Abstract. Improving the spatial and temporal coverage of volcanic records is essential to accurately quantify volcanic forcing and to provide reliable references for climate models validation. In this study, we present a new volcanic record derived from a 133 m ice core (DA2009) drilled at Dome A, Antarctica. Based on measurements of non-sea-salt sulfate concentrations, 95 volcanic events are identified. Using 15 volcanic age markers aligned with the West Antarctic Ice Sheet (WAIS) Divide ice core (WDC) record, the DA2009 core is dated to cover the past 3951 years, from 1951 BCE to 2000 CE. By comparing the DA2009 record with three Antarctic ice cores from WAIS Divide, Dome C and South Pole, 12 prominent volcanic events are recognized. The period between 1000 and 2000 CE exhibits the most intense volcanic activity of the past 4000 years. The mean snow accumulation rates calculated between adjacent age markers indicate a marked decline in accumulation at Dome A since the 13th century CE. This low-accumulation interval coincides with a pronounced cold phase on the East Antarctic Plateau, suggesting a potential connection between regional climate variability and local accumulation rates at Dome A.

Antarctic sea ice plays a crucial role in regulating regional and global climate, as well as ecosystem productivity of the Southern Ocean. Since sea ice data were rare before 1978C.E., reconstruction of past sea ice conditions is of vital importance for understanding their impact on past climate change. Methanesulfonate (MSA) in Antarctic ice cores is considered a potential proxy of sea ice extent (SIE). In this study, we tested this approach by measuring the variations of MSA flux (1950-2016C.E.) in samples collected from a snowpit at Dome A, the summit of Eastern Antarctic ice sheet, and investigating its relationship with the SIE in the Southern Ocean. The result shows a significant and positive correlation between the MSA flux and the observed mean SIE in the Indian Ocean sector of the Southern Ocean from 1979 to 2016C.E. In addition, our study shows that the MSA is mainly influenced by Southern Hemisphere westerly winds (zonal winds) and katabatic winds (flowing from inland to the coast). Enhanced winds in both systems promote sea ice production in the Southern Ocean. These wind systems significantly influence the MSA cycle, stronger westerlies and katabatic winds increase MSA production, whereas meridional winds facilitate the transport and subsequent deposition of MSA at Dome A. Our findings suggest that MSA recorded in snow from Dome A could serve as a reliable proxy or reconstruction for mean SIE. Consequently, MSA in deep ice cores from Dome A offers a valuable archive for investigating past sea ice conditions in the Indian Ocean sector of the Southern Ocean, biogenic sulfur, and their climatic impacts.

Accurate observations of surface mass balance are pivotal for assessing the Antarctic Ice Sheet mass balance and its link to climate dynamics. Studying regional changes in surface mass balance is challenging due to limited on-site observations and the susceptibility of measurements from snow pits and ice cores to localized disturbances. Satellite data and short-term localized measurements suggest no significant changes or a possible increase in surface mass balance across the East Antarctic Ice Sheet in recent decades, but these findings lack large-scale validation. Here we use observations from mass balance stakes to show a significant negative surface mass balance trend along the inland transect from Zhongshan Station to the Antarctic Ice Sheet summit (Dome A) during the period 2005–2020. The mean surface mass balance trend for the inland section over the 15-year period is −2.01 ± 0.37 kg m−2 yr–2, indicating a 35.5

