Impact of the winter cooling on the variability of the thermohaline characteristics of the active layer in the Black Sea

The influence of the winter atmospheric forcing on the interannual variability of the Black Sea’s active layer’s thermohaline structure during 1982–2008 is investigated. The results are based on the combined analysis of the hydrological measurements from a ship, satellite measurements of the sea’s surface temperature (SST), and the NCEP/NCAR reanalysis data for the surface air temperature (SAT). A high correlation between the variability of the winter mean SST/SAT and the thermohaline characteristics of the active layer during the following warm season was found. It is shown that the winter atmospheric forcing significantly affects the variability of the temperature, salinity, and density down to the 150–200 m depth, and this has to be considered in the analysis of the interannual and long-term variability of the Black Sea’s active layer.     

Methodology of the experimental study of the state of spent nuclear fuel on the bottom of arctic seas

A methodology of experimental simulation of the state of spent nuclear fuel that is situated on the sea bottom as a result of some catastrophes or dumping is developed. Data on long-term (more than 2000 days) experiments on the estimation of the ⁸⁵Kr and ¹³⁷Cs release rate from spent nuclear fuel (fragments of irradiated UO₂ pellets) were first obtained; these estimates prove the correctness of the hypothesis put forward by us in the early 1990s concerning an earlier ⁸⁵Kr release (by one order of magnitude higher than that of ¹³⁷Cs) as compared to other fission fragments in the case of the loss of integrity of a fuel containment as a result of corrosion on the sea bottom. The method and technique of the onboard ⁸⁵Kr and ¹³⁷Cs sampling and extraction (as well as the sampling of tritium, a product of triple ²³⁵U fission) and their radiometric analysis at coastal laboratories are developed. Priority data on the ⁸⁵Kr background in the bottom layers of the Barents and Kara Seas and the ¹³⁷Cs and ³H in these seas (state of 2003) are presented. Models necessary for the estimation of the dilution of the fission products of spent nuclear fuel and their transport on the bottom in accident and dumping regions are developed. An experimental method for the examination of the state of spent nuclear fuel on the sea bottom (1 expedition each 2–3 years) by the ⁸⁵Kr release into the environment (a leak tracer) is proposed; this release is an indicator of the destruction of a fuel containment and the release of products of spent nuclear fuel in the case of ²³⁵UO₂ corrosion in sea water.     

Role of the small-size fraction of mesozooplankton in the pelagic community of the northeastern part of the Black Sea in the autumn

The role of the small-size (SF; 0.1–0.5 mm) and large-size (LF; 0.5–20.0 mm) fractions in the biomass and abundance of mesozooplankton (0.1–20.0 mm) was assessed using the database of samples obtained during the cruises of RV Akvanavt in the northeastern Black Sea in November 2000 and October 2006. The mesozooplankton was collected by means of Juday nets (37/50, filtering gauze 160 μm) and Niskin bottles in two areas: (1) the shelf and continental slope (30–1480 m depth) and (2) the deep sea (depths of more than 1500 m). The plankton net was considerably less effective in collecting the SF of the mesozooplankton (by a factor of 30–36) than the Niskin bottles. When comparing the SF and LF, we estimated the abundance and biomass of the SF in the samples obtained with the Niskin bottles. The abundance of the SF in the deep-sea area was 2.5 times lower compared to the shelf and continental slope, and the LF abundance was 5.0 times lower in the same way. The abundance of the SF constituted 88% of the total mesozooplankton on the shelf and continental slope, and 78% in the deep-sea area. The biomass of the SF was higher as well on the shelf and continental slope. Meroplankton played a significant role in the SF zooplankton abundance (0.5 × 10³ + 0.16 ind. m⁻³) in this area. The SF grazing impact was 10% of the total mesozooplankton grazing on the shelf and continental slope, and 17% in the deepsea area. Appendicularia and nauplii of copepods had the greatest contribution to the mesozooplankton grazing among the SF group.     

