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

Российско-французский семинар 2015

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Климатическая перестройка в середине плейстоцена и проблема исследования древнейшего антарктического льда со станции Восток

Marine records indicate a dramatic change in the predominant periodicity of climate variability, from about 40 ka to about 100 ka around one million years ago. The reason for this major climatic shift, which is called the Mid-Pleistocene Transition or MPT, remains unknown – and is of great interest to the climate scientist. Could the core of the oldest meteoric ice bedded at Vostok between 3310 and 3539 m, which has experienced severe deformation, nevertheless be useful in deciphering some of the aspects of the MPT enigma? Reflecting upon this question and considering the available data from the disturbed section of the ice core, we feel impelled to propose a new project focused on the oldest Vostok meteoric ice, which could be named the Vostok Oldest Ice Challenge or VOICE.Результаты исследований морских донных осадков показывают, что около 1 млн лет назад изменился характерный период климатических колебаний, связанных с чередованием ледниковых и межледниковых эпох: циклы в 40 тыс. лет сменились циклами в 100 тыс. лет. Причины, которые привели к перестройке климатической системы планеты в середине плейстоцена (Mid Pleistocene Transition – MPT), пока не известны и приковывают к себе пристальное внимание климатологов. Может ли керн древнего деформированного льда, залегающего в районе станции Восток в интервале глубин 3310–3539 м, дать ответы хотя бы на часть вопросов, связанных с генезисом MPT? В статье анализируются предварительные результаты изучения этого керна и обосновывается программа дальнейших углублённых исследований древнейшего антарктического льда со станции Восток под общим названием Vostok Oldest Ice Challenge (VOICE)

Исследование погрешностей орбитального метода датирования льда по данным о его газосодержании на примере ледяного керна со станции Купол Фуджи (Антарктида)

We have further elaborated an algorithm for implementing a new method of ice core dating, which is based on the link between air content of ice and local insolation (Raynaud et al., 2007).Our study proves that continuous wavelet transform (CWT) is the most suitable tool for tuning the preliminary dated air content records on the calculated local insolation time series. The uncertainties associated with applying this technique to the experimental air content records have been thoroughly investigated. The new dating method was for the fi rst time applied to constructing the orbital time scale for the Dome Fuji ice core, using a composite air content record obtained from this site. A standard error of the thus obtained timescale was evaluated not to exceed ±2.1 ka, that is, close to the standard error of the optimized multi-proxy, multi-site AICC2012 chronology, previously developed for fi ve drilling sites in Antarctica and Greenland.Разработан алгоритм реализации нового метода датирования ледяных кернов, основанного на связи газосодержания ледникового льда с местной инсоляцией (Raynaud et al., 2007). Показано, что для совмещения рядов газосодержания с точно датированными расчетными рядами инсоляции идеально подходит техника непрерывного вейвлет-преобразования (CWT). Проведено тщательное исследование погрешностей орбитального тюнинга. Новый метод датирования впервые использован для построения орбитальной хронологической шкалы ледяных отложений в районе японской антарктической станции Купол Фуджи по данным о газосодержании полученного здесь ледяного керна. Стандартная ошибка возраста льда по этой шкале не превышает ±2,1 тыс. лет, т.е. близка к случайной погрешности оптимизированной временной шкалы AICC2012, разработанной ранее для пяти пунктов глубокого бурения в Антарктиде и Гренландии

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

Climatic variability in the era of MIS-11 (370-440 ka BP) according to isotope composition (delta D, delta O-18, delta O-17) of ice from the Vostok station cores

