challenging due to the uncertainties in the orientation and thickness of layering in such old, deformed, and often chronologically disturbed ice. Cryo-cell laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) offers a micro-destructive method to analyze spatial impurities in ice cores at a sub-millimeter scale, and preserves most of the ice material for paired, high-precision chemical analyses. This study investigates the application of LA-ICP-MS for high-resolution chemical layer analysis and orientation of Antarctic BIA cores. By imaging distribution of trace elements like Na, Mg, Ca, Al, and Sr at micrometer (µm) scales, LA-ICP-MS enables the chemical characterization of individual ice layers. To evaluate the technique’s effectiveness, we analyzed NIST 612 glass standard, Taylor Glacier ice, and an Allan Hills ice core (ALHIC 1903). Our findings reveal that LA-ICP-MS captures fine-scale spatial variations (65 µm) in elemental concentrations, highlighting the potential for annual layer identification within BIA ice cores. In the ALHIC 1903 sample, we identified a probable annual layer through a distinct peak in Na concentration across the length of a sample, demonstrating the ability of LA-ICP-MS to reveal layering within ice microstructure. The study emphasizes the importance of optimizing laser parameters and washout times to preserve microstructural details, ultimately enhancing the reconstruction of paleoclimate records from BIA ice cores.
How to cite: Ishraque, F., Weldeghebriel, M., Niespolo, E., and Higgins, J.: Investigating Antarctic Blue Ice Climate Archives Using Laser Ablation Impurity Imaging, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3459, https://doi.org/10.5194/egusphere-egu25-3459, 2025.
Due to its small particle size, nanoparticle (NPs) and and microparticles (μPs) could reside in the air for a long time affecting human health and the environment. Understanding of its sources and dynamics in the atmosphere remains a complex challenge since direct observations are limited. Ice cores drilled from glaciers around the world contain records of atmospheric composition over time. Single particle Inductively Coupled Plasma Time-of-Flight Mass Spectrometry (spICP-TOFMS) is uniquely capable of quickly (in ~10 minutes) measuring the estimated mass equivalent size distribution, number concentration, and elemental chemical composition (up to 70 elements excluding O, H, N, F, and the noble gases) of more than 100,000 individual insoluble mineral NPs and μPs using <0.5 mL of melted ice. spICP-TOFMS allows us not only to consider the total mass concentrations of each element but also assess distribution of particles within each sample depending on elemental composition. Here, we present the results of spICP-TOFMS application for three sets of discrete samples: 1) Ice samples from the "horizontal ice core" from the Taylor Glacier (coastal East Antarctica) (44 – 9 kyrs BP). 2) Mt. Ortles (European Alps) ice core samples spanning from the pre-Roman period (780 BCE) to the modern era (1955 CE). 3) Snow and ice samples at the Upper Fremont glacier, WY, USA collected in 2024.
Study of 28 Taylor Glacier samples using spICP-TOFMS reveals changes in the concentration, size distribution, composition, and inferred mineralogy of individual particles during the last glacial-interglacial transition providing a first assessment of natural background variability of NPs and μPs in Antarctica. Samples from the Last Glacial Maximum (LGM, 18–29 kyr) tend to contain more sub-micron particles with higher fractions of Al, Mg, Na and Ca, and lower fractions of Si suggesting an additional input of material of a different elemental composition most likely due to varying mineralogical sources during the LGM compared to the Holocene. spICP-TOFMS analysis of samples from Mt. Ortles and Upper Fremont glacier were used to investigate anthropogenic particles. We observed enrichments for: Pb, Sb, Bi, Cu, Zn, Sn, Cr, Mo and Ni in modern samples. The percentage of Pb-containing particles increased by about a factor of ten in the most modern samples compared to the oldest sample. The total % mass due to Sn, Bi, and Pb were 26 to 97x higher in the modern samples than in the pre-Roman Mt. Ortles samples, consistent with those elements having significant contributions from anthropogenic sources. This study was supported by NSF Award 1744961.
How to cite: Kutuzov, S., C. Lomax-Vogt, M., Carter, L., Gabrielli, P., Bland, G., Sullivan, R., Lowry, G., and Olesik, J. W.: Analysis of nano- and micro- particles in ice cores from polar and high altitude glaciers by spICP-TOFMS, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7227, https://doi.org/10.5194/egusphere-egu25-7227, 2025.
Polar ice cores represent a unique and invaluable archive, offering an exceptional resource for enhancing our understanding of the atmospheric composition over time and its aerosol content. These cores preserve, over millennia, crucial information such as air bubbles, solid particles trapped in ice, as well as isotopes, heavy metals, and radioactive elements. Among the various paleoclimatic proxies, mineral dust is widely recognized as a key component of the climate system, strongly linked to the glacial-interglacial climate oscillations of the Quaternary period. Nevertheless, its impact on the radiative balance of the planet system remains to be fully quantified, primarily due to the considerable variations in its optical properties that occur over both space and time. In this context, laser-sensing instruments emerge as a versatile and non-destructive tool suitable for in-line characterisation of particle radiative properties.
In this work, we present an optical technique which provides two optical parameters, namely the extinction cross-section and the polarizability, of each particle passing through a focused laser beam under continuous forced flow, called Single Particle Extinction and Scattering (SPES). This method, developed by the Instrumental Optics of the Physics Department of the University of Milan, is based on the far-field, self-reference interference between the zero-angle field scattered by each nano- or microparticle and the more intense field transmitted through the sample.
This analysis has been applied to the EPICA ice core drilled at Dome C, East Antarctica, with depth range from about 200 to 2900 m. In deeper sections, where growth and recrystallisation of ice grains might cause relocation of impurities, particular attention has been directed towards the identification of dust aggregates, which have the potential to alter the original paleoclimate signal. Preliminary results and insight on the SPES method will be presented.
How to cite: Raspagni, V., Potenza, M. A. C., Delmonte, B., Teruzzi, L., Cremonesi, L., Scaiano, G., and Maggi, W.: Optical characterisation of mineral dust in polar ice: towards an improved understanding of climate-regulating processes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18857, https://doi.org/10.5194/egusphere-egu25-18857, 2025.
Reconstructing past Antarctic climate typically relies on vertical drilling of deep ice cores. However, the ~1% of the Antarctic ice sheet exposes blue ice, which offers a unique resource for paleoclimate research. The typically old blue ice exposed at the surface presents a continuous horizontal age gradient. By sampling ice along a transect in blue ice, we can thus reconstruct past climate variations.
In this study, we treat surface blue ice transects as horizontal ice cores and analyze 444 ice samples from the Sør Rondane Mountains. Isotope (δ18O) measurements from these samples enable the estimation of surface paleotemperatures for both the current interglacial period and the Last Glacial Maximum. By combining these paleotemperatures with the spatially variable source elevations of the blue ice, we provide the first insights into the (absence of) lapse rate changes (variations in the elevation-temperature relationship) in Antarctica over the last deglacial warming.
The absence of lapse rate changes in the samples from Antarctica contrasts with lower latitudes, which have experienced elevation-dependent warming over the same period. Our results reaffirm the potential of blue ice as an archive for reconstructing past climatic variations in Antarctica, and the easily accessible samples offer complementary insights to those obtained from vertical ice core drilling.