Horizontal structure of the temperature field of the upper layer in the northwest part of the Tropical Atlantic

By using the data of observations over the spatial variability of the temperature field in the northwest part of the Tropical Atlantic carried out in a test range 400 × 400 miles in size with a horizontal resolution Δx ≈ 2 km and a vertical resolution Δ_z ≈ 0.5 m, we recorded quasiperiodic fluctuations of temperature with semidiurnal period in the subsurface layer. The internal baroclinic waves with the same period generated, most likely, on the northeast shelf of South America and propagating to the northeast are detected in the seasonal thermocline. The vertical fine structure of the temperature field has different intensities in the test range. The maximum levels of dispersions of temperature fluctuations are recorded on the boundary of the North Equatorial Countercurrent and the North Equatorial Current. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 44–52, November–December, 2006.     

A study on the polyculture of the algae, the shrimp and the crab

A study was made on the polyculture of the red algae Gracilaria tenuistipitata Chang et Xia f. Liui Zhang et Xia, f. nov. , the shrimp Penaeus penicillatus Alcock and the mud crab Scylla serrata (Forskal) . The photosynthesis of the algae produces the oxygen on which the shrimp and the crab breathe. The algae are the reproductive place of the organism for the food of the shrimp and the carb, also is the shelter of the shrimp and the crab. The shrimp and the crab regard the algae as the vegetable     

Mesozooplankton grazing during the Phaeocystis globosa bloom in the southern bight of the North Sea

During spring blooms 1998 and 1999, three complementary methods were used to evaluate the in situ feeding activities of the dominant copepod species of the Belgian coastal zone: gut pigment content analysis using HPLC, the ¹⁴C tracer method, and cell count experiments. The results obtained by all three methods consistently showed that Phaeocystis globosa is not an adequate food source for the spring copepods in the Belgian coastal zone. Our results demonstrated that, among the potential prey, copepods strongly selected diatoms and microzooplankton, and that these types of prey accounted for the major part of the ingested carbon. However, diatoms and microzooplankton ingestion did not always seem sufficient in terms of carbon to avoid food limitation. Comparison of clearance rates exerted on different potential prey types during the P. globosa peak with those before and after the P. globosa peak showed that the copepods' feeding pressure on diatoms was reduced during the P. globosa peak while that on microzooplankton was not. The low grazing pressure on P. globosa, together with the preferential grazing on diatoms, which reduces the competition for nutrients, and the predation on microzooplankton organisms, which reduces the microzooplankton grazing pressure on P. globosa cells, are likely to favour the P. globosa bloom in the Southern Bight of the North Sea.     

Unusual features of the distribution of Radon-222 in the bottom waters of the continental slope of the Mid-Atlantic Bight: Hydrodynamic implications

²²²Rn was measured in the near-bottom waters of the continental slope of the Mid-Atlantic Bight. Separate measurements of the ²²²Rn supported by dissolved ²²⁶Ra allowed the excess ²²²Rn that is derived from the underlying sediments to be distinguished. Measurements of production of ²²²Rn by the sediments were used to calculate fluxes of ²²²Rn from sediments that would be expected as a result of molecular diffusion. On the upper slope and on the lower slope excess ²²²Rn standing crops were, respectively, greater than and consistent with fluxes of radon from sediments by molecular diffusion as are typical of most ocean environments. On the middle slope, however, observed excess ²²²Rn concentrations and standing crops were significantly lower than what would be expected from the calculated fluxes from the underlying sediments. This unusual feature of low radon concentrations on the middle slope is referred to as the low-radon zone (LRZ). This LRZ was always present over several years and seasons, but was variable in intensity (excess-radon concentration and standing crop) and in location on the slope. Low concentrations of suspended particulate matter and low current velocities observed by others in the same region are consistent with low mixing as a possible cause of the LRZ. Radon profile shapes and recent work by others on near bottom mixing due to interactions between topography and internal waves, however, suggest that high mixing due to internal waves is a more likely cause of the LRZ.     

