CL1.7

EDI
The state-of-the-art in ice coring sciences (StatICS)

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 in ice, among many others. Several projects (e.g. Beyond EPICA Oldest Ice) are to surface ice as old as 1.5 million years old from very compressed layers at the very bottom of the Antarctic ice sheet in the coming years. Analysis and interpretation of this ice will bring new challenges, including the potential for in situ processes to impact the climatic signals. Furthermore, a variety of ice cores have been drilled recently in the framework of the ICE MEMORY initiative to preserve environmental and climate information from glaciers threatened by climate change.
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.

Co-organized by CR2
Convener: Thomas Blunier | Co-conveners: Anja Eichler, Vasileios Gkinis, Rachael Rhodes
vPICO presentations
| Mon, 26 Apr, 13:30–17:00 (CEST)

vPICO presentations: Mon, 26 Apr

Chairpersons: Rachael Rhodes, Vasileios Gkinis
13:30–13:32
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EGU21-1020
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ECS
Giyoon Lee, Jinho Ahn, Hyeontae Ju, Florian Ritterbusch, Ikumi Oyabu, Songyi Kim, Kenji Kawamura, Zheng-Tian Lu, Sangyoung Han, Sambit Ghosh, Yeongcheol Han, Sangbum Hong, Changhee Han, Soon Do Hur, Wei Jiang, and Guomin Yang

Among the paleoclimate archives, we may take advantage of ice cores to directly measure greenhouse compositions of ancient air. Nevertheless, ice cores from deep drilling projects recover limited amount of ice for a given time period and hence limiting the studies that need an extensive amount of ice such as trace gas isotopes. In contrast, blue ice areas (BIAs) may provide a large amount of ancient ice outcropped at the surface. However, ice flow makes the blue ice stratigraphy complicated in many areas, and accordingly makes it difficult to reconstruct a continuous stratigraphy. Recently, the oldest ice was discovered at Allan Hills BIA (about 2.7 Ma). However, the stratigraphy is not continuous for the older part. Here we show preliminary results from Larsen Glacier, East Antarctica. The Ground Penetrating Radar (GPR) results show parallel ice layers near the surface with dips of 1-5° and indicate that the ice thickness ranges of 200–400 m. δDice of a vertical core sample matches well with that in the horizontally spaced surface ice samples. Greenhouse gas concentrations are significantly altered at shallow depths of < ~4.5 m. The δ18Oatm, CH4 concentration and stable isotopes of ice (δ18Oice, δDice) indicate that the Larsen BIA cover the Last Glacial Termination at the studied sites. 81Kr ages, corrected by 85Kr for the modern air contamination, are less than 54 ka, supporting the ages constrained by the other chemistry data.

How to cite: Lee, G., Ahn, J., Ju, H., Ritterbusch, F., Oyabu, I., Kim, S., Kawamura, K., Lu, Z.-T., Han, S., Ghosh, S., Han, Y., Hong, S., Han, C., Hur, S. D., Jiang, W., and Yang, G.: Preliminary results for stratigraphy and chronology of blue ice in Larsen Glacier, East Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1020, https://doi.org/10.5194/egusphere-egu21-1020, 2021.

13:32–13:34
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EGU21-2191
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ECS
Marie G. P. Cavitte, Hugues Goosse, Sarah Wauthy, Jean-Louis Tison, Thore Kausch, Sainan Sun, Brice Van Liefferinge, Mana Inoue, Quentin Dalaiden, Jan T.M. Lenaerts, Stef Lhermitte, and Frank Pattyn

Several studies have shown that there is often a poor match between surface mass balance (SMB, mass gain at the surface of the ice sheet) simulated by regional climate models and the one locally measured from ice cores in Antarctica. Models’ representation of the physical processes that affect SMB is known to be imperfect, while ice core records may be strongly influenced by local processes such as post-depositional wind redistribution and precipitation intermittency. These two sources of uncertainty likely both have a role to play in the discrepancy identified between modeled and observed ice core SMB estimates over the past centuries.

The goal here is to estimate the uncertainties associated with the difference between a point-wise measurement of SMB as provided by the ice core and the SMB averages over a grid of several square kilometers of the models. To do so, we use ground-penetrating radar (GPR) data, collected over several ice rises, located along the high accumulation Princess Ragnhild Coast (East Antarctica), to obtain a multi-year resolution record that goes back ∼30-40 years, representing SMB spatial and temporal variability at the scale of a few km2 for each ice rise. Ice cores were collected during each radar field campaign, which allows us to place age constraints on the radar stratigraphy obtained and compare the GPR SMB estimates with the ice core SMB estimate.

Therefore, we are able to calculate an error of representativeness for each ice core SMB, estimated as the difference between the average GPR SMB over a few km2 and the ice core SMB. This representativeness error can be split into two components: a systematic error (on the order of ∼0.1 m w.e. yr-1) and a random error (on the order of ±1 cm w.e. yr-1). Finally, we then compare our corrected ice core SMB records to regional SMB derived from a state-of-the-art polar-oriented regional climate model to quantify the impact of ice core uncertainties on the modeled-observed SMB discrepancy.

How to cite: Cavitte, M. G. P., Goosse, H., Wauthy, S., Tison, J.-L., Kausch, T., Sun, S., Van Liefferinge, B., Inoue, M., Dalaiden, Q., Lenaerts, J. T. M., Lhermitte, S., and Pattyn, F.: Using ground-penetrating radar to determine the representativeness of ice core surface mass balance records at ice rises along the Princess Ragnhild Coast, East Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2191, https://doi.org/10.5194/egusphere-egu21-2191, 2021.

13:34–13:36
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EGU21-2225
Elisabeth Schlosser, Saeid Bagheri, Jordan G. Powers, Kevin W. Manning, Maria Hoerhold, Melanie Behrens, and Martin Werner

In Austral summer 2017/18 daily surface snow samples were taken (weather allowing) at two depths, 0-1cm and 6-7cm, at Neumayer III Station, Dronning Maud Land DML, Antarctica. Stable isotope ratios (18O, D, d-excess) of the snow samples were analysed in the AWI isotope lab. In parallel, water vapor stable isotopes were measured continuously on a routine base with a Picarro cavity ring-down spectroscope analyser (CRDS). Neumayer III is also a full meteorological observatory measuring all important meteorological variables including upper-air data. Meteorological data were directly compared to both snow and vapor isotope data. The corresponding synoptic situations were analysed using data from AMPS (Antarctic Mesoscale Prediction System), which employs WRF (Weather Research and Forecasting Model), a mesoscale atmospheric model that has been successfully used in earlier studies in DML. AMPS is run operationally at NCAR for Antarctic weather forecasting, particularly for flight operations of the US Antarctic Program (USAP). Additionally, back-trajectory calculations to investigate moisture sources and transport were carried out using FLEXPART, an open-source Lagrangian particle dispersion model. Due to logistical problems, the measuring period during the expedition was too short for statistical analysis, thus we focus on case studies here. In particular, periods with no precipitation were investigated, since earlier studies in Greenland have shown that the interaction of snow surface and atmosphere is important for the stable isotope ratio in the snow, thus in later ice cores that are used to derive paleo temperatures. A better understanding of the highly complex relationship between water vapor stable isotopes and meteorological conditions (including moisture source and transport) as well as the interaction between surface snow and water vapor is necessary for a correct paleoclimatic interpretation of ice cores.

How to cite: Schlosser, E., Bagheri, S., Powers, J. G., Manning, K. W., Hoerhold, M., Behrens, M., and Werner, M.: Atmospheric influences on water stable isotopes in Antarctic water vapor and surface snow – implications for ice core interpretation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2225, https://doi.org/10.5194/egusphere-egu21-2225, 2021.

