Nonlinear effects manifested in infrasonic signals in the region of a geometric shadow

Nonlinear effects manifested in infrasonic signals passing through different atmospheric heights and recorded in the region of a geometric shadow have been studied. The source of infrasound was a surface explosion equivalent to 20–70 t of TNT. The frequencies of the spectral maxima of infrasonic signals, which correspond to the reflections of acoustic pulses from atmospheric inhomogeneities at different heights within the stratosphere-mesosphere-lower thermosphere layer, were calculated using the nonlinear-theory method. A satisfactory agreement between experimental and calculated data was obtained.     

The origin and age of the Alpha-Mendeleev and Lomonosov ridges in the Amerasia Basin

The results of the bathymetry simulation indicate the emplacement of the Mesozoic Arctic plume into the lithosphere of the Alpha-Mendeleev and Lomonosov ridges. The study also presents a model of the thermal subsidence to the asthenosphere. The calculated coefficients are compared with those obtained for the Greenland-Iceland and Iceland-Faeroe ridges, which were formed in response to hotspot activity. It was shown that the coefficients of the thermal subsidence in the central part of the Alpha-Mendeleev and Lomonosov Ridges are similar to those calculated for the Greenland-Iceland and Iceland-Faeroe ridges. This indicates the thermal regime of the subsidence of the Alpha-Mendeleev and Lomonosov ridges since the Early Miocene and the increased influence of the Arctic plume on the ridge genesis. The ridges are interpreted to have formed over a broad geological timeframe, from the late Cretaceous to the Cenozoic. A geothermal method, which is highly informative in terms of the age of the lithosphere, provides better constraints on the timing of ridge formation. The age estimates for the Alpha-Mendeleev (97–79 Ma) and Lomonosov ridges (69–57 Ma) derived from the geothermal data allowed us to draw a convincing conclusion about the genesis of these ridges.     

Scenarios of nonlinear wave transformation in the coastal zone

On the basis of field experiments and numerical modeling, we show that coastal zones are classifiable according to manifestations of wind wave nonlinearity, which herein is recognized as periodic energy exchange between the first and second nonlinear wave harmonics depending on the average bottom slope and the Iribarren and Ursell numbers. The results offer a basis for developing vulnerability criteria for the coastal zone taking into account its nonlinear dynamics.     

Space-time variability of the field of mechanical energy transfer from the atmosphere to the Indian Ocean

An analysis of the spatial and temporal variability of the field of mechanical energy transfer (MET) from the atmosphere into the ocean is based on a separate numerical simulation of evolution for the terms of source function for a wind-wave model conducted in the Indian Ocean area for the period 1998 to 2009. The MET field is described by two integral values calculated per unit area: the total rate of energy flux from the wind to waves, I _E (x, t), and the rate of energy-loss flux for the wind waves, D _E (x, t). To solve this problem, the wind field W(x, t) is used, downloaded from the NCEP/NOAA archive [1], and the fields I _E (x, t) and D _E (x, t) were calculated using the numerical model WAM [2] with the modified source function proposed in [3]. Maps for the fields I _E (x, t) and D _E (x, t) were obtained by calculations with different scales of the space-time averaging, extreme and average values of the MET were found, seasonal and interannual variability was estimated, and the 12-year trend for several mean quantities was obtained.     

Interference of the mechanisms of influence that weak extremely low-frequency electromagnetic fields have on the human body and animals

This review is devoted to the problem of interference between the mechanisms of biological action of natural and artificial electromagnetic fields (EMFs) for different levels of the organization of life. We discuss the problem of specific and nonspecific responses of the human body and animals to the action of EMFs on cellular and organismal levels.     

Estimating climate changes in the northern hemisphere in the 21st century under alternative scenarios of anthropogenic forcing