Ice-core water isotopes contain valuable information on past climate changes. However, such information can be altered by post-depositional processing after snow deposition. Atmosphere-snow water vapor exchange is one such process, but its influence remains poorly constrained. Here we constructed a box model to quantify the atmosphere-snow water vapor exchange fluxes and the associated isotope effects at sites with low snow accumulation rates, where the effects of atmosphere-snow water vapor exchange are suspected to be large. The model reproduced the observed diurnal variations in delta 18O, delta D, and deuterium excess (d-excess) in water vapor at Dome C, East Antarctica. According to the same model framework, we found that under average summer clear-sky conditions, atmosphere-snow water vapor exchange at Dome A can cause diurnal variations in atmospheric water vapor delta 18O and delta D of 4.8 parts per thousand +/- 2.6 parts per thousand and 29 parts per thousand +/- 19 parts per thousand, with corresponding diurnal variations in surface snow delta 18O and delta D of 0.80 parts per thousand +/- 0.35 parts per thousand and 1.6 parts per thousand +/- 2.7 parts per thousand. The modeled results under summer cloudy conditions display similar patterns to those under clear-sky conditions but with much smaller magnitudes of diurnal variations. However, under winter conditions at Dome A, the model predicts few to no diurnal changes in snow isotopes, consistent with the stable boundary condition in winter that inhibits effective vapor exchange between the atmosphere and snow. In addition, after 24 h and continuous simulations of 11 d, the model predicts significant enrichments in snow isotopes under summer conditions, while in winter, the depletions also accumulate after each 24 h simulation but with a much smaller magnitude of change compared to the results from summer simulations. If the modeled snow isotope enrichments in summer conditions and the depletions in winter conditions represent the general situation at Dome A, this likely suggests that atmosphere-snow water vapor exchange tends to increase snow isotope seasonality, and the annual net effect would be overall enrichments in snow isotopes since the effects in summer appear to be greater than those in winter. This trend will need to be further explored in the future with more comprehensive model studies and/or field observations and experiments.

Conducting scientific drilling on subglacial lakes and obtaining samples of subglacial lake water holds great significance in unraveling the formation and evolution of Antarctic subglacial lakes and early Earth’s life forms. Despite various approaches to access and directly sample subglacial water and sediments, clean access and exploration of subglacial lakes remain challenging. To address this concern, Jilin University has developed the RECoverable Autonomous Sonde (RECAS) prototype. This technology enables sampling and in-situ detection of subglacial lake water while being isolated from the surface, thus minimizing the risk of pollution. Laboratory tests, including downward and upward drilling, long-running, remote-control, and cold-environment assessments, were conducted to validate the sonde’s principle and functionality. During the 38th Chinese National Antarctic Research Expedition, CHINARE (2021–2022 season), the RECAS prototype underwent testing on the flank region of Dålk glacier, 10 km from Zhongshan Station in Antarctica. Three boreholes with depths of 200.3, 183.2, and 133.5 m were successfully drilled, with the refrozen meltwater sealing the boreholes during the process. Approximately 600 mL of melted water samples were collected from each hole. Throughout the drilling tests, all systems of the RECAS prototype performed within the expected ranges.

The study of the fabric and microstructure of ice at the shear margin of the Antarctic ice sheet is of great significance for understanding the ice flow and its contributions to sea level rise. In this study, twenty-three one-meter-long ice cores were drilled from blue ice areas at the shear margin of the Dalk Glacier, Antarctica. The ice fabric and microstructure of these ice cores are analyzed using a G50 fabric analyzer. This study shows that the shallow ice cores in this region present a cluster fabric as a consequence of shear stress. The grain size decreases following the direction of the ice flow towards the exposed bedrock at the end of the glacier, due to the blocking and squeezing by the bedrock. The formation mechanism of the shallow ice layers is that the ice from the original accumulation area flows here, lifted by the bedrock and shaped by the summer ablation and denudation. The basal ice at the shear margin of the Dalk Glacier is strongly rubbed by the bedrock and demonstrates a cluster fabric. The analysis of stable water isotopes shows a weak negative correlation between shallow ice fabric and stable water isotopes with depth. Bedrock topography and shear stress have a greater influence on grain microstructure among different ice cores over long distances at shear margins.

The newly developed RECoverable Autonomous Sonde (RECAS) allows sampling and analysis of subglacial water while the subglacial lake remains isolated from the surface. The sonde was successfully tested in East Antarctica during the 2021–2022 field season: it reached the ice-sheet base at a depth of 200.3 m, sampled basal meltwater and measured its pressure, temperature, pH and conductivity and returned to the ice surface. The average downward penetration rate was 1.85 m h−1, and the average upward penetration rate was 2.94 m h−1. The successful test of a self-melting, recoverable probe in Antarctica marks further progress towards the clean exploration of subglacial water bodies.

To better understand snow chemistry in different environments across the Antarctic ice sheet, we investigated snow ions on a traverse from the coast to Dome A. Results show that the non-sea-salt (nss) fractions of K+, Mg2+, and Ca2+ are mainly from terrestrial particle mass and nssCl− is associated with HCl. Spatially, the non-sea-salt fractions of ions to the totals are higher in the interior areas than on the coast, and seasonally, the proportions are higher in summer than in winter. Negative nssSO42- on the coast indicates sea salts from the sea ice, and marine biogenic emissions dominate snow SO42- in interior areas throughout the year.

