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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.
Stable isotope ratios (δ18O and δD) in Antarctic snow and ice are basic proxy indices of climate in ice core studies. The relation between the ratios has important indicative significance for moisture sources. In general, the fractionation characteristics of the two isotopes vary with different meteorological and topographical conditions. This paper presents the spatial and temporal distribution of meteoric water line (MWL) slopes along a traverse from the Zhongshan Station (ZSS) to Dome A in East Antarctica. It is found that the slopes decrease with the increasing distance inland from the coast and the lowest slope occurred at Dome A, where the long-range transported moisture dominates and clear sky snowing have an influence. The slopes in different layers of the snowpack showed a decreasing trend with depth and this is attributed to the fractionation during the interstitial sublimation and re-condensation processes of the water vapor. Frost flower development on the interior plateau surface can greatly alter the depth evolution of the MWL slope. The coastal snow pits also go through the post-depositional smoothing effect, but their influences are not so significant as the inland regions.
Using frequency-modulated continuous wave radar data from the 32nd Chinese Antarctic Research Expedition in 2015/16, subsurface profiles were obtained along an East Antarctic inland traverse from Zhongshan station to Dome A, and four distinct regions were selected to analyze the spatiotemporal variability in historical surface mass balance (SMB). Based on depth, density, and age data from ice cores along the traverse, the radar data were calibrated to yield average SMB data. The zone 49–195 km from the coast has the highest SMB (235 kg m−2 a−1). The 780–892 km zone was most affected by the Medieval Warm Period and the Little Ice Age, and the SMB during ad 1454–1836 (71 kg m−2 a−1) was only one-quarter of that in the 20th century. The SMB in the 1080–1157 km zone fluctuates the most, possibly due to erosion or irregular deposition of snow by katabatic winds in low SMB areas with surface elevation fluctuations. Dome A (1157–1236 km) has the lowest SMB (29 kg m−2 a−1) and did not decrease during Little Ice Age. Understanding the spatiotemporal variability of SMB in a larger space can help us understand the complex climate history of Antarctica.
Ice-core drilling to depths of 200–300 m is an important part of research studies concerned with paleoclimate reconstruction and anthropogenic climate change. However, conventional drilling methods face difficulties due to firn permeability. We have developed an electromechanical ice-core drill with air reverse circulation at the hole bottom. We believe that the new drilling system will recover ice cores faster than shallow auger drills, with high efficiency and low energy consumption. The theoretically estimated up-hole speed of the airflow should be not <7.7 m s−1 to allow proper removal of ice cuttings from the borehole bottom. The computer simulation and test results showed that the design of the new ice-coring drill is feasible. The maximum allowed penetration rate depends by square law on airflow.
A detailed history of volcanism covering the last 2840 years is reconstructed from the top 100.42 m of a 109.91 m ice core from Dome A (DA2005 ice core), East Antarctica. Using two known volcanic stratigraphic markers, the mean accumulation rate during the period AD 1260-1964 is found to be 23.2 mmw.e. a-1, consistent with the previously reported accumulation rate at Dome A. This mean accumulation rate is used to date the entire core. Volcanic eruptions in the period 840 BC-AD1998 are detected as outstanding sulphate events. Seventy-eight eruptions are identified, with a mean of 2.7 eruptions per century. Comparisons with previous Antarctic ice-core volcanic records are made to assess the quality of this new DA2005 record. In terms of dates for volcanic events, the DA2005 record is in good agreement with previous records in the second millennium ad (ad 1000-1998). A series of volcanic signatures found in both the DA2005 record and several other Antarctic ice-core records in the first millennium ad (ad 1-1000) appear to validate the DA2005 record during this time period. For the older periods, direct comparisons are difficult between the DA2005 record and other Antarctic ice-core records due to the lack of well-dated stratigraphic horizons.
The Chinese First Deep Ice-Core Drilling Project DK-1 has commenced at Kunlun station in the Dome A region, the highest plateau in Antarctica. During the first season, within the 28th Chinese National Antarctic Research Expedition (CHINARE) 2011/12 the pilot hole was drilled and reamed in order to install a 100 m deep fiberglass casing. In the next season, 29th CHINARE 2012/13, the deep ice-core drilling system was installed, and all the auxiliary equipment was connected and commissioned. After filling the hole with drilling fluid (n-butyl acetate), three runs of ‘wet’ ice-core drilling were carried out and a depth of 131.24 m was reached. Drilling to the bedrock at the target depth of ∼3100 m is planned to be completed during a further four seasons. We describe the work in progress and the status of equipment for the Dome A drilling project.
In 2007–08, seismologists began deploying passive seismic stations over much of the Antarctic ice sheet. These stations routinely log their position by navigation-grade global positioning system (GPS) receivers. This location data can be used to track the stations situated on moving ice. For stations along the traverse from Zhongshan station to Dome A in East Antarctica and at the West Antarctic Ice Sheet divide the estimated velocities of the ice surface based on positions recorded by navigation-grade GPS are consistent with those obtained by high-accuracy geodetic GPS. Most of the estimated velocities have an angle difference of <28° with the steepest downhill vector of the ice surface slope at the stations. These results indicate that navigation-grade GPS measurements over several months provide reliable information on ice sheet movement of ≥1 m yr-1. With an uncertainty of ~0.3–1 m yr-1, this method is able to resolve both very slow ice velocities near Dome A and velocities of >100 m yr-1 on Thwaites Glacier. Information on ice velocity at three locations for which no data from satellite-based interferometric synthetic aperture radar are available have also been provided using this method.
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