Glaciochemical data sourced from ice cores in polar regions and the Alps have been extensively examined. However, quantitative studies on glaciochemical records of the Tibetan Plateau (TP) are scarce. To address this, we investigated annual variations in the major soluble ions (Ca²⁺, Mg²⁺, Na, K, NH⁺⁺₄⁺, Cl⁻, NO₃⁻, and SO₄²⁻) in the Aru ice core on the northwestern TP from 1850 to 2016. Applying a positive matrix factorization model, the sources of the major soluble ions and three factors to evaluate natural and agricultural impacts were identified. Factor 1, crustal dust with high loadings of Mg²⁺ (81.9%) and Ca²⁺ (68.7%), significantly positively correlated with wind speed and significantly negatively correlated with δ¹⁸O and net accumulation recorded by the ice core, suggesting that strong winds contributed to crustal dust transport from arid and semi-arid regions of Central Asia and deposition in the Aru glacier. However, relatively warm and wet climate prevented the transport of crustal dust. Factor 2 comprised salt lakes with high dominant loadings of Na (75.3%), SO⁺₄²⁻ (64.1%), Cl⁻ (60.8%), NO₃⁻ (52.2%), and K (49.4%). Declining lake water levels exposed salt lake minerals, which were carried to glaciers under the dynamic conditions of strong winds, whereas warming resulted in an expansion of glacial meltwater and lake water volume, which decreased the contribution of salt lake sediments. Therefore, the contribution of salt lake deposition decreased. Factor 3 was agricultural sources with a high loading of NH⁺₄⁺ (82%), whose trend aligned closely with the population number and N productions from agricultural sources in South and Central Asia, suggesting that NH₃ emissions from agricultural practices are a critical contributor to Factor 3. This study quantified the proportional contribution of natural and agricultural sources to glaciochemical composition, advancing our understanding of glaciochemical records in ice cores from source recognition to quantification.

How to cite: Yang, D., Yao, T., and Wu, G.: Identifying the natural and agricultural impacts on the glaciochemistry of the Aru ice core on the northwestern Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1813, https://doi.org/10.5194/egusphere-egu24-1813, 2024.

Ice core records of carbon dioxide (CO2) over the last 2000 years are critical to our understanding of global carbon cycle dynamics on centennial and multidecadal timescales. They also provide context for the unprecedented anthropogenic rise in atmospheric CO2. Yet for some time intervals throughout the period, the true atmospheric history of CO2 remains uncertain. One such example is the decrease in atmospheric CO2 after 1550 CE, for which the timing and magnitude is debated. To resolve this case, we measure CO2 and methane (CH4) in the new Skytrain Ice Rise ice core from 1450 to 1700 CE, presented alongside firn smoothing analysis and land carbon modelling. Our results suggest that a sudden decrease in ice core CO2 around 1610 CE in one widely used record is most likely an artefact of a small number of anomalously low values. Instead, we observe a more gradual decrease in CO2, with our analysis suggesting 0.5 ppm per decade between 1516 and 1670 CE. The resulting inferred land carbon sink of 2.6 PgC per decade agrees with modelled scenarios of large-scale reorganization of land use in the Americas following New World-Old World contact, for which a larger and more rapid CO2 decrease is incompatible.

How to cite: King, A., Bauska, T., Brook, E., Kalk, M., Wolff, E., Strawson, I., Rhodes, R., Nehrbass-Ahles, C., and Osman, M.: Reconciling ice core CO2 and land-use change following New World-Old World contact, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5333, https://doi.org/10.5194/egusphere-egu24-5333, 2024.

Understanding the processes during gas trapping in ice is essential to accurately interpret the gas records in ice cores. As a consequence, it is very desirable to have firn core and firn air sampling campaigns associated with deep ice coring. We know that elemental fractionation occurs during bubble close-off, hence largely affecting the δO₂/N₂ measurements further used to date the ice cores on orbital timescales. A recent study also suggested that this elemental fractionation can be linked to surface characteristics (i.e. temperature and / or accumulation rate). 

The aim of this study is to investigate the elemental and isotopic fractionation of N₂ and O₂ during bubbles close-off at two sites of very different characteristics (D47 located at the edge of the East Antarctic plateau with high temperature and accumulation rate and Little Dome C at the center of the East Antarctic plateau with low accumulation and accumulation rate). For this study, we did measurements both in the open and closed porosity of the firn in the lock-in zone. The D47 lock-in zone extends over nearly 20 m and, over these 20 m,  strong signals of increasing δO₂/N₂ (+ 7 permil) and decreasing δ¹⁵N (-0.05 permil) are observed with increasing depths. At Little Dome C, the site of the Beyond EPICA deep ice core, the lock-in depth is much thinner (a few meters thick only) and fractionation much smaller. We discuss how these signals relate to the signals measured in the closed porosity in both sites and present some perspectives for the interpretation of the gas records in the deep ice cores.   

How to cite: Landais, A., Harris Stuart, R., Orsi, A., Jacob, R., Teste, G., Prié, F., Brückner, L., Martinerie, P., Emmanuel, W., Elise, F., Emilie, C., Daniel, B., Hubertus, F., and Jochen, S.: Isotopic and elemental ratios in the open and closed porosity for two Antarctic firn cores (D47 and Little Dome C) of very different surface characteristics. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6585, https://doi.org/10.5194/egusphere-egu24-6585, 2024.

Recently, the Orbitrap Exploris instrument, a mass spectrometer designed for molecular identification and classification, has been diverted from its original purpose and transformed into a new tool for quantifying the stable isotope ratios of water-soluble compounds such as nitrates, sulfates or phosphates. At first glance, this new Orbitrap IRMS system is very attractive because it requires 10 to 100 times less ice than current standard procedures, works directly with liquid solutions, quantifies isotope ratios directly on the molecule of interest, and provides a broader range of isotope ratios by moving from the elemental isotope ratio paradigm to that of molecular isotope ratios and thus challenge the regular isotope ratio mass spectrometers (IRMS or ICPMS). Moreover, by leaving the chemical bonds of the molecules of interest intact contrary to IRMS or ICPMS, the Orbitrap technology provides access to clumped isotopes, i.e. doubly substituted isotopic substances, thereby enriching our knowledge of matter. Extending the range of molecular isotope ratios opens up exciting new prospects, particularly for unravelling the mechanisms by which compounds are formed before being incorporated in ice. Such a radical change in the way isotope ratios are measured inevitably raises the question of the real capabilities of this new instrument. With a deeper look into statistics, can the Orbitrap-IRMS challenge the standard IRMS/ICPMS precision for analyzing soluble species? Does its performance live up to expectations? Preliminary results show that the Allan variance for a large variety of molecular isotope ratios of nitrate and sulfate are in the range of one per mil precision, including some of the clumped isotope ratios. However, the bootstrapping approach aimed at reducing acquisition time and thus the drift associated with the instrument appears to be ineffective in improving the Allan variance, indicating a possible limitation of sampling randomization, probably during the electrospray ionization (ESI) process. Other statistics, tests and performances are still in progress and will also be presented.

