Flow Dynamics in the Rybinsk Headwork Tailrace and Its Environmental Assessment

The role of wave processes and turbulence in impurity transport, flow interaction with bottom sediments, and the formation and destruction of ice cover was determined on the basis of analysis of field measurement data on flow velocities and water levels in the Rybinsk Headwork tailrace in the presence and absence of water releases in summer and winter.__________Translated from Vodnye Resursy, Vol. 32, No. 3, 2005, pp. 274–281.Original Russian Text Copyright © 2005 by Debolskii, Dolgopolova, Eshchenko, Kotlyakov, Mordasov, Konov, Koreneva.     

Lead–lag relationships between atmospheric trends of temperature and carbon dioxide concentrations during the pliocene

Reconstructions of the average global near-surface air temperature and carbon dioxide concentration in the atmosphere for the late Pliocene are compared. For this purpose, a special technique of multiscale analysis based on wavelets was developed. It is found that temperature changes on timescales of 100 to 500 kyr lead the respective changes in the carbon dioxide concentration at about 10–25 kyr. It means that these reconstructions cannot be used for assessing the climate sensitivity to changes in the carbon dioxide concentration.     

Field investigations of the flow,partly covered by ice,in the lower pool of a hydrosystem during the passage of release waves

The hydrodynamic regime of water flow in the lower pool of a hydrosystem during winter releases is analyzed on the basis of field experiments. Measurement data on the velocities of currents and variations in water surface level are presented, these data being necessary for modeling bed deformations in non-steady-state open flows under the conditions of ice jam formation due to the effect of release wave on the ice cover in the hydrosystem lower pool.     

The effect of vibrations in the Zhigulevskii Hydropower Structure on soils in the nearby territories of Tolyatti City

The Zhigulevskii Hydropower Structure is used as an example to study the vibration impact of a dam on the soils of the coastal zone in the upper and lower pools. The effect of vibration of the hydropower structure on soils composing the shore in the nearby territory was evaluated on the qualitative level. The analysis of seismic monitoring data allowed the authors to conclude that the specific features of the seismic regime of the territory both during spring releases and in dry period are governed by the regime of hydropower structure operation.     

Significant features of the calendar of the late Pleistocene glacial cycles

Comparison of the δD deuterium record in the ice cores at the Antarctic Vostok and Dome C stations with the δ¹⁸ oxygen isotope in bottom oceanic sediments has elucidated the boundaries of glacial cycles in the late Pleistocene and revealed their inner symmetry: the longer the cycles, the more distant they were from the interglacial that occurred approximately 400 kyr ago. The symmetry is also manifested in the reversal of the sawtooth sequence of the cycles in that period. Wavelet analysis shows that symmetry was induced by amplitude modulation of climate oscillations on the precession and obliquity time scales and by frequency modulation on the scales of the eccentricity of the Earth’s orbital motion around the Sun.     

Punctuated equilibrium of the surface above subglacial Lake Vostok in antarctica

Progress in understanding the surface dynamics above the subglacial Lake Vostok is achieved owing to use of the ICESat satellite laser elevation measurements, which enabled us to determine surface fluctuations with precision up to 3 cm. A new idea on punctuated equilibrium of the surface above Lake Vostok is elaborated; this idea is concluded in irregular, sharp vertical displacements of the ice surface by up to 40 cm. Deformation of the surface is accompanied with a common raising or lowering, and with local vertical displacements up to 20 cm in amplitude. It has been proved experimentally that snow transport on the surface above the lake causes only redistribution of snow and forms fractal structures that do not have any effect on surface deformation. The form of the surface is not an inclined plane due to many bends that are particularly related to ice flowing on the lake water area.     

Changes in the mass balance of the Antarctic Ice Sheet over 50 years

The mass balance of the Antarctic Ice Sheet has been calculated based on instrumental estimates of the grounded ice discharge and snow accumulation data. The boundaries and sectional areas of the main ice catchment basins in West and East Antarctica have been determined, and the data on the grounded ice discharge and snow accumulation in these basins have been systematized. The intensity of accumulation and ablation processes in Antarctica has noticeably increased over the last 50 years. The mass balance of the ice sheet in East Antarctica has been and remains positive, while in West Antarctica it was positive in the middle of the last century and has become negative by now. The mass balance of the entire Antarctic Ice Sheet has been and remains positive, while the mass growth has noticeably decreased over the last 50 years.