Hydrochemical structure of the waters in the eastern part of the Laptev Sea in autumn 2015

The study of the Laptev Sea was a part of a comprehensive program for investigating Arctic seas during the cruise 63 of the R/V Akademik Mstislav Keldysh. On a transect along 130° E (September 8–14, 2015) from the estuary area of the Lena River on the traverse of the city of Tiksi to the continental slope (over 700 km), water samples were taken to study the hydrochemical structure of waters and the influence of the Lena River flow. From the obtained data, it was found that the effect of fresh water on the sea surface layer was very high and can be traced to a great distance from the river delta. An unconservative distribution of some hydrochemical parameters in the mixing zone was recorded. The concentration of nutrients in the surface layer, and a high turbidity can serve as limiting factors in the development of the phytoplankton community.     

Hydrochemistry of the Tumen River Estuary,Sea of Japan

The hydrological and hydrochemical parameters of the Tumen River estuary were collected at 13 stations in May and October 2015. Vertical temperature, conductivity, dissolved oxygen, chlorophyll fluorescence, and turbidity profiles were obtained. Water was sampled from the surface and bottom layer. The water samples were analyzed for major ions, pH, salinity, concentrations of dissolved oxygen, major nutrients, dissolved organic carbon, humic matter, and δ¹⁸О and δD isotopes. This estuary is attributed to microtidal type with a flushing time of about 10 h. A phytoplakton bloom occurred in the top layer of the estuary. For surface horizons, the hydrochemical parameters show a linear correlation with salinity. In the bottom horizons, all these parameters, except for major ions and δ¹⁸О and δD isotopes, reveal substantial nonconservative behavior. The nonconservative behavior of the hydrochemical parameters in the bottom waters was mainly caused by degradation of the phytoplankton biomass at the water/sediment interface. Hypoxic conditions were established in the bottom waters of the estuary in May.     

Hydrochemical variability in the surface mixed layer along the drift path of the North Pole 35 station

The variability of the phosphates, silicates, alkalinity, oxygen, CO₂ pressure, salinity, and temperature in the surface mixed layer (SML), as well as the variations of its thickness along the drift passage of the North Pole 35 station, are considered. The station drifted over the Nansen Basin mainly eastwards from ??105 to ??30° E. The surveys were performed from October of 2007 till June of 2008 at three-day intervals. The SML parameters are mainly determined by the advection and mixing with the underlying waters. The analysis of the hydrochemical variability shows that the surface waters at the eastern and western areas of the drift are of different origins. The waters of the eastern area were subjected to the impact of riverine runoff. These waters were spread westwards. The fraction of riverine waters in the eastern area amounts to 3%. In the western area of the drift, presumably transformed Atlantic waters were observed, which spread eastwards from the Fram Strait. The drift path of the station crosses the boundary of the water masses near 85° N and 45° E.     

One-dimensional nonstationary model of vertical exchange in the Black Sea with regard for the mechanism of winter convection in the surface layer

We construct a one-dimensional nonstationary isopycnic model of vertical exchange in the Black Sea with regard for the processes of draining and transformation of waters of the Sea of Marmara (or “plume”), vertical diffusion, and the action of winter convection in the upper layer. It is assumed that mixing in the basin is local in space and time and that the winter wind action remains constant from year to year in the analyzed version of the model. The temperature of the upper mixed layer introduced to simulate the winter conditions is regarded as the principal external variable factor. Within the framework of the accepted restrictions, the model enables us to study the annual and interannual variability of the thermohaline characteristics and hydrochemical parameters in the water column of the sea. As an example, we perform the numerical analysis of the periodic action of external thermal conditions on the characteristics of the system with a period of six years. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 3–21, September–October, 2006.     

Spatial features of tidal variability of the hydrological and hydrochemical characteristics in the Northern Dvina River mouth area during the winter low-water period

The paper considers tidal effects on the formation of the hydrological and hydrochemical characteristics of the mouth of the Northern Dvina River in the presence of ice cover were considered. The results of natural surveys at the river delta and near-mouth area in March 2014 were analyzed. No surveys as such were performed in winter formerly. It was found that short-term variations of flow rates during the winter low-water time might be traced at 85–95 km from the seaward border of the delta. The tidal effects upon the short-term variability of hydrochemical parameters appeared at 70 km from the delta seaward border. The tidal variations of all the considered parameters were most intense in the mixing zone of riverine and marine waters at the delta.     

Specific features of the vertical distribution of elements of the main biogenic cycles in waters of the Northwest shelf of the Black Sea

We study specific features of the vertical distribution of elements of the main biogenic cycle in the upper layers of waters on the northwest shelf of the Black Sea in spring and autumn and the correlation between the specific features of the vertical distributions of hydrochemical and hydrological characteristics. It is shown that the location of the halocline always specifies the location of the chemocline, whereas the effect of the thermocline on the distribution of hydrochemical characteristics is ambiguous. The vertical distribution of the hydrochemical parameters can be homogeneous in the presence of the seasonal thermocline. At the same time, in its absence, one may observe significant vertical gradients in the distributions of hydrochemical characteristics inside the upper mixed layer.     

