CL1.5 | The state-of-the-art in ice coring sciences
EDI
The state-of-the-art in ice coring sciences
Convener: Michael DöringECSECS | Co-conveners: Michael DyonisiusECSECS, Helle Astrid Kjær, Anja Eichler
Orals
| Mon, 24 Apr, 16:15–17:55 (CEST)
 
Room 0.31/32
Posters on site
| Attendance Mon, 24 Apr, 08:30–10:15 (CEST)
 
Hall X5
Posters virtual
| Attendance Mon, 24 Apr, 08:30–10:15 (CEST)
 
vHall CL
Orals |
Mon, 16:15
Mon, 08:30
Mon, 08:30
The half-century since the first deep ice core drilling at Camp Century, Greenland, has seen extensive innovation in methods of ice sample extraction, analysis and interpretation. Ice core sciences include isotopic diffusion analysis, multiple-isotope systematics, trace gases and their isotopic compositions, ice structure and physical properties, high-resolution analysis of major and trace impurities, and studies of DNA and radiochemistry in ice, among many others. Many climate and geochemical proxies have been identified from ice cores, with ongoing effort to extend their application and refine their interpretation. Great challenges remain in the field of ice coring sciences, including the identification of suitable sites for recovery of million-year-old ice; spatial integration of climate records (e.g. PAGES groups Antarctica2k and Iso2k); and deeper understanding of glaciological phenomena such as streaming flow, folding of layers and basal ice properties. This session welcomes all contributions reporting the state-of-the-art in ice coring sciences, including drilling and processing, dating, analytical techniques, results and interpretations of ice core records from polar ice sheets and mid- and low-latitude glaciers, remote and autonomous methods of surveying ice stratigraphy, and related modelling research.

Orals: Mon, 24 Apr | Room 0.31/32

Chairpersons: Michael Dyonisius, Helle Astrid Kjær, Anja Eichler
16:15–16:25
|
EGU23-6627
|
CL1.5
|
On-site presentation
Anders Svensson and the Bipolar volcano team

Precise synchronization of climate records is essential for deducing the dynamics of the climate system. Ice cores from the Greenland and Antarctic ice sheets have previously been synchronized by the use of cosmogenic isotopes, gas concentrations, and traces of large volcanic eruptions. Identification of identical sequences of volcanic sulfate depositions at both poles have been applied to synchronize ice cores in the Holocene, in the last deglaciation, in Marine Isotope Stage 3 (MIS3) and around the Indonesian Toba eruption occurring close to 74 ka. We now extend this inter-hemispheric volcanic synchronization approach to also cover MIS2 (16.5-24.5 ka BP), MIS4 and part of MIS5 (60-110 ka BP) allowing for a precise bipolar synchronization of the entire last glacial period. The synchronization is based on some 250 volcanic eruptions that are identified as acidity spikes in both Greenland and Antarctica. Similar to previous work, the identification of volcanic sequences at the two poles is supported by annual layer counting in both Greenland and Antarctica, although the identification of annual layers becomes increasingly difficult with depth. To support the synchronization we investigate the deduced annual layer thicknesses (not requiring layer counting) and the inferred depth-depth relation between synchronized ice cores. The precise bipolar synchronization allows to determine the exact inter-hemispheric phasing of abrupt climate change during the last glacial, and to investigate a possible relation between abrupt climate change and volcanism. Furthermore, the frequency and magnitude of large volcanic eruptions of the last glacial can be established.

How to cite: Svensson, A. and the Bipolar volcano team: Bipolar volcanic ice-core synchronization of the last glacial cycle, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6627, https://doi.org/10.5194/egusphere-egu23-6627, 2023.

16:25–16:35
|
EGU23-1327
|
CL1.5
|
ECS
|
On-site presentation
Carla Huber, Daniil Salionov, François Burgay, Anja Eichler, Theo Jenk, Sasa Bjelic, and Margit Schwikowski

Ice cores are unique natural archives that provide important information about the past evolution of the Earth’s atmosphere. Whereas the inorganic atmospheric aerosol fraction is well characterized, the organic composition is less understood. The organic aerosol burden is consistently underestimated in the current state-of-the-art models, thus highlighting major gaps in our understanding of the pathways by which organic aerosols accumulate and evolve in the atmosphere. So far, organic aerosols in ice cores have been primarily reported as either bulk (e.g., water insoluble or dissolved organic carbon) or specific parameters (e.g., biomass burning tracers).
To provide a more comprehensive characterization of the organic fraction, we applied a non-target screening approach optimised for determining oxidation products of volatile organic compounds to a firn core collected on the Corbassière glacier (Grand Combin, Swiss Alps), in 2020, covering the period 2008-2020. In comparison with a firn core drilled two years earlier (2018), we observe a drastic disturbance of seasonal trends for certain species, such as major ions at depths corresponding to the annual layers from 2008 to 2016, induced by meltwater percolation.

As organic tracers are present in low concentrations in the firn core, we performed solid phase extraction. The organic tracers were analysed with high-resolution mass spectrometry based on Orbitrap technology coupled with liquid chromatography. This technique makes it possible to study a wide range of individual compounds at low concentration and to identify them with MS/MS fragmentation. We can attribute molecular formulas to detected compounds by comparing the MS/MS spectra with spectral libraries (e.g., mzCloud) or reference standards. With this approach we will present a unique record of molecular composition of organic aerosol in the Corbassière firn core.
Furthermore, this firn core presents a unique opportunity to examine the effect of melting on the organic tracers. We found that specific burning tracers (e.g., vanillic acid, vanillin and syringaldehyde) are less affected than other biomass tracers (e.g., pinic acid) by meltwater percolation. In general, we observe a decrease in concentration of the organic tracers in the same firn core section where we also observe a decrease in major ion concentrations.