How to cite: Savarino, J., Saville, J., Gautier, E., Kuhlbusch, N., and Juchelka, D.: Can the Electrospray Orbitrap be a new frontier for the stable isotope analysis of oxyanions in ice cores? A statistical study of its performances, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8074, https://doi.org/10.5194/egusphere-egu24-8074, 2024.

Seasonal temperature reconstructions from ice cores are missing over glacial-interglacial timescales, preventing a good understanding of the driving factors of Antarctic past climate changes. Here we present a new total air content (TAC) record from the Antarctic EPICA Dome C (EDC) ice core covering the last 800 thousand of years (ka).

We show that the TAC record is highly correlated with the mean insolation over the local astronomical half-year summer. Benefiting from new climate transient simulations from the Earth system model of intermediate complexity LOVECLIM covering the past 440 ka, we evidence that the EDC TAC record is correlated with the simulated local summer temperature changes. Hence, our new results suggest that the EDC TAC record could potentially be used as a proxy for local summer temperature changes. We present also preliminary results exploring this link between TAC and past summer local surface temperature at other ice core sites in Antarctica and in Greenland.

Finally, our simulations show that local summer insolation is the primary driver of Antarctic summer surface temperature variations while changes in atmospheric greenhouse gas concentrations and northern hemisphere ice sheet configurations play a more important role on Antarctic annual surface temperature changes.

How to cite: Capron, E., Raynaud, D., Yin, Q., Wu, Z., Parrenin, F., Berger, A., Lipenkov, V., and Guilluy, H.: Past local summer temperature revealed by the total air content record from the Antarctic EPICA Dome C ice core, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8294, https://doi.org/10.5194/egusphere-egu24-8294, 2024.

Ice cores represent invaluable tools for palaeoclimatic reconstructions. Of particular interest is the gas trapped in air bubbles and clathrates within the ice. It serves as a direct record of the changes to atmospheric composition over the last several 100kyrs. Recently, the University of Bern established joint high precision greenhouse gas (GHG) analyses (CO₂, CH₄ & N₂O concentration, as well as δ¹³C – CO₂) on small ice core samples (15g) thanks to sublimation extraction and multi-beam quantum cascade laser spectrometry.

Although gas bubbles form a direct record of past atmosphere, they are not an unbiased record of past atmosphere. Several processes take place prior and during bubble formation which fractionate gas concentration and gas isotopes, requiring several corrections to be applied (especially for δ¹³C – CO₂ data). These corrections can be achieved by studying the isotope ratios of noble gases and N₂. However, this requires a mass spectrometry analysis which would normally call for the use of additional samples. This is problematic for two reasons: first, the corrections applied are most accurate when comparing the various isotope ratios of the same gas sample. Even ice in close proximity is subject to small scale disruptions within the ice and can skew the results. Second, near the bottom of ice cores, glacial thinning – compression of the ice caused by the overlying material – causes thousands of years of ice to be compacted in only one metre, making two different samples, even if adjacent, incomparable.

Hence, the objective of this study is to reuse gas samples which have already undergone laser- spectrometric GHG analysis to implement δ¹⁵N – N₂ & δ⁴⁰Ar analysis. We outline the development and building of an apparatus which reuses the previously extracted and analysed air and captures it for mass spectrometry. Sample recapture is achieved using a helium cryostat to cool dip tubes down to approximately 10K. When connected, the gas samples are drawn from the laser spectrometer into said tubes, where they are cryogenically trapped. To avoid interferences from other gases, the samples go through a liquid nitrogen trap to remove the already measured CO₂ and N₂O. The sample tubes are then disconnected, warmed up to room temperature and brought to an isotope-ratio mass spectrometer for major gas isotope analysis.

Despite significant fractionation of the isotopic composition of major gas compounds (N₂, O₂, Ar) during the recapture process, the developed method achieves its initial objectives, with a >99% recapture efficiency. It features a δ¹⁵N – N₂ reproducibility of standard gas measurements of ∼ 10 permeg and an offset of 0.1‰ and ∼ 30 permeg and 0.2‰ for δ⁴⁰Ar. With this reproducibility, sufficiently precise corrections of the gravitational enrichment of isotopes in the firn column are possible, however temperature reconstructions using thermodiffusion thermometry are not yet possible. Further improvements are thought to be possible to reduce the signal to noise ratio, as well as reducing the offset.

How to cite: Traeger, H., Krauss, F., Grimmer, M., Schmitt, J., Walther, R., Marending, S., Reinhard, C., and Fischer, H.: Recapturing sublimated ice core gas samples & implementing δ15N – N2 mass spectrometry measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9440, https://doi.org/10.5194/egusphere-egu24-9440, 2024.

The ³⁶Cl/¹⁰Be ratio has the potential to be a dating tool for old ice, as it decays with a combined half-life of  years and is thought to be independent of production changes, which affect the individual radionuclide concentrations in ice cores. However, when EDC samples with various ages between the Holocene and 887 kyr BP were analysed, the ³⁶Cl/¹⁰Be ratio was found to vary significantly between samples instead of decaying smoothly over time. Due to the different physical and chemical properties of ³⁶Cl and ¹⁰Be, different sensitivities to changes in climatic parameters, such as tropopause pressure and precipitation, are potentially the cause of the observed variability. Additionally, chlorine can be lost at low accumulation sites, such as EDC, as it can turn into hydrogen chloride and gas out from the firn. We present new measurements of the ³⁶Cl/¹⁰Be ratio from the Skytrain ice core, which should be unaffected by chlorine loss, due to the higher accumulation rate at its drilling site. The measurement series extends below the dated sections of the ice core to test the decay dating and help extend the Skytrain age scale. To analyse differences in transport and deposition between radionuclides, the ³⁶Cl/¹⁰Be ratio will also be determined with annual resolution in samples from 1982 – 2013 and compared to several climate parameters of the NOAA/CIRES/DOE 20^th century reanalysis (V3) dataset. However, the data of this project are not yet available.

How to cite: Kappelt, N., Wolff, E., Christl, M., Vockenhuber, C., and Muscheler, R.: 36Cl/10Be as a dating tool for old ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9695, https://doi.org/10.5194/egusphere-egu24-9695, 2024.

The isotopic composition (δD and δ¹⁸O) of snow precipitation, archived in the Antarctic ice sheet every year, is an important proxy of climatic conditions. This signal is observed to be dependent on several parameters including temperature, altitude and distance from the coast. The well-established correlation between water stable isotopes and local temperature - commonly used in paleoclimate reconstructions - is strongly observed in the earlier dataset of Antarctic surface snow isotopic composition (Masson-Delmotte et al. 2008), and the spatial variability of this relationship across the distinct regions of the continent was investigated to improve the use of this proxy.