The results of detailed isotopic studies of ice core samples from the Vostok station (East Antarctica) related to the MIS-11  era (the 11th sea isotope stage, i.e. 370–440 thousand years ago) are presented. Reconstruction of paleoclimatic conditions in this period of time was performed using the method of interpretation of the results of isotopic studies of ice, developed by the authors of the article, which is based on the joint analysis of three independent parameters: δD, d-excess, 17O-excess. The isotopic composition (δD) and the deuterium  excess depend on the following  three meteorological  parameters – the condensation temperature near the Vostok station, relative humidity,  and the sea surface temperature at the source of moisture, whereas 17O-excess depends only on the first two parameters. Accordingly,  the proposed method of interpretation allows reconstructing the paleoclimatic conditions (the condensation temperature and surface air temperature at the Vostok station; sea surface temperature and relative humidity  above the ocean) in two different regions in past epochs. For the first time, data on minor fluctuations in the relative humidity of the air in themoisture source throughout the MIS-11  era were obtained. The data resulted from the interpretation demonstrated that the relative humidity fluctuated within the measurement error of ±5%. Reconstructed climatic conditions in the era of MIS-11  were compared with published data for stations Vostok and Concordia, aswell as with the marine core data from 94-607 DSDP and ODP 177-1090. The results obtained on the basis of isotopic analysis of ice cores from stations Vostok and Concordia indicated that in the optimum MIS-11the air temperature was4 °C higher, and in the Termination V –8 °C lower than the present-day values. Thesimilarity of data between the marine columns DSDP  94-607 (North Atlantic), ODP 177-1090 (South Ocean)and our results points to the global nature of changes in the sea surface temperature during the MIS-11  era. The coordination  of the above results proves the high quality of the methods developed by the authors for measuring and interpreting the isotope composition of ice

Сохранность климатического сигнала в слоях древнего льда в районе Купола В (Антарктида)

In this work we have presented the results of numerical modeling of the age and temperature distribution in ice layers at Dome B site (79,02° S, 93,69° E, altitude 3807 m a.s.l., ice thickness about 2.5 km), located 300 km to the west from Russian Antarctic station Vostok. Dome B is situated on the onset of the ice flow line passing through deep borehole 5G, and is considered as one of the most promising places to search for and to study the Easth’s oldest ice with the age of up to 1.5 Ma. According to our calculations, all realistic scenarios show the ice age at 60 m above the ice base to be considerably older than 1 Ma, and the glacier base temperature is well below the pressure melting point (−1.8 °С for pressure = 23 MPa). For the most likely scenario (accumulation rate 1.8 g/(cm2 year), effective ice surface temperature −64 °С and geothermal heat flux 60 mW/m2) the ice age is 1.4 Ma and the basal temperature is about −13 °С that is close to the earlier predictions from a 2D‑model. Maximum estimate of the «diffusion length» in the old ice (for the scenario in which the basal temperature reaches the melting point, and in which 30% of «excess diffusion» is taken into account) is 5.2 cm. In 1.4 Ma-old ice a 40-ka climatic cycle is squeezed into a 290-cm thick ice layer. For this ratio of wave length and diffusion length the climatic signal attenuation (ratio between the signal amplitude after and before the diffusive smoothing) is 0.6%. Thus, due to the relatively low ice temperature here we may expect a nearly undisturbed climatic curve in the old ice core that will be drilled one day at Dome B. At the same time shorter oscillations with the wavelengths of < 1500 years will be totally erased by diffusion.Представлены результаты моделирования возраста и температуры льда для Купола В (79,02° ю.ш., 93,69° в.д., высота 3807 м над ур. моря, толщина льда около 2,5 км) в Антарктиде. Для всех сценариев возраст льда на отметке 60 м выше ложа ледника составляет более 1 млн лет, а для наиболее вероятного сценария – 1,4 млн лет. Температура ложа для всего диапазона реалистичных оценок геотермального потока тепла находится ниже точки плавления и для наиболее вероятного сценария равна около −13 °С. Расчётное ослабление амплитуды 40‑тысячелетнего климатического цикла в древнем льду за счёт молекулярной диффузии составляет около 0,6%. Результаты исследования позволяют сделать вывод, что Купол В – перспективное место для извлечения нового глубокого керна, с помощью которого можно будет получить ненарушенный климатический сигнал за последние 1,4 млн лет

Изменения климата в индоокеанском секторе Восточной Антарктиды за последние 350 лет