How to cite: Legrain, E., Tollenaar, V., Goderis, S., and Zekollari, H. and the BlueIceLapseRate Team: « Horizontal coring » in blue ice areas of Antarctica: an accessible approach for assessing paleoclimate variations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-147, https://doi.org/10.5194/egusphere-egu25-147, 2025.
The aim of the Australian Million Year Ice Core Project (MYIC) is to drill and recover an ice core that extends to well over a million years ago. Due to the highly thinned nature of the ice close to the bedrock of the MYIC, good vertical sampling resolution, and thus small sample capabilities, is key to resolve the variability in the climate records. This requirement demands major development of new ice core measurement capability, including a state-of-the-art ice continuous flow analysis facility and development and build of a new ice core gas laboratory.
The main capabilities for the gas laboratory include a small-volume (~50g) sublimation extraction system, a QCL absorption spectrometer, and a MAT 253+ mass spectrometer, to produce 1) concentration measurements of the primary greenhouse gases CO2, CH4, N2O to constrain changes in radiative forcing, 2) isotope ratio measurements of CO2 on discrete ice samples to screen measured concentrations for contamination artefacts and constrain carbon cycle source and sink changes, 3) measurements of δ18O-O2 and δ15N-N2 for understanding of site conditions, gas trapping, firnification processes and to aid dating. We present our plans and progress in establishing the new Hobart ice core gas facility to achieve these measurements.
How to cite: Baggenstos, D., Menking, J., and Pedro, J.: A new Australian gas lab for the Million Year Ice Core project, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-94, https://doi.org/10.5194/egusphere-egu25-94, 2025.
Water stable isotopes signals recorded in snow, firn and ice cores were successfully used to investigate past temperatures on glacial/interglacial scales. However, many uncertainties hampered the interpretation of water isotope records at sub-annual to decadal resolution as a proxy of past temperature variations only. Condensation, sublimation and/or redistribution of snow triggered by strong katabatic winds as well as diffusion within firn lessen the representativeness of a single isotopic profile to reconstruct past temperature in this region. In order to mitigate the non-representativeness of a single isotopic profile, a solution consists of averaging several records to increase signal to noise ratios.
In this study, we present an analysis of 3 stacked δ18O temporal series from the coast-to-plateau transition in Adélie land. Each of these stacks was built from three shallow firn cores (~20 m-long) drilled at 3 locations (so called D47, Stop5 and Stop0) with high accumulation rates (~200 mm w.eq ·yr-1) during the ASUMA campaign in December 2016 - January 2017. The sites feature different elevations (from 1516 m to 2416 m above sea level) and katabatic winds influence. We present a comparison of each of these stacks with virtual firn cores produced from the outputs of two atmospheric general circulation models including isotopes, ECHAM6wiso and LMDZ6iso for the period 1979 - 2016. In particular, we show how much of the climatic information we can retrieve from our δ18O stacked series.
How to cite: Tcheng, T., Fourré, E., Leroy-Dos Santos, C., Parrenin, F., Le Meur, E., Prié, F., Jossoud, O., Jacob, R., Minster, B., Magand, O., Agosta, C., Dutrievoz, N., Favier, V., Casado, M., Werner, M., Cauquoin, A., Arnaud, L., Jourdain, B., Picard, G., and Landais, A.: Investigating the possibility to retrieve climate information from three stacked δ18O series in Adélie Land: a comparison between data and virtual firn cores, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4393, https://doi.org/10.5194/egusphere-egu25-4393, 2025.
The measurement of atmospheric δO₂/N₂ trapped in ice is an incredible tool for ice core dating, as it is directly linked to local summer insolation. Numerous studies conducted between 2005 and 2022 have focused on determining the δO₂/N₂ composition of the EPICA Dome C (EDC) ice core. However, discrepancies between the datasets from these studies have emerged, raising questions about the potential causes of variability. Notably, inconsistencies between datasets measured years apart (e.g. 2012 vs. 2022) are investigated using newly acquired high-resolution δO₂/N₂ data in the age range from 450 to 550 ka BP. In this presentation, we present this new data together with a compilation of all available δO₂/N₂ values on the EDC ice core.
One significant factor influencing the δO₂/N₂ composition is gas loss during the storage of the ice samples, which appears to correlate with the storage temperature. Our results reveal that the storage temperature plays a critical role in preserving the δO₂/N₂ signature. Samples transported at -20°C, even for only a few months, exhibit a substantially more depleted δO₂/N₂ signature (approximately -5‰) compared to those consistently stored at -50°C. Additional factors influencing δO₂/N₂ values include the local accumulation rate and other regional conditions, for which the δD of the ice is a proxy. By comparing local summer insolation, δD of the ice, and δO₂/N₂ of the trapped air, one can distinguish the effects of orbital forcing from higher-frequency, non-orbital influences. Accurately interpreting the EDC δO₂/N₂ record is essential for the best use of this tool for the construction of the chronology of the new Beyond EPICA ice core.
How to cite: Brückner, L., Landais, A., Klüssendorf, A., Teste, G., Prié, F., and Brugère, É.: Limitations on the Use of Atmospheric δO₂/N₂ for Ice Core Dating: Insights from the EPICA Dome C Ice Core , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5176, https://doi.org/10.5194/egusphere-egu25-5176, 2025.
Ice cores drilled from polar ice sheets in Antarctica and Greenland contain ancient atmospheric air trapped in air bubbles. The reconstruction of past atmospheric greenhouse gas (GHG) concentrations, such as carbon dioxide (CO2) and methane (CH4), has enhanced our understanding of the glacial-interglacial climate cycles and their relationship to surface temperature. However, processes that alter the GHG concentrations of the trapped air poses a challenge for accurate GHG reconstruction and paleoclimate interpretation. Previous studies report excess GHG concentration related to various factors, such as ice impurities, organic carbon oxidation, methods of extracting trapped air, refrozen ice layers, and biological activity. Despite these findings, the causes and mechanisms of GHG alteration within glacial ice remain incompletely understood, for example, the alterations observed in shallow ice in blue-ice areas (BIAs). GHGs in shallow ice cores from BIAs in Antarctica show excess CO2 and CH4 concentration values and even extremely lower CH4 concentration than other non-contaminated ice core records at the same gas ages. Here, we aim to decipher the cause of excess GHG (CO2, CH4) concentration and depleted CH4 concentration observed in the shallow ice from Larsen BIA, East Antarctica. CO2 concentration in the Larsen blue ice shows a gradual decrease from the surface until a depth of ~4.6 m where the concentration variation stabilizes. In contrast, CH4 concentration records show an increasing trend from the surface to a depth of ~0.35–1.15 m. Then gradually decreases until it reaches stabilized values at ~4.6 m depth. Measurements of δ15N-N2, ion concentrations (Ca2+ and Na+), and Pb isotopes indicate that excess GHG concentrations are not associated to the modern air/aerosol intrusion. The pronounced excess GHG concentrations in the surface ice are not related to dust content. The observed δ18Oatm depletion in the surface ice suggests that photochemical reactions have occurred within the ice. Therefore, we infer that GHG alterations observed in the surface ice from Larsen BIA are attributed to UV photochemistry. Based on δ13C of CO2, we suggest that photolysis of both organic and inorganic carbon by ultraviolet light from sun is a primary source for the excess CO2 concentration.
