Tidal oscillations in the Caspian Sea

Long-term hourly data from 12 tide gauge stations were used to examine the character of tidal oscillations in the Caspian Sea. Diurnal and semidiurnal tidal peaks are well-defined in sea level spectra in the Middle and South Caspian basins. High-resolution spectral analysis revealed that the diurnal sea level oscillations in the Middle Caspian Basin have a gravitational origin, while those in the South Caspian Basin are mainly caused by radiational effects: the amplitude of diurnal radiational harmonic S₁ is much higher than those of gravitational harmonics О₁, P₁, and K₁. In the North Caspian Basin, there are no gravitational tides and only weak radiational tides are observed. A semidiurnal type of tide is predominant in the Middle and South Caspian basins. Harmonic analysis of the tides for individual annual series with subsequent vector averaging over the entire observational period was applied to estimate the mean amplitudes and phases of major tidal constituents. The amplitude of the M₂ harmonic reaches 5.4 cm in the South Caspian Basin (at Aladga). A maximum tidal range of 21 cm was found at the Aladga station in the southeastern part of the Caspian Sea, whereas the tidal range in the western part of the South Caspian Basin varies from 5 to 10 cm.     

Ostracod communities in the Caspian Sea

A total of 15 communities of ostracods have been recorded based on the dominant species in the bottom sediments sampled at 204 stations in the Caspian Sea. The distribution of the communities is determined by the bathymetric zonality of the sea, the currents, the topography of the water mass boundaries, the hydrochemical parameters of the water, the continental runoff, and the concentrations of O₂ and C_org in the water and sediments.     

Diatomaceous oozes of the Middle Caspian Sea

Ten cores taken by a gravity corer from an area 5 × 5 km in size at the foot of the western slope of the Derbent Basin recovered uniform sections composed of variegated clotted diatomaceous oozes and soft gray clays with hydrotroilite-enriched spots, lenses, and laminae, the abundance of which increases downward. The diatom assemblages indicate a strongly freshened basin, which was replaced in the Holocene (Novocaspian time) by the brackish-water and then present-day saline sea. The grain-size composition of the sediments was determined by the gravitational deposition of suspended particles and by the near-bottom currents. The latter likely promoted the concentration of diatom frustules and accumulation of diatomaceous oozes.     

Tsunamis in the central part of the Caspian Sea

This paper describes the geotectonics of the Caspian Sea basin and the seismicity of its central part. The seismicity analysis enables us to identify the most probable zones of tsunami generation. We also present a brief review of the historical records of tsunamis in the Caspian Sea. In order to estimate the tsunami risk, we used the method of numerical hydrodynamic simulation while taking into account the real topography of the Caspian Sea. The computation of the wave field for the possible tsunamis occurring in the central part of the Caspian Sea allowed us to estimate the maximum expected heights of the waves along the coast of the CIS countries (Russia, Azerbaijan, Kazakhstan, and Turkmenistan). On the basis of the earthquake statistics in the region and the results of numerical experiments, we show that the extreme wave heights can reach 10 m at certain parts of the coast. Such extreme events correspond to extended (up to 200 km) seismic sources with M _S ～ 8 and a recurrence period of T ≈ 1600 years. The tsunami wave heights are expected to be as high as 3 m for sources of lesser extent (<50 km) with earthquake magnitudes of M _S ～ 7 and a recurrence period of 200 years.     

On vertical particle fluxes in the Caspian Sea

The first results of studies of vertical fluxes of sediment particles using the sediment traps at the Trans-Caspian section are presented. The flux values and distribution regularities are established. The fluxes of particles forming the sediment are also determined. The intra-annual variability in the fluxes corresponds to the seasonal variability of the biological activity. Above the northern slope of the Derbent Basin, the maximum vertical fluxes are recorded in the winter, which is caused by the intensification of the near-bottom currents.     

From the Geophysical Contrasts of the Caspian Sea to Morphogenetic Differences of Caspian Seals

Izvestiya, Atmospheric and Oceanic Physics - This paper proposes an approach to differentiating the Caspian seal population into separate subpopulations. The Caspian seal, despite the island nature...     

Age of Khvalynian transgressions in the Caspian Sea region

As follows from a geomorphologic analysis of the Khvalynian sediments in the North Caspian region, radiocarbon dating of their molluskan and plant remains provided more or less reliable age estimates, according to which the Khvalynian transgression occurred approximately 11–20 ka B.P. This value corresponds, however, to the terminal transgressive-regressive phase of the latter, i.e., rather to the Late Khalynian transgression than to its Early Khvalynian peak. It is inferred that the high terraces that formed during the maximal Early Khvalynian transgression are unambiguously older, being 70 to 40 ka in age.     

