Surface Mass Balance of the Antarctic Megadune Plateau

1. E. Le Meur et al., Spatial and temporal distributions of surface mass balance between Concordia and Vostok stations, Antarctica, from combined radar and ice core data: first results and detailed error analysis. The Cryosphere 12, 1831-1850 (2018). 2. G. Traversa, D. Fugazza, M. Frezzotti, Megadunes in Antarctica: migration and evolution from remote and in situ observations. The Cryosphere Discuss. 2022, 1-30 (2022). 3. R. Nardin et al., Dating of the GV7 East Antarctic ice core by high-resolution chemical records and focus on the accumulation rate variability in the last millennium. Clim. Past 17, 2073-2089 (2021). 4. B. Narcisi, J. R. Petit, B. Delmonte, V. Batanova, J. Savarino, Multiple sources for tephra from AD 1259 volcanic signal in Antarctic ice cores. Quaternary Science Reviews 210, 164–174 (2019). 5. E. Gautier, J. Savarino, J. Erbland, A. Lanciki, P. Possenti, Variability of sulfate signal in ice core records based on five replicate cores. Climate of the Past (Print), 12(1), 103–113 (2016). [email protected] @ jbur2 Jacek Bursztynowicz1, 2 b) a) Fig. 1. a) Localisation of EAIIST transect and b) sites, where ice cores were collected (red stars). Surface Mass Balance (SMB) can be defined as the net difference between the processes of accumulation and ablation on the glacier surface: where ∆𝑚 refers to the change in mass, S is the area of the ice sheet, and t describes the time over which the mass loss or gain occurred. Therefore, SMB describes the mass added to the surface of the Ice Sheet. SMB can vary over time and space, depending, for instance, on the type of terrain features. Lack of knowledge about SMB values and patterns can contribute to the uncertainty of Ice Sheet mass, its changes, and other factors, such as Antarctic temperatures or sea levels. Introduction Surface Mass Balance of the Antarctic Megadune Plateau Ice cores Fig. 3. Electron Microprobe, using for analysing of vocanic tephra particles Fig. 2. The main part of the CFA system Deposition in Antarctica Volcanic event SO42SO42HSO4HSO4SO2 SO2 SO2 SO2 SO2 SO2 Electron Microprobe Analysis (EM) Continous Flow Analysis (CFA) Methodology Further research will be focused on associating selected sulfate, sulfur, and conductivity peaks with well-dated volcanic events, comparison between conductivity, sulfate, and sulfur profiles for the same and different cores, and also on spatial variability at short distances, since some cores were drilled multiple times from the same site, at a distance of around 1 m from each other. Fig. 5 shows sulfate concentration profiles for VOLSOL1 with the same marked peaks used for dating the Paleo core, along with relevant profiles for the WindCrust and MegaEro 48-meter cores, both of which come from the megadune area. It is clearly visible that associating selected peaks in the reference core with their counterparts in both megadune cores is more complicated, as there is no similarity in peak position or intensity. This highlights the complexity of dating ice cores from the megadune area and creates the need to find another technique for dating ice cores from this area. Fig. 4 represents sulfate concentration profiles for the Paleo 48-meter core, which was drilled outside of the megadune area, and for the VOLSOL1 reference core, where volcanic events are well dated. Selected sulfate peaks, corresponding to volcanic events present in VOLSOL1, were attributed to their counterparts in the Paleo 48-meter core. Since these volcanic events are well dated, the timescale, depending on depth, was calculated between selected points for the Paleo 48-meter core. Results Joel Savarino1, Benjamin Daviet1, Patrick Ginot1, Emmanuel Le Meur1, Julien Witwicky1, Elsa Gautier1, Lenneke Jong3, Andrea Spolaor4, Barbara Stenni5 1Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, INRAE, IGE, F-38000 Grenoble, France; 2Institute for Marine and Antarctic Studies, University of Tasmania, Hobart TAS, Australia, 3Australian Antarctic Program Partnership, Institute of Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia, 4Institute of Polar Sciences, National Research Council of Italy, Venice, Italy, 5Ca’ Foscari University of Venice, Department of Environmental Sciences, Informatics and Statistics, Venice, Italy Summary 1. Surface Mass Balance (SMB) is one of the most important factors that can describe polar ice sheet loss or gain over time, directly correlated with past, present, and future climate change. Megadune areas in Antarctica lack knowledge of snow accumulation patterns, leading to uncertainty contributing to estimations of ice sheet mass changes. 2. Among several methods for dating ice cores, one based on marking volcanic eruptions and comparison to literature is widespread. 3. To obtain the dependency of SMB over time and space, several chemical, physical techniques, and computational methods will be applied: Ground Penetrating Radar, Continuous Flow Analysis, Electron Microprobe analysis, and Python programming. 4. Dating ice cores from outside megadune areas, using well-dated reference cores, is clearer and easier than dating cores from megadune areas, which show less similarity in the position and intensity of volcanic peaks compared to counterparts from reference cores." The East Antarctic Plateau contains areas with megadunes and windglazed surfaces, exhibiting distinct patterns of snow accumulation and its variability over time and space. Despite its significance for sea levels, ocean circulation, and weather patterns, knowledge about snow accumulation in these areas remains limited. Several ice cores, coming from different parts of Plateau, were drilled during the East Antarctic International Traverse (EAIIST) in 2014. Cores were drilled both from Megadunes ares: 1MegaEro, 2MegaAcc, 3WindCrust as well as from regular flatter part of the Plateau: 4Paleo, 5AGO5. Length of cores vary from 18 to even 200 meters. 1-2 years Conductivity, S, SO4 2ice core drillig chemical analysis 1. Selection of specific ice core segments X-Rays 2. Melting and filtering tephra particle Comparison with literature --- Ground Penetrating Radar (GPR) data analysisdensity profiles and internal reflection horizons (IRHs) of volcanic events preserved in ice cores Continous Flow Analysis (CFA)- high-resolution multi-tracer analysis on a signle ice bar as well as an auto sampler for discrete measurements in off-line chromatography. Electron Microprobe (EM)- obtaining chemical composition of tephra particles from volcanic eruption preserved in ice cores, using X-ray radiaton. Data Processing and calculations: 1. Based on sulfate, sulfur and conductivity profiles, finding characteristic volcanic events in order to obtain time-depth dependency of ice cores from different areas 2. Based on density profiles, calculation of mass accumulation against time. Reconstructing SMB both in time and space and study these variations in context of climate change CFA We intend to reconstruct the SMB of the Megadune Plateau in both time and space for the last approximately 2000 years, where accumulation is largely unknown. To achieve this goal, ice cores will be melted and analyzed using various instruments to determine the content of stable isotopes, ions, and elements (e.g., metals). Volcanic horizons, combined with Ground Penetrating Radar measurements, will be used as time markers, allowing for the assessment of specific dates corresponding to ice depth. Finally, the variability of Surface Mass Balance (SMB) will be studied in the context of past and current climate change. Fig. 4. Sulfate concentration profiles for Paleo 48 meters core (against depth and time) and VOLSOL1 reference core. Fig. 5. Sulfate concentration profiles for WindCrust, MegaEro 48 meters cores and VOLSOL1 reference core. - Megadunes Accumulation Megadunes Erosion Wind Crust AGO5 Paleo Megadunes Accumulation Megadunes Erosion Wind Crust 2 Oxides percentage mass composition: SiO2, TiO2, FeO, MgO, CaO, Na2O, K2O 1 3 4 5