How to cite: Lee, G., Ahn, J., Oyabu, I., M. Peterson, J., Han, C., Hirabayashi, M., J. Brook, E., Kawamura, K., Goto-Azuma, K., and Hong, S.: Deciphering the cause of greenhouse gas (CO2, CH4) alteration in shallow ice at Larsen blue-ice area, East Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6313, https://doi.org/10.5194/egusphere-egu25-6313, 2025.
The RICE ice core was drilled on the NE edge of the Ross Ice Shelf, at the summit of Roosevelt Island (79.364°S, 161.706°W, 550 m a.s.l.), an ice rise 764 m thick, locally-grounded 214 m below sea level (Bertler et al., 2018). The climate record documented in the ice core covers the last 83 ka, providing rich insights on the coastal Antarctic climate. Insoluble impurities in the RICE ice core mainly consist of mineral dust particles. Direct SEM and X-Ray diffraction analyses on single-grains from discrete dust samples extracted from RICE sections show evidence of extensive englacial diagenesis, in particular below ca. 650 m depth. Within the upper part of the core, dust particles are mostly volcanic or aeolian. In the deepest part of the core, conversely, aeolian dust particles show authigenic, eudral crystals grown on their surface. Also, individual crystals not showing signs of atmospheric transport both possibly resulting from in situ mineralization have been observed. Mineral neoformation likely results from the interaction between dust and fluids concentrating in ice crystal boundaries and triple junctions. Newly-formed minerals include Fe-bearing compounds such as Jarosite, Goethite, Magnetite and Hematite. These results are in line with the ice-weathering model proposed for ice deeper than about 1500 meters at Talos Dome (Baccolo et al., 2021a, 2021b), although in the case of RICE the depth of englacial mineralization is much shallower. Our results corroborate the finding that weathering and englacial diagenesis is a common process at depth inside thick ice sheet, potentially affecting the climatic interpretation of dust records in deep ice cores. Considering the different depth at which such processes have been found in RICE and Talos Dome ice cores, it remains to be understood which are the limiting factors controlling the initiation of such englacial reactions.
Bertler, Nancy AN, et al. "The Ross Sea Dipole–temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years." Climate of the Past 14.2 (2018): 193-214.
Baccolo, G., Delmonte, B., Niles, P.B., ... Snead, C., Frezzotti, M. Jarosite formation in deep Antarctic ice provides a window into acidic, water-limited weathering on Mars, Nature Communications, 2021, 12(1), 436
Baccolo, G., Delmonte, B., Di Stefano, E., ... Marcelli, A., Maggi, V. Deep ice as a geochemical reactor: Insights from iron speciation and mineralogy of dust in the Talos Dome ice core (East Antarctica), Cryosphere, 2021, 15(10), pp. 4807–4822
How to cite: Lanci, L., Delmonte, B., Mattioli, M., Valentini, L., Baccolo, G., and Bertler, N.: Mineral dust weathering in the RICE ice core, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5530, https://doi.org/10.5194/egusphere-egu25-5530, 2025.
Recent work demonstrates that the Skytrain ice core, retrieved from the Weddell Sea Embayment in West Antarctica, can inform us about the (in-)stability of the Ronne-Filcher Ice Shelf and the West Antarctic Ice Sheet in past warm periods. Here we switch our focus to the Last Glacial period at Skytrain and describe our “Calcium Conundrum”, which may be linked to ice sheet dynamics.
The Skytrain calcium record diverges from those of other Antarctic ice cores across several distinct time intervals. The increased Ca at Skytrain is not accompanied by a corresponding increase in other terrigenous elements such as Al. We hypothesize that the elevated Ca intervals result from additional input of relatively local dust, unique to Skytrain. To test this, we present new geochemical measurements on the soluble phase and fully digested dust particles from a ‘regular Ca’ interval (20–31 ka) and an ‘excess Ca’ interval (42–49 ka).
Trace element data confirm elevated Ca levels during the excess Ca interval, associated also with a significant Ba increase relative to Al. However, terrigenous elements associated with silicate minerals exhibit no significant difference between the two intervals when normalised to Al. Radiogenic Sr and Nd isotopes of the regular Ca interval fall within range of South American source areas, typical for Antarctica during the Last Glacial Period. In contrast, 87Sr/86Sr and eNd values for the excess Ca interval are significantly different from those of the regular Ca interval. Using a collation of Sr and Nd isotope data of potential source regions, complemented by new measurements on rocks from the nearby Ellsworth Mountains, we assess the possibility that the recurring excess Ca signal during the Last Glacial fingerprints a dynamic ice sheet in the Weddell Sea Embayment that intermittently exposed nearby nunataks to physical erosion and dust transport.
Additionally, we report the first (to our knowledge) Ca isotope measurements on ice cores in an effort to further fingerprint the source of the excess Ca.
How to cite: Rhodes, R., Pryer, H., Simpson, R., Hoffmann, H., Grieman, M., Stevenson, E., Bradbury, H., Turchyn, A., Humby, J., Marschalek, J., Archibald, E., Bauska, T., and Wolff, E.: Could the calcium conundrum in Skytrain shed light on West Antarctic Ice Sheet dynamics? , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7037, https://doi.org/10.5194/egusphere-egu25-7037, 2025.
Aerosol-related impurities trapped in ice cores can supply important insights into the mechanics of our climate system. Mineral dust particles can provide information on past atmospheric transport and ice sheet size. This information is encoded in the geochemical composition and size of the dust particles: Local dust sources are characterised by large particles. As a prominent example, changes in dust particle sizes in the RECAP ice core from the Renland ice cap (East Greenland) have been shown to reflect smaller ice cap extent during interglacial periods [1]. To better understand dust chemistry and size changes at high resolution, we applied several state-of-the-art analytical methods to samples of the RECAP and EGRIP ice cores from East Greenland: Cryo-Raman spectroscopy, Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) 2D mapping, coulter counter (CC), time-of-flight single particle analysis (SP ICP-TOFMS), and Low- Background Instrumental Neutron Activation Analysis (LB-INAA). We show that high-resolution LA-ICP-MS maps of Na, Al, Mg, and Fe, in accordance with Raman spectroscopy data from the same samples, reveal the clustering of particles in the microstructure and a species-dependent preferred localisation. Subsequent measurements, taken where possible on the same samples, provide new insoluble particle size and concentration data (CC) and further in-depth elemental characterisation of the dust particles (cryo-Raman, SP ICP-TOFMS, LB-INAA). We can thus reveal changes in size and composition of the dust particles between the Holocene and the last glacial period, as well as within the last glacial. We further introduce a new approach to estimating particle sizes by utilising previously gathered data, exploiting SP analyses' vast, largely untapped potential for ice core science. The know-how in combining these different state-of-the-art methods and their insight into high-resolution dust chemistry and size will also provide important assistance for interpreting the dust signal stored in the upcoming deepest ice of the Beyond EPICA – Oldest Ice Core. Work performed in the framework of the Arctic Research Program of Italy (project PRA2021-0009 “Abrupt climate change and Greenlandice cover in a high-resolution ice core record”).