中国第35次南极考察队内陆考察期间在东南极中山站–Dome A断面沿线采集了4个雪坑,利用火山标志层确定了Dome A地区雪坑年层序列(1962—2018年).雪坑离子浓度时空的分析表明,沿海地区Cl–和Na+浓度受海洋来源影响相对较高,Cl–/Na+比值从沿海到内陆逐渐增加,表明Cl–除海盐源外存在其他来源或受到挥发性HCl沉积的影响.内陆地区雪坑SO2–4平均浓度较高,可能与该地区雪低积累率和中低纬度SO2–4远距离输入有关.海拔2000 m以上雪坑中非海盐硫酸根(nssSO2–4)占总SO2–4的比重大于90％,表明nssSO2–4的远距离输入是南极高海拔地区SO2–4离子的主要来源.积累率、下降风和沉积后作用等造成NO–3浓度变化复杂,显示出较大的空间异质性.离海岸距离800 km处雪坑的NO–3浓度较高,推测是受该地区地貌、太阳辐射冰壳和沉积后作用等因素所致.沿海地区和800 km处雪坑海盐离子、NO–3和nssSO2–4浓度随时间变化呈现出不同的季节性特征,而离海岸距离520 km和内陆地区雪坑无明显季节变化趋势,认为是物质源区、下降风、沉积后过程和积累率等共同作用的结果.基于海冰形成的高盐度"霜花"和风吹雪,可能是沿海地区雪坑海盐离子浓度随时间增加的原因.

Oceans play a key role in the global mercury (Hg) cycle, but studies on Hg isotopes in seawater are rare due to the extremely low Hg concentration and the lack of a good preconcentration method. Here, we introduce a new coprecipitation method for separating and preconcentrating Hg from seawater for accurate isotope measurement. The coprecipitation was achieved by sequential addition of 0.5 mL of 0.5 M CuSO4, 1 mL of 0.5 M Na2S, and 1 mL of 0.5 M CuSO4 reagents, which allowed for quantitatively precipitating Hg from up to 10 L of seawater. The protocol was validated by testing synthetic solutions with varying Hg and iodide (I-) concentrations and by comparing the reaction times of various reagents added. The method resulted in a quantitative recovery of 98 ± 12% (n = 32, two standard deviations, 2 SD) and a relatively low procedure blank (103 pg of Hg, n = 8). The precipitates were filtrated and analyzed for Hg isotopes. Repeated measurements of synthetic seawaters spiked with certificated standard materials (NIST 3133 and 3177) using the entire method gave identical Hg isotope ratios with near-quantitative Hg recovery, indicating no isotope fractionation during preconcentration. A total of six nearshore seawater samples from the Yellow Sea and the Bohai Sea (China) were analyzed using the coprecipitation method. The data showed a large fractionation of Hg isotopes and revealed the possible impact of both atmospheric and anthropogenic inputs to the coastal seawater Hg budget, implying the potential application of this method in studying marine Hg systematics and global Hg cycling.

我国于2012年1月在南极Dome A区域正式开展实施了南极昆仑站深冰芯科学钻探工程,截至2021年,钻孔深度已达803.54 m.该工程是我国第一个深冰芯钻探工程,也是国际上第一个在Dome A地区开展的深冰芯钻探项目.本文介绍了昆仑站深冰芯科学钻探工程实施的整体情况,对过去近10年的钻探活动以及取得的成果和经验进行了总结,以期为后续的深冰芯钻探工作提供理论和经验指导.

Abstract A deep ice core was drilled at Dome A, Antarctic Plateau, East Antarctica, which started with the installation of a casing in January 2012 and reached 800.8 m in January 2017. To date, a total of 337 successful ice-core drilling runs have been conducted, including 118 runs to drill the pilot hole. The total drilling time was 52 days, of which eight days were required for drilling down and reaming the pilot hole, and 44 days for deep ice coring. The average penetration depths of individual runs were 1 and 3.1 m for the pilot hole drilling and deep ice coring, respectively. The quality of the ice cores was imperfect in the brittle zone (650−800 m). Some of the troubles encountered are discussed for reference, such as armoured cable knotting, screws falling into the hole bottom, and damaged parts, among others.