13:36–13:38
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EGU21-3624
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ECS
Florian Ritterbusch, Jinho Ahn, Ji-Qiang Gu, Wei Jiang, Giyoon Lee, Zheng-Tian Lu, Lili Shao, Lide Tian, A-min L. Tong, and Guo-Ming Yang

Paleoclimate reconstructions from ice core records can be hampered due to the lack of a reliable chronology, especially when the stratigraphy is disturbed and conventional dating methods cannot be readily applied. The noble-gas radioisotopes 81Kr and 39Ar can in these cases provide robust constraints as they yield absolute, radiometric ages. 81Kr (half-life 229 ka) covers the time span of 50-1300 ka, which is particularly relevant for polar ice cores, whereas 39Ar (half-life 269 a) with a dating range of 50-1800 a is suitable for high mountain glaciers. For a long time the use of 81Kr and 39Ar for dating of ice samples was hampered by the lack of a detection technique that can meet its extremely small abundance at a reasonable sample size.

Here, we present 81Kr and 39Ar dating of Antarctic and Tibetan ice cores with the detection method Atom Trap Trace Analysis (ATTA), using 5-10 kg of ice for 81Kr and 2-5 kg for 39Ar. Recent advances in further decreasing the sample size and increasing the dating precision will be discussed. Current studies include 81Kr dating in shallow ice cores from the Larsen Blue ice area, East Antarctica, in order to retrieve climate signals from the last glacial termination. Moreover, an 39Ar profile from a central Tibetan ice core has been obtained in combination with layer counting based on isotopic and visual stratigraphic signals. The presented studies demonstrate how 81Kr and 39Ar can constrain the age range of ice cores and complement other methods in developing an ice core chronology.

 

[1] Z.-T. Lu, Tracer applications of noble gas radionuclides in the geosciences, Earth-Science Reviews 138, 196-214, (2014)
[2] C. Buizert, Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica, Proceedings of the National Academy of Sciences, 111, 6876, (2014)

[3] L. Tian, 81Kr Dating at the Guliya Ice Cap, Tibetan Plateau, Geophysical Research Letters, (2019)

http://atta.ustc.edu.cn

How to cite: Ritterbusch, F., Ahn, J., Gu, J.-Q., Jiang, W., Lee, G., Lu, Z.-T., Shao, L., Tian, L., Tong, A.-L., and Yang, G.-M.: Constraining ice core chronologies with 39Ar and 81Kr, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3624, https://doi.org/10.5194/egusphere-egu21-3624, 2021.

13:38–13:40
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EGU21-3791
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ECS
Tamara Annina Gerber, Christine Hvidberg, Aslak Grinsted, Daniela Jansen, Steven Franke, Sune Olander Rasmussen, Giulia Sinnl, and Dorthe Dahl-Jensen

The North East Greenland ice-stream (NEGIS) is the largest active ice-stream on the Greenland ice-sheet and is a crucial contributor to the ice-sheet mass balance. To investigate the ice-stream dynamics and to gain information about the past climate, a deep ice-core is drilled in the upstream part of the NEGIS, termed the East Greenland ice-core project (EastGRIP). Upstream flow effects introduce non-climatic bias in ice-cores and are particularly strong at EastGRIP due to high ice-flow velocities and the location in an ice-stream on the eastern flank of the Greenland ice-sheet. Understanding and ultimately correcting for such effects requires information on the source area and the local atmospheric conditions at the time of ice deposition. We use a two-dimensional Dansgaard-Johnsen model to simulate ice-flow along three approximated flow-lines between the summit of the ice-sheet and EastGRIP. Model parameters are determined using a Monte Carlo inversion by minimizing the misfit between modeled isochrones and isochrones observed in radio-echo-sounding images. We calculate backward-in-time particle trajectories to determine the source area of ice found in the EastGRIP core today and present estimates of surface elevation and past accumulation-rates at the deposition site. The thinning function and accumulated strain obtained from the modeled velocity field provide useful information on the deformation history in the EastGRIP ice. Our results indicate that increased accumulation in the upstream area is predominantly responsible for the constant annual layer thickness observed in the upper part of the ice column at EastGRIP. Inverted model parameters suggest that the imprint of basal melting and sliding is present in large parts along the flow profiles and that most internal ice deformation happens close to the bedrock. The results of this study can act as a basis for applying upstream corrections to a variety of ice-core measurements, and the model parameters can be useful constraints for more sophisticated modeling approaches in the future. 

How to cite: Gerber, T. A., Hvidberg, C., Grinsted, A., Jansen, D., Franke, S., Rasmussen, S. O., Sinnl, G., and Dahl-Jensen, D.: Upstream flow effects revealed in the EastGRIP ice-core using a Monte Carlo inversion of a 2D ice-flow model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3791, https://doi.org/10.5194/egusphere-egu21-3791, 2021.

13:40–13:42
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EGU21-3949
Fumio Nakazawa and Kumiko Goto-Azuma

The storage of melted snow and/or ice samples from snow pits and ice cores in a refrigerator for long durations may be limited by an increase in particle concentration caused by microbial growth after approximately 1–2 weeks. In this study, we examined an ultraviolet (UV) disinfection method for the storage of melted snow and/or ice samples. Surface snow obtained from Glacier No. 31 in the Suntar-Khayata Range, eastern Siberia, Russia was divided into two portions for UV treatment and untreated controls. Particle concentrations in the samples were measured using a Coulter counter (Multisizer 4e; Beckman Coulter, USA). Whereas the particle concentration in untreated samples increased, no obvious increase was observed over 53 days in the samples subjected to UV treatment. In addition, the original particle concentrations were unaffected by UV treatment. These findings indicate that the antimicrobial effect of UV radiation is effective for long-term sample storage of melted water samples. A detailed analysis of the particle size distribution for untreated samples indicated that particles of 0.7–1.2 µm appeared within the first 7–14 days. Measurements using a viable particle counter (XL-10BT2 and XL-28A1; RION Co. Ltd., Japan) confirmed that these were biological particles, suggesting that microbial growth occurs during this period. Subsequently, the particles shifted to a smaller size and a higher concentration, suggesting that the decomposition of microorganisms occurred in the water samples. Therefore, the size distribution of particles in untreated samples reflected the growth and decomposition of microorganisms over time.

How to cite: Nakazawa, F. and Goto-Azuma, K.: Examination of ultraviolet germicidal radiation for inactivating microorganisms in melted snow and ice samples, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3949, https://doi.org/10.5194/egusphere-egu21-3949, 2021.

13:42–13:44
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EGU21-4944
Yuki Komuro, Fumio Nakazawa, Kumiko Goto-Azuma, Motohiro Hirabayashi, Wataru Shigeyama, and Naoko Nagatsuka

Seasonal changes of meteorological and ground surface conditions can cause seasonal changes of source area of mineral particles supplied to the Greenland ice sheet. Difference in metal composition and size distribution of them reflects their source area difference. To clarify seasonal changes in the source area of mineral particles, we examined the metal composition and size distribution of them in snow pit samples obtained from EGRIP (East Greenland Ice Core Project).

In summer 2017, we dug a 2.01 m snow pit at EGRIP camp. Snow samples were collected at 0.03 m intervals. The snow samples were melted, then fractions of them were analyzed for the particle size distribution (0.52-12μm) with a Coulter counter (Beckman Coulter: Multisizer 4). Other fractions of the samples were treated with a microwave acid digestion method to decompose particulates. Total concentrations of Al, Ca and Na in samples were measured by inductively coupled plasma mass spectrometry.

Total concentrations of Al (t-Al) and concentrations of non-sea-salt Ca (nssCa) showed peak values in winter to spring layers. In those layers, nssCa/t-Al ratios and volume fractions of fine particles (<4 μm) tended to be relatively high. In some of those layers, the nssCa/t-Al ratios were 2-3 times higher than the crustal average of Ca/Al ratio. This result suggests that fine Ca-rich mineral particles originated from remote desert areas were supplied to EGRIP in those seasons. In contrast, in summer to autumn layers, the nssCa/t-Al ratios and volume fractions tended to be relatively low. This result can be explained by supplies of coarse (≥ 4 μm) Ca-poor mineral particles originated from soil areas near Greenland in those seasons.