[1] Simonsen, M.F., Baccolo, G., Blunier, T. et al. East Greenland ice core dust record reveals timing of Greenland ice sheet advance and retreat. Nat Commun 10, 4494 (2019). https://doi.org/10.1038/s41467-019-12546-2
How to cite: Masiol, M., Stoll, N., Larkman, P., Clases, D., Gonzalez de Vega, R., Di Stefano, E., Delmonte, B., Barbante, C., and Bohleber, P.: New insights on dust particles in Greenland ice cores combining state-of-the-art methods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7265, https://doi.org/10.5194/egusphere-egu25-7265, 2025.
The bottommost sections of ice cores are often difficult to date, due to the low temporal resolution and possible disturbances, such as folding and missing layers. One possible tool for dating this ice is the 36Cl/10Be ratio, which decays with a combined half-life of 384 kyr years. Individual radionuclides are created by galactic cosmic rays in the atmosphere, but the ratio has been modelled to remove the varying production signal. The chronology of the recently drilled Skytrain ice core from West Antarctica ends with an age of 126 kyr BP 24 m above bedrock. Our aim was to obtain age estimates for samples in the undated section below, while improving our understanding of the 36Cl/10Be ratio as a dating tool. Two datasets were measured: an annually resolved record of the last few decades and a series of older samples from the Holocene, the last interglacial and five samples from the undated section. The data from recent decades was used to test whether the Skytrain site is affected by 36Cl loss, which occurs at low accumulation sites, such as EPICA Dome C and Little Dome C in East Antarctica, where 36Cl is gassing out as HCl. By measuring anthropogenic 36Cl from nuclear bomb tests in the 50s and 60s, we were able to confirm that the peak is found at the expected depth and that no 36Cl loss occurs. In older samples, there was a marked difference between glacial and interglacial data, with higher individual 36Cl and 10Be concentrations in glacial times. This is observed at other sites as well and can most likely be attributed to a dilution effect. However, the 36Cl/10Be ratio was also found to be higher in the last glacial period and correlated with the d18O signal, which likely results from the different physical and chemical properties of 36Cl and 10Be. While 36Cl can be found in its gaseous form or attached to particles, 10Be is always attached to particles, which yields different sensitivities to changes in temperature or precipitation. Possible mechanisms include a washout en-route, which may affect one radionuclide more than the other or an increased scavenging efficiency for 36Cl in mixed-phase clouds. While not fully understood, the correlation with d18O was used to detrend the data and estimate the age of five samples below the dated section, the oldest being 541 +55-61 kyr old.
How to cite: Kappelt, N., Wolff, E., Christl, M., Vockenhuber, C., and Muscheler, R.: Dating old ice with the 36Cl/10Be ratio, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8532, https://doi.org/10.5194/egusphere-egu25-8532, 2025.
Global warming driven by human activities has a greater impact on polar regions than the global average, a phenomenon known as polar amplification (Casado et al. 2023; England et al. 2021). Strong warming has been directly observed in West Antarctica and in the Antarctic Peninsula. Yet, evidences in the East Antarctic Plateau region remains anecdotal (Clem et al. 2020), even though this region, characterised by thicker ice sheet, represents the largest potential source of global sea-level rise and plays a key role in understanding climatic feedbacks essential for future projections. The ERA5 reanalysis data suggest a warming trend over the recent 30-year at multiple sites on the plateau. However, the natural variability at decadal scale observed on the plateau complicates the isolation of a multi-decadal forced warming trend. In addition, the reliability of this trend estimation is constrained by the time series’ limited coverage, starting in 1940 and exhibiting a discontinuity around 1980, coinciding with the assimilation of satellite data. To address this, ice core records offer a valuable long-term climatic archive. Water stable isotopes (δ¹⁸O and δD) from ice cores, with their well-establish relationship to local temperature – commonly referred to as “paleo-thermometer” – are crucial for reconstructing past temperature variations.
In this study, we present isotopic records from four firn cores collected at the Paleo site, located in the interior of the East Antarctic Plateau. The 18-meter-deep cores were drilled during the austral summer 2019-2020 as part of the East Antarctic International Ice Sheet Traverse (EAIIST) project. By stacking the four ice cores, we enhance the signal-to-noise ratio, resulting in a record that effectively captures climate information at a scale better than interdecadal. These results are first compared to reanalysis data to evaluate their ability to represent the climatic conditions in this remote area on the plateau, which lacks direct observations. Subsequently, the extended time series is presented, offering valuable insights into climatic variability over the past ~350 years and potentially improving the isolation and quantification of the anthropogenic warming trend in this region.
How to cite: Petteni, A., Casado, M., Savarino, J., Spolaor, A., Fourré, E., Becagli, S., Ooms, A., Gautier, E., Landais, A., Samin, E., Frezzotti, M., Dreossi, G., and Stenni, B.: Regional patterns of anthropogenic warming in East Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11852, https://doi.org/10.5194/egusphere-egu25-11852, 2025.
Water isotopes records in polar ice cores provide insights into past climate variability through oxygen and hydrogen fractionation. The EPICA Dome C (EDC) deep ice core in Antarctica has provided δ18O and δD records over the last 800,000 years, which are known to be valuable proxies for tracking temperature variation. Combining both, the deuterium excess (d-excess = δD − 8 * δ18O) gives us information on the hydrological cycle, as it is known to reflect the evaporation stage and air mass transport. However, it is sensitive to the variations of seawater δ18O and the distillation effect of the air mass. The 17O-excess (17O-excess = ln(δ17O+1) − 0.528×ln(δ18O+1)) can provide complementary information to d-excess as it is rather sensitive to air mass mixing and supersaturated conditions along the path.
Here, we present the first record of 17O-excess for the EDC ice core, spanning over the past 126,000 to 800,000 years. We aim to investigate the potential of this tool for interpreting the reorganization of the hydrological cycle in the Southern Hemisphere. 17O-excess variations along the core show the alternation of glacial and interglacial cycles, comparable with other water isotopes and related to orbital parameters. We scrutinize the glacial-interglacial 17O-excess amplitude shift around 400,000 years ago, with amplification of variations in the most recent part, with lower minima, while maxima reach similar levels. This shift could have emerged after the Mid-Pleistocene Transition.
How to cite: Samin, E., Landais, A., Combacal, T., Grisart, A., Jouzel, J., Masson-Delmotte, V., Minster, B., Prié, F., and Stenni, B.: First 17O-excess record for the EPICA Dome C deep ice core, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11227, https://doi.org/10.5194/egusphere-egu25-11227, 2025.
