115 research outputs found
Climate related variations in lead concentration and sources in Vostok Antarctic ice from 65,000 to 240,000 years BP
No full text[1] Pb has been measured in various sections of the 3,623-m Vostok deep Antarctic ice core dated from 65,000 to 240,000 years BP, i.e. back to the beginning of the penultimate ice age and the preceding interglacial (isotopic stage 7.5). Pb concentrations were highly variable during this time interval, with low values down to similar to0.5 pg/g during warm climatic stages and much higher values up to similar to20 pg/g during cold climatic stages, especially isotopic stages 4.2 and 6.2 to 6.6. Rock and soil dust accounts for virtually 100% of Pb measured in the ice during cold climatic stages, while the contribution from volcanoes might be significant during warm stages.11Nsciescopu
Underestimation of snow accumulation rate in Central Antarctica (Vostok Station) derived from stake measurements
No full textIt is shown that the snow stake measurements in central Antarctica systematically underestimate the value of the snow build-up. Two methods for the calculation of the corresponding correction to the snow stake measurements at Vostok station are developed to take this underestimation into account. The first method is based on the Sorge’s law to calculate the rate of compaction of snow layers using the vertical profile of snow density. The second method is based on the direct field measurements of this compaction. Two independent methods for the estimation of the snow accumulation rate in the vicinity of Vostok station are also considered: geodetic data on the rate of snow layer sinking and glaciological data from snow pits. The most reliable estimate of the snow accumulation rate in this region is 2.26 ± 0.10 g/cm2 per year, that is 8 ± 4% higher than uncorrected values from snow accumulation measurements.Fil: Ekaykin, A. A.. Arctic And Antarctic Research Institute; RusiaFil: Tebenkova, N. A.. Arctic And Antarctic Research Institute; RusiaFil: Lipenkov, V. Y.. Arctic And Antarctic Research Institute; RusiaFil: Tchikhatchev, K. B.. Arctic And Antarctic Research Institute; RusiaFil: Veres, A. N.. Arctic And Antarctic Research Institute; RusiaFil: Richter, Andreas Jorg. Universidad Nacional de la Plata. Facultad de Cs.astronomicas y Geofisicas. Laboratorio Maggia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin
Remote sensing and mathematical modelling of Lake Vostok, East Antarctica: past, present and future research
No full textThe paper presents a review of the studies carried out in the area of the subglacial Lake Vostok (East Antarctica) to date. They include geophysical, glaciological, geodesic, and geological investigations. The most important geophysical investigations were carried out by the Polar Marine Geosurvey Expedition. They included reflection and refraction seismic, and also radio-echo sounding. The major contribution to the study of this region was made by American researchers, who in the 2000/01 field season performed a complex airborne geophysical survey on a regular network. Their work included magnetometric, gravimetric, and radio-echo sounding measurements. All the research conducted found that the water surface area is 15790 km2, and its altitudinal height changes from -600 to -150 m. The average depth of Lake Vostok is 400 m, and the maximum marks reach 1200 m. The water body volume is estimated at 6 100 km3. There are 11 islands in the lake, and their total area is 365 km2. In addition, 56 isolated subglacial water bodies were found around the lake. A special section is devoted to a review of mathematical models of heat and mass transfer processes in the glacier and water movement in Lake Vostok.Fil: Popov, S. V.. Polar Marine Geosurvey Expedition; Rusia. Saint Petersburg State University; RusiaFil: Boronina, A. S.. State Hydrological Institute; RusiaFil: Ekaykin, A. A.. Arctic And Antarctic Research Institute; RusiaFil: Klepikov, A. V.. Arctic And Antarctic Research Institute; RusiaFil: Leitchenkov, G. L.. All-Russia Research Institute for Geology and Mineral Resources of the World Ocean; Rusia. Saint Petersburg State University; RusiaFil: Lipenkov, V. Ya.. Arctic And Antarctic Research Institute; RusiaFil: Lukin, V. V.. Arctic And Antarctic Research Institute; RusiaFil: Masolov, V. N.. Polar Marine Geosurvey Expedition; RusiaFil: Richter, Andreas Jorg. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Laboratorio Maggia; Argentina. Technische Universität Dresden; AlemaniaFil: Vorobiov, D. M.. Polar Marine Geosurvey Expedition; RusiaFil: Cui, X.. Polar Research Institute Of China; ChinaFil: Qiao, G.. Tongji University; ChinaFil: Scheinert, M.. Technische Universität Dresden; AlemaniaFil: Dietrich, R.. Technische Universität Dresden; Alemani
A climatic control on the accretion of meteoric and super-chondritic iridium–platinum to the Antarctic ice cap
No full textThe Impact of Mesoscale Processes on the Atmospheric Circulation of Mars
Get PDFThe study of the modern martian atmosphere is (1) a key to the climate of Mars’s past; (2) useful for comparison with other terrestrial planets such as the Earth; and (3) can support hazard analysis and weather forecasting for future exploration and habitation of the planet. Recently, it was found that middle atmospheric downwelling near the south pole during southern winter is much more vigorous than predicted by most Mars general circulation models. This underestimate may be due to models erroneously representing the radiative forcings in the atmosphere due to aerosol and/or the mechanical forcings due to wave breaking. Errors of this kind would influence middle atmospheric dynamics and likely would result from incomplete understanding of lower atmospheric processes such as dust transport. Here, retrievals of vertical profiles of temperature, pressure, dust, and water ice from the Mars Climate Sounder (MCS) on Mars Reconnaissance Orbiter (MRO) are used to characterize the atmospheric