How to cite: Komuro, Y., Nakazawa, F., Goto-Azuma, K., Hirabayashi, M., Shigeyama, W., and Nagatsuka, N.: Recent seasonal changes of metal composition and size distribution of mineral particles in snow at EGRIP, Greenland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4944, https://doi.org/10.5194/egusphere-egu21-4944, 2021.

13:44–13:46
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EGU21-5105
Pascal Bohleber, Marco Roman, Sebastiano Vascon, Marcello Pelillo, and Carlo Barbante

Due to its micron-scale resolution and micro-destructiveness, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is especially suited for the analysis of the oldest and highly thinned sections of polar ice cores. State-of-the-art 2D elemental imaging by LA-ICP-MS has great potential for investigating the location of impurities on the ice sample surface and is crucial to avoid misinterpretation of ultra-fine resolution signals. The impurity imaging with LA-ICP-MS comprises several millions of laser shots fired over just a few square mm. This technique combines new chemical images with visual analysis and, in so doing raises new questions that may be answered through techniques in automated image analysis and computer vision. As an illustration of this new frontier, a selected set of key problems is presented, with first examples of how automated image analysis techniques can help solving them. This concerns the relationship between impurity localization and the grain boundary network as well as the paleoclimate significance of single line profiles along the main core axis. Ultimately, this demonstrates that it is the right time to spark an intensified exchange among the two scientific communities of computer vision and ice core science.

How to cite: Bohleber, P., Roman, M., Vascon, S., Pelillo, M., and Barbante, C.: Two-dimensional impurity imaging in polar ice cores sparks new demand for automated image analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5105, https://doi.org/10.5194/egusphere-egu21-5105, 2021.

13:46–13:48
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EGU21-5504
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ECS
Mackenzie Grieman, Helene Hoffmann, Jack Humby, Robert Mulvaney, Christoph Nehrbass-Ahles, Isobel Rowell, Elizabeth Thomas, and Eric Wolff

The aim of the WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial (WACSWAIN) project is to investigate the possible collapse of the West Antarctic Ice Sheet (WAIS) and its surrounding ice shelves during the Last Interglacial (~120,000 years ago).  As part of this project, a 651-meter ice core was drilled to bedrock at Skytrain Ice Rise in Antarctica during the 2018/2019 field season.  Ions and elements originating from marine sources along with water isotope content in this ice core can be used to infer changes in ice sheet and ice shelf extent.  The stable water isotope signal has the potential to capture both regional climate change and changes in the elevation of the drilling site through time.  Marine chemical content in the ice core could indicate variability in the proximity of the site to a marine environment.  Water isotopes and chemical impurities in the ice core were analysed continuously using cavity ring down spectroscopy and inductively coupled plasma mass spectrometry, respectively. As expected, δ18O and δD increase from the last glacial maximum to the Holocene.  δ18O and δD increase and sodium and magnesium levels decline from deglaciation into the early Holocene. δ18O and δD show an abrupt increase in the early Holocene at about 8,000 years before present.  Sea salt similarly increases 2-fold and becomes more variable about 1,000 years later (7,000 years before present).  These increases could indicate a retreat of the ice shelf to its current position.

How to cite: Grieman, M., Hoffmann, H., Humby, J., Mulvaney, R., Nehrbass-Ahles, C., Rowell, I., Thomas, E., and Wolff, E.: WACSWAIN project: isotope and chemical ice core records from Skytrain Ice Rise, Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5504, https://doi.org/10.5194/egusphere-egu21-5504, 2021.

13:48–13:50
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EGU21-5890
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ECS
Dorothea Elisabeth Moser, Elizabeth R. Thomas, Sarah Jackson, Joel B. Pedro, and Bradley Markle

Climate data from the sub-Antarctic region are extremely sparse, with few records available beyond the instrumental period. Here, we investigate the suitability of the first-ever ice core collected from Young Island, in the NW Ross Sea, to capture changes in climate. Despite the presence of surface melt at this maritime location, our findings indicate that stable water isotope and trace element records can still hold potential for paleoclimate reconstruction. We apply two multi-proxy dating approaches based on winter and summer signatures, develop an ice core chronology, and contextualize our findings using a local automatic weather station and reanalysis data. Subsequently, we draw first conclusions about the surface conditions at Young Island and discuss the site’s potential for future studies aimed at paleoclimate reconstruction and resolving the effects of surface melt on proxy records.

How to cite: Moser, D. E., Thomas, E. R., Jackson, S., Pedro, J. B., and Markle, B.: The Young Island Ice Core - Climate Information of a Melty Archive, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5890, https://doi.org/10.5194/egusphere-egu21-5890, 2021.

13:50–13:52
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EGU21-5973
Stanislav Kutuzov, Vladimir Mikhalenko, Ivan Lavrantiev, Pavel Toropov, Diana Vladimirova, Andrey Abramov, and Vladimir Matskovsky

Meteorological regime and glacier surface heat balance, GPR measurements of the ice thickness and seasonal snow cover were investigated in the crater of the Eastern Summit of Mt. Elbrus In the period from 18 to 30 August 2020 at 560 m a.s.l. On the base of preliminary data analysis, the predominance of fluctuations in the synoptic scale over the diurnal ones was revealed; high values of the average and maximum wind speed associated with the influence of jet currents and with the effects of leeward storms were identified; extremely high temporal variability of relative humidity and its very high deficit in cloudless conditions, which contributes to intensive evaporation and sublimation from the snow surface, were explored. The maximum ice thickness in the crater reaches 100 m, with an average of 45 m. A new 96.01 m ice core from glacier surface to bedrock has been recovered. The drilling speed varied from 11 to 1 m / h, decreasing on average with depth from 4.5 to 4.0 m / h. The thickness of the snow-firn strata is about 20 m, which is three times less than on the Western Plateau. The borehole temperature was measured. The temperature on the glacier bedrock was -0.6 °С. The calculated heat flux was 0.39 W/m2. Air sampling was carried out in the crater of the Eastern Summit of Elbrus and on the Garabashi glacier. The repeated measurement of the soil temperature in the fumarole field on the Elbrus Eastern Summit outer crater rim suggests that the temperature regime is stable.

The research was carried out on the territory of the Elbrus National Park with the financial support of the Russian Science Foundation (project 17-17-01270).

How to cite: Kutuzov, S., Mikhalenko, V., Lavrantiev, I., Toropov, P., Vladimirova, D., Abramov, A., and Matskovsky, V.: A new ice core from the Eastern Summit of Mt. Elbrus, Caucasus, Russia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5973, https://doi.org/10.5194/egusphere-egu21-5973, 2021.

13:52–13:54
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EGU21-6278
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ECS
Delia Segato, Francois Burgay, Niccolò Maffezzoli, Azzurra Spagnesi, Clara Turetta, Federico Scoto, Federico Dallo, Daniele Zannoni, Tobias Erhardt, Camilla Marie Jensen, Alfonso Saiz-Lopez, Helle Astrid Kjær, Dorthe Dahl-Jensen, Carlo Barbante, and Andrea Spolaor

Arctic sea ice has been melting at unprecedented rates in the past decades. Understanding past sea ice variability is of paramount importance to contextualize recent changes and constrain global climate models. Bromine enrichment (Brenr), relative to sea-water ratio, has been introduced as a proxy of first-year sea ice conditions within the ocean region influencing the ice core location (Spolaor et al., 2013). Brenr has been measured in ice cores from Greenland, that is the NEEM and RECAP cores. NEEM sea ice proxies are influenced by the region of the Canadian Arctic and Baffin Bay, while for the RECAP core it is mainly the North Atlantic Ocean. In this study we present the first high-resolution record of bromine enrichment from the EGRIP ice core in Greenland for the last 15.7 kyr BP, covering the Holocene-Glacial transition.