How to cite: Huber, C., Salionov, D., Burgay, F., Eichler, A., Jenk, T., Bjelic, S., and Schwikowski, M.: Non-target screening of organic aerosol tracers applied to a high-alpine firn core, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1327, https://doi.org/10.5194/egusphere-egu23-1327, 2023.

16:35–16:45
|
EGU23-2398
|
CL1.5
|
ECS
|
Highlight
|
On-site presentation
Emilia Bushrod, Elizabeth Thomas, and Chiara Giorio

Terrestrially emitted biogenic volatile organic compounds (BVOCs) can be oxidised within the troposphere and become components in secondary organic aerosol (SOA). SOA can be transported and deposited at glacial regions. Due to Antarctica’s geography being removed from the terrestrial sources of BVOCs, it was unclear if SOA-markers of such BVOCs could become incorporated in Antarctic ice, at a detectable concentration. Terrestrial SOA-markers have never before been found to be present in Antarctic ice cores, until this study. The implementation of liquid chromatography coupled with triple quadrupole mass spectrometry has allowed for the development of a novel method that can detect targeted organic compounds at concentrations as low as 1.5ppt. Using this method, 2-methylerythritol, a SOA-marker of isoprene, has been detected in Jurassic, an ice core drilled in Antarctica. Though difficult to quantify due to the low concentration, this is the first time that such a compound has been found in Antarctic ice.

How to cite: Bushrod, E., Thomas, E., and Giorio, C.: A Novel Method for Quantifying Terrestrial SOA-Markers in Antarctic Ice, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2398, https://doi.org/10.5194/egusphere-egu23-2398, 2023.

16:45–16:55
|
EGU23-4873
|
CL1.5
|
ECS
|
Virtual presentation
Nasrin Salehnia and Jinho Ahn

One of the primary proxies for ancient atmospheric air compositions is the fossil air occluded in polar ice sheets. Ice cores are significant archives for the atmospheric Greenhouse Gas (GHG) concentrations during the last 800 kyr (thousand years). GHG records from polar ice cores have provided valuable information on past climatic, atmospheric, and glaciological changes. For example, nitrous oxide (N2O) is a long-lived GHG and gives us information on nitrogen cycles. However, the time resolution and missing gaps of N2O records limit our understanding of the control mechanisms in the atmosphere. One of the well-known state-of-the-art methods is AI (Artificial Intelligence) techniques, and its main branch is ML (Machine Learning) method. To fill the N2O gaps during the last 800 kyr, we used CO2 and CH4 concentration data from Antarctic ice cores (Vostok and EPICA Dome C ice cores). The ML methods were run in two steps. First, the gap parts were deleted from the time series, and modeling was performed with CO2 and CH4 concentration data with six various ML methods (Linear, Support Vector Machine, Tree, Gaussian Process Regression (GPR), Artificial Neural Network (ANN), and Ensemble). Then, the best model was selected for the second step to reconstruct the N2O in the data gaps. Although other AI methods revealed acceptable results in the first step, the GPR method produced a high-quality simulation with R2= 0.86, RMSE= 7.38 ppb, and MAE= 4.15 ppb. Finally, the simulation for the N2O gaps was performed with the GPR method. Our results confirm that AI techniques have a high potential to produce continuous paleo atmospheric GHG concentrations. Future research includes modeling with other AI and ML methods and applying the AI techniques to other ice core records, such as water isotope ratios (temperature proxy) over various past periods.

How to cite: Salehnia, N. and Ahn, J.: Filling N2O data gaps during the last 800,000 years via Artificial Intelligence Techniques, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4873, https://doi.org/10.5194/egusphere-egu23-4873, 2023.

16:55–17:05
|
EGU23-3787
|
CL1.5
|
On-site presentation
Hubertus Fischer, Andrea Burke, James Rae, Eric Wolff, Helena Pryer, Emily Doyle, Mirko Severi, Bradley Markle, Maria Hörhold, Johannes Freitag, and Tobias Erhardt

An important ingredient in the glacial reduction of atmospheric CO2 is the increase of marine biological productivity in the Southern Ocean region due to an alleviation of Fe limitation in glacial times. This is indeed documented in marine sediments north of the modern Antarctic Polar Front (APF). In contrast, productivity south of it appears to be reduced, however the marine information is incomplete due to the prevalence of winter and summer sea ice in major parts of this region during glacial times. The high-resolution Antarctic ice core sulfate aerosol record, which, among other sources, is influenced by the marine biogenic emission of dimethylsulfide, was so far unable to provide unambiguous estimates of such productivity changes. In particular, sulfate deposition fluxes in the EPICA Dome C ice core (EDC) showed no glacial/interglacial changes whatsoever, while the same data in the EPICA Dronning Maud Land core (EDML) suggested a slight increase in the glacial, despite the fact that these records should be dominated by biogenic sources south of the APF.

New high-precision stable sulfur isotope measurements on ice core sulfate over termination II on the EDML core together with high-resolution sulfate, sea-salt and mineral dust aerosol concentration records allow us for the first time to perform a quantitative decomposition of the sea salt, terrestrial, volcanic and biogenic sulfate contributions. This shows that despite a significant increase in terrestrial sulfate in the glacial, marine biogenic emissions are still by far the dominating source of sulfate during that time at least for the Atlantic sector of Antarctica but likely for the entire Antarctic plateau.

Using a simple atmospheric aerosol transport model to correct for the loss of sulfate aerosol en route by wet and dry deposition, we are able to reconstruct the atmospheric sulfate aerosol concentrations changes over the Atlantic sector of the Southern Ocean source region mainly south of the APF. This shows that despite lower sulfate ice concentrations at EDML during interglacials, atmospheric aerosol concentration at the ocean source south of the APF - hence marine biogenic sulfur emissions - were up to a factor of 2 higher during the last interglacial and the late termination II than during the penultimate glacial maximum.