Estimating the characteristics of the vertical turbulent viscosity in the upper 200-m layer of the Black Sea

The influence of high vertical velocity gradients in the Black Sea Rim Current on the intensity of the vertical turbulent exchange is demonstrated on the basis of numerical modeling based on CTD data. The vertical turbulent exchange is confirmed by the anomalous distribution of the hydrochemical parameters in the redox layer. A system of equations for the kinetic energy of the turbulence and dissipation rate (k-? model) is used for the calculation of the coefficient of the vertical turbulent viscosity (diffusivity).     

Identification of local upwelling zones in the Bering Sea using hydrochemical parameters

Based on the data for the oxygen in the surface layer of the Bering Sea, the areas of pronounced undersaturation (down to 75–80% and below) were distinguished in the surface layer of the Bering Sea. The low percentage values as such of the oxygen saturation might be sustained at the sites of quasi-stationary upwellings. However, in this case, the surface layer should be characterized by decreased temperature and increased salinity as related to the surrounding waters, as well as by increased concentrations of nutrients (phosphates, nitrates, and silicon). The corresponding tests showed that most of the distinguished “patches” of oxygen undersaturation were verified by the oceanological parameters; i.e., these were local upwellings. Some of them were studied quite thoroughly (even with the mechanisms proposed for the formation of steady water lifting), particularly in the area of the Aleutian Islands. However, there are some poorly studied areas (so-called questionable ones) at which the low oxygen content is not confirmed by the hydrochemical parameters (plainly, they are not available); this requires more profound and detailed study.     

Short-Term Variability of Hydrological and Hydrochemical Characteristics of the Kyanda Estuary in Onega Bay,the White Sea (July 28–August 15, 2016)

The paper presents information on joint research of the short-term (tidal and synoptic) variability of the hydrological and hydrochemical parameters during the summer 2016 low-water period in mesotidal estuary of the Kyanda River, which flows into Onega Bay, the White Sea. It is demonstrated that semidiurnal, diurnal, and synoptic variations of almost all observed parameters are significant and differ notably along the estuary.     

Isothermal,mixed, and barrier layers in the subtropical and tropical Atlantic Ocean during the ARAMIS experiment

The ARAMIS project (Altimétrie sur un Rail Atlantique et Mesures In Situ) provides a long term survey (2002–2008) for thermohaline structures in the tropical Atlantic Ocean. Here, these data are used to address questions regarding the existence and formation of barrier layers. The analysis presented which uses different criteria to calculate isothermal layer depth and mixed layer depth, shows the sensitivity of different methods to a variety of variables. A 0.5 °C criterion for the isothermal layer and its equivalent in density change for the mixed layer are found to be the most adaptable due to their robustness. Barrier layers observed with ARAMIS data sets are in good agreement with climatologies and in-situ Argo floats along the route. Three systems of barrier layers are observed during the voyages. Their variability and formation as described in previous works concerned with the tropical Atlantic are analyzed. Different processes such as subduction, frontal activity, and precipitation are needed to explain their presence.     

Volume of the Ob Bay waters as a factor of the formation of the hydrochemical inhomogeneity

This report presents a new analysis of the results of two hydrochemical surveys over the Ob Bay in 2010 performed by the Institute of Fisheries and Oceanography (VNIRO) and the Institute of Oceanology (IO RAS). The unique world feature of the Ob River-Ob Bay system is shown. The water volume in the bay exceeds the average annual runoff of the Ob River, being somewhat under the total runoff of all the inflowing rivers. Because of this, the complete renovation of the waters in the bay requires a long time. The within-year distribution of the runoff is characterized by both the flood waters and those of the Ob River winter runoff characterized by much different hydrochemical parameters registered even in the course of summer surveys in the bay. This fact, but not the biological transformation of the waters, as assumed previously, is the primary cause of the variability of the water composition in the bay. The summer waters of the Ob River reach the sea-ward boundary of the bay only in the next spring, enter the Kara Sea with the spring flood, and form lenses of desalinated waters in the sea. The autumn expeditions by the IO RAS found that the waters in the lenses were quite similar to the autumn waters in the bay, although these were the Ob River waters of different years, which was disregarded formerly.     

Spatial and Temporal Variability of the Transformation of Dissolved Matter Runoff in the Mezen River Estuary

Oceanology - The spatial and temporal variability of the transformation of dissolved matter runoff in the Mezen River estuary is studied from data on comprehensive hydrological–hydrochemical...     

文登区浅层地下水化学演化与海水入侵研究

作者采用水化学演化图(hydrochemical facies evolution diagram,HFE-D)和海水入侵地下水质量指数(GQISWI)对山东威海文登区地下水的化学演化和海水入侵情况进行了分析.Piper图的结果表明文登区从北到南地下水的化学组成分别是Ca-HCO3、Ca-Mg-Cl、Na-Cl.HFE...     

