Пространственная изменчивость изотопного состава и скорости накопления снега на снегомерном полигоне станции Восток (Центральная Антарктида)

The knowledge of the spatial distribution of the snow accumulation rate and isotopic composition in different scales, from local to continental, over the Antarctic Ice Sheet is critically important for the interpretation of the paleoclimate data obtained from deep ice cores, for correct assessment of the ice sheet mass balance, etc. With this in mind, we have synthesized geodetic, glaciological and geochemical data collected in the vicinity of central Antarctic Vostok station in 1970–2017 in order to shed light on the processes governing the spatial distribution of snow isotopic composition and accumulation rate in the spatial scale from 100 to 1000 m. First, we have discovered that snow surface height and snow accumulation rate field are strongly affected by the influence of the logistic convoy route annually operating between Russian Antarctic stations Vostok and Progress. This influence is detectable up to 1 km leeward from the route. At the same time the isotopic composition of the upper 10 cm of the snow does not show any anomalies in the vicinity of the route. This is an unexpected result, because large anomalies of the ice sheet surface (e.g., megadunes) are known to affect the snow isotopic composition. Second, in the undisturbed part of the snow surface near Vostok station we have discovered quasi-periodic (with the wavelength of about 400 m) low-amplitude variations of the surface height that are covariant with the corresponding waves in snow accumulation and isotopic composition. We suggest that spatial variability of the snow isotopic composition is due to the different ratio of summer and winter precipitation deposited in different locations, as evident from a strong negative correlation between δD and dxs parameters. The results of this study may explain the nature of the low-frequency noise (with the time-scale from decades to centuries) observed in the climate records obtained from shallow and deep ice cores in central Antarctica.Изучение пространственного распределения скорости накопления и изотопного состава снега в различных масштабах на поверхности антарктического ледяного покрова критически важно для интерпретации палеоклиматических данных по глубоким ледяным кернам, для корректной оценки баланса массы ледяного щита и т.д. Впервые на основании большого объема геодезических, гляциологических и геохимических данных была детально изучена пространственная изменчивость изотопного состава и скорости накопления снега в районе станции Восток (Центральная Антарктида) в пространственном масштабе от 100 до 1000 м. Показано, что высота снежной поверхности и скорость накопления снега изученной территории существенно преобразованы влиянием проходящей здесь трассы санно-гусеничных походов между станциями Восток и Прогресс. В ненарушенной части данной территории выявлены квазипериодические колебания высоты поверхности с горизонтальными размерами порядка 400 м («мезодюны») и ассоциированные с ними аномалии изотопного состава и скорости накопления снега. Полученные результаты могут прояснить природу низкочастотного шума, наблюдаемого в климатических рядах, полученных по антарктическим ледяным кернам

DETERMINATION OF THE ICE SHEET SURFACE ELEVATION PROFILES ALONG THE INLAND TRACKS IN ANTARCTICA BY KINEMATIC GPS-OBSERVATIONS

Surface height profiles of the Antarctic ice sheet were derived from kinematic GPS observations on continental traverses with an accuracy of20 cm. The spectral analysis of the height profile allowed distinguishing different zones of distinct relief properties. The obtained surface height profiles were compared to ICESat satellite laser altimetry data and four different DEMs. A good agreement, within a few decimeters, is found between the in-situ observations and the altimetry data. Among the considered DEMs the model published by Bamber et al., 2009 [3] agrees best with the GPS observations. For three separate elevation zones the standard deviations of the differences of this DEM and the GPS results amount to 0.90 (above3300 melevation), 2.27 (2800–3300 m), and13.92 m(below2800 m). For the Rémy [13] and RAMPv2 [11] DEMs we obtained standard deviations of1.98 mand2.58 m(above3300 m), and4.03 mand5.67 m(2800–3300 m), respectively

Validation of CryoSat-2 products over the East Antarctica Ice Sheet

A main goal of the CryoSat-2 mission is to observe the variations in the elevation of the polar ice sheets within a few centimeters accuracy. To fulfill this challenging objective the CryoSat-2 Level 2 products need to be validated against independent measurements. Kinematic GNSS is a well established method to derive ground based surface elevation profiles with high accuracy, thus providing independent data to investigate the reliability of the radar altimetry observations. During the last decade a variety of such measurements could be realized in cooperation with the Russian Antarctic Expedition (RAE). Since 2007 we have realized the installation of several geodetic GNSS equipments on vehicles of the scientific and logistic convoys. These profiles between the Russian Antarctic research station Vostok (78° 28' S, 106° 50' E) and the coastal stations Mirny and Progress have a length of about 1,600 km each. Over several years the repetition of these profiles show that the elevation change is negligibly small in this region which forms an important precondition when comparing older GNSS profiles with recent CryoSat-2 data. Thus, the GNSS profiles give us the unique opportunity to validate both CryoSat-2 LRM-Mode data in the flat interior of the Antarctic Ice Sheet and SARIn-Mode data in the steep and rough coastal area. Validation results of the crossover analysis with Baseline B data are presented. We show how the new Baseline C processor version improves the observation quality. Furthermore, the alternate AWI processing version is used for comparison. Additionally, we will test the performance of the advanced swath processing technique in areas covered by the SARIn mode. Besides the Level 2 products we furthermore present the results of the validation of different digital elevation models (DEM). The probably most popular DEM for Antarctica, Bedmap2, is based mainly on ICESat, ERS-1 and small-scale local datasets. We show that a DEM based on CryoSat-2 data only has the advantage of a much higher consistency and of less interpolation errors due to the dense satellite ground tracks

ОПРЕДЕЛЕНИЕ ПРОФИЛЕЙ ВЫСОТ ПОВЕРХНОСТИ ЛЕДНИКА ВДОЛЬ ВНУТРИКОНТИНЕНТАЛЬНЫХ ТРАСС В АНТАРКТИДЕ ПОСРЕДСТВОМ КИНЕМАТИЧЕСКИХ GPS НАБЛЮДЕНИЙ

Surface height profiles of the Antarctic ice sheet were derived from kinematic GPS observations on continental traverses with an accuracy of20 cm. The spectral analysis of the height profile allowed distinguishing different zones of distinct relief properties. The obtained surface height profiles were compared to ICESat satellite laser altimetry data and four different DEMs. A good agreement, within a few decimeters, is found between the in-situ observations and the altimetry data. Among the considered DEMs the model published by Bamber et al., 2009 [3] agrees best with the GPS observations. For three separate elevation zones the standard deviations of the differences of this DEM and the GPS results amount to 0.90 (above3300 melevation), 2.27 (2800–3300 m), and13.92 m(below2800 m). For the Rémy [13] and RAMPv2 [11] DEMs we obtained standard deviations of1.98 mand2.58 m(above3300 m), and4.03 mand5.67 m(2800–3300 m), respectively.С помощью кинематических GPS-наблюдений получены профили высот поверхности Антарктического ледникового щита на внутриконтинентальных трассах с точностью 20 см. Спектральный анализ позволяет выделить зоны с различными свойствами рельефа. Полученные профили высот поверхности сравниваются с данными лазерной альтиметрии спутника ICESat и четырьмя цифровыми моделями высот DEM. Установлено, что данные альтиметрии и наблюдения in-situ согласуются в пределах30 см. Соответствие современных цифровых моделей высот данным GPS-наблюдений для верхней части ледникового купола находится в пределах нескольких метров