How to cite: Fischer, H., Burke, A., Rae, J., Wolff, E., Pryer, H., Doyle, E., Severi, M., Markle, B., Hörhold, M., Freitag, J., and Erhardt, T.: Sulfate isotopes over termination II - Source decomposition and Southern Ocean productivity changes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3787, https://doi.org/10.5194/egusphere-egu23-3787, 2023.

17:05–17:15
|
EGU23-12369
|
CL1.5
|
ECS
|
On-site presentation
Andreas Plach, Sabine Eckhardt, Ignacio Pisso, Joseph R. McConnell, and Andreas Stohl

Atmospheric transport modeling with the Lagrangian Particle Dispersion Model (LPDM) FLEXPART has been used for the interpretation of ice core records in several studies in the recent past. Here we present (1) the methodology and results of a study looking into the historical black carbon (BC) emissions based on inverse modeling of ice core records, (2) discuss preliminary results and further plans for a similar study looking into the historical sulphur dioxide (SO2) emissions, (3) and give a short overview of other ice core studies using FLEXPART simulations.

Both, BC and SO2 emissions, are caused by anthropogenic as well as natural processes, e.g., (incomplete) combustion of fossil fuels / biomass and volcanic eruptions. And, both negatively influence our health and environment, e.g., causing premature mortality, lowering surface albedo, producing acid rain. However, both species also act as climate forcers, and therefore an accurate knowledge of past BC/SO2 emissions is essential to quantify and model associated global climate forcing. Nowadays, commonly used bottom-up BC/SO2 emission inventories for historical Earth System Modeling (ESM), e.g., for the Coupled Model Intercomparison Project Phase 5 / Phase 6 (CMIP5/CMIP6) are poorly constrained by observations prior to the late 20th century.

In a recent study, we revisit and evaluate these historical 1850 to 2000 BC emission inventories used for ESM simulations, based on an array of deposition ice core records, Lagrangian atmospheric modeling with the FLEXPART model, and an objective inversion technique in order to bring the spatial-temporal patterns of emission inventories in accordance with observed deposition at the ice core sites. We find substantial discrepancies between our reconstructed BC emissions and the existing bottom-up inventories which do not fully capture the complex spatial-temporal BC emission patterns. Our findings imply changes to existing historical BC radiative forcing estimates are necessary, with potential implications for observation-constrained climate sensitivity.

How to cite: Plach, A., Eckhardt, S., Pisso, I., McConnell, J. R., and Stohl, A.: Lagrangian modeling used for improving ice core interpretation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12369, https://doi.org/10.5194/egusphere-egu23-12369, 2023.

17:15–17:25
|
EGU23-12653
|
CL1.5
|
ECS
|
On-site presentation
Johanna Kerch, Kyra Streng, Nicolas Stoll, Jan Eichler, Julien Westhoff, Daniela Jansen, Paul Bons, and Ilka Weikusat

We present the results from a microstructural analysis of more than 1000 thin section samples from the East Greenland Ice Core Project (EastGRIP) ice core that is being drilled at the onset of the fast-flowing North East Greenland Ice Stream (NEGIS) since 2017, focusing on the grain boundary network and bubbles.

The data were recorded directly at the drilling site with a Large Area Scanning Macroscope from the polished and sublimated surface of samples from between 0 and 2121 m ice depth. Most samples are cut vertically, along the core axis, but a selected number of perpendicular vertical and horizontal sections from volume samples are included, providing the opportunity to deduce the three-dimensional microstructure in these depths. Processing of the image data was done with the open source software Ice Microstructure Analyser, extracting a fully digitalized grain boundary network by applying machine learning for the classification of grain boundaries and air inclusions.

We analysed the shape-preferred orientation (SPO) of grains and bubbles based on statistically computed parameters from the data set under consideration of available azimuthal core-orientation data reconstructed from visual stratigraphy data. These SPO parameters include grain size distribution, grain shape and derived measures like perimeter ratio and aspect ratio, and grain boundary orientation angle.

The data show varying trends throughout the core and on different length scales, supporting and complementing earlier observations in the crystallographic-preferred orientation data from the same set of samples. We provide microstructural evidence for dynamic recrystallisation driven by deformation throughout the core. Specifically, we will discuss our findings of heterogeneities that point to internal deformation due to the occurrence of high strain localisation and link them to the observed complex pattern of anisotropy in the ice column.

How to cite: Kerch, J., Streng, K., Stoll, N., Eichler, J., Westhoff, J., Jansen, D., Bons, P., and Weikusat, I.: Characterisation of multi-scale deformation in NEGIS from microstructure analysis of the EastGRIP ice core, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12653, https://doi.org/10.5194/egusphere-egu23-12653, 2023.

17:25–17:35
|
EGU23-10308
|
CL1.5
|
ECS
|
Highlight
|
Virtual presentation
Dieter Tetzner, Elizabeth Thomas, and Claire Allen

The Southern Hemisphere Westerly Winds play a critical role in the global climate system by modulating the upwelling and the transfer of heat and carbon between the atmosphere and the ocean. Since observations started, the core of the westerly wind belt has increased in strength and has contracted towards Antarctica. It has been proposed that these deviations are among the main drivers of the observed widespread warming in West Antarctica. However, the lack of long-term wind records in the Southern Hemisphere mid-latitudes hinders our ability to assess the wider context of the recently observed changes.

Here, we present the diatom record preserved in an ice core retrieved from the Ellsworth Land region, West Antarctica. The diatom abundances and species assemblages from this ice core represent the regional variability in wind strength and atmospheric circulation patterns over the Atlantic sector of the Southern Ocean. We use this novel proxy to produce an annual reconstruction of winds in the Atlantic sector of the Southern Hemisphere Westerly Wind belt over the last 300 years. This wind reconstruction allows tracking changes in the strength and position of the westerly winds during the late Little Ice age and exploring the link between the recent increase in wind strength, greenhouse gases and ozone depletion in the atmosphere.