Here, we aim to explore the temperature vs water stable isotopes on the East Antarctic Plateau characterized by very low snow accumulation. The surface (a few cm average) and bulk (top 1 m average) snow samples were collected as a part of the East Antarctic International Ice Sheet Traverse (EAIIST) in the summer 2019-2020. Our sampling covers the area from Dumont D'Urville to Dome C and the unexplored area from Dome C towards the South Pole.The linear relationship between surface temperature and isotopic composition is completely lost in the latter part of the traverse. This area is subject to strong post-depositional processes such as wind redistribution and sublimation effect (Windcrust and Megadune sites). For this reason, ahead of evaluating the post-depositional effects able to modify surface snow composition, we decided to investigate a priori the snow depositional conditions and processes, which define the original isotope signal over 600 km on the Antarctic Plateau. While geographical parameters are constant, such as the altitude and the distance from the coast (increasing distance from the Indian Ocean but decreasing distance from the Pacific and Atlantic Ocean), we investigate the origin of the air masses for the different sampling sites, observing significant variations moving towards the Megadunes area. The 10-day back trajectories of the air masses were calculated for each sampling site at a 12-hour resolution, spanning from January 2016 to January 2020, using the FLEXPART - FLEXible PARTicle dispersion model. For each sampling site, we estimated the corresponding annual mean footprint. To assign greater weight to air masses responsible for precipitation on the Antarctic Plateau, those footprints are calculated through a weighted average of back-trajectories using the ERA5 precipitation rate.

The different origins can contribute to distinct isotopic signals, despite similar climatic and geographic factors on the East Antarctic Plateau. This divergence poses a challenge in the determination of the post-depositional processes affecting the isotopic composition of snow and in the reliable use of this proxy in reconstructing past temperatures in the context of Antarctic ice core science.

How to cite: Petteni, A., Casado, M., Leroy-Dos Santos, C., Stenni, B., Dreossi, G., Landais, A., Savarino, J., Spolaor, A., Delmonte, B., Becagli, S., and Frezzotti, M.: The Air Mass Back-trajectories: A Key Factor in the Interpretation of Isotopic Depositional Processes on the East Antarctic Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10936, https://doi.org/10.5194/egusphere-egu24-10936, 2024.

Whereas water isotopic records from polar deep ice cores can be interpreted at first order in terms of site temperature, the isotopic signature recorded in shallow cores from Adelie Land (coastal East Antarctica) is less straightforward to decipher (Goursaud et al. 2017, 2019; Leroy-Dos Santos, PhD 2021, 2023). The origin of moist air masses bringing precipitation, the influence of blowing snow, redistribution or sublimation strongly imprint the isotopic signal recorded in firn cores of this region where katabatic winds blow hard. Nonetheless these firn archives are our best way to reconstruct the recent past climatic trend and variability in this area where meteorological monitoring is very sparse and recent.

In this study we compare the water isotopic profiles from firn cores (20 to 70m deep) drilled only a few kilometers apart, in the so-called “D47” area, about 150km inland from Dumont d’Urville at an altitude of 1500m. This site is characterized by very strong katabatic winds and mean accumulation rates can locally vary by several tens of percent. We can thus investigate the effect of very locally different deposition conditions on the isotopic records while the recorded regional climate is the same.

How to cite: Fourré, E., Orsi, A., Tcheng, T., Brückner, L., Jacob, R., Lassalle Bernard, C., Baubant, L., Jossoud, O., Prié, F., Minster, B., Agosta, C., Leroy-Dos Santos, C., Casado, M., Favier, V., Magand, O., Lemeur, E., Teste, G., Cauquoin, A., Werner, M., and Landais, A. and the ASUMA raid team: Impact of accumulation rate on firn core water isotopic records from a same region of Adelie Land with high katabatic winds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12740, https://doi.org/10.5194/egusphere-egu24-12740, 2024.

Total air content (TAC) from ice cores mainly reflects air pressure when the air is occluded and is therefore a proxy for elevation. However, there are several complications, such as melt, changes in firn structure and air pressure variability.  

We measured TAC in the RECAP ice core drilled in 2015 on the Renland Icecap in East Greenland, currently at an elevation of 2340 m. The upper 529 m of the 584 m core cover the Holocene. There is extensive melting in this part of the core, which is reflected in low air content values. Assuming constant altitude and air pressure, lower TACs at the beginning of the Holocene indicate more melting and therefore higher summer temperatures. Simulations with the regional climate model HIRHAM5 allow us to translate the observed melt fractions into summer temperatures. We conclude that summer temperatures in the early Holocene were ~2 to 3°C warmer than today, in agreement with previous findings in Greenland. The core extends into the Eemian. The air content is very low in this section, indicating excessive melting. Using the same metric as for the Holocene, we conclude that the temperature in the Eemian was at least 5°C higher than today.

The ~22m of glacial ice in RECAP from 11.7 to 119 kyr BP appear to be unaffected by melting. However, we observe large variations in total air content during periods of rapid climate change. In Greenland, similar effects have been found at NGRIP (Eicher et al., 2016). These effects cannot be due to changes in elevation. All the evidence points to a dynamic effect in the firn column that changes the pore volume. If we do not understand these effects, the interpretation of TAC in terms of elevation changes is questioned.

How to cite: Blunier, T., Vudayagiri, S., Vinther, B., Sowers, T., Freitag, J., and Langen, P. L.: Total Air Content measurements from the RECAP core, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13000, https://doi.org/10.5194/egusphere-egu24-13000, 2024.

Hyperspectral imaging (HSI) technology has been increasingly used in Earth and planetary sciences. This imaging technique has been successfully tested on ice cores using VNIR (visible and near-infrared, 380-1000 nm) (Garzonio et al., 2018) and near-infrared (900 - 1700 nm) (McDowell et al, 2023)  line-scan cameras. Results show that  HSI data greatly expand ice core line-scan imaging capabilities, previously used with gray or RGB cameras (see summary in Dey et al., 2023). Combinations of selected HSI bands from the hyperspectral data cube improve feature detection in ice core stratigraphy, and map distribution of volcanic material, dust, air bubbles, fractures, and ice crystals in ice cores. Captured spectral information provides unique fingerprints for specific materials present in ice cores. This method helps to guide ice core sampling because it provides non-destructive, rapid visualization of microstructural properties, layering, bubble contents, increases in dust, or presence of  tephra material. Precise identification of these atmospheric components  is important for understanding past climate drivers reconstructed from ice cores. 

As part of the COLDEX project (Brook et al., this meeting) we adapted the SPECIM SisuSCS HSI system for ice core imaging. The ice core scanning system is housed inside the ca. -20ºC main NSF ICF freezer, and externally computer-controlled. The operator monitors scanning operations and communicates with personnel inside of the freezer via radio.  The system is equipped with a SPECIM FX10 camera that measures up to 224 bands in the VNIR range. We modified the ice core holder tray and installed a heated enclosure for the camera. The system uses SCHOTT DCR III Fiber Optic light sources with an OSL2BIR bulb from Thorlabs. IR filters are removed to extend the light spectral range beyond the 700 nm limit without heating the ice core surface during rapid (<5 minutes) scanning of an entire meter-long section. Emitted light enters ice at a 45º angle from two top and two bottom light sources. To calibrate absolute reflectance we use three Spectralon panels with 100, 50 and 20% reflectance values with every scan as well as several secondary reflective standards and USAF targets for geometric corrections. We are developing Python-based open source data processing routines and currently comparing HSI data with existing ice core physical and chemical measurements. The goal is to fully integrate the ice core HSI system with ice core processing at the NSF ICF. 

Dey et al., 2023. Application of Visual Stratigraphy from Line-Scan Images to Constrain Chronology and Melt Features of a Firn Core from Coastal Antarctica. Journal of Glaciology 69(273): 179–90. https://doi.org/10.1017/jog.2022.59.