Ice cores from the Allan Hills (AH) Blue Ice Area, Antarctica, are up to 6 million years of age, providing novel snapshots in time reaching back into the Miocene. However, AH ice core records are often discontinuous, probably caused by a complicated flow behaviour and, so far unknown, history. Deriving a better understanding of the past and current deformation via ice crystal orientation and microstructure analysis will help interpret these precious ice samples. We, therefore, apply a cascade of structural glaciology methods focusing on four depth regimes around identified age reversals from the 159 m long AH1901 core. Visible features in this, and other AH cores, are large, strongly elongated bubbles. We thus analyse the 2D shape preferred orientation (SPO) of almost 20,000 air bubbles within polished AH samples using established optical mapping methods. Bubble elongation (aspect ratio) is up to 3 times larger than in, e.g., the WAIS divide ice core and is comparably consistent throughout all samples, implying a critical ice-strain rate for a significant time. Similar results were derived via 3D micro-CT investigations. High-resolution grain boundary network analyses via Large Area Scanning Macroscope (LASM) reveal comparably large, bulging crystals with amoeboid shapes, indicating strong recrystallisation. Mean crystal sizes in horizontally (to the core axis) orientated samples are roughly 2-5 times larger than in vertically oriented crystals indicating highly elongated crystal shapes. Finally, we investigated the crystal-preferred orientation (CPO or fabric) within polished thin sections (300 μm) with an automated fabric analyser (G50). Preliminary data show broad single maxima CPOs with several deviating crystals. Closer investigations identify these diverging crystals as bands of crystals with a different orientation intruding the matrix of similar-orientated crystals. Comparable observations were made in the NEEM core (tilted lattice bands), and they could indicate highly localised shear zones. Further investigations on additional samples will help characterise the flow history of AH ice.
How to cite: Stoll, N., Hishamunda, V., Shaya, M., Shaw, C. A., Shackleton, S., Brook, E., Higgins, J., and Fudge, T. J.: Novel insights into the microstructure and crystal-preferred orientation of million-year-old Allan Hills ice, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12402, https://doi.org/10.5194/egusphere-egu25-12402, 2025.
In recent years, laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) applied to ice-core samples has become the go-to method to investigate climate signals in highly thinned sections of ice cores and the interaction of impurities and the ice’s microstructure. Ablation is typically performed using DUV (deep UV, 193 nm or 213 nm) excimer laser sources. However, at these wavelengths ice is virtually transparent leading to high penetration of the laser energy into the ice. That means that ablation is sometimes non-controlled and likely depends on the impurity load of the ice, and may require very high on-sample fluence. This makes it challenging to generate calibrated ice-core impurity records using cryo-LA-ICPMS. One approach to overcome this is to utilize a laser wavelength that is absorbed by the ice, resulting in shallower penetration. To implement this, we have built a unique custom-designed dual-wavelength LA system that can use both 193 nm and 157 nm excimer lasers. At 157 nm, ice is strongly absorbent, which implies good energy transfer into the sample. Our setup has already been successfully used to ablate other DUV-transparent materials such as fused silica and quartz.
Here we present the design of the system and the accompanying purpose-built cryo sample holder that allows us to use both 193 nm and 157 nm laser light for the analysis of ice-core samples. The holder is designed to enable high sample throughput by keeping three 14 cm long ice core samples alongside reference materials and frozen standards inside the proven Laurin Technic S155 ablation chamber. In addition to showcasing the design of our system we will show initial results of laser ablation analyses from Greenland ice core samples over Stadial/Interstadial transitions using an Agilent 8900 ICP-MS/MS. In the presented setup the system can be used both to generate high-depth-resolution down-core time series as well as high-resolution impurity maps, both of which are essential to further our understanding of the signal preservation in the ice and to ultimately reconstruct climate variability from highly thinned ice-core records such as the >1Ma old Beyond EPICA Oldest Ice core.
How to cite: Erhardt, T., Norris, C. A., Shelly, M., Rittberger, R., Marko, L., Schmidt, A., and Müller, W.: First results from a dual-wavelength (157 & 193 nm) LA-ICP-MS/MS System for spatially-resolved chemical analysis of ice cores, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12745, https://doi.org/10.5194/egusphere-egu25-12745, 2025.
Nitrous oxide (N2O) is a potent greenhouse gas also involved in the destruction of stratospheric ozone. Unlike carbon dioxide (CO2) and methane (CH4), there is no continuous record of past atmospheric concentrations of N2O from ice cores over the last 800,000 years. This is due to the production of excess N2O in dust-rich Antarctic ice during glacial periods.
We investigated the production of N2O that happens in the ice sheet - referred to as in situ production - with the aim of systematically identifying affected ice core samples. To this end, we measured the nitrogen bulk and position-specific isotopic composition of N2O in dust-rich samples affected by in situ production in the EDC, Vostok, EDML, and Taylor Glacier ice cores. We calculated the isotopic signature of in situ-produced N2O with a mass balance approach. For this calculation, we had to determine the amount of N2O enrichment from in situ production relative to an unaffected atmospheric baseline for N2O concentration and isotopic composition. We chose to use as the atmospheric baseline the N2O record from the TALDICE ice core, which has a low dust content and is supposed to be the least affected by in situ production. To investigate a potential nitrogen precursor, we then compared the nitrogen isotopic signature of in situ-produced N2O with that of nitrate (NO3-) measured in the same samples.
These measurements reveal that the isotopic composition of the central-position N atom in the N2O molecule (δ15Nα) correlates with the nitrogen isotopic composition of NO3- with a slope of 1. However, there is no correlation between the nitrogen isotopic composition of the terminal-position N atom in N2O (δ15Nβ) and that of NO3-. Therefore, our study shows that the N2O produced in situ is hybrid, i.e., the two N atoms in the N2O molecule come from two distinct nitrogen sources. Our hypothesis is based on a reaction involving three reactants. NO3- present in the ice provides the central-position N atom in N2O. It is first converted to NO2- by a reducing species contained in the dust (e.g. Fe2+), and NO2- reacts with a yet unknown nucleophilic species that is the source of the terminal-position N atom.
How to cite: Soussaintjean, L., Schmitt, J., Savarino, J., Menking, A., Brook, E., Seth, B., Röckmann, T., and Fischer, H.: Towards understanding the N2O production in dust-rich Antarctic ice using bulk and position-specific isotope analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8910, https://doi.org/10.5194/egusphere-egu25-8910, 2025.
The West Antarctic Ice Sheet (WAIS), holding close to five metres sea level equivalent of ice, has long been considered one of the major tipping elements in the Earth’s climate system. A recent study suggests that WAIS is perhaps one of the most decisive elements in this system as well (Wang et al., 2023). Total Air Content (TAC) data (a proxy for ice sheet elevation) from the Skytrain Ice Rise ice core (~79°S, 078°W, 784 m altitude) shows rapid elevation changes of around 100 m within decadal timescales around 8,000 years ago at this site (Grieman et al.,2024), which provides strong evidence towards the vulnerability of this region and the need to understand its past behaviour in high spatial and temporal resolution.
Here, we present a complete record of TAC during the Holocene from the Fletcher Promontory ice core (~78°S, 082°W, 873 m altitude) located around 220 km from the Skytrain Ice Rise site. The record covers the entire Holocene until ~11,000 years BP, measured on a high-accuracy TAC system. Using the two records from Skytrain Ice Rise and Fletcher Promontory, the long-term trends and offsets in this region during the Holocene are investigated. The reliability of the TAC data and the robustness of our measurement system are also discussed, along with implications for WAIS and possible future studies.
Wang, S. et al: Mechanisms and Impacts of Earth System Tipping Elements. Reviews of Geophysics 61, 1 (2023). https://doi.org/10.1029/2021RG000757
Grieman, M.M., Nehrbass-Ahles, C., Hoffmann, H.M. et al.: Abrupt Holocene ice loss due to thinning and ungrounding in the Weddell Sea Embayment. Nat. Geosci. 17, 227–232 (2024). https://doi.org/10.1038/s41561-024-01375-8
How to cite: Venkatesh, J., King, A., Chapman, K., Miller, S., Nehrbass-Ahles, C., Mulvaney, R., Wolff, E., Faïn, X., Capron, E., and Bauska, T.: Placing the Weddell Sea Holocene elevation drop in context: New records of total air content from Fletcher Promontory and Skytrain Ice Rise, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20335, https://doi.org/10.5194/egusphere-egu25-20335, 2025.