How to cite: Tetzner, D., Thomas, E., and Allen, C.: New ice core proxy for reconstructing past wind variability in the Atlantic sector of the Southern Hemisphere Westerly Wind belt, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10308, https://doi.org/10.5194/egusphere-egu23-10308, 2023.

17:35–17:45
|
EGU23-14843
|
CL1.5
|
ECS
|
On-site presentation
Isobel Rowell, Robert Mulvaney, Dieter Tetzner, Liz Thomas, Mackenzie Grieman, Carlos Martin, Helena Pryer, Julius Rix, and Eric Wolff

The West Antarctic Ice Sheet (WAIS) is vulnerable to retreat as a result of climate change and has the potential to contribute several metres to global sea level in the coming centuries. Glaciers flowing into the Amundsen Sea, in particular the Thwaites and Pine Island Glaciers, are undergoing accelerated mass loss. Ice core records from the Amundsen coast in this region are lacking and WAIS cores typically extend back in time from a few decades, up to approximately 300 years before present. Here we present new climate records from Sherman Island, located in the Abbott Ice Shelf and close to Pine Island and Thwaites. These records extend to greater than 1000 years before present, more than doubling the length of existing coastal WAIS records. Trends in stable water isotopes are compared with proximal cores to set the Sherman Island data into a regional spatial context over the last few hundred years. We find that Sherman Island demonstrates no overall trend in stable water isotope ratios or in accumulation rate over the last 50 to 100 years, in contrast to other sites, and we relate this finding to previously identified changes in the Southern Annular Mode and Amundsen Sea. We investigate atmospheric transport to the site using reanalysis data and records of chemical impurities in the Sherman Island samples. The data present an exciting and significant new contribution to palaeoclimatic datasets and reconstructive efforts including the PAGES-2k network. Importantly, taken together the records from this unique site will help to set the current changes in this highly vulnerable sector of the WAIS into the context of the last millennium. 

How to cite: Rowell, I., Mulvaney, R., Tetzner, D., Thomas, L., Grieman, M., Martin, C., Pryer, H., Rix, J., and Wolff, E.: New climate records from Sherman Island and insights into coastal West Antarctic climate variability over the last 1000 years, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14843, https://doi.org/10.5194/egusphere-egu23-14843, 2023.

17:45–17:55
|
EGU23-3195
|
CL1.5
|
On-site presentation
Eric Wolff, Mackenzie Grieman, Helene Hoffmann, Jack Humby, Robert Mulvaney, Christoph Nehrbass-Ahles, Sentia Goursaud Oger, Rachael Rhodes, and Isobel Rowell

Antarctic ice core records covering the last glacial cycle generally reflect a common climate and environmental history overlain with local influences such as changes in altitude, atmospheric circulation, local dust sources, or regional sea ice extent. Here we investigate records from the 651 m Skytrain Ice Rise core, drilled within the WACSWAIN (WArm Climate Stability of the West Antarctic ice sheet in the last Interglacial) project. This ice rise is adjacent to the Ronne Ice Shelf and the WAIS, and extends into the last interglacial period, including a continuous record of the last glacial cycle.   

The water isotope record shows the clearly recognisable pattern of all the Antarctic Isotopic Maxima of the last 100 kyr, but with different amplitudes to those seen in the well-known WAIS Divide or EPICA ice cores. We will consider what these differences in amplitude tell us about ice elevation at Skytrain, using total air content data to aid our interpretation. The information from sea salt ions can tell us about ice shelf extent, and taking the water isotopes and ions together will allow us to diagnose the status of the Ronne Ice Shelf throughout the glacial. Terrestrial material (Ca, dust) reflects both a common continent-wide input of dust from other continents (especially South America) but also local inputs. We will use the differences for terrestrial dust between Skytrain Ice Rise and other sites to diagnose the input of local dust from the Ellsworth Mountains.

Finally combining all three sources of information we expect to make statements about the wider advance and retreat of the West Antarctic Ice Sheet and Ronne Ice Shelf in the region surrounding Skytrain Ice Rise.

How to cite: Wolff, E., Grieman, M., Hoffmann, H., Humby, J., Mulvaney, R., Nehrbass-Ahles, C., Goursaud Oger, S., Rhodes, R., and Rowell, I.: Skytrain Ice Rise, Antarctica, during the last glacial period, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3195, https://doi.org/10.5194/egusphere-egu23-3195, 2023.

Posters on site: Mon, 24 Apr, 08:30–10:15 | Hall X5

Chairpersons: Michael Döring, Helle Astrid Kjær, Anja Eichler
X5.132
|
EGU23-157
|
CL1.5
|
ECS
Michaela Mühl, Jochen Schmitt, Barbara Seth, James E. Lee, Jon S. Edwards, Edward J. Brook, Thomas Blunier, and Hubertus Fischer

Air trapped in polar ice provides unique records of the past atmospheric composition ranging from key greenhouse gases such as methane (CH4) to short-lived trace gases like ethane (C2H6) and propane (C3H8). Interpreting these data in terms of atmospheric changes requires that the analyzed species accurately reflect the past atmospheric composition.