Garzonio et al., 2018. A Novel Hyperspectral System for High Resolution Imaging of Ice Cores: Application to Light-Absorbing Impurities and Ice Structure. Cold Regions Science and Technology 155: 47–57. https://doi.org/10.1016/j.coldregions.2018.07.005.

McDowell et al., 2023. A Cold Laboratory Hyperspectral Imaging System to Map Grain Size and Ice Layer Distributions in Firn Cores. Preprint. Ice sheets/Instrumentation. https://doi.org/10.5194/egusphere-2023-2351.

How to cite: Kurbatov, A., Brook, E., Buizert, C., Carr, T., Fegyveresi, J., Fudge, T., Hargreaves, G., Hoefen, T., Kirkpatrick, L., Labombard, C., Nunn, R., Powers, L., Rock, K., and Zhizhin, M.: Hyperspectral imaging system for ice core studies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13878, https://doi.org/10.5194/egusphere-egu24-13878, 2024.

Mineral dust affects climate through direct radiative forcing by scattering and absorbing solar radiation in the atmosphere and by accelerating snow and ice melting through reduced albedo when deposited on snow surfaces. The concentration and composition of dust deposited on glaciers reflect the surface conditions of the source regions and atmospheric conditions during transportation. Dust records in ice cores provide insights into historical atmospheric and land surface environments. However, ice cores drilled in high-altitude Himalayan glaciers are limited. To investigate historical variations in dust concentration in the Himalayas, we conducted ice core drilling at an elevation of 5862m on the Trambau Glacier in the Rolwaling region of the Nepal Himalaya. The ice core, covering 146 years (1874-2019), was dated using seasonal variations in NO₃^- and Ca²⁺. The 81-m ice core was divided into 1637 samples (~5 cm interval), and dust concentration (particle size ranging from 0.6 to 10.0 µm) was measured using the Coulter Counter Multisizer ^TM3. The Trambau ice core exhibits a higher dust concentration than the other Himalayan ice cores, particularly with an abundance of small particles (<2 µm in diameter). This suggests that the dust concentration in the Trambau ice core are mainly controlled by the supply of small particles from relatively distant regions. Furthermore, the dust concentration shows periodic fluctuations with a 20-30-year cycle, consistent with the Atlantic Multi-decadal Oscillation (AMO). This suggests a connection between the environmental changes (precipitation, temperature, and land surface conditions) in the dust source regions and AMO.

How to cite: Esashi, N., Tsushima, A., Uemura, R., Matoba, S., Iizuka, Y., Adachi, K., Kinase, T., Kayastha, R. B., and Fujita, K.: Atmospheric dust record preserved in an ice core from Trambau Glacier, Nepal Himalaya, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14084, https://doi.org/10.5194/egusphere-egu24-14084, 2024.

Ice core ages have been typically determined by counting the layer boundaries of various proxies that represent annual cycles. Some studies in Greenland have identified winter and summer layers, but it is difficult to identify them at higher resolutions (several months resolution) in ice cores drilled at sites with low accumulation rates due to diffusion. Furukawa et al. (2017) proposed a precise age model by matching the oxygen isotope (δ¹⁸O) pattern of precipitation isotope between ice core record and isotope-incorporated general circulation models. They applied this dating method to the SE-Dome I (SE1) ice core drilled from a high snow accumulation area (1.02 m w.e. a^-1) in southeast Greenland. However, the SE1 core covered for the past 60 years only. Here, we report the age scale based on δ¹⁸O data of the SE-Dome II (SE2) ice core (length: 250.79 m) drilled in 2021 in southeast Greenland. The δ¹⁸O was analyzed using a cavity ring-down spectrometer (L2130-i, Picarro) with a precision (1σ) of ±0.04‰. The SE2 core δ¹⁸O highly correlated with the SE1 core δ¹⁸O (r = 0.90), suggesting that the within-year peaks in the SE core are climatic signals. The age scale was created using the SE1 core method, but for this study, we used iso-GSM nudged to historical reanalysis data (20CRv2) for 1870-1979 and created a longer age scale. There was a high correlation between the ice core data and the model (r = 0.76), and by matching the within-year patterns (typically negative peaks during the warm season). Based on this age scale, we analyzed the day on which the maximum and minimum peaks of the mean H₂O₂ concentration data (Kawakami et al., 2023). The maximum and minimum of H₂O₂ concentrations for 1980-2020 were estimated on July 20 and January 7, respectively.

REFERENCES
Furukawa, R. et al. , Seasonal-Scale Dating of a Shallow Ice Core From Greenland Using Oxygen Isotope Matching Between Data and Simulation, Journal of Geophys. Res. Atmospheres, 122, 20, 10,873-10,887, 2017, https://doi.org/10.1002/2017JD026716
Kawakami, K., et al., SE-Dome II Ice Core Dating With Half-Year Precision: Increasing Melting Events From 1799 to 2020 in Southeastern Greenland, Journal of Geophys. Res.  Atmospheres, 128, 20, 2023, https://doi.org/10.1029/2023JD038874

How to cite: Hamamoto, S., Matoba, S., Kawakami, K., Sasage, M., Matsumoto, M., Yoshimura, K., Okazaki, A., Bong, H., Iizuka, Y., and Uemura, R.: Seasonally Resolved Age Scale based on Oxygen Isotope Record from SE-Dome II Ice Core, Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14086, https://doi.org/10.5194/egusphere-egu24-14086, 2024.

An exceptional heatwave impacted on East Antarctica between March 15 and 19, 2022, causing some of the highest temperature anomalies ever measured on Earth. The heat transport was associated to an atmospheric river bringing a moisture flux from lower latitudes to inner Antarctica. Several locations, from coastal sites to the high Antarctic Plateau, experienced record temperatures. The air temperature measured at Concordia Station by the automatic weather station of the Italian Antarctic national research program (PNRA) reached a maximum of -11.7°C.

The temperature signal is imprinted in the oxygen and hydrogen isotopic composition of precipitation: this is what allows paleoclimate reconstructions from the isotopic records in ice cores, although post-depositional processes such as the interactions between snow and atmosphere and within the snow column might affect the pristine isotopic signal.

Since 2008, precipitations have been collected daily at Concordia Station for δ¹⁸O and δD measurements; the activities have been carried out under the PNRA project WHETSTONE and will continue in the framework of the PNRA project AIR-FLOC. Isotopic values from 2008 to 2021 range between -82.63‰ and -26.97‰ for δ¹⁸O and between -595.1‰ and -223.0‰ for δD, while water stable isotope data from February to April 2022, show unprecedented high values (δ¹⁸O =-18.97‰, δD=-147.9‰), the highest recorded over the last 15 years, in correspondence to the exceptional temperatures and snow precipitations. Moreover, the daily snowfall collected during the same period reached a cumulative value of ~4.3 mm w.e. representing ~18% of the 2022 cumulative annual value (24.1 mm w.e.)

How to cite: Dreossi, G., Masiol, M., Zannoni, D., Scarchilli, C., Ciardini, V., Grigioni, P., Del Guasta, M., and Stenni, B.: The March 2022 exceptional heatwave recorded in the isotopic composition of precipitation at Dome C, East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15921, https://doi.org/10.5194/egusphere-egu24-15921, 2024.