The impact of mesoscale eddies on plankton dynamics in the upper ocean

A coupled QuasiGeostrophic mixed-layer ECOsystem model (QGECO) is used to investigate the impact of the underlying mesoscale eddy field on the spatial and temporal scales of biological production and on overall rates of primary productivity. The model exhibits temporal trends in the biological and physical fields similar to those observed in the North Atlantic; i.e. the mixed layer shallows in spring causing a rapid increase in phytoplankton concentrations and a corresponding decline in nutrient levels. Heterogeneity is produced in the mixed layer through Ekman pumping velocities resulting from the interaction of windstress and surface currents. This variability impacts on biological production in two ways. Firstly, spatial variations in the depth of the mixed layer affect the photosynthetically active radiation (PAR) availability and hence production rates, and secondly, eddy enhanced exchange between the surface water and those at depth bring additional nutrients into the euphotic zone. These processes result in significant spatial and temporal heterogeneity in the ecosystem distributions.Investigation of the spatial heterogeneity of the biological system finds variability to be significantly greater than that of the mixed layer. The relationship between the eddy field and the ecosystem is investigated. The structure and correlation of the biogeochernical fields change with time. The biological fields are found to have a shorter horizontal scale, but whiter spectrum than the underlying eddy field.Overwinter conditions are found to have a profound effect on the variability, size and timing of the following spring bloom event. Variations in the nitrate levels are primarily responsible for the variability in the biological system in the first year. In subsequent years the variation in the overwintering population is found to be dominant.     

Regularities of C<Subscript>org</Subscript> distribution in bottom sediments of the Russian part of the Sea of Azov

The principal regularities were ascertained for the spatiotemporal distribution of organic carbon in the water and bottom sediments of the Russian part of the Sea of Azov. The relationships between allo- and autochthonous organic matter in water and bottom sediments from different parts of the sea aquatic area were found. The behavior of organic carbon in the water-bottom sediments system was characterized as the effect of the variability of hydrochemical, biological, and hydrological factors ad processes.     

Simulation of the Atlantic Ocean seasonal variability, using a quasi-isopycnic model

The paper discusses the data derived from a numerical experiment on the ocean’s response (between the equator and 64°N) to the seasonal variability of the atmospheric forcing (wind and heat flux through the ocean surface). A multilayer (7 layers) non-linear model is used incorporating the upper mixed layer interacting with the internal layers in the regimes of entraining and subduction. The restructuring of the layer composition, the currents and temperature variability, as well as the alternation of the entrainment and subduction regimes are analysed. Translated by Vladimir A. Puchkin.     

Inter-annual variability of the hydrological-chemical characteristics in the north-western Black Sea shelf area over recent decades (1960–1990)

A number of significant hydrologicla and chemical parameters of the Black Sea shelf area have been identified and investigated: the inter-annual variability of the mean annual and seasonal (winter and summer) values of the air and seawater temperatures and salinity in the vicinity of Odessa; silicon and phosphate concentrations averaged over the north-western Black Sea shelf area (NWBS); discharges of the Danube and Dnieper rivers; mean surface and near-bottom oxygen concentrations in summer acquired through the analysis of the summarized data collected at three oceanographic stations occupied between Bolshoi Fontan and the Tendra isthmus from the early 1950s up to date. From these data, the variability of the areas subject to oxygen deficit in the near-bottom layer of the NWBS shelf during the summers of 1973–1994 has been assessed. Predominant oscillation periods and trends in the inter-annual variability of the studied parameters have been revealed and their relationship and climatic dependence has been demonstrated. Translated by Vladimir A. Puchkin.     

Hydrochemical features of the Kara Sea aquatic area in summer 2015

During cruise 65 of the R/V Akademik Mstislav Keldysh in the Kara Sea, three transects were executed: one eastwards from the Novaya Zemlya Archipelago and two in the St. Anna and Voronin troughs. It was noted that the continental runoff affected the entire surveyed aquatic area, even at the northern extremity of the Novaya Zemlya Archipelago. The transect along the St. Anna Trough showed the presence of a slope frontal zone overlaid at the surface by a desalinated layer. The Voronin Trough was characterized by sliding of slope waters. The hydrochemical parameters show that the surveys were carried out during a recession of biological activity of the waters and that the peak bloom was over by that time. The hydrochemical structure of waters conformed to early autumn conditions, but before the beginning of intense cooling of surface waters.     

Variability of suspended organic matter in the northwestern Black Sea

The peculiarities in the distribution pattern of the concentration of suspended organic matter (SOM) components were studied for the long-term period of 1979–1995. We have analyzed their seasonal, annual, and interannual variability in the surface water layer and in the photosynthetic water layer in the northwestern Black Sea. Four areas pertaining to different concentrations of SOM components were defined according to the effect of riverine discharge and of open sea water masses, i.e. western, northern, central, and eastern areas. We have found an increase in the concentrations of SOM components in the summer-autumn period in the late 1980s and early 1990s, with the highest values observed in 1992. The concentration of suspended organic carbon was estimated for the concentration of Chlorophyll a in the surface water layer. These calculations are based on the regression relationship between simultaneous measurements of these two parameters in situ. It was found that the seasonal interannual variability in the concentrations of SOM components was affected by the volume of riverine discharge, its run to the sea, and climatic shifts.