The temperature and snow accumulation rate anomaly over the past 350 years have been reconstructed based on isotopic composition of shallow ice cores and snow pits samples as well as glaciological observations in pits and at stake farms located in Indian Ocean sector of East Antarctica. The relationship of temporal variability of isotopic composition of precipitation and surface air temperature in ensemble with sea surface temperature has been analyzed. The fingerprints of Little Ice Age and climatic shift 1970s have been defined. We have also figured out the influence of non-climatic drivers on the formation of signal in stable water isotopic series.По данным об изотопном составе ледяных кернов, полученных из скважин, пробуренных в индоокеанском секторе Восточной Антарктиды между трассами Мирный – Восток и Прогресс – Восток, восстановлено изменение температуры воздуха и скорости снегонакопления за последние 350 лет. Проанализирована связь временнóй изменчивости изотопного состава осадков с местной приземной температурой воздуха и температурой в источнике влаги. Обнаружено проявление малого ледникового периода, а также так называемого климатического сдвига 1970‑х годов в исследуемом секторе Антарктиды. Обсуждается роль неклиматических факторов, влияющих на формирование долгопериодных трендов в рядах изотопного состава осадков, получаемых по ледяным кернам

Вариации скорости снегонакопления в Центральной Антарктиде за последние 250 лет

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.Современные изменения температуры воздуха и скорости накопления снега, полученные инструментальным путём на антарктической станции Восток, сопоставлены с палеоклиматическими реконструкциями за последние 250 лет. Показано, что период 1985–2015 гг., вероятно, был самым тёплым 30-летием за последние 2,5  века. Скорость снегонакопления положительно коррелирует с изменчивостью температуры воздуха – это показывает, что повышение температуры в будущем будет сопровождаться ростом количества снега, накапливаемого в Антарктиде, что частично скомпенсирует рост уровня Мирового океана. Вместе с ростом температуры воздуха на протяжении последних 50  лет имело место и увеличение количества осадков, однако являются ли современные значения скорости снегонакопления аномальными для последних 250 лет на основании имеющихся данных сказать трудно

Evolution of climate, glaciation and subglacial environments of Antarctica from the deep ice core and Lake Vostok water sample studies (Key results of implementation of the Russian Science Foundation project, 2014–2016)

Work on the project focused on the following five areas: 1)  field works in Antarctica at Vostok and Concordia stations; 2)  experimental and theoretical studies in the field of ice core and paleoclimate research; 3) experimental and theoretical works related to the exploration of subglacial Lake Vostok; 4) development of technology and drilling equipment for deep ice coring and exploration of subglacial lakes; 5) upgrading the analytical instrumentation in the Climate and Environmental Research Laboratory (CERL) of the Arctic and Antarctic Research Institute. The main achievements in the field of ice core and paleoclimate research include 1) further elaboration of a new method of ice core dating, which is based on the link between air content of ice and local insolation, 2) investigation of the possible applications of the 17O-excess measurements in ice core to the paleoclimate research, 3)  a better understanding of the mechanisms of the formation of relief-related variations in the isotopic content of an ice core drilled in the area of Antarctic megadunes, and 4) obtaining the first reliable data set on the variations of the 17O-excess in the Vostok core corresponding to marine isotope stage 11. As part of our studies of subglacial Lake Vostok, we have obtained a large body of new experimental data from the new ice core recovered from the 5G-3 borehole to the surface of the subglacial lake. Stacked profiles of isotopic composition, gas content and the size and orientation of the ice crystals in the lake ice have been composed from the data of three replicate cores from boreholes 5G-1, 5G-2 and 5G-3. The study reveals that the concentration of gases in the lake water beneath Vostok is unexpectedly low. A clear signature of the melt water in the surface layer of the lake, which is subject to refreezing on the icy ceiling of Lake Vostok, has been discerned in the three different properties of the accreted ice (the ice texture, the isotopic and gas content of the ice). These sets of data indicate in concert that poor mixing of the melt (and hydrothermal) water with the resident lake water and pronounced spatial and/or temporal variability of local hydrological conditions are likely to be the characteristics of the southern end of the lake. A considerable part of the funding allocated by the RSF to this project was used for upgrading the analytical instrumentation for ice core studies in the CERL of AARI. Using this grant, we purchased and started working with the Picarro L-2140i, a new-generation laser mass analyzer, and set the upgraded mass spectrometer Delta V Plus into operation. The new equipment was used to carry out research planned as part of the project, including the setting up and carrying out of new measurements of 17О in ice cores