In the deeper part of polar ice sheets, air clathrate hydrates (commonly referred to as air hydrates) trap most of the ancient air molecules in their crystal structure, which is the only direct paleo-atmosphere access used for paleoclimatic reconstructions. They form the cubic structure II (sII or CS-II), which consists out of cages formed by water molecules in which the air molecules are enclosed. However, their microstructure and crystallinity are poorly understood.
Studying air hydrates in polar ice is challenging because they are thermodynamically unstable and dissociate under the temperature and pressure conditions in the cold-laboratories. However, the surrounding ice acts as a pressure cell to keep them metastable for a certain amount of time (in the order of years to tens of years).
We use transmitted light microscopy paired with Cryogenic Scanning Electron Microscopy (Cryo-SEM) to investigate air hydrates in polar ice cores. Transmitted light microscopy enables the localization of air hydrates inside the ice sample. Ice grain boundaries and ice relaxation features, such as plate-like inclusions, are useful for orientation during SEM analysis. Air hydrates at or close to the samples surface already dissociate in the cold-laboratory during sample preparation, and form a characteristic structure. Controlled sublimation inside the SEM chamber allows to observe air hydrates previously located inside the ice sample and to investigate their dissociation behavior with sub-micron resolution. For the first time, we perform Electron Backscatter Diffraction (EBSD) analysis on air hydrates in polar ice, which is a powerful method to study the crystallographic structure of materials.
How to cite: Painer, F., Hamers, M., Drury, M., Kipfstuhl, S., and Weikusat, I.: Cryo-SEM and EBSD on air clathrate hydrates in polar ice, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15678, https://doi.org/10.5194/egusphere-egu25-15678, 2025.
The ocean is the largest heat reservoir of the planet active on millennial to orbital time scales. By observing and reconstructing its temperature changes – together with the evolution of ice sheet volume – insights on the distribution of Earth’s energy balance may be traced though time (Baggenstos et al., 2019).
MOT is reconstructed in our studies from noble gases trapped within ice cores. Noble gases are inert: as a result, they partition in a simple two reservoirs system: the atmosphere and the ocean and are not affected by biological cycles in the ocean. As the atmospheric concentration of noble gases is tied to their solubility in the ocean, and the latter is in turn mostly temperature dependent, the concentration recorded within ice cores gas bubbles or clathrates creates a continuous atmospheric record through time. As heat and noble gases are conservatively entrained into the interior of the ocean, we stress that with our MOT approach we obtain the integrated ocean heat content at a given point in time, integrating over all water parcels of the ocean which have different ventilation ages, hence which have equilibrated at the ocean surface at different points back in time. Accordingly, MOT is a convoluted signal of past sea surface temperatures biased towards regions of deep and intermediate water formation.
The majority of MOT analyses carried out thus far have focused on glacial terminations. Here, we build upon the already existing TIV & TIII data to present early results focused on the glacial cycle in-between. The EPICA Dome C ice core is used to reconstruct MOT fluctuation during Marine Isotope Stage 8 (MIS 8: 255 – 330 ka) with a millennia-scale resolution. This allows to look in the detail of a glacial inception and investigate the mechanisms triggering the onset of glaciation.
Baggenstos, D., Häberli, M., Schmitt, J., Shackleton, S. A., Birner, B., Severinghaus, J. P., Kellerhals, T., & Fischer, H. (2019). Earth’s radiative imbalance from the Last Glacial Maximum to the present. Proceedings of the National Academy of Sciences of the United States of America, 116(30), 14881–14886. https://doi.org/10.1073/pnas.1905447116
How to cite: Traeger, H., Grimmer, M., Schmitt, J., Baggenstos, D., and Fischer, H.: Reconstructing Mean Ocean Temperature over a full glacial cycle using noble-gas ratios from the EDC ice core, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14884, https://doi.org/10.5194/egusphere-egu25-14884, 2025.
The European Project for Ice Coring in Antarctica (EPICA) Beyond EPICA – Oldest Ice aims at retrieving a continuous ice core record of climate feedback and forcing spanning about 1.5 Ma back in time. In that period the cyclicity of glacial/interglacial changes in continental ice sheet volume and temperature changed from 40 ka to the well-known 100 ka cycles encountered over the last 800 ka. After determining a suitable drill site Little Dome C (LDC), 35 km southwest of Concordia station, during an extensive pre-site survey, we penetrated to 2800 m depth during the third deep drilling season 2024/25, roughly spanning at least 1.2 Ma and a basal unit below 2584 m. We will report on the drilling and core processing activities, completed to the bottom at 2800 m depth.
How to cite: Wilhelms, F. and the BELDC field participants 2022/23, 23/24, 24/25, stable isotope field measurements team, dating team: Beyond EPICA Little Dome C (BELDC) field seasons to bedrock, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14784, https://doi.org/10.5194/egusphere-egu25-14784, 2025.
Ice cores constitute a valuable archive for reconstructing climate and atmospheric composition from glacial-interglacial to annual timescales. The Total Air Content (TAC), corresponding to the total volume of air trapped in ice, reflects changes in atmospheric pressure, temperature, and pore volume at the bubble close-off at the bottom of the firn. Building on these properties, TAC has been employed as a paleoelevation proxy and more recently as an orbital dating tool. Pore volume at bubble close-off depends not only on atmospheric pressure but also on local surface conditions driving firn densification and air entrapment efficiency through processes like compaction and snow grain metamorphism.
Investigating the relative impact of different surface climate parameters on the TAC signal, requires evaluating variables such as local insolation, accumulation rate, and seasonal temperature variations. Previous studies have mainly focused on site-specific analyses, limiting broader insights into regional and global patterns. To address this gap, we compiled TAC data from 30 ice cores across Antarctica and Greenland, combining published datasets with new measurements from the EDC, EDML and TALDICE ice cores. This data compilation includes sites with highly contrasting local climatic conditions, in terms of accumulation rates (1150 to 22 mm w.e. yr-1) and surface temperatures (-14 to -58°C). In addition to surface parameters (e.g. reconstructed annual surface temperatures and accumulation rates, Half Year local Summer Insolation index and atmospheric pressures), simulated summer temperatures from an Earth system model of intermediate complexity were used to be compared to past TAC changes. Then, we apply a series of statistical analyses on the compiled dataset, including linear and multiple regression analyses as well as residual analyses, to evaluate the relationships between TAC and the different environmental parameters at orbital and millennial scales. We also compare the measured TAC datasets with TAC outputs from the IGE firn densification model.
Our results highlight regional contrasts in the relationship between TAC variations and the different surface climate parameters. For Greenlandic ice cores we observed strong correlations observed between TAC and climatic parameters. For instance, at NGRIP and GRIP sites, coefficients of determination (R2) between TAC and Half Year Summer Insolation are higher than 0.6. Antarctic sites, including those on the East plateau, exhibited more variable and site-specific responses. For example, at EDC and Dome Fuji sites, the R2 between TAC and Half Year Summer Insolation is respectively 0.3 and 0.6. These findings underline the critical importance of addressing site-dependent dynamics to use TAC as a robust environmental proxy and orbital dating tool.