Recent comparisons of Greenland CH4 records obtained using different extraction techniques revealed discrepancies in the CH4 concentration for the last glacial. Elevated methane levels (excess methane or CH4(exs)) were detected in dust rich ice core sections measured by discrete melt extraction techniques pointing to an artefact sensitive to the measurement technique. To shed light on the underlying mechanism, we analyzed Greenland ice core samples for methane and other short-chain alkanes (ethane and propane) covering the time interval from 12 to 42 kyr using a classic wet extraction technique. The artefact production happens during the melting and extraction step (in extractu) and reaches 14 to 91 ppb CH4(exs) in dusty ice samples. For the first time in ice core analyses, we document a co-production of excess methane, ethane, and propane (excess alkanes) with the observed concentrations for ethane and propane exceeding, at least by a factor of 10, their past atmospheric concentration. Independent of the produced amounts, excess alkanes were produced in a fixed molar ratio of approximately 14:2:1, indicating a common production. We also discovered that the amount of excess alkanes scales generally with the amount of mineral dust (or Ca2+ as a proxy for mineral dust) within the ice samples. Moreover, applying the Keeling-plot approach we are able to isotopically characterize CH4(exs) revealing a relatively heavy carbon isotopic signature of (-46.4 ± 2.4) ‰ and a light deuterium isotopic signature of (-326 ± 57) ‰ of the excess methane in the samples analyzed.

The co-production ratios of excess alkanes and the isotopic composition of excess methane allows us to confine potential formation processes. We discovered that this specific alkane pattern is not in line with an anaerobic methanogenic origin but indicative for abiotic decomposition of organic matter as also found in sediments, soils, and plant leaves. From the present-day state of research little is known about this process and there is urgent need to improve our understanding for future ice core measurements. Moreover, the already existing discrete records of atmospheric CH4 in Greenland ice need to be corrected for excess CH4 contribution (CH4(exs), δ13C-CH4(exs), δD-CH4(exs)) in dust-rich intervals.

While the size of the excess methane production has little effect on reconstructed radiative forcing changes of CH4 in the past, it is in the same range as the Inter-Polar Difference (IPD) for CH4. Knowing the empirical relation of excess CH4(exs)/ Ca2+ and CH4(exs)/ C2H6 allows us to derive a first-order correction of existing CH4 data sets to revise previous interpretations of the relative contribution of high latitude northern hemispheric CH4 sources based on the IPD.

How to cite: Mühl, M., Schmitt, J., Seth, B., Lee, J. E., Edwards, J. S., Brook, E. J., Blunier, T., and Fischer, H.: Excess methane, ethane, and propane production in Greenland ice core samples and a first characterization of the δ13C-CH4 and δD-CH4 signature, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-157, https://doi.org/10.5194/egusphere-egu23-157, 2023.

X5.133
|
EGU23-9346
|
CL1.5
|
ECS
Johanna Schäfer, Francois Burgay, Thomas Singer, Margit Schwikowski, and Thorsten Hoffmann

The assessment of global warming and its far-reaching influences on our planet necessitates reliable and accurate climate models. For this purpose, past atmospheric conditions like aerosol composition must be studied to understand their influence on the Earth’s climate. Ice cores are valuable climate archives that preserve organic compounds from atmospheric aerosols, which can be utilized as marker species for their respective emission sources.

Secondary organic aerosols (SOAs) are formed in the atmosphere by the oxidation of volatile organic compounds (VOCs), which can be either of anthropogenic or biogenic origin. The most common precursors of SOAs are monoterpenes, which are naturally emitted by vegetation in large amounts. Furthermore, organic compounds formed during biomass burning events contribute to the aerosol budget and allow the reconstruction of paleo-fire activity. Of great interest as a marker species is the anhydrosugar levoglucosan, which is formed during the combustion of cellulose. In addition to its combustion products, intact polymeric lignin, digested via alkaline oxidative degradation, can provide information about the type of vegetation which it originated from. A large variety of these markers were analyzed in an ice core extracted from the Belukha glacier located in the Altai region of Southern Siberia covering a time span of three centuries. A sample preparation method including multiple solid phase extractions and UHPLC-HRMS analysis was employed.

Chiral compounds have the same molecular formula and atom connectivity but act like mirror images of each other. In most environmental studies, no distinction is made between these so-called enantiomers. However, chirality can affect chemical and physical properties and thus influence particle formation reactions in the atmosphere. The enantiomeric ratio of a chiral compound can also further elucidate possible emission sources. Here we present the first chiral analysis of monoterpene oxidation products in ice cores and thus on a long-term scale. For this purpose, a multiple heartcut two-dimensional liquid chromatography method (mLC-LC) was developed that allows the simultaneous determination of the enantiomeric ratios of the monoterpene oxidation products cis-pinic acid and cis-pinonic acid in complex ice core samples. This novel method was successfully applied to Belukha ice core samples.

How to cite: Schäfer, J., Burgay, F., Singer, T., Schwikowski, M., and Hoffmann, T.: Analysis of organic aerosol markers and chiral compounds in an ice core from the Siberian Altai using UHPLC-HRMS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9346, https://doi.org/10.5194/egusphere-egu23-9346, 2023.

X5.134
|
EGU23-15249
|
CL1.5
|
ECS
|
Eirini Malegiannaki, Vasileios Gkinis, Simon Alexander Munk Wael Fassel, Daniele Zannoni, Giuliano Dreossi, Barbara Stenni, Hans Christian Steen-Larsen, Pascal Bohleber, Carlo Barbante, and Dorthe Dahl-Jensen

Thinning of the deep ice core layers must be considered when the water isotopic composition of the Oldest Ice Core is to be analyzed. From an experimental point of view, a novel instrument combining a micro-destructive cold femtosecond - Laser Ablation (LA) sampling system, that provides high spatial resolution together with minimal usage of ice sample, and a Cavity Ring Down Spectrometer is being built for high-quality water isotope measurements. Laser ablation results in crater formation and its morphology depends on the laser parameters used. Optical images that show crater morphology under different experimental conditions allow crater characterization towards an efficient cold LA sampling. An ablation chamber and a transfer line are both the connecting parts between the LA system and the CRDS instrument. They are to be designed and constructed in the optimal size and shape to collect the ablated mass and guarantee its smooth delivery to the CRDS analyzer with minimum disturbance. 