From preliminary back-trajectory analyses we suggest that EGRIP sea ice proxy sources are located in a wide region in the Baffin Bay and North Atlantic Ocean. We find EGRIP Brenr values of ~1 during cold periods, that is the Younger Dryas (12.9 – 11.7 kyr BP) and the last part of the Oldest Dryas (15.7 – 14.7 kyr BP), which we associate with predominant multi-year sea ice conditions. During warmer periods, instead, we observe higher Brenr values, ~3 for the Bølling-Allerød period (14.7 – 12.9 kyr BP) and progressively higher values from the early Holocene onwards, likely associated with an increased seasonal sea ice area. EGRIP Brenr is consistent with NEEM and RECAP records and it has the potential to extend our knowledge on Arctic past sea ice variability.

 

Bibliography

Spolaor, A., Vallelonga, P., Plane, J. M. C., Kehrwald, N., Gabrieli, J., Varin, C., Turetta, C., Cozzi, G., Kumar, R., Boutron, C., and Barbante, C.: Halogen species record Antarctic sea ice extent over glacial–interglacial periods, Atmos. Chem. Phys., 13, 6623–6635, https://doi.org/10.5194/acp-13-6623-2013, 2013.

How to cite: Segato, D., Burgay, F., Maffezzoli, N., Spagnesi, A., Turetta, C., Scoto, F., Dallo, F., Zannoni, D., Erhardt, T., Jensen, C. M., Saiz-Lopez, A., Kjær, H. A., Dahl-Jensen, D., Barbante, C., and Spolaor, A.: A shift to predominant multi-year sea ice conditions in the Baffin Bay and North Atlantic Ocean during the Holocene-Glacial transition inferred from the EGRIP ice core, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6278, https://doi.org/10.5194/egusphere-egu21-6278, 2021.

13:54–13:56
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EGU21-6918
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ECS
Jacob Morgan, Christo Buizert, and Jeff Severinghaus

Ice core gas records are an invaluable paleoclimatic archive. The three most abundant gases in air, nitrogen (N2), oxygen (O2), and argon (Ar), provide paleoclimatic information about both global and regional processes including tropical rainfall patterns and local surface temperature changes. We present a large dataset of elemental and isotopic ratios of N2, O2, and Ar (O2/N2, Ar/N2, δ15N, δ18O, & δ40Ar) from the South Pole Ice Core between 0 – 52,000 yr BP, with a focus on high precision δ15N and δ40Ar measurements between 5,000 – 32,000 yr BP. The unprecedented precision of our measurements allows us to use δ15Nexcess (= δ15N - δ40Ar/4) to reconstruct past temperature change at the South Pole. Although this proxy has been widely applied in Greenland, this is the first time it has been successfully applied to Antarctic ice and provides a valuable independent check on the more traditional water isotopes temperature proxy. We find good agreement between the two during the relatively stable climate of the glacial period and the Holocene. However the temperature reconstructions diverge during the deglaciation. We present several hypotheses that could explain the discrepancy and look to other emerging ice core temperature proxies to support our interpretation.

How to cite: Morgan, J., Buizert, C., and Severinghaus, J.: Isotopes of molecular nitrogen, oxygen, and argon in the South Pole ice core document local and global climate change through the last deglaciation., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6918, https://doi.org/10.5194/egusphere-egu21-6918, 2021.

13:56–13:58
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EGU21-7473
Theo Jenk, Daniela Festi, Margit Schwikowski, Valter Maggi, and Klaus Oeggl

Dating glaciers is an arduous yet essential task in ice core studies, which becomes even more challenging for the dating of glaciers suffering from mass loss in the accumulation zone as result of climate warming. In this context, we present the dating of a 46 m deep ice core from the Central Italian Alps retrieved in 2016 from the Adamello glacier (Pian di Neve, 3100 m a.s.l.). We will show how the timescale for the core could be obtained by integrating results from the analyses of the radionuclides 210Pb and 137Cs with annual layer counting derived from pollen and refractory black carbon concentrations. Our results clearly indicate that the surface of the glacier is older than the drilling date of 2016 by about 20 years and that the 46 m ice core reaches back to around 1944. Despite the severe mass loss affecting this glacier even in the accumulation zone, we show that it is possible to obtain a reliable timescale for such a temperate glacier. These results are very encouraging and open new perspectives on the potential of such glaciers as informative palaeoarchives. We thus consider it important to present our dating approach to a broader audience.

How to cite: Jenk, T., Festi, D., Schwikowski, M., Maggi, V., and Oeggl, K.: Dating of ice cores from temperate glaciers - Significant mass loss in the accumulation area of the Adamello glacier indicated by the chronology of a 46 m ice core, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7473, https://doi.org/10.5194/egusphere-egu21-7473, 2021.

13:58–14:00
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EGU21-7935
Yuko Motizuki, Yoichi Nakai, Kazuya Takahashi, Junya Hirose, Yu Vin Sahoo, Yasushige Yano, Masaki Yumoto, Masayuki Maruyama, Michio Sakashita, Kiwamu Kase, and Satoshi Wada

Ice cores preserve past climatic changes and, in some cases, astronomical signals. Here we present a newly developed automated ice-core sampler that employs laser melting. A hole in an ice core approximately 3 mm in diameter is melted and heated well below the boiling point by laser irradiation, and the meltwater is simultaneously siphoned by a 2 mm diameter movable evacuation nozzle that also holds the laser fiber. The advantage of sampling by laser melting is that molecular ion concentrations and stable water isotope compositions in ice cores can be measured at high depth resolution, which is advantageous for ice cores with low accumulation rates. This device takes highly discrete samples from ice cores, attaining depth resolution as small as ~3 mm with negligible cross contamination; the resolution can also be set at longer lengths suitable for validating longer-term profiles of various ionic and water isotopic constituents in ice cores. This technique allows the detailed reconstruction of past climatic changes at annual resolution and the investigation of transient ionic and isotopic signals within single annual layers in low-accumulation cores, potentially by annual layer counting.

How to cite: Motizuki, Y., Nakai, Y., Takahashi, K., Hirose, J., Sahoo, Y. V., Yano, Y., Yumoto, M., Maruyama, M., Sakashita, M., Kase, K., and Wada, S.: A novel high-resolution laser-melting sampler for discrete analyses of ion concentrations and stable water isotopic compositions in firn and ice cores, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7935, https://doi.org/10.5194/egusphere-egu21-7935, 2021.

14:00–14:02
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EGU21-8842
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Highlight
Patrick Ginot, Jérôme Chappellaz, Carlo Barbante, Margit Schwikowski, and Anne-Catherine Ohlmann

With global change and its amplified impact at high altitudes or in certain regions of the world, mountain glaciers are particularly sensitive to warming. These same glaciers, which have been studied for several decades, have made it possible to reconstruct, through the study of ice cores, unique information on the evolution of the climate or the environment on a regional and global scale since they are located closer to the main regions and sources of aerosol emissions. Unfortunately, these archives are in the process of being altered and are disappearing. It is in this context that the international project ICE MEMORY was initiated in 2015. ICE MEMORY is built on four pillars : 1) Identify, select glacier and extract several complete ice cores, at least two, from sites that have already demonstrated their high scientific potential before they are altered, 2) Analyse one of the cores in order to extract the maximum parameters of information using all currently available technologies and make this data available to the scientific community of today and tomorrow, 3) Store the remaining cores in a naturally adapted site such as the French-Italien Concordia station in Antarctica so that they can be preserved and donated to future generations of scientists, and 4) to set up a sustainable governance system based on an accredited international organization in charge of managing these ice and data archives in the future.

This presentation will highlight all the operations, analyses and organization already achieved as well as the future vision and development of ICE MEMORY.