circulation of Mars and its forcings. First, I consider the annual cycle of the thermal structure and aerosol distributions of the lower and middle atmosphere and investigate the degree of coupling between the lower and middle atmospheric mean meridional circulations. To evaluate the role of wave breaking, I look for local convective instabilities in the Martian middle atmosphere: a key indicator of saturating vertically propagating waves such as the gravity waves and the thermal tides, which are important sources of wave drag in the Earth’s mesosphere. I then characterize the vertical distribution of dust and its approximate radiative effects during northern spring and summer and show there is usually a maximum in dust mass mixing ratio at ~15—25 km above the tropics, which is not currently simulated by models. Next, I evaluate the relative importance of dust storm activity, pseudo-moist convection due to the solar heating of dust, orographic effects, and scavenging by water ice clouds in producing this maximum. Finally, I show that published models underestimate the thickness and altitude of water ice clouds in northern summer
Height changes over subglacial Lake Vostok, East Antarctica: Insights from GNSS observations
Get PDFHeight 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
Surface Mass Balance Models Vs. Stake Observations: A Comparison in the Lake Vostok Region, Central East Antarctica
Get PDFThe surface mass balance (SMB) is very low over the vast East Antarctic Plateau, for example in the Vostok region, where the mean SMB is on the order of 20–35 kg m-2 a-1. The observation and modeling of spatio-temporal SMB variations are equally challenging in this environment. Stake measurements carried out in the Vostok region provide SMB observations over half a century (1970–2019). This unique data set is compared with SMB estimations of the regional climate models RACMO2.3p2 (RACMO) and MAR3.11 (MAR). We focus on the SMB variations over time scales from months to decades. The comparison requires a rigorous assessment of the uncertainty in the stake observations and the spatial scale dependence of the temporal SMB variations. Our results show that RACMO estimates of annual and multi-year SMB agree well with the observations. The regression slope between modelled and observed temporal variations is close to 1.0 for this model. SMB simulations by MAR are affected by a positive bias which amounts to 6 kg m-2 a-1 at Vostok station and 2 kg m-2 a-1 along two stake profiles between Lake Vostok and Ridge B. None of the models is capable to reproduce the seasonal distributions of SMB and precipitation. Model SMB estimates are used in assessing the ice-mass balance and sea-level contribution of the Antarctic Ice Sheet by the input-output method. Our results provide insights into the uncertainty contribution of the SMB models to such assessments.Fil: Richter, Andreas Jorg. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Astrometría; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Technische Universität Dresden; AlemaniaFil: Ekaykin, Alexey A.. Arctic And Antarctic Research Institute; Rusia. Saint Petersburg State University; RusiaFil: Willen, Matthias O.. Technische Universität Dresden; AlemaniaFil: Lipenkov, Vladimir Ya.. Arctic And Antarctic Research Institute; RusiaFil: Groh, Andreas. Technische Universität Dresden; AlemaniaFil: Popov, Sergey V.. Polar Marine Geosurvey Expedition; Rusia. Saint Petersburg State University; RusiaFil: Scheinert, Mirko. Technische Universität Dresden; AlemaniaFil: Horwath, Martin. Technische Universität Dresden; AlemaniaFil: Dietrich, Reinhard. Technische Universität Dresden; Alemani
Physical parameters and stable isotopes of ice core VAV78/79
No full textPhysical parameters and stable isotopes of ice core VAV78/7
Climatic variability in Princess Elizabeth Land (East Antarctica) over the last 350 years
Get PDFWe use isotopic composition (δD) data from six
sites in Princess Elizabeth Land (PEL) in order to reconstruct air
temperature variability in this sector of East Antarctica over the last
350 years. First, we use the present-day instrumental mean annual surface air
temperature data to demonstrate that the studied region (between Russia's
Progress, Vostok and Mirny research stations) is characterized by uniform
temperature variability. We thus construct a stacked record of the
temperature anomaly for the whole sector for the period of 1958–2015. A
comparison of this series with the Southern Hemisphere climatic indices shows
that the short-term inter-annual temperature variability is primarily
governed by the Antarctic Oscillation (AAO) and Interdecadal Pacific
Oscillation (IPO) modes of atmospheric variability. However, the
low-frequency temperature variability (with period > 27 years) is mainly
related to the anomalies of the Indian Ocean Dipole (IOD) mode. We then
construct a stacked record of δD for the PEL for the period of
1654–2009 from individual normalized and filtered isotopic records obtained
at six different sites (PEL2016 stacked record). We use a linear
regression of this record and the stacked PEL temperature record (with an
apparent slope of 9 ± 5.4 ‰ °C−1) to convert
PEL2016 into a temperature scale. Analysis of PEL2016 shows a
1 ± 0.6 °C warming in this region over the last 3 centuries,
with a particularly cold period from the mid-18th to the mid-19th century. A
peak of cooling occurred in the 1840s – a feature previously observed in
other Antarctic records. We reveal that PEL2016 correlates with a
low-frequency component of IOD and suggest that the IOD mode influences the
Antarctic climate by modulating the activity of cyclones that bring heat and
moisture to Antarctica. We also compare PEL2016 with other Antarctic stacked
isotopic records. This work is a contribution to the PAGES (Past Global
Changes) and IPICS (International Partnerships in Ice Core Sciences)
Antarctica 2k projects
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