Extreme precipitation events (EPE), defined as the top 10% of daily precipitation amounts, play a major role in Antarctica surface mass balance as they account for more than 40% of the total annual precipitation across the continent. These EPEs are often associated with high temperatures and have major consequences on the Antarctic surface mass balance. Though, it is key to estimate their recent evolution in terms of frequency and intensity in the context of climate change. As water stable isotopic composition of firn cores is known to record the temperature signal modulated by precipitation intermittency, and to be imprinted as well as by the large-scale atmospheric circulation, we can ask if EPEs could be detected in firn cores thanks to a particular isotopic signature.

In this study we construct Virtual Firn Cores (VFC) across Antarctica to investigate how winter EPEs can be misinterpreted as summer maxima in firn cores. We create VFC using (1) temperature, precipitation rate and a linear temperature-d18O relationship from atmospheric regional model MAR, (2) d18O in precipitation from ECHAM6-wiso and (3) d18O in precipitation from LMDZ6-iso, for the period 1979-2022. Additionally to standard VFCs, we generate a second set of VFCs excluding each year the highest winter precipitation event (5-days period). We then run a detection algorithm to find local maxima for both sets of VFCs. We observe some regions with nearly 20% more “summer” detected in standard VFCs compared to VFCs without the winter maximum precipitation event. We argue that firn cores drilled in those regions are more likely to contain isotopic signals that could be used to detect EPEs temporal variability.

How to cite: Agosta, C., Leroy-Dos Santos, C., Fourré, E., Casado, M., Cauquoin, A., Werner, M., and Landais, A.: Extreme precipitation events in firn core isotopic records: where to find the best drilling site?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15991, https://doi.org/10.5194/egusphere-egu24-15991, 2024.

To extract climatically relevant chemical signals from the deepest, oldest ice in the polar ice sheets, we must first understand the degree to which chemical ions diffuse within solid ice. Volcanic sulfate peaks are the ideal target for such an investigation because they have a uniform peak shape at deposition. Processes of chemical diffusion and ice sheet thinning modify sulfate peak shapes with depth/age in an ice core. Our previous work developed a forward model, which simulates sulfate peak evolution in the ice sheet, and identifies the optimum effective diffusion rate for individual peaks. Analysis of the EPICA Dome C (EDC) sulfate record over the last 450 kyr suggests that the rate of sulfate diffusion is initially relatively rapid (2.4 ± 1.7 x 10^-7 m²yr^-1 median for Holocene ice) and slows down over time to rates on the order of 1 x 10^-8 m² yr^-1 or less. We hypothesize this may result from a switch in the mechanism of diffusion resulting from the changing location of sulfate ions within the ice microstructure. Here we apply our forward model to three other ice cores: NGRIP (Greenland), EDML (East Antarctica) and WAIS Divide (West Antarctica) to determine sulfate diffusion rates and their evolution over depth/age. These ice cores are different to each other, and to EDC, in terms of their temperature profiles, ice grain size evolution and dust loading, all factors which may influence sulfate diffusion rates.

How to cite: Rhodes, R., Bollet-Quivogne, Y., Clarke, D., Barnes, P., and Wolff, E.: Comparison of effective diffusion rates in multiple ice cores, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17285, https://doi.org/10.5194/egusphere-egu24-17285, 2024.

In this study we report on the first continuous records of three dimensional firn structure reconstructions using archive pieces of firn cores that cover the whole depth range of firn starting from surface down to the transition to bubbly ice. The CT-measurements have been performed on 1m-core segments with the means of the AWI-X-ray-computer tomograph especially designed for ice applications. Flyby recording in helical mode under a time-optimized measurement protocol enabled us to reduce the scanning time to 25 minutes per meter firn. The reconstructed volumes have a spatial resolution of 120 µm, giving about 1 million cross-section images per firn core. The analytical work flow includes three steps of pre-processing with denoising, image segmentation and a manual check for outliers at break positions and a layer-wise (5.5 mm thick) calculation of several geometrical parameters like density, ice and pore cluster sizes, intercept lengths, autocorrelation functions, structural anisotropy, Euler number (connectivity), coordination number, bubble number density, closed and open porosity.

The method was applied to archive pieces of EGRIP-S6 (firn air pumping site, 2018, North-East-Greenland, 75.6°N ,35.9°W), B40 (Kohnen station, 2013, Dronning Maud Land, East Antarctica, 75.0°S, 0.1°E) and B51 (CoFi-Traverse 2013, Dronning Maud Land, East Antarctica, 75.1°S ,15.4°E). Temperature and accumulation rates at the different core sites vary between -30°C and -50°C and 130 mm w.eq./a and 40 mm w.eq./a respectively. The selected sites cover a wide range of recent environmental conditions of polar regions.

In this contribution we present several fundamental relationships between the derived geometrical parameters. The evolution of firn structure with depth will be discussed in respect to the dominant processes acting at different sintering/densification stages. The potential value for densification modelling, gas transport and enclosure modelling will be highlighted.

How to cite: Freitag, J. and Salamon, M.: Digital twins – fast flyby-X-ray CT measurements of polar firn, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17500, https://doi.org/10.5194/egusphere-egu24-17500, 2024.

The ability to infer past temperatures from ice core records has in the past relied on the assumption that after precipitation, the stable water isotopic composition of the snow surface layer is not modified before being buried deeper into the snowpack and transformed into ice. However, in extremely dry environments, such as the East Antarctic plateau, the precipitation is so sparse that the surface is exposed to the atmosphere for significant time before burial. Several processes have been recently identified as impacting the snow isotopic composition after snowfall, including moisture exchanges between the snow and the lower atmosphere, wind effects and diffusion inside the snowpack.

Here we present the result of a study that combines existing and new datasets of the precipitation, snow surface and subsurface isotopic compositions (δ¹⁸O and d-excess), meteorological parameters, ERA5 reanalysis products, outputs from the isotope-enabled climate model ECHAM6-wiso and a simple modelling approach to investigate the transfer function of water stable isotopes from precipitation to the snow surface and subsurface at Dome C, East Antarctica. We find that (i) moisture fluxes at the surface of the ice sheet lead to a net sublimation of snow throughout the year, from 3.1 to 3.7 mm water equivalent over the 2018-2021 period, (ii) the precipitation isotopic signal only cannot account for the intra-annual to seasonal variability observed in the snow isotopic composition and (iii) the cumulative impact of post-depositional processes at the surface over five years lead to an enrichment in δ¹⁸O of the snow surface by 3.3‰ and a lowering of the snow d-excess by 3.5‰ compared to the precipitation isotopic signal. This study reinforces previous findings about the complexity and multiple origin of the snow isotopic composition at Dome C and provides a first step toward a quantitative attribution of the different processes building up of the isotopic signal in the snow surface that is crucial for the interpretation of isotopic records from ice cores.

How to cite: Ollivier, I., Steen-Larsen, H. C., Stenni, B., Dreossi, G., Casado, M., Picard, G., Arnaud, L., Cauquoin, A., Werner, M., and Landais, A.: Surface processes and drivers of the snow water stable isotopic composition at Dome C, East Antarctica – a multi-datasets and modelling analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17885, https://doi.org/10.5194/egusphere-egu24-17885, 2024.