How to cite: Ginot, P., Chappellaz, J., Barbante, C., Schwikowski, M., and Ohlmann, A.-C.: Ice Memory, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8842, https://doi.org/10.5194/egusphere-egu21-8842, 2021.

14:02–15:00
Break
Chairpersons: Anja Eichler, Thomas Blunier
15:30–15:32
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EGU21-9337
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ECS
Sambit Ghosh, Sakae Toyoda, Jinho Ahn, Youngjoon Jang, and Naohiro Yoshida

The increase in mixing ratio of greenhouse gas (GHG) has been believed to be the primary driver for the ongoing global warming. Among the GHGs, the mixing ratio of nitrous oxide (N2O) has increased by 23% since 1750 CE. N2O has a long residence time of ca. 120 years, and a potential to destruct the ozone layer. The Global Warming Potential of N2O is about 300 times greater than that of CO2 over 100 years. However, the temporal changes in magnitude and geographic distribution of different N2O sources are uncertain, hence, understanding the dynamics of atmospheric N2O has been a challenge to the researcher during the last few decades. Here, we present new stable isotope data of N2O from the firn air at Styx Glacier, East Antarctica to comprehend the atmospheric evolution for the last 100 years. Our results show that the N2O mixing ratio has increased, whereas the δ15Nbulk (‰, AIR) and δ18O (‰, VSMOW) values decreased during the last 100 years, consistent with the existing firn air records. The progressive increase in the N2O mixing ratio and the decrease in the isotope ratios suggest a higher contribution from the anthropogenic sources assuming that the N2O flux from the natural sources is constant. Our box model analysis using the stable isotopes and mixing ratio data of N2O of Styx firn air suggests that anthropogenic N2O emission at 2014 CE was ca. 37.5% higher than 1919 CE. The box model calculation with Styx and other firn air and ice core data suggests that in comparison to the pre-industrial era, the total N2O emission is ca. 61% higher at present (2014 CE), where ca. 62% and 38% contributions are from natural and anthropogenic sources, respectively to the total N2O emission. The isotope-based mass-balance calculation indicates that continental emission was ca. 45% higher in 2014 CE than in 1919 CE. Although there is a large scatter in existing data, the site preference of 15N in N2O molecules (δ15NSP ‰, AIR) shows an increasing trend during the post-industrial era, which is consistent with the idea that enhanced fertilization increased soil N2O emissions by activating nitrification processes.

How to cite: Ghosh, S., Toyoda, S., Ahn, J., Jang, Y., and Yoshida, N.: Understanding the evolution of atmospheric nitrous oxide over the last century from the stable isotopes of the firn air at Styx Glacier, East Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9337, https://doi.org/10.5194/egusphere-egu21-9337, 2021.

15:32–15:34
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EGU21-9900
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ECS
Nicolas Stoll, Jan Eichler, Maria Hörhold, Tobias Erhardt, and Ilka Weikusat

Soluble and insoluble impurities play a crucial role regarding the deformability and thus the flow of polar ice. To better understand this interplay from a mechanistic point of view it is especially important to investigate the location and chemical composition of micro-inclusions (Stoll et al., 2021), which are among the most abundant impurities in polar ice.

New results from a systematic analysis of micro-inclusions in Holocene ice from the East Greenland Ice Core Project (EGRIP), which has been drilled near the onset of the Northeast Greenland Ice Stream (NEGIS), offer unique insights into the dynamics of fast flowing ice over different scales, ranging from kilometres to micrometres.

Investigating the small-scale properties of eleven samples from Holocene ice, i.e. the upper 1340 m of the EGRIP ice core, we mapped the locations of several thousand micro-inclusions inside the ice. The use of cryo-Raman spectroscopy allowed us to obtain a representative overview of the mineralogy of these inclusions in the ice without the risk of contamination.

We identified a variety of Raman spectra, mainly from sulphates (dominated by gypsum) and terrestrial dust, such as quartz, mica and feldspar. The observed mineralogy changes with depth and EGRIP Holocene ice can be categorised in two different depth regimes, i.e. the upper (100-900 m) and lower (900-1340 m) regimes, depending on their mineralogy. Furthermore, micro-inclusions show certain spatial patterns, such as clustering or layering, which are partly related to their mineralogy. We thus conclude that Greenlandic Holocene ice has a broader, and more variable, mineralogy than previously reported and that chemical reactions might take place within the ice sheet, possibly altering the paleo-climate record. Our approach further demonstrates the added value of systematic, combined high-resolution impurity and microstructural studies, and the importance of considering different spatial scales and is thus another step towards a more holistic understanding of impurities in ice.

Ref:
Stoll N, Eichler J, Hörhold M, Shigeyama W and Weikusat I (2021) A Review of the Microstructural Location of Impurities in Polar Ice and Their Impacts on Deformation. Front. Earth Sci. 8:615613. doi: 10.3389/feart.2020.615613

How to cite: Stoll, N., Eichler, J., Hörhold, M., Erhardt, T., and Weikusat, I.: Micro-inclusions in the EGRIP ice core identified with Raman-spectroscopy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9900, https://doi.org/10.5194/egusphere-egu21-9900, 2021.

15:34–15:36
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EGU21-10171
Xavier Faïn, Rachael Rhodes, Philip Place, Vasilii Petrenko, Kévin Fourteau, Nathan Chellman, Edward Crosier, Joe McConnell, Edward Brook, Thomas Blunier, Michel Legrand, Sophie Szopa, Kostas Tsigaridis, Vaishali Naik, and Jérôme Chappellaz

Carbon monoxide (CO) is a regulated pollutant and one of the key components determining the oxidizing capacity of the atmosphere. Obtaining a reliable record of atmospheric CO mixing ratios since pre-industrial times is necessary to evaluate climate-chemistry models in conditions different from today. We present high-resolution measurements of CO mixing ratios from ice cores drilled at five different sites on the Greenland ice sheet which experience a range of snow accumulation rates, mean surface temperatures, and different chemical compositions. An optical-feedback cavity-enhanced absorption spectrometer (OF-CEAS) was coupled to continuous melter systems and operated during four analytical campaigns conducted between 2013 and 2019. The CFA-based CO measurements exhibit excellent external precision (ranging 3.3 - 6.6 ppbv, 1σ), and achieve consistently low blanks (ranging from 4.1±1.2 to 12.6±4.4 ppbv). Good accuracy and absolute calibration of CFA-based CO records enable paleo-atmospheric interpretations. The five CO records all exhibit variability in CO mixing ratios that is too large and rapid to reflect past atmospheric mixing ratio changes. Complementary tests conducted on discrete ice samples demonstrate that such patterns are not related to the analytical process (i.e., production of CO from organics in the ice during melting), but very likely are related to in situ CO production within the ice before analyses. Evaluation of signal resolution and co-investigation of high-resolution records of CO and TOC show that past atmospheric CO concentration can be extracted from the records’ baselines at four sites with accumulation rates higher than 20 cm water equivalent per year (weq yr-1). However, such baselines should be taken as upper bounds of past atmospheric CO burden. CO records from four sites are combined to produce a multisite average ice core reconstruction of past atmospheric CO for the Northern Hemisphere high latitudes, covering the period from 1700 to 1957 CE. From 1700 to 1875 CE, this record reveals stable or slightly increasing values remaining in the 100-115 ppbv range. From 1875 to 1957 CE, the record indicates a monotonic increase from 114±4 ppbv to 147±6 ppbv. The ice-core multisite CO record exhibits an excellent overlap with the atmospheric CO record from Greenland firn air which span the 1950-2010 time period. The combined ice-core and firn air CO history, spanning 1700-2010 CE, largely exhibits patterns that are consistent with the recent anthropogenic and biomass burning CO emission inventories. This brand new time series will be compared with the most recent results from Earth System Models involved in the CMIP6-AerChemMIP multi-model exercise.

