The region of Ridge B in central East Antarctica is one of the last unexplored parts of the continent and, at the same time, ranks among the most promising places to search for Earth's oldest ice. In January 2020, we carried out the first scientific traverse from Russia's Vostok Station to the topographical dome of Ridge B (Dome B, 3807 m above sea level, 79.02°S, 93.69°E). The glaciological programme included continuous snow-radar profiling and geodetic positioning along the traverse's route, installation of snow stakes, measurements of snow density, collection of samples for stable water isotope and chemical analyses and drilling of a 20 m firn core. The first results of the traverse show that the surface mass balance at Dome B (2.28 g cm−2 year−1) is among the lowest in Antarctica. The firn temperature below the layer of annual variations is −58.1 ± 0.2°C. A very low value of heavy water stable isotope content (-58.2‰ for oxygen-18) was discovered at a distance of 170 km from Vostok Station. This work is the first step towards a comprehensive reconnaissance study of the Ridge B area aimed at locating the best site for future deep drilling for the oldest Antarctic ice.

The origin and stability of ground ice in the stable uplands of the McMurdo Dry Valleys remains poorly understood, with most studies focusing on the near-surface permafrost. The 2016 Friis Hills Drilling Project retrieved five cores reaching 50 m depth in mid-Miocene permafrost, a period when Antarctica transitioned to a hyper-arid environment. This study characterizes the cryostratigraphy of arguably the oldest permafrost on Earth and assesses 15 Myr of ground ice evolution using the REGO model. Four cryostratigraphic units were identified: 1) surficial dry permafrost (0–30 cm), 2) ice-rich to ice-poor permafrost (0.3–5.0 m) with high solute load and δ18O values (-16.2 ± 1.8‰) and low D-excess values (-65.6 ± 4.3‰), 3) near-dry permafrost (5–20 m) and 4) ice-poor to ice-rich permafrost (20–50 m) containing ice lenses with low solute load and δ18O values (-34.6 ± 1.2‰) and D-excess of 6.9 ± 2.6‰. The near-surface δ18O profile of ground ice is comparable to other sites in the stable uplands, suggesting that this ice is actively responding to changing surface environmental conditions and challenging the assumption that the surface has remained frozen for 13.8 Myr. The deep ice lenses probably originate from the freezing of meteoric water during the mid-Miocene, and their δ18O composition suggests mean annual air temperatures ~7–11°C warmer than today.

Under the potential to reconstruct the past climatic and atmospheric conditions from a deep ice core in the coastal Antarctic site (Styx Glacier), an 8.84 m long firn core (73°50.975′ S, 163°41.640′ E; 1623 m a.s.l.) was initially studied to propose a reliable age scale for the local estimation of snow accumulation rate. The seasonal variations of δ18O, methanesulfonic acid (MSA) and non-sea-salt sulfate (nssSO42–) were used for the firn core dating and revealed 25 annual peaks (from 1990 to 2014) with volcanic sulfate signal. The observed declining trend in annual accumulation rate with a mean value of 146 ± 60 kg m–2 a–1 is likely to be linked to the changes of sea-ice extent in the Ross Sea region. Moreover, the temporal variation of the annual mean δ18O, an annual flux of MSA and nssSO42– also likely to be under the influence of ice-covered and open water area. This study suggests a potential to recover past changes in an oceanic environment and will be useful for the interpretation of the long ice core drilled at the same site.