The temperature distribution through the ice sheet is a record of past climate changes. This allows reconstructing the past surface temperature history from the vertical temperature profile measured in a borehole (‘borehole palaeothermometry’). Such a reconstruction from the inversion of the heat advection-diffusion equation is independent from the analysis of oxygen isotopes in the ice but requires high-precision measurements of the borehole-temperature on the milli-Kelvin level. 

The precision and accuracy of the measurements is influenced by the spatial and temporal (seasonal to multi-hour) variations of the borehole temperature, the influence of the measurement setup (disturbance of the temperature profile from the borehole or snow pit drilling), the heat transfer between the ice/snow and the sensor as well as the uncertainty of the measurements (depth uncertainty and sensor precision and accuracy).  

Here, we report on our efforts to quantify these uncertainties of near surface (10m) firn and shallow (~200m) borehole temperature measurements using a newly developed winch-based borehole measurement system as well as stationary chains of borehole/firn temperature sensors at replicate sites near the EDML drilling site, Antarctica.

How to cite: Laepple, T., Hirsch, N., Zuhr, A., and Shaw, F.: Minimizing the uncertainty in shallow borehole-temperature logging, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18685, https://doi.org/10.5194/egusphere-egu24-18685, 2024.

Measurements of greenhouse gases (GHGs) in ice cores have provided invaluable data, offering insights into the role of GHGs in the climate system over millennia. While previous research has successfully employed continuous analysis techniques to achieve high resolution records of methane (CH₄) variations, analyses of nitrous oxide (N₂O) and carbon dioxide (CO₂) concentrations have historically been limited to discrete, dry-extraction, measurements due to the gases’ high solubility. Obtaining records of centennial-scale (or finer) variability in N₂O and CO₂, akin to that of CH₄, necessitates a new approach. In this work, we employ a new laser spectrometer designed for low flow rates, accompanied by a novel, custom-built gas extraction unit, to re-extract dissolved N₂O and CO₂ from a synthetic melt-stream. We modify physical parameters at the gas extraction site, controlling temperature, downstream pressure and flow rate. Through optimisation of these parameters, we aim to achieve a high and consistent rate of extraction. Our findings demonstrate the potential of these developments in improving re-extraction of N₂O and CO₂ to obtain more accurate concentrations from analysis of a mock continuous ice core melt stream. This work marks a step towards refining and applying the method to an Antarctic ice core, contributing to a more comprehensive understanding of the finer scale palaeoclimatic variations of all major GHGs.

How to cite: Rowell, I., Bauska, T., Fisher, E., Strawson, I., and Rhodes, R.: Towards continuous ice core measurements of N2O and CO2, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19981, https://doi.org/10.5194/egusphere-egu24-19981, 2024.

The sulfur (S) isotope composition of ice cores represents a novel proxy to quantify variability in the sources of atmospheric sulfate. Sulfate aerosols exert a crucial but highly uncertain feedback on the climate system, acting as cloud condensation nuclei and scattering incoming solar radiation. Ice cores from Antarctica indicate that the majority of sulfate aerosols are sourced from marine biogenic activity, with little variability in emissions between glacial and interglacial periods. However, there are currently no published S isotope studies from the Arctic extending beyond the Common Era, and it is unclear how processes could differ between hemispheres. We present a high-resolution S isotope record of the NEEM ice core from Greenland, covering an entire glacial cycle from 0-128 ka BP. S isotope values appear to co-vary with the climate, exhibiting far lighter isotopic compositions during the Last Glacial compared to the Holocene or Last Interglacial. Systematic variability of S isotope values across Dansgaard–Oeschger events and strong linear relationships with water isotope compositions and calcium concentrations of the ice are also observed. We interpret these trends to show climatically controlled changes in the key sources of sulfate reaching the NEEM ice core site. During peak glacial conditions, the budget is dominated by sulfate sourced from terrestrial dust and volcanic emissions, with a negligible marine biogenic component. This finding suggests that we can use S isotopes to identify time periods when the source region for marine biogenic emissions reaching Greenland may have been completely ice-covered. Overall, this study provides new insights into the processes controlling sulfate aerosols in the Arctic and how the S cycle interacts with the climate.

How to cite: Pryer, H., Hansson, M., Fischer, H., Rhodes, R., Burke, A., Rae, J., Újvári, G., Turchyn, A., Mulvaney, R., and Wolff, E.: Sulfur isotope compositions of the NEEM ice core reveal glacial-interglacial and millennial-scale variability in the sources of sulfate aerosols , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21625, https://doi.org/10.5194/egusphere-egu24-21625, 2024.

Ice that will be extracted from close to the bedrock of the Antarctic ice sheet during the Beyond EPICA Oldest Ice (BE-OI) project is expected to have more than 14,000 years of climatic information contained in a single vertical meter of ice. High-resolution analysis is required to extract meaningful climate signals from the impurities contained in this ice. This analysis should be comparable to the currently established continuous flow analysis (CFA) approach, which acquires a 1-dimensional impurity signal at approximately centimetre resolution. To date, it has been shown that smoothed high-resolution profiles taken using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) are comparable to CFA signals. However, the physical origin of this link needs to be better understood, especially in view of the imprint of the impurities on the ice crystal matrix recently revealed by 2D imaging on the micron scale.

Here we present a framework to generate and explore 3-dimensional models mapping the location of soluble impurities within ice samples. This framework helps link experimentally acquired smoothed LA-ICP-MS profiles, 2-dimensional LA-ICP-MS maps of impurities, and CFA data. The conceptual step into 3-dimensions allows exploration of the distortions of the climate signal due to interactions of impurities with the ice matrix. In shallow ice with relatively small grains and well resolved stratigraphy, this distortion is likely not significant enough to compromise analysis that takes large sample volumes with large mixing, such as seen during CFA. In order to extract signals in deep ice with large crystal sizes and dense layering, where this distortion will be most relevant, we find that carefully designed LA-ICP-MS experiments coupled with post-processing upscaling techniques are required. For a test against experimental data, this work is now being applied to a comparative study involving Antarctic ice measured with both CFA and LA-ICP-MS systems to prove its application to shallower, better-understood ice intervals. Ultimately, the goal is to develop a combination of cm-scale CFA, micron-scale LA-ICP-MS imaging and 3D modelling that will provide key insight on the impurity-related climate signals in deep ice at the BEOI core and elsewhere.

How to cite: Larkman, P., Stoll, N., Rhodes, R., Barbante, C., Stenni, B., Lee, G., Zeppenfeld, C., Fischer, H., Šala, M., and Bohleber, P.: A new 3D approach to linking high-resolution analysis on impurities for application to deep ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16818, https://doi.org/10.5194/egusphere-egu24-16818, 2024.

Sulfur dioxide (SO₂) is an air pollutant which can have harmful effects on both human health and the environment. Furthermore, SO₂ also contributes to climate change — SO₂ emissions form sulfate aerosols that act as cloud condensation nuclei, increasing cloud formation and decreasing solar radiation reaching the surface. An accurate knowledge of past SO₂ emissions is therefore essential to quantify and model the associated global climate forcing. Current bottom-up SO₂ emission inventories used for historical Earth System Modeling (ESM) are poorly constrained by observations prior to the late 20^th century.