How to cite: Faïn, X., Rhodes, R., Place, P., Petrenko, V., Fourteau, K., Chellman, N., Crosier, E., McConnell, J., Brook, E., Blunier, T., Legrand, M., Szopa, S., Tsigaridis, K., Naik, V., and Chappellaz, J.: Atmospheric history of carbon monoxide since preindustrial times reconstructed from multiple Greenland ice cores, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10171, https://doi.org/10.5194/egusphere-egu21-10171, 2021.

15:36–15:38
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EGU21-10362
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ECS
Thomas Münch, Maria Hörhold, Johannes Freitag, Melanie Behrens, and Thomas Laepple

Ice cores constitute a major palaeoclimate archive by recording, among many others, the atmospheric variations of stable oxygen and hydrogen isotopic composition of water and of soluble ionic impurities. While impurities are used as proxies for, e.g., variations in sea ice, marine biological activity and volcanism, stable isotope records are the main source of information for the reconstruction of polar temperature changes.

However, such reconstruction efforts are complicated by the fact that temperature is by far not the only driver of isotopic composition changes. A single isotopic ice-core record will comprise variations caused by a multitude of processes, from variable atmospheric circulation and moisture pathways to the intermittency of precipitation and finally to the mixing and re-location of surface snow by wind drift (stratigraphic noise). Under the assumption that specific trace components are originally deposited with the precipitated snow and its isotopic composition, the retrieved impurity records should display a similar spatial and seasonal to interannual variability as the isotope records, caused by local stratigraphic noise as well as the time-variable and intermittent precipitation patterns, respectively.

In this contribution, we investigate the possible relationship between isotope and impurity data at the East Antarctic low-accumulation site EDML. We sampled and analysed isotopic composition and major impurity species on a four metre deep and 50 metre long trench. This enables us (1) to study the spatial (horizontal times vertical) relationship in the data, and (2) to analyse and compare the seasonal and interannual variability after removing the strong contribution of local stratigraphic noise. By this, the study improves our understanding of the depositional mechanisms that play an important role for the formation of ice-core records, and it offers to investigate the potential of using impurities to correct isotopic variability in order to improve temperature reconstructions.

How to cite: Münch, T., Hörhold, M., Freitag, J., Behrens, M., and Laepple, T.: On the relationship between stable isotopes and major impurity species as inferred from a two-dimensional firn sampling approach at EDML, East Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10362, https://doi.org/10.5194/egusphere-egu21-10362, 2021.

15:38–15:40
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EGU21-11820
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ECS
Helle Astrid Kjær, Margaret Harlan, Paul Vallelonga, Anders Svensson, Thomas Blunier, Todd Sowers, James Andrew Menking, Aylin de Campo, Janani Venkatesh, Jesper Liisberg, David Soestmeyer, Valerie Morris, Bruce Vaughn, and Bo Vinther
The Dye-3 ice core was drilled to bedrock at the Southern part of the central Greenland ice sheet (65°11'N, 43°50'W) in 1979-1981. The southern location is characterized by high accumulation rates compared to more central locations of the ice sheet. Since its drilling, numerous analyses of the core have been performed, and the ice has since been in freezer storage both in the USA and in Denmark.
In October and November 2019, the remaining ice, two mostly complete sections covering the depths of 1753–1820m and 1865–1918m of the Dye-3 core, were melted during a continuous flow analysis (CFA) campaign at the Physics of Ice, Climate, and Earth (PICE) group at the University of Copenhagen. The data represents both Holocene, Younger Dryas and Glacial sections (GS 5 to 12).
 
The measured data consist chemistry and impurities contained in the ice, isotopes, as well as analysis of methane and other atmospheric gases. 
The chemistry measurements include NH4+, Ca2+, and Na+ ions, which besides being influenced by transport, provide information about forest fires, wind-blown dust, and sea ice, respectively, as well as acidity, which aids in the identification of volcanic events contained in the core. The quantity and grain size distribution of insoluble particles was analyzed by means of an Abakus laser particle counter.
 
We compare the new high-resolution CFA record of dye3 with previous analysis and thus evaluate the progress made over 40 years. Further we compare overlapping time periods with other central Greenland ice cores and discuss spatial patterns in relation to the presented climate proxies.

How to cite: Kjær, H. A., Harlan, M., Vallelonga, P., Svensson, A., Blunier, T., Sowers, T., Menking, J. A., de Campo, A., Venkatesh, J., Liisberg, J., Soestmeyer, D., Morris, V., Vaughn, B., and Vinther, B.: Forty years later: High resolution continuous flow analysis of the Dye3 ice core, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11820, https://doi.org/10.5194/egusphere-egu21-11820, 2021.

15:40–15:42
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EGU21-12455
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ECS
Stratigraphic noise in isotope records on the East Antarctic Plateau; new insights from an array of firn profiles
(withdrawn)
Nora Hirsch, Alexandra Zuhr, Thomas Münch, Maria Hörhold, Johannes Freitag, Remi Dallmayr, and Thomas Laepple
15:42–15:44
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EGU21-12552
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ECS
Ji-Woong Yang, Amaëlle Landais, Margaux Brandon, Thomas Blunier, Frédéric Prié, Stéphanie Duchamp-Alphonse, Thomas Extier, and Nathaëlle Bouttes

The primary production, or oxygenic photosynthesis of the global biosphere, is one of the main source and sink of atmospheric oxygen (O2) and carbon dioxide (CO2), respectively. There has been a growing number of evidence that global gross primary productivity (GPP) varies in response to climate change. It is therefore important to understand the climate- and/or environment controls of the global biosphere primary productivity for better predicting the future evolution of biosphere carbon uptake. The triple-isotope composition of O217O of O2) trapped in polar ice cores allows us to trace the past changes of global biosphere primary productivity as far back as 800,000 years before present (800 ka). Previously available Δ17O of O2 records over the last ca. 450 ka show relatively low and high global biosphere productivity over the last five glacial and interglacial intervals respectively, with a unique pattern over Termination V (TV) - Marine Isotopic Stage (MIS) 11, as biosphere productivity at the end of TV is ~ 20 % higher than the four younger ones (Blunier et al., 2012; Brandon et al., 2020). However, questions remain on (1) whether the concomitant changes of global biosphere productivity and CO2 were the pervasive feature of glacial periods over the last 800 ka, and (2) whether the global biosphere productivity during the “lukewarm” interglacials before the Mid-Brunhes Event (MBE) were lower than those after the MBE.
Here, we present an extended composite record of Δ17O of O2 covering the last 800 ka, based on new Δ17O of O2 results from the EPICA Dome C and reconstruct the evolution of global biosphere productivity over that time interval using the independent box models of Landais et al. (2007) and Blunier et al. (2012). We find that the glacial productivity minima occurred nearly synchronously with the glacial CO2 minima at mid-glacial stage; interestingly millennia before the sea level reaches their minima. Following the mid-glacial minima, we also show slight productivity increases at the full-glacial stages, before deglacial productivity rises. Comparison of reconstructed interglacial productivity demonstrates a slightly higher productivity over the post-MBE (MISs 1, 5, 7, 9, and 11) than pre-MBE ones (MISs 13, 15, 17, and 19). However, the mean difference between post- and pre-MBE interglacials largely depends on the box model used for productivity reconstruction.

How to cite: Yang, J.-W., Landais, A., Brandon, M., Blunier, T., Prié, F., Duchamp-Alphonse, S., Extier, T., and Bouttes, N.: Global biosphere primary productivity over the last 800,000 years reconstructed from the triple-isotope composition of dioxygen trapped in polar ice cores, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12552, https://doi.org/10.5194/egusphere-egu21-12552, 2021.

