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Climate reconstructions of the last millennium rely on networks of high-resolution and well-dated proxy records. This study presents age-at-depth data and preliminary results from the new Mount Brown South (MBS) ice cores, collected at an elevation of 2084 m on the boundary of Princess Elizabeth Land and Kaiser Wilhelm II Land in East Antarctica. We show an initial analysis of the site meteorology, mean annual chemical species concentrations and seasonal cycles, including the identification of a seasonal cycle in fluoride concentrations. The annually resolved chronologies were developed from the chemistry data using a site-specific layer-counting methodology that employed seasonally varying trace chemical species and stable water isotopic ratios, combined with alignment to known volcanic horizons. The uncertainty in the determination of annual horizons via layer counting was also quantified. The chronologies developed include the "Main" 295 m record spanning 1137 years (873–2009 CE) and three surface cores spanning the most recent 39–52 years up to the surface age at the time of drilling (austral summer 2017/2018). Mean annual trace chemical concentrations are compared to the Law Dome ice core (located 1130 km east of the Mount Brown South site) and discussed in terms of atmospheric transport. The MBS chronologies presented here – named MBS2023 – will underpin the development of new palaeoclimate records spanning the past millennium from this under-represented region of East Antarctica. [ABSTRACT FROM AUTHOR]

Bromine enrichment (Br enr) has been proposed as an ice core proxy for past sea-ice reconstruction. Understanding the processes that influence bromine preservation in the ice is crucial to achieve a reliable interpretation of ice core signals and to potentially relate them to past sea-ice variability. Here, we present a 210 years bromine record that sheds light on the main processes controlling bromine preservation in the snow and ice at Dome C, East Antarctic plateau. Using observations alongside a modelling approach, we demonstrate that the bromine signal is preserved at Dome C and it is not affected by the strong variations in ultraviolet radiation reaching the Antarctic plateau due to the stratospheric ozone hole. Based on this, we investigate whether the Dome C Br enr record can be used as an effective tracer of past Antarctic sea ice. Due to the limited time window covered by satellite measurements and the low sea-ice variability observed during the last 30 years in East Antarctica, we cannot fully validate Br enr as an effective proxy for past sea-ice reconstructions at Dome C. [ABSTRACT FROM AUTHOR]

Sub-Antarctic islands and Antarctic coastal regions provide valuable sites for investigating environmental processes in the Southern Ocean. The fact that these sites are situated within the sea ice zone underscores their significance in investigating the impact of sea ice on the chemical composition of the boundary layer. In this study we report multi-year average levels of marine aerosols, including bromine, sodium, methanesulphonic acid and iodine, measured in five firn cores collected from sub-Antarctic Islands and coastal Antarctic sites. The records are compared with published Antarctic records to explore the spatial distribution of these species in the Antarctic region and their relationship with sea ice variability. Being mainly sourced from sea-salt aerosols, sodium and bromine exhibit the largest concentrations in the sub-Antarctic region, with progressively reduced deposition from the coast towards the central Antarctic plateau. Due to its gas-phase chemistry, bromine is depleted with respect to sodium in the sub-Antarctic sites. Bromine emitted in the form of sea-salt aerosols undergoes multi-phase recycling in the lower troposphere and, together with gas-phase bromine emitted from sea ice, is likely to be transported away from the source, depositing in enriched concentrations in the plateau compared to the Br/Na sea-water mass ratio. Similarly to bromine and sodium, methanesulphonic acid and iodine are found in higher concentrations in the sub-Antarctic sites, especially where the ocean is sea ice-covered during spring as primary production is stronger than in the ice-free ocean. Sea-salt mediated recycling of gas-phase iodine enhances its atmospheric lifetime, delivering enriched iodine depositions to the Antarctic plateau. Depicting the spatial distribution of these elements is of great importance for understanding the processes delivering these impurities around Antarctica. • Sub-Antarctic islands provide unique ice core records. • Br, Na, MSA and I are highest in the sub-Antarctic region. • Bromine is depleted in the sub-Antarctic region with respect to coastal Antarctica. • Iodine reaches is enriched in inner Antarctica following the leapfrog mechanism. [ABSTRACT FROM AUTHOR]

The climate of the sub-Antarctic is important in understanding the environmental conditions of Antarctica and the Southern Ocean. However, regional climate proxy records from this region are scarce. In this study, we present the stable water isotopes, major ion chemistry, and dust records from the first ice core from the (sub-)Antarctic Young Island. We present and discuss various dating approaches based on commonly used ice core proxies, such as stable water isotopes and seasonally deposited ions, together with site-specific characteristics such as melt layers. The dating approaches are compared with estimated precipitation rates from reanalysis data (ERA5) and volcanic cryptotephra shards likely presenting an absolute tie point from a 2001 CE eruption on neighboring Sturge Island. The resulting ice core age scale spans the period 2016 to 1995, with an uncertainty of ±2 years. [ABSTRACT FROM AUTHOR]

The role of deposition fluxes on the mercury cycle at Concordia station, on the high Antarctic plateau have been investigated over the Austral summer between December 2017 to January 2018. Wet/frozen deposition was collected daily from specially sited tables, simultaneously with the collection of surface (0–3 cm) and subsurface (3–6 cm) snow and the analysis of Hg0 in the ambient air. Over the course of the experiment the atmospheric Hg0 concentrations ranged from 0.58 ± 0.19 to 1.00 ± 0.33 ng m−3, surface snow Hg concentrations varied between (0–3 cm) 0.006 ± 0.003 to 0.001 ± 0.001 ng cm−3 and subsurface snow (3–6 cm) concentrations varied between 0.001 ± 0.001 to 0.003 ± 0.002 ng cm−3. The maximum daily wet deposition flux was found to be 23 ng m−2 d−1. Despite the low temporal resolution of our measurements combined with their potential errors, the linear regression of the Hg deposition fluxes against the snow accumulation rates allowed us to estimate the mean dry deposition rate from the intercept of the graph as −0.005 +- 0.008 ng m−2 d−1. From this analysis, we conclude that wet deposition accounts for the vast majority of the Hg deposition fluxes at Concordia Station. The number of snow events, together with the continuous GEM measurements have allowed us to make a first estimation of the mean snow scavenging factor at Dome C. Using the slope of the regression of mercury flux on snow accumulation we obtained a snow scavenging factor that ranges from 0.21 to 0.22 ± 0.02 (ng Hg /g snow)/(ng Hg /m3 air). Our data indicate that the boundary layer height and local meteorological effects influence Hg0 reemission from the top of (0–3 cm) the snowpack into the atmosphere and into the deeper snowpack layer (3–6 cm). These data will help constrain numerical models on the behaviour of mercury in Antarctica. • The daily collection of snow accumulation at Dome C station and from this an estimation of the depositional fluxes of mercury. • Surface snow sublimation is apparently linked with the net release of mercury from the snowpack in the summer. • Estimated of the net dry deposition velocity of mercury , the results show a net release of mercury from the snowpack. • We have made a first estimation of the snow scavenging factor for mercury on the high Antarctic plateau. [ABSTRACT FROM AUTHOR]