Here we revisit and evaluate the historical SO₂ emission inventories of the last 150 years used in the Coupled Model Intercomparison Project Phase 6 (CMIP6). Our emission reconstruction is based on an inversion technique employing an array of ice core records of deposited sulfur and atmospheric transport/deposition modeling. The inversion technique minimizes discrepancies between the spatial-temporal patterns of emission inventories and the observed deposition at the ice core sites.

We find substantial differences between reconstructed SO₂ emissions and existing bottom-up inventories which do not fully capture the spatial-temporal emission patterns. Our results imply that changes to existing historical emission inventories might be necessary in order to ensure an accurate modeling of the Earth’s climate sensitivity within future ESM simulations.

How to cite: Plach, A., Eckhardt, S., Pisso, I., Chellman, N., McConnell, J. R., and Stohl, A.: Evaluation of historical SO2 emissions based on an inversion of ice core records using atmospheric transport modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2650, https://doi.org/10.5194/egusphere-egu24-2650, 2024.

Innovative enhancements to the bioanalytical Orbitrap mass spectrometer now allow quantification of stable isotope ratios of soluble species. The novel technique, known as Orbitrap-iso, enables deeper-than-ever isotopic analysis of ice core oxyanions, including nitrate and sulfate.

On paper, the Orbitrap-iso methodology presents a compelling alternative to the established Isotope Ratio Mass Spectrometry (IRMS) approach for quantification of isotope ratios of ice core oxyanions. Unlike IRMS, which necessitates the conversion of nitrate samples into gases (N₂, O₂) for analysis, Orbitrap-iso directly measures isotopologue ratios on intact ions in liquid solution. This streamlined process significantly simplifies sample preparation and enables additional quantification of enrichments in multiply-substituted (clumped) isotopologues in ice core oxyanions. These enrichments can offer valuable insights into the historical oxidative environment of Earth's atmosphere.

Moreover, Orbitrap-iso boasts the capability to deliver simultaneous measurements of multiple isotopologue ratios from minuscule sample quantities, as low as nanomoles. This requirement represents a monumental reduction in sample size compared to IRMS, empowering the extraction of higher temporal resolution records from ice cores.

Despite these notable advantages of the Orbitrap-iso method, questions linger regarding its accuracy, reproducibility, and precision relative to the long-established industry standard, IRMS. In an effort to validate the quality of Orbitrap-iso isotopologue ratio measurements, our study rigorously compares the analysis of identical ice core nitrate samples using both systems, aiming to establish a ground truth for the Orbitrap-iso methodology.

How to cite: Saville, J., Gautier, E., Savarino, J., and Lamothe, A.: Ground-truthing the performance of Orbitrap-iso for ice core nitrate stable isotope ratios by comparison to traditional Isotope Ratio Mass Spectrometer (IRMS) measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5349, https://doi.org/10.5194/egusphere-egu24-5349, 2024.

Ice cores can supply high-resolution insights into abrupt changes within the climate system. The RECAP ice core from the Renland ice cap, East Greenland, contains a substantial variety in dust particle size throughout its record, reaching back to the Eemian. Changes in dust particle sizes have been shown to reflect smaller ice cap extent during interglacial periods. Thus, local dust sources are only periodically available and can be characterised by large dust particles. For abrupt changes during the last glacial period, it is necessary to disentangle the potential imprint of dust sources and the role of snow accumulation. To better understand dust chemistry and size changes at high resolution, we apply several analytical methods in an ongoing investigation: Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) 2D imaging, 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 (10-40 µm) 2D chemical images, focusing on Na, Al, Mg, and Fe, 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 (LB-INAA). Furthermore, first results from SP analyses display their potential for ice core research regarding largely unexplored areas, such as the characterisation of rare earth elements of dust deposited in Greenland. The expertise and insight on high-resolution dust chemistry and size gained during this multi-method approach on ice with partly highly thinned annual layers will eventually be crucial for interpreting the dust signal stored in future Antarctic ice cores reaching back up to 1.5 Myr.

How to cite: Stoll, N., Larkman, P., Clases, D., Gonzalez de Vega, R., Di Stefano, E., Delmonte, B., Barbante, C., and Bohleber, P.: Characterising dust particles in the RECAP ice core with a multi-method approach to investigate abrupt climate changes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9596, https://doi.org/10.5194/egusphere-egu24-9596, 2024.

Paleoclimate and paleoenvironmental stratigraphic reconstructions from temperate glaciers are hindered by surface melting and ice metamorphism, which cause mobilization and concentration of impurities, as well as their interaction through englacial reactions.

Despite meltwater intrusions, other impurities such as pollen grains and other palynomorphs remain to their original depth of deposition thanks to their large grain-size. Temperate glaciers close to vegetated areas, therefore, can include palynomorphs of different types that i) can be reliable annual markers for ice-core dating and, ii) allow reconstructing paleoenvironmental changes through time.

The Adamello Glacier (Central Alps, Italy) is a temperate glacier that extends over ca 14.35 km² (2020) at elevations ranging between 2560 and 3420 m a.s.l. In the framework of the CLIMADA Project, a 224 m long ice core (ADA 270) was recovered in 2021 from Pian di Neve, the summit plateau at about 3200 m a.s.l. in the accumulation area of the glacier. Preliminary estimates date the surface ice of the glacier to the 1980s while the bottom of the core might be Medieval in age. Radionuclide-based dating (³H, ¹⁴C, ¹³⁷Cs, ²¹⁰Pb) is in progress.

The multiproxy approach adopted in this study includes black carbon, dust grain size and mineralogy, oxygen and hydrogen stable isotopes and palynomorphs, these last being the main object of this work. Given the site location, the palaeoecological signal is believed to be of regional significance.

Despite the stratigraphy may not be preserved for some soluble chemical species, the core contains a high variety of palynomorphs, which allow the reconstruction of palaeoenvironmental and paleoclimatic variations at subannual resolution. The mean ice accumulation rate is about 0.9 m w.eq. yr^-1. Consequently, the mean sampling resolution adopted for the palynomorph study is 0.1 m, increased to 0.01 m in specific intervals. Palynomorphs are mainly found in layers representing the spring-summer deposition while their concentration is very low during other periods of the year. Pollen grains, spores, diatom frustules, phytoliths and charcoals characterize the spring-summer layers; glass shards of volcanic origin and green algae have been observed in few intervals. Sporadic but massive Saharan dust events, carrying characteristic dust particles and pollen of African provenance, were identified throughout the core. The comparison between these intervals and the historical “red rain” events in Northern Italy will help better constraining the ice core dating.

At ca 66 m depth, an ice interval characterized by a high impurity content has been investigated at 0.01 m resolution. Different palynomorphs are recorded in this interval, implying a quasi-continuous presence of humans and animals on the glacier for few years. Preliminary results link these layers to World War I, intensively fought between Italians and Austro-Hungarians on the slopes surrounding the Pian di Neve. The comparison between historical, archeological and ice core data allow delineating, at subannual resolution, the climate and environmental changes that characterized those years.