Coupling a Laser Ablation system with a CRDS analyzer has already been achieved using a laser operating at the nanosecond regime and a cryo-cell as the ablation chamber. Comparison of the two Laser Ablation systems, by the means of ice sampling and collection of the ablated material, will be of great importance to understand the ablation mechanism and post-ablation processes on ice and further develop a system dedicated to water isotope measurements. 

How to cite: Malegiannaki, E., Gkinis, V., Munk Wael Fassel, S. A., Zannoni, D., Dreossi, G., Stenni, B., Steen-Larsen, H. C., Bohleber, P., Barbante, C., and Dahl-Jensen, D.: Investigating two possible schemes of Laser Ablation – Cavity Ring Down Spectrometry for water isotope measurements on ice cores, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15249, https://doi.org/10.5194/egusphere-egu23-15249, 2023.

X5.135
|
EGU23-12385
|
CL1.5
|
Highlight
Anja Eichler, Petr Nalivaika, Theo Jenk, Thomas Singer, Sergey Kakareka, Tamara Kukharchyk, Stella Eyrikh, Tatjana Papina, Andreas Plach, and Margit Schwikowski

Atmospheric heavy metal pollution caused by metal smelting, mining, waste incineration and fossil fuel combustion presents a significant issue for human health and the environment. Anthropogenic emissions from the territory of the former Soviet Union (FSU) considerably influenced atmospheric concentrations of heavy metals. However, due to scarce monitoring data and fragmentary reporting, emissions quantities from this region are not well-known and it is even unclear if emissions decreased or increased after collapse of the Soviet Union. This is underlined by the fact that existing ice-core records and emission estimates based on national inventories for the FSU reveal an opposing trend for the most recent ~30 years. 

Here we present new records of post-Soviet Union anthropogenic heavy metal  emissions (Bi, Cd, Cu, Pb, Sb, Zn) derived from three ice cores; from the Mongolian Altai (Tsambagarav ice core, period 1710-2009 AD) and the Siberian Altai (two Belukha ice cores, period 1680-2018 AD), covering a large regional footprint of emissions. The major source region of air pollution arriving at the Altai is primarily the territory of the FSU except for the eastern-most Siberian parts. Heavy metal concentrations at ultra-trace levels in the studied ice cores were analysed using inductively coupled plasma sector-field mass spectrometry (ICP-SF-MS). These records were complemented with new heavy metal emission estimates based on the available inventory data (1975-2015 AD) to derive a robust reconstruction of recent FSU heavy metal emissions. Consistent with the emission estimates, ice-core concentrations of Cd, Cu, Pb, Sb, Zn during the 2010s correspond to 20-40% of the maximum values in the 1970s and are comparable to their 1940s-1950s levels. A similar magnitude was also estimated for the decrease in Bi between 1975 and 2015, however, ice-core concentrations do not show a substantial downward trend.

How to cite: Eichler, A., Nalivaika, P., Jenk, T., Singer, T., Kakareka, S., Kukharchyk, T., Eyrikh, S., Papina, T., Plach, A., and Schwikowski, M.: Recent heavy metal pollution from the territory of the former Soviet Union (FSU) – ice core records and emission estimates, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12385, https://doi.org/10.5194/egusphere-egu23-12385, 2023.

X5.136
|
EGU23-1684
|
CL1.5
Lindsay Powers, Andrei Kurbatov, Charles Kershaw, Geoffrey Hargreaves, Curtis Labombard, and Tyler J. Fudge

The National Science Foundation Ice Core Facility (NSF-ICF, fka NICL) is in the process of building a new facility including freezer and scientist support space. The facility is being designed to minimize environmental impacts while maximizing ice core curation and science support. In preparation for the new facility, we are updating research equipment and integrating ice core data collection and processing by assigning International Generic Sample Numbers (IGSN) to advance the “FAIR”ness and establish clear provenance of samples, fostering the next generation of linked research data products. The NSF-ICF team, in collaboration with the US ice  core science community, has established a metadata schema for the assignment of IGSNs to ice cores and samples. In addition, in close coordination with the US ice core community, we are adding equipment modules that expand traditional sets of physical property, visual stratigraphy, and electrical conductance ice core measurements. One such module is an ice core hyperspectral imaging (HSI) system. Adapted for the cold laboratory settings, the SPECIM SisuSCS HSI system can collect up to 224 bands using a continuous line-scanning mode in the visible and near-infrared (VNIR) 400-1000 nm spectral region. A modular system design allows expansion of spectral properties in the future. The second module is an updated multitrack electrical conductance system. These new data will guide real time optimization of sampling for planned analyses during ice core processing, especially for ice with deformed or highly compressed layering. The aim is to facilitate the collection of robust, long-term, and FAIR data archives for every future ice core section processed at NSF-ICF. The NSF-ICF is fully funded by the National Science Foundation and operated by the U.S. Geological Survey.

How to cite: Powers, L., Kurbatov, A., Kershaw, C., Hargreaves, G., Labombard, C., and Fudge, T. J.: The next generation U.S. National Science Foundation Ice Core Facility: supporting state-of-the-art science., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1684, https://doi.org/10.5194/egusphere-egu23-1684, 2023.

