Height changes over subglacial Lake Vostok, East Antarctica: Insights from GNSS observations

Height changes of the ice surface above subglacial Lake Vostok, East Antarctica, reflect the integral effect of different processes within the subglacial environment and the ice sheet. Repeated GNSS (Global Navigation Satellite Systems) observations on 56 surface markers in the Lake Vostok region spanning 11 years and continuous GNSS observations at Vostok station over 5 years are used to determine the vertical firn particle movement. Vertical marker velocities are derived with an accuracy of 1 cm/yr or better. Repeated measurements of surface height profiles around Vostok station using kinematic GNSS observations on a snowmobile allow the quantification of surface height changes at 308 crossover points. The height change rate was determined at 1 ± 5 mm/yr, thus indicating a stable ice surface height over the last decade. It is concluded that both the local mass balance of the ice and the lake level of the entire lake have been stable throughout the observation period. The continuous GNSS observations demonstrate that the particle heights vary linearly with time. Nonlinear height changes do not exceed ±1 cm at Vostok station and constrain the magnitude of spatiotemporal lake-level variations. ICESat laser altimetry data confirm that the amplitude of the surface deformations over the lake is restricted to a few centimeters. Assuming the ice sheet to be in steady state over the entire lake, estimates for the surface accumulation, on basal accretion/melt rates and on flux divergence, are derived.Fil: Richter, Andreas Jorg. Technische Universitaet Dresden; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Popov, Sergey V.. Polar Marine Geosurvey Expedition; RusiaFil: Fritsche, Mathias. Technische Universitaet Dresden; AlemaniaFil: Lukin, Valery V.. Arctic And Antarctic Research Institute; RusiaFil: Matveev, Alexey Yu. Oao Aerogeodeziya; RusiaFil: Ekaykin, Alexey A.. Arctic And Antarctic Research Institute; RusiaFil: Lipenkov, Vladimir Ya. Arctic And Antarctic Research Institute; RusiaFil: Fedorov, Denis V.. Oao Aerogeodeziya; RusiaFil: Eberlein, Lutz. Technische Universitaet Dresden; AlemaniaFil: Schröder, Ludwig. Technische Universitaet Dresden; AlemaniaFil: Ewert, Heiko. Technische Universitaet Dresden; AlemaniaFil: Horwath, Martin. Technische Universitaet Dresden; AlemaniaFil: Dietrich, Reinhard. Technische Universitaet Dresden; Alemani

Variations of snow accumulation rate in Central Antarctica over the last 250 years

The present-day global climate changes, very likely caused by anthropogenic activity, may potentially present a serious threat to the whole human civilization in a near future. In order to develop a plan of measures aimed at elimination of these threats and adaptation to these undesirable changes, one should deeply understand the mechanism of past and present (and thus, future) climatic changes of our planet. In this study we compare the present-day data of instrumental observations of the air temperature and snow accumulation rate performed in Central Antarctica (the Vostok station) with the reconstructed paleogeographic data on a variability of these parameters in the past. First of all, the Vostok station is shown to be differing from other East Antarctic stations due to relatively higher rate of warming (1.6 °C per 100 years) since 1958. At the same time, according to paleogeographic data, from the late eighteenth century to early twenty-first one the total warming amounted to about 1 °C, which is consistent with data from other Antarctic regions. So, we can make a conclusion with high probability that the 30-year period of 1985–2015 was the warmest over the last 2.5 centuries. As for the snow accumulation rate, the paleogeographic data on this contain a certain part of noise that does not allow reliable concluding. However, we found a statistically significant relationship between the rate of snow accumulation and air temperature. This means that with further rise of temperature in Central Antarctica, the rate of solid precipitation accumulation will increase there, thus partially compensating increasing of the sea level

A record of volcanic eruptions over the past 2,200 years from Vostok firn cores, central East Antarctica

Introduction: The products of volcanic eruptions found in the snow, firn and ice deposits of the polar ice sheets are precious sources of information on the volcanic forcing of the climate system in the recent or remote past. On the other hand, the layers containing the traces of well-known eruptions serve as absolute age markers that help to construct the depth-age scale for the snow-firn thickness.Methods: In this study we present new records of the sulfate concentrations and electrical conductivity (ECM) from three shallow (up to 70 m depth) firn cores drilled in the vicinity of Vostok station (central East Antarctica).Results: In the non-sea-salt sulfate and ECM profiles we were able to identify 68 peaks that can be interpreted as traces of volcanic events.Discussion: 22 of these peaks can be unambiguously attributed to well-known volcanic eruptions (including Tambora 1816 CE, Huaynaputina 1601 CE, Samalas 1258 CE, Ilopango 541 CE and others), which allowed to construct a robust depth-age scale for the cores. 37 events have their counterparts in other Antarctic cores, but cannot be associated with welldated eruptions. Finally, 9 peaks do not have analogues in the other cores, i.e., they may be traces of so far unknown volcanic events. According to the newly constructed depth-age function, the deepest studied firn layers (70.20 m) are dated by 192 BCE

Fifty years of instrumental surface mass balance observations at Vostok Station, central Antarctica