Possible changes in the climate characteristics of the Northern Hemisphere in the 21st century are estimated using a climate model (developed at the Obukhov Institute of Atmospheric Physics (OIAP), Russian Academy of Sciences) under different scenarios of variations in the atmospheric contents of greenhouse gases and aerosols, including those formed at the OIAP on the basis of SRES emission scenarios (group I) and scenarios (group II) developed at the Moscow Power Engineering Institute (MPEI). Over the 21st century, the global annual mean warming at the surface amounts to 1.2?C2.6°C under scenarios I and 0.9?C1.2°C under scenarios II. For all scenarios II, starting from the 2060s, a decrease is observed in the rate of increase in the global mean annual near-surface air temperature. The spatial structures of variations in the mean annual near-surface air temperature in the 21st century, which have been obtained for both groups of scenarios (with smaller absolute values for scenarios II), are similar. Under scenarios I, within the extratropical latitudes, the mean annual surface air temperature increases by 3?C7°C in North America and by 3?C5°C in Eurasia in the 21st century. Under scenarios II, the near-surface air temperature increases by 2?C4°C in North America and by 2?C3°C in Eurasia. An increase in the total amount of precipitation by the end of the 21st century is noted for both groups of scenarios; the most significant increase in the precipitation rate is noted for the land of the Northern Hemisphere. By the late 21st century, the total area of the near-surface permafrost soils of the land of the Northern Hemisphere decreases to 3.9?C9.5 10⁶ km² for scenarios I and 9.7?C11.0 × 10⁶ km² for scenarios II. The decrease in the area of near-surface permafrost soils by 2091?C2100 (as compared to 2001?C2010) amounts to approximately 65% for scenarios I and 40% for scenarios II. By the end of the 21st century, in regions of eastern Siberia, in which near-surface permafrost soils are preserved, the characteristic depths of seasonal thawing amount to 0.5?C2.5 m for scenarios I and 1?C2 m for scenarios II. In western Siberia, the depth of seasonal thawing amounts to 1?C2 m under both scenarios I and II.     

Terrigenous pyroclastic matter as a source of dissolved calcium in the ocean

It has been found experimentally that the intensity of the leaching under the interaction of volcanic ash and seawater decreases as Ca > Mg > Si, and the mobilization of calcium and magnesium is more intense compared to silicon by factors of 30?C70 and 20?C50, respectively. Calcium and magnesium supplied to seawater owing to the halmyrolysis of the terrigenous pyroclastic matter may then interact with the products of organic matter oxidation to fix the free carbon dioxide in the form of autochthonous carbonates. It was shown that the halmyrolysis of terrigenous pyroclastic matter could not provide the complete immobilization of the autochthonous CO₂ produced in the ocean by the oxidation of organic matter. Thus, some other sources exist for the reactive silicates of calcium and magnesium, and these might probably be the silicates of the continental runoff of solid substances.     

Observational data assimilation in the problem of Black Sea circulation and sensitivity analysis of its solution

The problem of the variational data assimilation of the sea-surface temperature for the model of the Black Sea dynamics has been formulated and numerically studied to reproduce surface heat fluxes. An analysis of sensitivity of the optimal solution to errors in observation data has been conducted. The results of numerical experiments have been presented.     

Peculiarities of the rare-earth element distribution in the modern bottom sediments of the White Sea and the lower reaches of the Severnaya Dvina River

The study of the rare-earth element (REE) systematics in the modern bottom sediments of the White Sea and the lower reaches of the Severnaya Dvina River showed that they were derived by the simple mixing of the detrital material from two geochemically contrasting provenances: the Kola-Karelian geoblock almost completely consisting of Archean rocks and the northwestern Mezen syneclise made up of the Upper Vendian, Paleozoic, and Mesozoic rocks. This is best manifested by the changes in ?_Nd(0). In terms of the Gd_N/Yb_N and Eu/Eu*, most of the studied samples are comparable with the Post-Archean craton complexes, some of which resemble the average composition of the Archean mudstone. Based on the ΣREE and La_N/Yb_N, the modern bottom sediments are subdivided into two groups: (1) those close to basalts and granites and (2) those approximating common sedimentary rocks. From the lower reaches of the Pinega River to the Tersky coast, the maximal average (La/Yb)_RPSC, (Gd/Yb)_RPSC, La_N/Yb_N, and Gd_N/Yb_N ratios were determined in the samples taken at the boundary of Dvina Bay with the Basin, i.e., in the sediments with the highest content of the pelitic component. In general, the geochemical composition of the modern bottom sediments of almost the entire White Sea area was defined by input of the eroded products of the mature continental crust with the Severnaya Dvina River, the main river of the region. Such a setting, when the formation of the sediments in a peri- or intracontinental marine basin is controlled by one large river system, presumably may be propagated to the sedimentation in the Laptev Sea, the eastern Kara Sea, the Bay of Bengal, and other basins.     

Ekman Convective Layer Flow of a Viscous Incompressible Fluid

Analytical solutions for generalizing the Ekman stationary flow of a viscous incompressible fluid in an infinite layer are obtained. The solution of an overdetermined system of the Oberbeck–Boussinesq equations is considered. It is suggested to use a class of exact solutions for this problem. It is shown that the structure of the solutions allows one to preserve the advective derivative in the heat-conductivity equation; this makes it possible to model the stratification of the temperature and pressure fields and describe the oceanic countercurrents.