X5.137
|
EGU23-10179
|
CL1.5
Felix Ng

Diffusive smoothing of signals on the water stable isotopes in ice sheets limits the climatic information retrievable from these ice-core proxies. Previous theories explained how, in polycrystalline ice below the firn, fast diffusion in the network of intergranular water veins short-circuits the slow diffusion in crystal grains to cause “excess diffusion”, enhancing the signal smoothing rate above that implied by self-diffusion in ice monocrystals. However, the controls of excess diffusion remain poorly understood. I show that vein-water flow amplifies excess diffusion, by altering the three-dimensional field of isotope concentrations and isotope transfer between the veins and crystals. The rate of signal smoothing depends not only on temperature, vein and grain sizes, and signal wavelength, but also on vein-water flow velocity, which can increase the rate by 1 to 2 orders of magnitude. This modulation can significantly impact signal smoothing at ice-core sites in Greenland and Antarctica, as demonstrated by simulations for the GRIP and EPICA Dome C sites, which show sensitive modulation of their diffusion-length profiles when vein-water flow velocities reach ~ 101–102 m yr–1. Thus vein-flow mediated excess diffusion may help explain the mismatch between modelled and spectrally-derived diffusion lengths in other ice cores. I also show that excess diffusion biases the spectral estimation of diffusion lengths from isotopic signals and the reconstruction of surface temperature from diffusion-length profiles. These findings caution against using the single-crystal isotopic diffusivity to represent the bulk-ice diffusivity. The need to predict excess diffusion in ice cores calls for extensive study of isotope records for its occurrence and better understanding of vein-scale hydrology in ice sheets.

How to cite: Ng, F.: Isotope diffusion in ice enhanced by vein-water flow, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10179, https://doi.org/10.5194/egusphere-egu23-10179, 2023.

X5.138
|
EGU23-8369
|
CL1.5
Fyntan Shaw, Andrew Dolman, Torben Kunz, Vasileios Gkinis, and Thomas Laepple

Water isotopes in ice cores offer a window into the climate of the past. Often the measurement of these water isotopes is done discretely, with the ice cores cut into many regularly spaced samples. Determining the optimal sampling rate for these measurements is a question of balancing high temporal resolution with processing time and effort. Furthermore, the effect of isotopic diffusion smooths the record, attenuating high frequency variability far below the measurement noise level. This results in some climate information becoming unobtainable and limits the usefulness of very high resolution data. Deconvolving (un-diffusing) the time-series can further enhance the signal but strongly depends on the precision of the isotope data that is mainly determined by the measurement error.

Here, we discuss the optimal measurement specifications in terms of sampling resolution and precision for different uses of the water isotope data, such as the estimation of the diffusion length, the direct interpretation of the time-series and the interpretation of the time-series after it has been deconvolved. We do this theoretically, based on how we model diffusion, and empirically through simulations of surrogate ice core records. Our findings can provide guidance on how to process new deep ice cores such as the Oldest Ice Core record.

How to cite: Shaw, F., Dolman, A., Kunz, T., Gkinis, V., and Laepple, T.: Optimal sampling resolution for water isotope records in ice cores, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8369, https://doi.org/10.5194/egusphere-egu23-8369, 2023.

X5.139
|
EGU23-14910
|
CL1.5
|
ECS
Lela Gadrani, Andrei V. Kurbatov, Elena Korotkikh, Pascal Bohleber, Paul A. Mayewski, and Michael Handley

We report interlaboratory comparisons of a methodology to measure and calculate concentrations of impurities in ice core samples using the Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) system developed at the W. M. Keck Laser Ice Facility at the Climate Change Institute, University of Maine (UMaine). Here, we will summarize results of measured artificial samples with known levels of  Ca, Al, Fe, Mg, Na, Cu, Pb. We adapted a method for LA-ICP-MS analysis of the frozen standard that was developed in the laboratory at Ca’ Foscari University of Venice, and we tested its applicability to the UMaine system. This work will help to measure and interpret very old and highly compressed ice core records from the Allan Hills Blue Ice Area, Antarctica, sampled with different analytical tools.  

How to cite: Gadrani, L., Kurbatov, A. V., Korotkikh, E., Bohleber, P., Mayewski, P. A., and Handley, M.: Interlaboratory Calibration for Laser Ablation of Ice Cores, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14910, https://doi.org/10.5194/egusphere-egu23-14910, 2023.

X5.140
|
EGU23-14700
|
CL1.5
Hans Christian Steen-Larsen, Laura Dietrich, Sonja Wahl, Michael Town, Abigail Hughes, Maria Hoerhold, Alexandra Zuhr, Melanie Behrens, Xavier Fettweis, and Martin Werner

Research over the last five years dedicated to identifying and quantifying the processes responsible for driving the climate signal in the isotopic composition of the snow have documented the role of the humidity exchange between the snow and atmosphere in changing the initial precipitation isotopic composition. Laboratory and field experiments combined with direct vapor isotope flux measurements have shown that not only does the depositional flux changes the surface snow isotopic composition, but sublimation from the snow surface induces isotopic fractionation leading to changes in the snow isotopic composition. Thus, it was shown that for the EastGRIP ice core location, including fractionation during sublimation, atmosphere-snow exchange processes explain between 35 and 50 % of the day-to-day variations in the snow surface signal when no precipitation occurs.

Until recently, it was unknown on which time scales these surface exchange processes are important for the isotope signal.

Here we combine direct accumulation and eddy-covariance humidity flux measurements with high resolution regional climate model simulations. Focusing on the EastGRIP ice core site, we find that during the summer season up to 40% of the accumulation is sublimated and about 10% is re-deposited. Such relative high fluxes compared to the amount of precipitated snow would naturally lead to an influence of the seasonal isotopic composition of the snow.

By combining outputs from an isotope-enabled general circulation model (ECHAMwiso) and a regional polar climate model (MAR) with the SNOWISO exchange and snowpack model, we find that the influence on the snowpack isotopic composition is not only isolated to the summer isotope signal but influences the full seasonal cycle. In fact, we find that that the atmosphere-snow exchange influence on the annual mean isotopic composition results in a significant bias in the source region condition deduced from the isotopic composition of the ice core.