We present the surface mass balance (SMB) dataset from Vostok Station's accumulation stake farms which provide the longest instrumental record of its kind obtained with a uniform technique in central Antarctica over the last 53 years. The snow build-up values at individual stakes demonstrate a strong random scatter related to the interaction of wind-driven snow with snow micro-relief. Because of this depositional noise, the signal-to-noise ratio (SNR) in individual SMB time series derived at single points (from stakes, snow pits or firn cores) is as low as 0.045. Averaging the data over the whole stake farm increases the SNR to 2.3 and thus allows us to investigate reliably the climatic variability of the SMB. Since 1970, the average snow accumulation rate at Vostok has been 22.5 ± 1.3 kg m−2 yr−1. Our data suggest an overall increase of the SMB during the observation period accompanied by a significant decadal variability. The main driver of this variability is local air temperature with an SMB temperature sensitivity of 2.4 ± 0.2 kg m−2 yr−1 K−1 (11 ± 2% K−1). A covariation between the Vostok SMB and the Southern Oscillation Index is also observed

Изменение температуры в Центральной Антарктиде после крупных вулканических извержений во втором тысячелетии нашей эры

Volcanic forcing is one of the major drivers of climatic variability on Earth during the last millennium before the beginning of the industrial era, combined with solar activity, Milanković orbital forcing and greenhouse gas concentration. Large volcanic eruptions (with Volcanic Explosivity Index of 6 or more) eject a huge amount of sulfur dioxide into stratosphere thus reducing the amount of incoming solar radiation. The corresponding cooling may exceed 1 °C and lasts about 5 years. The identification of the volcanic events is carried out with the use of firn and ice core data drilled in the polar ice sheets, while the climatic response to the eruptions is studied with the use of dendrochronology and other terrestrial data, mainly in the Northern Hemisphere. Thus, the reaction of the Southern Hemisphere’s climate to the volcanic forcing is understood to a lesser extent. Here we use stable water isotope data (δ18O and dxs parameter, dxs = δD – 8 · δ18O) from 4 firn cores in order to study the temperature change in central Antarctica (in the vicinity of Vostok Station) after 5 major eruptions of the 2nd millennium of the Common Era: Samalas (1257), Unknown Event 1459 CE, Huaynaputina (1600), Parker (1641) and Tambora (1815). The isotopic composition of the cores was measured in the Climate and Environmental Research Laboratory of the Arctic and Antarctic Research Institute (St. Petersburg) with the use of Picarro L2130-i and L2140-i laser analyzers. We show that a post-eruption cooling in central East Antarctica is about 0.52 °C and lasts for about 5 years. At the same time, the temperature in the moisture source decreases to a lesser extent (0.46 °C), but the cooling lasts longer. We need to emphasize that only through using 4 parallel cores was it possible to significantly reduce the amount of the “deposition noise” in the isotopic records and detect the post-volcanic cooling in central East Antarctica.Вулканическая активность является одним из важнейших факторов естественной климатической изменчивости позднего голоцена до начала индустриальной эпохи. Влияние вулканов на климат изучается в основном по дендрохронологическим записям Северного полушария, тогда как о влиянии крупных извержений на температуру воздуха в полярных широтах Южного полушария известно существенно меньше. В настоящей работе использованы данные по изотопному составу (δ18O и δD) из 4 фирновых кернов для изучения изменения температуры в Центральной Антарктиде (окрестностях станции Восток) после 5 крупных извержений второго тысячелетия нашей эры: Самалас (1257 г.), Неизвестное Событие (1459 г.), Уайнапутина (1600 г.), Паркер (1641 г.) и Тамбора (1815 г.). Показано, что похолодание после извержения составляет около 0,52 °C и длится около 5 лет, при этом температура в источнике влаги снижается в меньшей степени (0,46 °С), но холодный период длится дольше

В ПОИСКАХ ДРЕВНЕЙШЕГО ЛЬДА АНТАРКТИДЫ

One of the key priority tasks for the international Antarctic community is drilling and studying old Antarctic ice with age exceeding 1  million years in order to investigate possible reasons for the Mid-Pleistocene Transition. During the 2017–2018 austral season at Vostok Station, we carried out microscopic study of geometrical properties of the crystalline inclusions of air hydrates in ice core samples from boreholes 5G‑3 (Vostok) and DC2 (EPICA DC) in depth intervals where the age of the ice exceeded 400,000 years. The obtained data confirmed the existence of a robust linear relationship between the mean radius of the hydrates and the age of the ice in the bottom part of the East Antarctic ice sheet, and will be useful for further development of the new dating technique based on the phenomena of hydrate growth in polar ice. Preliminary, the age of the atmospheric ice bedded at Vostok at a depth of3538 m, inferred from the data on the size of the hydrates, amounts to 1.3±0.17 million years. The existence of ice older than 1 million years in the vicinity of Vostok implies that in the area of Ridge B, where the ice flow line which passes through Vostok Station originates, even older ice, with undisturbed stratigraphy, may exist. It would be desirable therefore to carry out a glacio-geophysical traverse to Ridge B in order to implement a detailed study of Dome B area aimed at identifying the most suitable site for a new deep drilling of the Antarctic ice sheet.Сделан краткий обзор деятельности международного антарктического сообщества по поиску древнего льда в Антарктиде. Приведены предварительные результаты работ, полученные на станции Восток в период 63-й Российской антарктической экспедиции, которые подтверждают, что возраст льда в уже полученном на станции керне превышает 1 млн лет. Сформулированы первоочередные задачи дальнейших исследований древнего антарктического льда на станции Восток и в районе Ледораздела В