Mineral composition of sedimentary matter in the Caspian Sea

Data on the mineral composition of sedimentary matter and its fluxes in the sediment system of the Caspian Sea are presented. River runoff, aerosols, particulate matter from sediment traps, and the upper layer (0–1 cm) of bottom sediments are considered. The contents of detrital minerals (quartz, albite, and K-feldspar), clay minerals (illite, chlorite, and kaolinite), and carbonates (calcite, Mg-calcite, dolomite, aragonite, and rhodochrosite) are determined. Gypsum was found in bottom sediments but is absent in the other object of the sediment system.     

Metal Concentrations in the Coastal Fauna of the Caspian Sea

Ocean Science Journal - Metal concentrations were measured in predominant coastal fauna of the Caspian Sea including six macro-invertebrates (Mnemiposis leidyi, Balanus improvisus, Pontogammarus...     

水下滑翔机海上试验研究

介绍了水下滑翔机工程样机"海翔1"号2015年在南海的海上试验情况,包括试验对象、试验海区、试验步骤和试验数据分析等。本次试验最大下潜深度达到503.7 m,最大垂直速度为0.15m/s,最大水平航速为0.33 m/s,水中航行里程总计41.2 km。在4级海况下完成了通信定位、数据传输、布放与回收作业,搭载了CTD、叶绿素和溶解氧浓度传感器进行海洋环境参数测量,获得了500 m深度剖面内的温度、电导率、叶绿素浓度和溶解氧浓度参数信息。本次海上试验为水下滑翔机产品设计定型和示范应用奠定基础。     

Field Measurements of Sea Currents on the Mangistau Shelf of the Caspian Sea

Oceanology - The pilot Kazakhstan–Russia project provided the first systematic data in a long time on coastal currents in one of the least studied areas of the Caspian Sea, namely the...     

俄罗斯里海深部构造和含油气性

1957-2004年间俄罗斯科学院海洋研究所在亚速海、黑海和里海完成的地震测深-折射波法（гC3-мпB）海洋地震研究工作提供了大量有关其深部构造的信息。在离震源不同距离记录到的震波场的分析使我们查明了来自地幔顶部、结晶基底和沉积盖层内部主要岩层的折射波和广角反射波。     

Stable Isotopic Composition of Particulate Organic Carbon in the Caspian Sea

The data on the isotopic composition of particulate organic carbon (δ¹³C_POC) in the Caspian Sea water in summer–autumn 2008, 2010, 2012, and 2013 are discussed in the paper. These data allowed as to reveal the predominant genesis of organic carbon in suspended particulate matter of the active seawater layer (from 0 to 40 m). The δ¹³C_POC =–27‰ (PDB) and δ¹³C_POC =–20.5‰ (PDB) values were taken as the reference data for terrigenous and planktonogenic organic matter, respectively. Seasonal (early summer, late summer, and autumn) variations in the composition of suspended particulate matter in the active sea layer were revealed. A shift of δ¹³C_POC towards greater values was seen in autumn (with a slight outburst in the development (bloom) of phytoplankton) in comparison with summer (with large accumulations and an extraordinary phytoplankton bloom confined to the thermocline area). The seasonal dynamics of autochthonous and allochthonous components in the suspended particulate matter of the Middle and Southern Caspian Sea was studied with the use of data on the concentration of particulate matter and chlorophyll a, the phytoplankton biomass and the POC content.     

The Caspian Sea shelf during the pleistocene regressive epochs

During the Pleistocene regressive epochs, the Caspian Sea shelf became entirely (the Atel and Mangyshlak regressions) or partly (the Cheleken and Enotaevka regressions) exposed, which was accompanied by a change in the relief formation and sedimentation settings in the drained areas. The adjacent offshore areas were subjected to the transformation of the seawater salt composition, the temperature regime, and the biotic communities. The sea level falls during the Caspian Sea regressions were accompanied by large-scale environmental changes: the desiccation of spacious sea bottom areas, transformations of the landscapes and the relief formation and sedimentation settings, alterations of the seawater??s salt composition in the offshore areas, and the transformation of the biotic communities. The largest regressions were characteristic of the Tyurkyan, Bakuan-Khazarian, Khazarian-Khvalynian (Atel), and post-Khvalynian epochs. The shelf became entirely exposed (234 000 km²) during the maximal Atel and Mangyshlak regressions. During the Cheleken and Enotaevka regressions, the shelf was half drained. The epochs when the Caspian shelf was entirely exposed were marked by different climatic events in the Caspian Sea region and the adjacent glacier-affected areas of the Russian Plain. In general, the main regressive epochs correspond to interglacials on the Russian Plain, although this correlation was much more complex.     