How to cite: Guilluy, H., Capron, É., Parrenin, F., Lipenkov, V., Schmitt, J., Wu, Z., Yin, Q., Klüssendorf, A., Landais, A., Martinerie, P., Seth, B., Fischer, H., and Raynaud, D.: Investigating the relationship between Total Air Content (TAC) variations in polar ice cores and surface climate conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16850, https://doi.org/10.5194/egusphere-egu25-16850, 2025.
An unprecedented heatwave affected East Antarctica between 15 and 19 March 2022, triggering record-high temperatures from the coastal regions to the Antarctic plateau. The event was caused by an intense atmospheric river that transported heat and moisture from the central and southwestern subtropical Indian Ocean at lower latitudes into the interior of continental Antarctica. Although the poleward moisture advection ceased after 18 March, a counterclockwise flow of clouds around a blocking anticyclone trapped the residual moisture over Antarctica. This led to sustained high surface temperatures for several days following the atmospheric river event (Wille et al., 2024a).
The heatwave brought rain and caused significant surface melting in coastal areas and intense snowfall events in the inner Antarctic region, which contributed to an overall positive mass balance. The Italian stake farm close to Concordia Station observed an accumulation of ~7 cm from 15 February to 22 March, which represents almost 90% of the local amount of accumulation.
Although the March 2022 heatwave lasted only for some days, model results suggest that this anomaly can be retrieved from ice core records over the equivalent of several years of snow accumulation (Wille et al., 2024b).
Since 2008, daily precipitation has been collected at Concordia Station, East Antarctica. The snow collected during the March 2022 heatwave exhibits δ¹⁸O and δ²H values that are the highest recorded since precipitation collection began. On 9 January 2023, a high-resolution snow pit, sampled at 2 cm intervals, was dug at Concordia. The isotopic analysis revealed a significant peak between 12 and 16 cm in depth, with three δ¹⁸O values exceeding -40‰. These unusually high values can be directly linked to the precipitation from the March 2022 heatwave.
The oceanic origin of the water vapor was also observed in tritium (3H) levels: in the Dome C 2022 precipitation reconnaissance measurements, values were as low as 10 TU (compared to between 20 and 400 TU during the rest of the year), which is in good agreement with GNIP observation sites closer to the Antarctic coast at similar latitudes.
Understanding the effects of single heatwave events on the isotopic signal stored in snow, firn and in ice cores is fundamental to better constrain palaeoclimatological studies, where isotopic analysis is widely used in climate reconstruction studies.
Wille, J. D., and Coauthors, 2024a. https://doi.org/10.1175/JCLI-D-23-0175.1
Wille, J. D., and Coauthors, 2024b. https://doi.org/10.1175/JCLI-D-23-0176.1
How to cite: Dreossi, G., Masiol, M., Zannoni, D., Stefanini, C., Scarchilli, C., Ciardini, V., Grigioni, P., Del Guasta, M., Landais, A., Casado, M., Ollivier, I., Terzer-Wassmuth, S., Copia, L., and Stenni, B.: March 2022 warm event detected in precipitation and surface snow at Concordia Station in East Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19112, https://doi.org/10.5194/egusphere-egu25-19112, 2025.
Paleoclimate reconstructions from ice core records can be hampered due to the lack of a reliable chronology, especially in deep ice, when the stratigraphy is disturbed and conventional dating methods cannot be applied. The noble gas radioisotopes 81Kr and 39Ar can in these cases provide robust constraints as they yield absolute, radiometric ages. 81Kr (t1/2=229 ka) covers the time span of 30-1500 ka, which is especially relevant for polar ice cores, whereas 39Ar (t1/2=268 a) with a dating range of 50-1600 a is suitable for alpine glaciers. The anthropogenic 85Kr (t1/2=10.8 a) is particularly useful to quantify contamination with modern air. Due to advances in the detection of 81Kr, 85Kr and 39Ar with Atom Trap Trace Analysis (ATTA), the sample size has been reduced to ~ 1 kg of polar ice. However, this amount can still be difficult to obtain, for example from the upcoming deepest sections of the “Beyond EPICA – Oldest Ice Core” (BEOI), for which no archive piece will be conserved.
Here, we present 85Kr and 81Kr results for gas samples from an Antarctic ice core extracted at the debubbler waste line of a continuous flow analysis (CFA) system. From the continuous melting of ~3 m long core, discrete ~ 100 mL STP gas samples have been extracted, and subsequently analyzed offline for 85Kr and 81Kr. The 85Kr results indicate a minor contamination with modern air of 1-2 %, which can likely be reduced by an earlier bypassing of contaminant air from cracks within a CFA stick and transitions between sequential CFA sticks.
The presented extraction system enables 81Kr and 39Ar dating of an ice core at numerous depths without additional ice demand, which is particularly relevant for upcoming CFA-melting campaigns of deep polar ice cores.
How to cite: Wachs, D., Ritterbusch, F., Baumbusch, C., Dallmayr, R., Feng, X., Lin, Q.-S., Spagnesi, A., Urbach, K., Wang, J., Aeschbach, W., Barbante, C., Jiang, W., Lu, Z.-T., Oberthaler, M., Yang, G.-M., and Bohleber, P.: Gas extraction from continuous flow analysis for dating ice cores with 39Ar and 81Kr, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10761, https://doi.org/10.5194/egusphere-egu25-10761, 2025.
The capability of ice-covered surfaces to reflect solar electromagnetic radiation is significantly influenced by mineral dust, one of the primary components of aerosols. This dust alters the reflectance of the ice, causing a larger portion of the radiation to be absorbed, depending on the properties of the dust layer.
The aim of this work is to apply a novel hyperspectral, microphysical and mineralogical interdisciplinary approach for the characterisation of ice cores and the entrapped mineral dust. More than 120 m of the 224 m long ADA270 ice core drilled in 2021 from the Adamello glacier (Pian di Neve, Italian Alps) has been analysed trough this method. A non-destructive Hyperspectral imaging sensor is used to create high-spatial and high-spectral resolution images in the VNIR wavelength range (380-1000 nm).
Hyperspectral measurements were performed at the EuroCold Laboratory of the University Milano-Bicocca (Italy). From these, some optical descriptors such as Albedo, Snow Darkening Index (SDI) and Impurity Index (II) (Di Mauro B. et al, 2015) were extracted. We compared results with independent measurements of dust concentration, grain size (Coulter Counter) and mineralogy (X-Ray Diffraction). Also, single-grain analyses with a Hyperspectral Imaging Microscope Spectrometer (HIMS, Central Washington University, USA) generating reflectance spectra in the same VNIR range were performed in order to explore the possibility to associate the optical footprint of dust layers to specific mineralogical mixtures.