15:44–15:46
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EGU21-12623
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ECS
Ji-Woong Yang, Thomas Extier, Martin Kölling, Amaëlle Landais, Gaëlle Leloup, Didier Paillard, Margaux Brandon, and Thomas Blunier

Atmospheric abundance of oxygen (O2) has been co-evolved with different aspects of the Earth system since appearance of oxygenic photosynthesis by cyanobacteria around 2.4 109 years before present (Ga). Therefore, much attention has been paid to understand the changes in O2 and the underlying mechanisms over the Earth’s history. The pioneering work by Stolper et al. (2016) revealed the long-term decreasing trend of O2 mixing ratios over the last 800,000 years using the ice-core composite record of molar ratios of O2 and nitrogen (δ(O2/N2)), implying a slight imbalance between sources and sinks. Over geological time scale, O2 is mainly controlled by burial and oxidation of organic carbon and pyrite, but also by oxidation of volcanic gases and sedimentary rocks. Nevertheless, the O2 cycle of the late Pleistocene has not been well understood, partly due to the lack of knowledge about the individual sources and sinks. Since then, Kölling et al. (2019) proposed a simple model to estimate the O2 release/uptake fluxes due to the pyrite burial/oxidation that predicts up to ~70% of the O2 decrease of the last 800,000 years could be explained by pyrite burial/oxidation.

Building on this, we present here our preliminary, tentative attempt for reconstruction of the net organic carbon burial flux over the last 800,000 years by combining available information (including new δ(O2/N2) data) and assuming constant O2 fluxes associated with volcanic outgassing and rock weathering. The long-term organic carbon burial flux trend obtained with our new calculations is similar to the global ocean δ13C records but also to simulations using a conceptual carbon cycle model (Paillard, 2017). These results partly support the geomorphological hypothesis that the major sea-level drops during the earlier period of the last 800,000 years lead to enhanced organic carbon burial, and that significant changes in the net organic carbon happen around Marine Isotopic Stage (MIS) 13. In addition, we present the long-term decreasing trend of the global biosphere productivity, or gross photosynthetic O2 flux, reconstructed from new measurements of triple-isotope composition of atmospheric O2 trapped in ice cores. As the largest O2 flux, the observed decrease in gross photosynthesis requires to be compensated by parallel reduction of global ecosystem respiration.

How to cite: Yang, J.-W., Extier, T., Kölling, M., Landais, A., Leloup, G., Paillard, D., Brandon, M., and Blunier, T.: A tentative attempt to better trace the late Pleistocene oxygen cycle, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12623, https://doi.org/10.5194/egusphere-egu21-12623, 2021.

15:46–15:48
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EGU21-13150
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ECS
Julien Westhoff, Nicolas Stoll, Steven Franke, Ilka Weikusat, Paul Bons, Johanna Kerch, Daniela Jansen, Sepp Kipfstuhl, and Dorthe Dahl-Jensen

Ever since the first deep ice cores were drilled, it has been a challenge to determine their original, in-situ orientation. In general, the orientation of an ice core is lost as the drill is free to rotate during transport to the surface. For shallow ice cores, it is usually possible to match the adjacent core breaks, which preserves the orientation of the ice column. However, this method fails for deep ice cores, such as the EastGRIP ice core in Northeast Greenland. We provide a method to reconstruct ice core orientation using visual stratigraphy and borehole geometry. As the EastGRIP ice core is drilled through the Northeast Greenland Ice Stream, we use information about the directional structures to perform a full geographical re-orientation. We compared the core orientation with logging data from core break matching and the pattern of the stereographic projections of the crystals’c-axis orientations. Both comparisons agree very well with the proposed orientation method. The method works well for 441 out of 451 samples from a depth of 1375–2120 m in the EastGRIP ice core. It can also be applied to other ice cores, providing a better foundation for interpreting physical properties and understanding the flow of ice.

How to cite: Westhoff, J., Stoll, N., Franke, S., Weikusat, I., Bons, P., Kerch, J., Jansen, D., Kipfstuhl, S., and Dahl-Jensen, D.: A stratigraphy-based method for reconstructing ice core orientation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13150, https://doi.org/10.5194/egusphere-egu21-13150, 2021.

15:48–15:50
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EGU21-13253
Sophie Darfeuil, Patrick Ginot, Joel Savarino, Nicolas Caillon, Xavier Faïn, Gregory Teste, Amaelle Landais, Elise Fourré, Bénédicte Minster, and Frédéric Prié

Since 2018, under the impetus of the IGE (Grenoble) and the LSCE (Saclay) and the common interest of the "Carottes de Glace France" consortium, an analytical platform dedicated to glacier archives was created to meet the growing analytical needs requested by projects involving French partners (Ice Memory, EAIIST, BE-OI ...) and international collaborations with a ten-year vision. Within this framework 5 modules have been developed between the IGE and the LSCE. 3 modules are installed at the IGE, including a CHEMISTRY module which includes a large number of instruments coupled to the CFA (Continuous Flow Analysis) system, allowing high-resolution multi tracer analysis on a single ice stick (water isotopes, dust, conductivity, colorimetry, black carbon, trace metals and gas) as well as several auto-samplers for discrete analyses (major ions, organic species, trace metals, sugars ...). The GAS module is shared between continuous analyses on the CFA system (laser spectrometry CH4/CO) and discrete analyses (Gas chromatography CH4/CO2). The ISOTOPY module allows the analysis of nitrogen (N), sulfur (S) and oxygen (O) isotopes. At the LSCE, the WATER ISOTOPY module allows continuous (Picarro coupled to a CFA line equipped with conductivity cells and auto-sampler) or discrete (Picarro or mass spectrometer) analyses for δD, δ18O and δ17O in water. The AIR ISOTOPY module completes the platform for analyses by mass spectrometry of δ15N of N2, the triple isotopic composition of O2 and noble gases isotopes (36/38/40 Ar; 82/84/86 Kr; 129-132 Xe). An overview of the capacity and performance of the platform will be presented.

How to cite: Darfeuil, S., Ginot, P., Savarino, J., Caillon, N., Faïn, X., Teste, G., Landais, A., Fourré, E., Minster, B., and Prié, F.: PANDA, the French analytical platform dedicated to ice core, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13253, https://doi.org/10.5194/egusphere-egu21-13253, 2021.

15:50–15:52
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EGU21-14089
Thomas Laepple, Thomas Münch, Torben Kunz, Mathieu Casado, and Maria Hoerhold

To recover very old climate information from ice core records, one needs to interpret the deepest part of an ice core. As the oldest record, the Dome-C ice core can serve as an analogue for the Beyond EPICA Oldest Ice Core that is currently being drilled.

Pol et al., EPSL 2010 analyzed high resolution water isotope data from the Dome-C ice core and found evidence for a limited preservation of climate variability in the deep section of the core due to mixing and diffusion. For instance, for Marine Isotope Stage 19, the study estimated a mixing/diffusion length between 40 and 60 cm, a value more than double than what is predicted by current firn and ice diffusion models. Knowing the diffusion length is important to interpret the isotope signal and is the basis to deconvolve climate records. As a result, it is key to bridge the gap in the estimation of the diffusion length between potentially biased statistical methods and firn and ice diffusion models.
We review this diffusion length estimate for MIS19, and also outline a new general method how to estimate the diffusion length in highly thinned deep ice.  This approach presents an important tool for better characterizing the preservation of the climate signal in old ice and thus for designing optimal sampling and recovery strategies.

 

How to cite: Laepple, T., Münch, T., Kunz, T., Casado, M., and Hoerhold, M.: Estimating the diffusion length in the deepest section of ice cores; A case study for MIS19 in Dome-C, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14089, https://doi.org/10.5194/egusphere-egu21-14089, 2021.