How to cite: Mangili, C., Delmonte, B., Pini, R., Artoni, C., Baccolo, G., Cremonesi, L., Di Stefano, E., Fiorini, D., and Maggi, V.: The Adamello Glacier: paleoenvironmental and paleoclimatic variations at subannual resolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11175, https://doi.org/10.5194/egusphere-egu24-11175, 2024.

Organic aerosols make up to 70-90% of the total aerosol mass, yet ice-core studies have predominantly focused on a limited set of compounds or bulk fractions altogether. Previous investigations have centered on biomass burning tracers, marine phytoplankton oxidation products, low molecular weight carboxylic acids and persistent organic pollutants, leaving a large majority of molecules unidentified. Advances in high-resolution mass spectrometry (HRMS) have recently enabled the exploration of a wider chemical space through the development of non-target screening (NTS) workflows.

In this work, we present three applications of a novel NTS method. Designed to detect secondary organic aerosol compounds in ice-core and snow samples, the method has contributed to a more comprehensive characterization of past molecular aerosol composition and has supported the development of new molecular proxies. Initially, the method was applied to the Belukha ice core (Siberian Altai, 4072 m. a.s.l.) between 1830 and 1980 CE, providing the first NTS ice-core record that embraces both the pre-industrial and industrial periods. More than 400 compounds were identified, and a clear anthropogenic fingerprint was recognized over the industrial period. Subsequently, the ice core samples from Colle Gnifetti (Switzerland, 4500 m. a.s.l.) covering the period from 1750 to 2000 CE were analyzed. Here, a smaller number of molecules was detected (≈200), consistent with the lower concentrations of dissolved organic carbon observed at this site. In both cores, most of the molecules are composed of carbon (C), hydrogen (H) and oxygen (O) and are associated with atmospheric oxidation of monoterpenes and isoprenes (e.g., succinic acid, pinic acid, azelaic acid). The industrial onset was characterized by an increase in nitrogen and sulfur containing compounds, likely due to the atmospheric reactions with anthropogenic NO_x and  SO₂. The higher occurrence of compounds with higher O/C ratios during the industrial period observed at both locations, suggests an increase in the atmosphere oxidative capacity. Lastly, the method was applied to 56 snow samples collected in springtime close to Ny-Ålesund (Svalbard Archipelago) and covering both pre- and phytoplankton bloom periods. Together with marine observations of algal bloom, the NTS results suggest promising evidence towards new ice-core marine productivity proxies for long-term reconstructions.

How to cite: Burgay, F., Singer, T., Salionov, D., Sharkov, D., Eichler, A., Jenk, T., Bruetsch, S., Huber, C., Vogel, A., Barbaro, E., Maffezzoli, N., Scoto, F., Isaksson, E., Ramirez, L., Bjelic, S., and Schwikowski, M.: Non-target screening analysis on ice and snow samples: a new opportunity to enhance our understanding on past and present atmospheric aerosol composition., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11478, https://doi.org/10.5194/egusphere-egu24-11478, 2024.

The EastGRIP ice core is drilled through the Northeast Greenland Ice Stream, which has a surface velocity of 55 m/yr towards NNE at the drill site. Deriving a better understanding of internal deformation and the rheology within an ice stream is crucial for ice flow models and projections of future solid ice discharge. We use the line scanner to make the stratigraphy visible and document disturbances in the layering in the depth region from 1375 to 2120 m covering a large part of the Glacial Period. Disturbances are visible in cuts perpendicular to the ice flow direction, and not in cuts parallel to flow. Between these two extremes, we have a gradual change in type and amount of disturbances. As with all other ice cores, the ice in the EastGRIP ice core is thinned vertically. Due to the advanced thinning of layers, it is clear that the visible structures are not the remnants of surface features, such as sastrugi.  However, the disturbances, or deformation structures, are the result of strain caused by the stress field at the EastGRIP site, which is described by a compressional component perpendicular to and an extensional component parallel to the ice flow direction. In most samples cut perpendicular to ice flow, i.e. with the compressional setting visible, we find structures, very similar to geological duplex structures. We identify duplex structures extending the width of the core by the sudden change of layer tilt within one bag at a time. Duplex structures are confined by layer parallel shear zones, with tilted layers in between them. The small-scale shear zones only become evident due to the deformation they cause and can extend well beyond these visible structures. We furthermore suggest, that shear zones are present parallel to layering, but do not show up, as a lateral displacement of layers, does not disrupt the vertical profiles. We discuss one example, from a depth of 1651 m (26 ky b2k), in detail. We further investigate approx. 30 m of chemical CFA data, mainly NH₄⁺ and Ca⁺⁺, from the same depth. We find peaks that double, in both the visual stratigraphy as well as the CFA data. These may be a result of the duplex structures that stack the stratigraphy and have the potential to disturb the climate record. Our results display the importance of understanding internal deformation when interpreting the climate record.

How to cite: Westhoff, J., Bons, P., Stoll, N., Weikusat, I., Zeppenfeld, C., Erhardt, T., and Dahl-Jensen, D.: Duplex Structures in the EastGRIP Ice Core - the Loss of Stratigraphic Integrity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15771, https://doi.org/10.5194/egusphere-egu24-15771, 2024.

How to cite: Sanchez Moreno, M., Lamott, A., Kipfstuhl, S., and Dahl-Jensen, D.: Microstructural insights during Abrupt events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16768, https://doi.org/10.5194/egusphere-egu24-16768, 2024.

Addressing the intricate challenges of water isotope analysis in polar ice cores, especially in extracting detailed climate records from older and thinner ice layers, the innovative integration of Laser Ablation (LA) with Cavity Ring Down Spectroscopy (CRDS) is introduced. The micro-destructive LA technique, which employs a nanosecond excimer pulsed laser operating at 193 nm for ice surface irradiation, demonstrates potential in achieving continuous, high-resolution sampling and gas phase sample generation, complementing the CRDS analyzer's precision in measuring water isotopes in gaseous state. Recent advancements include the successful adaptation of an existing LA system, previously coupled with an Inductively Coupled Plasma - Mass Spectrometer (ICP-MS) for ice core impurity analysis, to establish a connection with the CRDS analyzer. This was accomplished by making adjustments to the coupling procedure and laser parameters, to ensure efficient gas sample generation and robust delivery for water isotope analysis. A method for creating ice standard samples by transforming liquid water standards into ice yielded ice isotope standards, crucial for setting up initial measurement protocols. Their implementation on both standard ice samples and sections of ice cores revealed valuable insights into areas for improvement. This represents a significant step towards establishing a reliable method for high-quality water isotope analysis in ice cores, aiming to significantly enrich our understanding of long-term climate trends.

How to cite: Malegiannaki, E., Zannoni, D., Bohleber, P., Stremtan, C., Petteni, A., Stenni, B., Barbante, C., Dahl-Jensen, D., and Gkinis, V.: Advancing towards high-quality water isotope measurements in ice cores: a micro-destructive approach using Laser Ablation coupled with Cavity Ring Down Spectroscopy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12902, https://doi.org/10.5194/egusphere-egu24-12902, 2024.