On the nature of the Khvalynian transgression of the Caspian Sea

This paper presents a reconsideration of the hypothesis that the Khvalynian transgression of the Caspian Sea resulted from an abundant inflow of meltwaters from Siberian proglacial lakes through the Aral Sea and via the Uzboi channel and may be considered as a prototype of Noah’s Flood. A thorough analysis of the evidence suggested by the proponents of this hypothesis revealed a lack of factual substantiation; there are no facts indicating the existence of the Aral flow-through lake or of the Siberian proglacial water supply to the Caspian Sea. The spatial distribution of the mollusk fauna provides no support for the view that the Khvalynian transgression was essentially influenced by thawing of ice sheets on the Russian Plain. The Khvalynian transgression, though geologically short-term, could not be an analogue of Noah’s catastrophic flood. The sea level rose at a rate of a few centimeters per year for a few thousand years; this interval covered the lifetimes of many generations of the Caspian coast inhabitants. The Khvalynian water overflowing via the Manych Strait into the Pontian basin provided an even smaller influence. It resulted in flooding of the middle part of the Black Sea shelf, in a 30-m sea level rise, and in a water salinity increase by 5‰.     

Late pleistocene-holocene ostracod assemblages of the Northern Caspian Sea shelf

Analysis of the ostracod assemblages and the distribution of benthic foraminifera Ammonia beccarii in the core section GS 194-08-1 recovered at a depth of 7.5 m near the Volga delta front showed changes in environmental conditions in response to sea-level fluctuations. The pre-Novocaspian ostracod assemblage reflects the conditions that were dominant during the Late Khvalynian transgression, with a depth of about 20–30 m, and a salinity range of 12–13‰. The Early Novocaspian sediments contain an ostracod assemblage that represents a deeper water environment compared to the present, with an inferred depth of 12–16 m. The faunas from the younger Novocaspian sediments with abundant monospecific populations of Cyprideis torosa and co-occurring benthic foraminifera Ammonia beccarii represent modern-like environmental conditions.     

Hydrocarbons in the Surface Layer of Bottom Sediments in the Northwestern Caspian Sea

The paper presents research results on the concentrations and compositions of aliphatic and polycyclic aromatic hydrocarbons in the surface layer of bottom sediments in the Northwestern Caspian Sea (2014) and compares them to data for sediments of the Middle and Southern Caspian (2012–2013). The seepage of hydrocarbons out of the sediment mass, resulting in abnormally high concentrations of aliphatic hydrocarbons per dry weight (up to 468 μg/g), as well as within the C_org composition (up to 35.2%), is considered the main source of hydrocarbons in sediments in the surveyed area of the Northern Caspian. This is also confirmed by the absence of any correlation between the hydrocarbon and C_org distributions, as well as by the transformed oil composition of high-molecular alkanes. The distribution of markers within polycyclic aromatic hydrocarbons points to a mixed genesis—petrogenic and pyrogenic—with prevalence of the latter. Unlike the shallow-water northern part of the Caspian Sea, the content and composition of hydrocarbons in deep-seated sediments are affected by facial conditions of sedimentation and by matter exchange at the water–bottom interface. Therefore, despite high C_org concentrations (up to 9.9%), sediments in deep-water depressions are characterized by a quite low concentration of aliphatic hydrocarbons (52 μg/g on average; 0.2% of C_org) with prevailing natural allochthonous alkanes.     

Synoptical three-dimensional circulation of the upper layer of the Caspian Sea

A non-stationary, three-dimensional model of the circulation of the upper active layer in the Caspian Sea is presented. Cited are the results of calculations characterizing the spatial structure of currents arising from the effect of synoptical atmospheric processes. Numerical experiments show that the scheme used provides for appropriate solution accuracy and calculation stability.UDK 551.465.42 (262.81)     

Satellite observations of surface manifestations of internal waves in the Caspian Sea

Results of satellite observations of surface manifestations of internal waves in the Caspian Sea are presented. It is proposed that the possible cause of generation of the revealed internal waves is uninodal seiches with a nodal line located in the vicinity of the Apsheron Sill. The basic parameters of internal waves in the Caspian Sea, having the form of classical soliton trains, are determined. Seasonal variability of surface manifestations of the internal waves is revealed. The horizontal current velocity of the solitons is assessed. According to the estimation, velocity is about 0.2 m/s, which is sufficient for wind ripple modulation.     

鄂霍茨克海的超长柱状剖面

大部分俄罗斯考察船采集的海洋沉积物柱状剖面的长度,通常都不超过5～6m。国外使用的活塞取样管,在软泥中能取到20～28m长的岩心。法国制造的“卡利普索(KaJIHIIin-co)”系统是一个超长活塞取样管,其外径为127mm。使用这种设备可以采集长达50～60m的底质柱状剖面。