15:52–15:54
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EGU21-14131
Valerie Morris, Julien Westhoff, Bruce Vaughn, Ilka Weikusat, Tyler Jones, Bradley Markle, Abigail Hughes, William Skorski, Chloe Brashear, Vasileios Gkinis, Bo Vinther, and James White

With recent advances in analytical techniques, water stable isotope ratios can be measured in astounding detail in ice core records (~mm scale or equivalent to subannual resolution). While this has enabled the study of past climates across a vast range of timescales, the full set of processes driving the highest frequency variability in these water isotope records remains poorly understood. In the EastGRIP ice core, we observe a strong relationship between high-frequency water isotope anomalies (sharp transitions on the scale of cms) and variability in the visual stratigraphy of the ice. The water isotope timeseries reveals these anomalies that would otherwise be missed using traditional lower resolution discrete sampling methods (5-50 cm scale).  A comparison with the dark-field imaging of stratigraphic layers (high-resolution line-scanning system; 50µm/pix) from the EGRIP ice core indicates a correlation between bubble-free ice layers and the sharp transitions observed in the isotope record.  Prior to this comparison, such anomalies in high-resolution isotope records were often dismissed as analytical artifacts. The striking correspondence to the bubble-free ice layers, which is a parameter measured independently from the isotopes, suggests the isotope variability is real. We are investigating a range of depositional and post-depositional processes that may may be able to explain the origin of this variability and its relationship to the physical properties of the ice. This study has implications for frequency analysis of the isotope data, and the related analysis of isotope diffusion and its effects on the recorded climate signal. Understanding these anomalies opens new doors to the interpretation of climate signals in ice cores.

How to cite: Morris, V., Westhoff, J., Vaughn, B., Weikusat, I., Jones, T., Markle, B., Hughes, A., Skorski, W., Brashear, C., Gkinis, V., Vinther, B., and White, J.: Post-depositional processes visible in the integration of EGRIP high-resolution water isotope record and visual stratigraphy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14131, https://doi.org/10.5194/egusphere-egu21-14131, 2021.

15:54–15:56
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EGU21-14405
Anais Orsi, Ilaria Crotti, Roxanne Jacob, Amaelle Landais, and Elise Fourré

In the search for very old ice, finding the age of the ice is a key parameter necessary for its interpretation. Most ice core dating method are based on chronological markers that require the ice to be in stratigraphic order. However, the oldest ice is likely to be found at the bottom of ice sheets, where the stratigraphy is disturbed, or in ablation areas, where the classical methods cannot be used. Absolute dating techniques have recently been developed to provide new constraints on the age of old ice, but their development in the context of ice cores is limited by the large sample size required. Here, we discuss the analytical performances of a new technique for 40Ar dating, which allows us to provide a reliable age with 80g of ice rather than 800g, as previously published. We present an application to the dating of the bottom of the TALDICE and Dome C ice cores. This method represents a significant advance for its application to the very precious ice at the bottom of ice cores.

How to cite: Orsi, A., Crotti, I., Jacob, R., Landais, A., and Fourré, E.: Progress on absolute dating of ice cores with Argon isotopes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14405, https://doi.org/10.5194/egusphere-egu21-14405, 2021.

15:56–15:58
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EGU21-15782
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ECS
Margaret Harlan, Helle Astrid Kjær, Tessa Vance, Paul Vallelonga, Vasileios Gkinis, Thomas Blunier, Anders Svensson, Andrew Moy, Chris Plummer, Sarah Jackson, Kerttu Peensoo, and Aylin de Campo

The Mount Brown South (MBS) ice core is an approximately 300-meter-long ice core, drilled in 2016-2017 to the south of Mount Brown, Wilhelm II Land, East Antarctica. This location in East Antarctica was chosen as it produces an ice core with well-preserved sub-annual records of both chemistry and isotope concentrations, spanning back over 1000 years. MBS is particularly well suited to represent climate variations of the Indian Ocean sector of Antarctica, and to provide information about regional volcanism in the Southern Indian Ocean region.

A section of ice spanning the length of the MBS core was melted as part of the autumn 2019 continuous flow analysis (CFA) campaign at the Physics of Ice, Climate, and Earth (PICE) group at the University of Copenhagen. During this campaign, measurements were conducted for chemistry and impurities contained in the ice, in addition to water isotopes. The data measured in Copenhagen include measurements of H2O2, pH, electrolytic conductivity, and NH4+, Ca2+, and Na+ ions, in addition to insoluble particulate concentrations and size distribution measured using an Abakus laser particle counter.

Here, we present an overview of the CFA chemistry and impurity data, as well as preliminary investigations into the size distribution of insoluble particles and the presence of volcanic material within the ice. These initial chemistry and particulate size distribution data sets are useful in order to identify sections of the MBS core to subject to further analysis to increase our understanding of volcanic activity in the Southern Indian Ocean region.

How to cite: Harlan, M., Kjær, H. A., Vance, T., Vallelonga, P., Gkinis, V., Blunier, T., Svensson, A., Moy, A., Plummer, C., Jackson, S., Peensoo, K., and de Campo, A.: Continuous flow analysis of the Mount Brown South ice core, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15782, https://doi.org/10.5194/egusphere-egu21-15782, 2021.

15:58–16:00
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EGU21-15893
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ECS
Dieter Tetzner, Liz Thomas, and Claire Allen

In the last decade, several efforts have been carried out to assess the causes of the current rapid recent warming measured on West Antarctica and Antarctic Peninsula. The increase in wind strength and shifts in atmospheric circulation patterns have shown to play a key role in driving the advection of warm air from mid-latitudes to high-latitudes. Winds are also responsible for driving surface melting in the ice shelves, enhancing the removal of surface snow, and for promoting basal melting through the upwelling of deep warm water. All these combined have shown to produce substantial effects on environmental parameters, such as sea surface temperatures, sea ice extension, air surface temperatures and precipitation.

Even though winds are fundamental components of the climatic system, there is a lack of reliable long-term observational wind records in the region. This has hindered the ability to place the recent observed changes in the context of a longer time frame.

In this work, we present annual and sub-annual records of marine diatoms preserved in a set of ice cores retrieved from the southern Antarctic Peninsula and Ellsworth Land region, Antarctica. The diatom abundance and species assemblages from these ice cores prove to represent the local/regional variability in wind strength and circulation patterns that influence the onshore northerly winds.  The spatial distribution of these ice cores enabled to identify regional trends (coastal/inland) and to validate the proxy across the region. Our findings highlight the potential this novel proxy to produce an annual reconstruction of westerly winds in the Amundsen - Bellingshausen seas region.

 

How to cite: Tetzner, D., Thomas, L., and Allen, C.: Diatoms in Ice Cores, a new proxy for reconstructing past wind strength in the Amundsen-Bellingshausen Seas region, Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15893, https://doi.org/10.5194/egusphere-egu21-15893, 2021.

16:00–16:02
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EGU21-16037
Rachael Rhodes, Xin Yang, and Eric Wolff

It is important to understand the magnitude and rate of past sea ice changes, as well as their timing relative to abrupt shifts in other components of Earth’s climate system. Furthermore, records of past sea ice over the last few centuries are urgently needed to assess the scale of natural (internal) variability over decadal timescales. By continuously recording past atmospheric composition, polar ice cores have the potential to document changing sea ice conditions if atmospheric chemistry is altered.  Sea salt aerosol, specifically sodium (Na), and bromine enrichment (Brenr, Br/Na enriched relative to seawater ratio) are two ice core sea ice proxies suggested following this premise.

Here we aim to move beyond a conceptual understanding of the controls on Na and Brenr in ice cores by using process-based modelling to test hypotheses. We present results of experiments using a 3D global chemical transport model (p-TOMCAT) that represents marine aerosol emission, transport and deposition. Critically, the complex atmospheric chemistry of bromine is also included allowing us to explore the partitioning of Br between gas and aerosol phases.  

How to cite: Rhodes, R., Yang, X., and Wolff, E.: Exploring ice core sea ice proxies through process-based modelling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16037, https://doi.org/10.5194/egusphere-egu21-16037, 2021.

16:02–17:00