Mineral resources are essential to prosperity and security of modern societies. How mineral resources can guar- antee sustainable development of economy in countries, especially those developing countries, has long been a focus of attention of international communities. This paper provides a comprehensive summary for major ad- vance of the research on mineral resources in past decades, and proposes some key issues regarding ore-forming mechanism, exploration and utilization of major and critical mineral resources. On the basis of these aspects, we also identify four priority science issues to be addressed in the future, including (1) mechanism of both metal circulation and extremely high concentration, (2) theories and technologies of prospecting deep-earth resources, (3) investigation of mineral resources in seafloor and polar regions, and (4) efficient, clean and recycling utiliza- tion of mineral resources. It can be expected that new advances in these four issues would tremendously promote the innovation of mineral resource science, and provide scientific and technologic support to meet the demand of mineral resources for human activities and the harmonious development of both mineral-resource exploration and ecological restoration.

Atmospheric samples and surface seawater collected on a Chinese Antarctic Research Expedition (CHINARE) transect are used to investigate sources and production of nitrate (NO3−) in the atmosphere and its contribution to the surface NO3− pool in the ocean. Most atmospheric NO3− is concentrated on intermediate size particles, and much higher concentrations were observed in the northern hemisphere than in the high southern latitudes. Isotopes of NO3− (δ15N, δ18O and Δ17O) suggest that elevated atmospheric NO3− in coastal areas was associated with human activities, while NO3− in the high southern latitudes tends to be influenced by precursor Antarctic snowpack emissions driven by photolysis. In general, no clear association was found between the isotopes of surface seawater and atmospheric NO3−, suggesting that the ocean is unlikely to be an important direct source of atmospheric NOx on this transect. A significant linear relationship between δ18O and Δ17O of NO3− is used to interpret important pathways for NO3− production. In the tropics, >59% of atmospheric NO3− is produced via OH oxidation of NO2, while the elevated oxygen isotopic ratios (δ18O and Δ17O) in the high southern latitudes suggest increased NO3− production via BrO and/or DMS pathways assuming a minor contribution of the N2O5 channel. In surface seawater, high NO3− concentrations are present in the coastal areas and in the Southern Ocean. In coastal areas of China, positive Δ17O values in seawater NO3− (1.7 ± 1.0‰) provide direct evidence of uncycled atmospheric deposition contribution, with a calculated contribution of at least 2-3% to total surface NO3−. A Δ17O=0 was found everywhere else in seawater, suggesting that atmospheric deposition has a minimal presence in the surface NO3− pool. Near Antarctica, deposition of atmospheric NO3− with extremely low δ15N (<−30‰) could lower δ15N found in sea ice, and this process could be isotopically important to evaluate nitrogen cycling in sea ice.

The uncertainties in Antarctic climate reconstructions due to scarcity of proxy records have restricted the understanding of mechanisms of climate change, and further hindered the improvement of climate models. Here, we provide a new climate record derived from water stable isotopes in a Dome A, East Antarctica ice core. Together with six other ice core records, the Dome A record is used to investigate temperature changes in East Antarctic Plateau (EAP) during period 1–1900 CE. Our results show that, a previously reported long‐term cooling trend in EAP during the recent (pre‐1900 CE) 1900 years is only robust between 550 and 1550 CE. A combination of solar and volcanic forcing may have induced the EAP centennial‐scale cold events, and further caused the long‐term cooling trend from 550 to 1550 CE with a small contribution from orbital forcing.

Stable isotopic composition (δ18O and δD) in Antarctic snow/ice cores serves as the proxy of past temperature. However, the accuracy of temperature reconstruction is largely dependent on the relationship between water isotopes and local temperature (δ-T) derived from present conditions. Thus, it is crucial to quantitatively understand the spatial δ-T relationship and the influencing factors of δ18O and δD in surface snow besides temperature. In this work, we characterized the spatial and temporal variation of stable isotopes in surface snow using a comprehensive assessment of observations and simulations on the traverse from the coast to Dome A, the summit of East Antarctica ice sheet. The δ18O and δD from surface snow and snow pit samples show an insignificant variation at interannual scale, possibly suggesting that interannual changes in controlling factors are not remarkable during the investigation period. Along the traverse, the spatial δ18O-T slope is 0.91‰·oC−1 based on averages of δ18O measurements for snow pits and annual mean temperature at the sampling site. Results from the mixed cloud isotope model (MCIM) suggest that the effects of evaporative conditions and transportation paths of moisture on water isotopes for specific sites are insignificant. Therefore, it is more important to consider other effects on water isotopes (e.g. post-depositional processes) when interpreting ice core records, particularly in interior Antarctica.