The hyperspectral analysis of the ice core, spanning depths from 3.4 to 124 meters, revealed a sequence of melting-refreezing zones, bubbled regions, and dusty layers, these latter particularly abundant in the upper part of the core. Comparison of the SDI signal with the mineral dust concentrations confirms that, as expected, reflectance diminishes as mineral dust content rises. The mineralogical analyses indicate a notable presence of Quartz, Chlorite, and Biotite, likely due to local transport, along with Kaolinite, a secondary mineral typically linked to Saharan dust transport. By means of the HIMS system various reflectance spectra were extracted from dust samples, providing valuable insights into the optical effects of mineral dust transport through the atmosphere and aiding in the identification of its source region.
By integrating hyperspectral, microphysical, and XRD data, a comprehensive characterization of the inorganic content of the Adamello ice core can be achieved. Micro-hyperspectral measurements offer a qualitative assessment of the optical impact of individual minerals, helping to assess their influence on atmospheric optics, glacier melting rates, and the response of hyperspectral scanning systems.
How to cite: Fiorini, D., Delmonte, B., Di Stefano, E., Mangili, C., Andò, S., Cavallo, A., Kaspari, S., Artoni, C., and Maggi, V.: High resolution hyperspectral, microphysical and mineralogical interdisciplinary approach applied on the 224 m long ice core drilled on the Adamello glacier (Italian Alps), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18499, https://doi.org/10.5194/egusphere-egu25-18499, 2025.
Posters virtual: Fri, 2 May, 14:00–15:45 | vPoster spot 5
EGU25-2329 | Posters virtual | VPS7
Cryptotephra fingerprinting of 1458 CE and 426 BCE volcanic events in East Antarctic ice coresFri, 02 May, 14:00–15:45 (CEST) | vP5.2
Powerful volcanic eruptions inject into the stratosphere sulphur and tephra that may be spread globally and affect the Earth’s climate. Over the last 2500 years, Sigl et al. (2015) made a synthesis of the polar ice core atmospheric sulphur record and climate anomalies from dendrochronological records. Aside from a few historical events, most large eruptions with a bipolar imprint and a significant climate anomaly are from the tropical latitudes, but their sources are unknown.
We analysed the micron-size crytotephra composition accompanying the (stratospheric) sulphate of the 1458 CE and 426 BCE volcanic events recorded in three Antarctic ice cores. The 1458 CE event occurred within a cool climate and was initially attributed to the Kuwae (Vanuatu) eruption. This link is however questioned by Hartman et al. (2019) from their study of a South Pole ice core. The 426 BCE event appears concomitant with a significant global climate cooling, but its source is unknown.
Within the sulphate peak, the particle size distribution, when available, helps documenting the dynamics of the arrival of the stratospheric plume. Cryptotephra are collected by filtration and after carbon-coating, analysed by an EPMA microprobe. We applied the analytical procedure of Narcisi et al. (2019) (who identified the 1257 CE Samalas eruption), adapted to the micron-size of the crytotephra.
For the 1458 CE event, a medium-K dacite to rhyolite composition is consistently observed from Vostok and Dome C ice core samples (218 values). The dacite patch (SiO2~68%) fits well the composition of proximal Kuwae deposits as well as that of an ash layer (~140 values) on Efate Island (Standberg et al, 2023). The rhyolite composition patch (SiO2~72%) is unlikely from a South American source, but appears discretely represented in proximal Kuwae deposits as well as in sediments in the nearby Epi Submarine zone. We suggest that rhyolite is a daughter product from dacite by evolving in the upper layers of the magmatic chamber, and it was spread out first and far away by the eruption.
For the 426 BCE event, the cryptotephra composition (220 values) is consistently found within the three ice cores (Vostok, Dome C, Talos Dome) and belongs to high-K rhyodacite. Coincidentally such composition is very close to Kuwae’s (except for higher K) suggesting it was issued from a very similar magmatic chamber. The 10 km wide Ambrym caldera located 50 km north of Kuwae, collapsed ~2000 years ago appears the best candidate.
References
Hartman et al. (2019). Nature Sci. Rep. 9. https://doi.org/10.1038/s41598-019-50939-x.
Narcisi, B. et al., 2019. Quat. Sci. Rev. 210, 164-174 https://doi.org/10.1016/j.quascirev.2019.03.005.
Sigl, M., et al. Nature 523, 543–549 (2015). https://doi.org/10.1038/nature14565
Strandberg NA et al., (2023). Front. Ecol. Evol. 11: 1087577.doi: 10.3389/fevo.2023.1087577
How to cite: Petit, J.-R., Savarino, J., Delmonte, B., Gautier, E., Ginot, P., and Batanova, V.: Cryptotephra fingerprinting of 1458 CE and 426 BCE volcanic events in East Antarctic ice cores, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2329, https://doi.org/10.5194/egusphere-egu25-2329, 2025.
EGU25-8574 | Posters virtual | VPS7
Aeolian dust and diatoms at Roosevelt Island (Ross Sea, Antarctica) over the last two millennia reveal the local expression of climate changes and the history of the Ross Sea polynya.Fri, 02 May, 14:00–15:45 (CEST) | vP5.3
Aeolian mineral dust and diatom influxes at the summit of Roosevelt Island (79.364°S, 161.706°W, 550 m a.s.l.) were investigated over the last 2 kyrs from the RICE ice core (Bertler et al., 2018). Mineral dust at the site is mainly related to large-scale atmospheric circulation patterns within the Eastern Ross and Amundsen Seas, while aeolian diatoms, mainly consisting of Fragilariopsis spp. (F. nana , F. cylindrus, , F. curta), depend on the local oceanic influence of air masses from the marine boundary layer. Thus, the complementarity of these proxies allows appreciating climatic and atmospheric changes experienced at Roosevelt Island over the last 2000 years, in response to some major forcing factors such as ENSO. During the 550-1470 CE period, when higher/less depleted stable water isotope values are observed, the increased importance of blocking ridges in the Amundsen Sea and a weakened Amundsen Sea Low promoted dust-rich air mass advection to RICE. This pattern was accompanied by an increasing trend in snow accumulation and reduced sea ice in the Eastern Ross and Amundsen Seas. At about 1300 CE, the maximum expression of the Ross Sea dipole is reached, with enhanced katabatic outflow in the Western Ross Sea and reactivation of the Ross Sea polynya. At the same time, the Eastern part of the Ross Sea was still under the influence of blocking ridges promoting maritime air mass advection to RICE and southward shift of the South Westerly Winds. After 1470 CE, unprecedented peaks of aeolian diatom concentration suggest a rapid reorganization of local atmospheric circulation, that probably occurred in relation to the eastward enlargement of the Ross Sea polynya culminating with the opening of the Roosevelt Island polynya.
For the RICE site, we suggest that several drivers contribute to the long-term dust, sea-ice and polynya variability, but ENSO-driven teleconnections are particularly prominent. On a longer (multidecadal) timescale it seems that El Niño-dominating conditions promoted the establishment of the Ross Sea dipole, while La Niña conditions favored a deeper Amundsen Sea Low and an eastward expansion of the polynya.
How to cite: Delmonte, B., Lagorio, S., Tetzner, D., Malinverno, E., and Bertler, N.: Aeolian dust and diatoms at Roosevelt Island (Ross Sea, Antarctica) over the last two millennia reveal the local expression of climate changes and the history of the Ross Sea polynya., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8574, https://doi.org/10.5194/egusphere-egu25-8574, 2025.