How to cite: Steen-Larsen, H. C., Dietrich, L., Wahl, S., Town, M., Hughes, A., Hoerhold, M., Zuhr, A., Behrens, M., Fettweis, X., and Werner, M.: On the importance of atmosphere-snow humidity exchange for the climate signal stored in the snow isotopic composition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14700, https://doi.org/10.5194/egusphere-egu23-14700, 2023.

X5.141
|
EGU23-2498
|
CL1.5
|
ECS
Jinhwa Shin, Seungmi Lee, Heejin Hwang, and Yeongcheol Han

The radioisotope Plutonium-239 (239Pu) was artificially produced to the environment by atmospheric nuclear weapons tests during 1940-1980 CE. Although 239Pu is the most abundant one among isotopes of Plutonium, it exists in Antarctic ice cores at very low level of sub-fg g-1. Accordingly, the historical records of 239Pu fallout in Antarctica have not been well reconstructed. In this study, we determined 239Pu concentrations in three coastal ice cores in Northern Victoria Land, East Antarctica. Discrete samples with sub-annual resolution for the period 1940-1980 CE were analyzed using inductively coupled plasma sector field mass spectrometry (ICP-SFMS) without purification or preconcentration. The fallout records of the three sites showed consistent fluctuations and also agreed with the records recovered from inland dome sites (Hwang et al., 2019), which allowed for constructing an Antarctic composite record. The composite 239Pu record was characterized by two major peaks in 1954 and 1964 CE and a minor peak in 1970s, which could be ascribed to the major atmospheric nuclear test events. Those synchronous 239Pu peaks are expected to serve as useful age markers in other regions in Antarctica, which can improve depth-age relationships of ice core records and enable more precise interregional comparisons. In addition, it will contribute to a more precise comparison of ice core records with reanalysis data back to the 1950s (e.g., ERA5).

How to cite: Shin, J., Lee, S., Hwang, H., and Han, Y.: 239Pu concentrations reconstructed using three Antarctic ice cores during 1940-1980 CE, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2498, https://doi.org/10.5194/egusphere-egu23-2498, 2023.

X5.142
|
EGU23-14208
|
CL1.5
Thomas Laepple, Remi Dallmayr, Maria Hörhold, Nora Hirsch, Daniela Jansen, Melanie Behrens, Thomas Münch, and Johannes Freitag

Oxygen isotopes of snow, firn, and ice cores provide valuable information on past climate variations. Yet, multiple processes, such as stratigraphic noise and the advection of spatial isotope variations linked to topographic anomalies create non-climatic variations (‘noise’) in the ice-core record and limit the quality of high-resolution climate reconstructions. All of these processes are site specific and vary depending on the environmental conditions at and around the ice-core location.  In the last years, based on field studies, numerical experiments and theoretical considerations, we improved our quantitative understanding of these noise generating processes and their dependency on the depositional conditions. Building on this work, we here ask the question how the potential quality of ice-core based climate reconstructions depends on the drilling site location.  Making use of digital elevation models,  ice flow-velocity maps and statistical relationships between the surface topography, accumulation anomalies,  isotopic anomalies and stratigraphic noise, we predict the site and time-scale dependent noise contribution to ice-core records of the last millennium. The created maps provide a step towards choosing optimal ice coring and  sampling locations for high-resolution climate reconstructions from Antarctic ice-cores and provide testable predictions for the quality of future ice-core records.




How to cite: Laepple, T., Dallmayr, R., Hörhold, M., Hirsch, N., Jansen, D., Behrens, M., Münch, T., and Freitag, J.: Optimal coring locations for high resolution climate reconstructions from the East Antarctic Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14208, https://doi.org/10.5194/egusphere-egu23-14208, 2023.

Posters virtual: Mon, 24 Apr, 08:30–10:15 | vHall CL

Chairperson: Michael Döring
vCL.1
|
EGU23-11819
|
CL1.5
|
ECS
|
Giyoon Lee, Jinho Ahn, Ikumi Oyabu, Kajal Kumari, and Kenji Kawamura

CO2 and CH4 records from polar ice cores have greatly enhanced our understanding of the control mechanisms of atmospheric greenhouse gas (GHG) concentrations and their relationship to surface temperature. However, multiple ice cores show offsets of 1–3 % and concerns about in situ production in trapped air were raised. Recently, GHGs in shallow ice cores from blue-ice areas (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. We aim to decipher the processes of GHG production and CH4 destruction in the shallow ice at Larsen BIA. CH4 concentration records from the Larsen BIA generally show an increasing trend from the subsurface to a depth of ~0.35–1.15 m. Then gradually decreases until it reaches the true ancient atmospheric CH4 values at ~4.6 m depth. In contrast, CO2 concentration in the Larsen blue ice shows a gradual decrease from the subsurface until a depth of ~4.6 m where the concentration variation stabilizes, but still has a 10–20 ppm difference with other existing non-contaminated ice core records. These alterations might be due to mixing with modern air through cracks and/or microbial activity inside the occluded air bubbles. The vertical distribution of δ15N-N2 in several Larsen BIA ice cores indicates that alteration by modern atmospheric air is not significant at the top ~10 m. Depleted δ18Oatm in a depth of ~0.15–1.65 m might indicate in situ microbial activity consuming O2 gas in Larsen blue ice samples, but δ18Oatm values in a depth of 1.95–10 m might indicate little microbial activity. Our future study may include analysis of Pb concentration and isotopes to investigate the effect of modern aerosol intrusion. In addition, we may measure CH4 concentration in ice after receiving UV light in order to check whether UV photolysis is included in the mechanism for CH4 destruction.

How to cite: Lee, G., Ahn, J., Oyabu, I., Kumari, K., and Kawamura, K.: Greenhouse gas (CO2, CH4) alteration in shallow ice at Larsen blue-ice area, Northern Victoria Land, East Antarctica, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11819, https://doi.org/10.5194/egusphere-egu23-11819, 2023.