Abstract. There is a large variability in environmental conditions across the Antarctic ice sheet, and it is of significance to investigate the snow chemistry at as many locations as possible and over time, given that the ice sheet itself, and precipitation and deposition patterns and trends are changing. The China inland Antarctic traverse from coastal Zhongshan Station to the ice sheet summit (Dome A) covers a variety of environments, allowing for a vast collection of snow chemistry conditions across East Antarctica. Surface snow and snow pit samples were collected on this traverse during five campaigns, to comprehensively investigate the spatial and temporal variations in chemical ions (Cl−, NO3−, SO42−, Na+, NH4+, K+, Mg2+, and Ca2+) and the related controlling factors. Results show that spatial patterns of ions in surface snow are consistent among the five campaigns, with Cl−, Na+, K+, and Mg2+ decreasing rapidly with distance from the coast and NO3− showing an opposite pattern. No clear spatial trends in SO42−, NH4+ and Ca2+ were found. In the interior areas, an enrichment of Cl− versus Na+ with respect to seawater composition is ubiquitous as a result of the deposition of HCl, which can account for up to ~40 % of the total Cl− budget, while enriched K+ and Mg2+ are associated with terrestrial particle mass. Ca2+ and SO42− in surface snow are significantly enriched relative to Na+, related to terrestrial dust inputs and marine biogenic emissions, respectively. Snow NH4+ is mainly associated with marine biological activities, with higher concentrations in summer than in winter. On the coast, parts of the winter snow are characterized with a depletion of SO42− versus Na+, and a significant negative correlation between nssSO42− and Na+ was found, suggesting that sea salts originated from the sea ice. In the interior areas, the negative nssSO42− signal in winter snow resulted from inputs of sea salts being completely swamped by the contribution of marine biogenic emissions. Ternary plots of Cl−, Na+, and SO42− suggest that sea salt modification is generally negligible on the coast, while the degree of modification processes to sea salts is high in the interior areas, especially during the summertime. Ion flux assessment suggests an efficient transport of nssSO42− to at least as far inland as the ~2800 m contour line. The interannual variations in ion concentrations in surface snow on the traverse are likely linked to the changes in the Southern Indian Ocean low (SIOL) from year to year, and the deepening of the SIOL in summer tends to promote the transport of marine aerosols to Princess Elizabeth Land.

极地冰钻技术是获取冰芯,研究冰盖-冰架-海洋相互作用,以及获取极地冰下基岩与冰下水环境样品,开展冰下环境探测的重要手段.目前极地冰钻技术的难点与前沿主要包括深冰芯钻探、冰架热水钻、冰下基岩钻和冰下水环境采样与观测技术.本文针对以上4个极地冰钻关键技术,对国内外相关技术的研究进展与项目开展情况进行了总结与梳理.综合来看,虽然我国开展极地钻探技术研究起步较晚,但随着我国极地战略不断推进,我国的极地冰钻关键技术与装备的研究正持续向着赶超极地钻探强国方向迈进,这必将为我国的极地科学研究提供强有力的技术支撑.

Abundant ferromanganese oxide deposits were recovered from the Chukchi Sea in the Arctic Ocean during the 7th Chinese Arctic Scientific Expedition in August 2016. Representative samples were collected to perform a mineralogical and geochemical analysis and elucidate their origin. Their mineral phases consist of todorokite, buserite, and birnessite, along with a small quantity of detrital minerals (quartz, feldspar, serpentine, kaolinite, and illite). Their elemental composition is rich in Ni and Mn compared to ferromanganese oxide deposits from other locations in the Chukchi Sea. The total rare earth element (REE) concentration varied from 138.95 to 207.23 μg/g with an average of 164.75 μg/g. The post-Archean Australian shale–normalized REE patterns have a slightly negative Ce anomaly and a positive Eu anomaly. The comprehensive geochemical and mineral data show that they have a mixed hydrothermal and diagenetic origin.