Peculiarities of the primary production process in the Kara Sea at the end of the vegetation season

Research was implemented from September 15 through October 4, 2011 in the Kara Sea along transects located southeastwards Novaya Zemlya, in the St. Anna Trough, the Yenisei River estuary, and the adjacent shelf. The concentration of chlorophyll a was the highest in the photic zone (0.05–2.30 mg/m³, on average, 0.80 ± 0.37 mg/m³). The maximal concentration of Chl a at most of the stations located in the water layer of 7–30 m. Integral primary production in the water column varied from 3.0 to 151.0 mg C/m² per day, on average, 37.2 ± 36.6 mg C/m² per day. The maximal rate of primary production at most of the stations has been observed for the surface layer of the water column. Within the upper mixed water layer, relative primary production was from 31 to 100% (on average, 77 ± 20%). The most productive zone was the waters along Yenisei transect. In the estuary and at the adjacent shelf, primary production was 50 mg C/m² per day, exceeding the range observed for other areas by 1.5–2.0 times. The concentrations of silica and nitrogen together with light regime and water temperature were the major limiting factors affecting the primary production rate in the Kara Sea in autumn.     

Interannual variability of the zooplankton on the shelf of the northeastern Black Sea in the autumn period

The variability of the mesozooplankton stock in the shelf pelagic communities was studied in the late summer and autumn of 2006–2008. The plankton community’s structure and distribution were described for the shoreward transect (Gelendzhik city vicinity). The indirect and direct effect of the ctenophores Mnemiopsis leidyi and Beroe ovata on the mesozooplankton community was studied. The long-term changes in the meso- and macroplankton communities of the Black Sea were analyzed for the period of 2001–2008. The effects of the climatic factors, the water mass circulation, and the factors’ interplay on the mesozooplankton dynamics were assessed. Despite the wide range of the environmental conditions, the stock biomass of Mnemiopsis leidyi appeared to be quite stable within the studied period.     

On the influence of the sea surface temperature on the carbon dioxide exchange with the atmosphere

The influence of the sea surface temperature (SST) on the carbon dioxide (CO₂) exchange with the atmosphere at different spatial and temporal scales, which has a multidirectional character, was studied. The initial data included the monthly averages of the CO₂ flux during the period of 1982–2011 at grid nodes of 4° by latitude and 5° by longitude, as well as the SST satellite data from January 1, 1982 to December 31, 2012 at the geographical grid nodes of 0.25° × 0.25°. Statistical models of estimation of the resulting global CO₂ flux were suggested on the basis of data on SST anomalies. It is demonstrated that the SST variations in the equatorial zone mostly control the interannual fluctuations of the resulting CO₂ flux in the ocean-atmosphere system.     

Modeling the seasonal variability of marine ecosystem in the region of the Central-Eastern Atlantic

A 3D eco-hydrodynamical model of high resolution (0.25° × 0.25°, 27 σ-levels) is used to simulate the seasonal variability of the ocean circulation and marine ecosystem in the Central-Eastern Basin of the North Atlantic including the Canary upwelling system. According to the model results, in the winter period, the “patches” of maximal phytoplankton and zooplankton biomass are often located in upwelling zones in the open ocean on the periphery of cyclonic eddies rather than in the coastal upwelling zones. In the summer period, when the phytoplankton biomass reaches maximal (in the annual cycle) values, the maxima of the phytoplankton are located in the coastal upwelling zones. As shown, there is no simple relationship between the nitrate distributions, on the one hand, and the phytoplankton and zooplankton ones, on the other hand.     

Formation of Thermocline in the Equatorial Zone of the Oceans

We study the formation of the vertical distribution of temperature in the upper layer of the oceans (0– 300m) at low latitudes (10°N-10°S) by using the nonlinear dependence of the vertical heat flow on the vertical temperature gradient with regard for the influence of the bulk absorption of solar radiation and heat sink on the temperature of water. The thermocline is formed under the condition that the modulus of temperature gradient attains values for which their subsequent increase leads either to insignificant variations of the heat flow or even to its decrease. We consider the possibility of solution of inverse problems for the evaluation of the heat-exchange coefficient and the parameter of the heat sink. For the Equatorial Atlantic considered as an example, we compare the theoretical results with the data of instrumental measurements.__________Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 10–16, November–December, 2004.     

Simulation of the impact of internal waves on the oxygen/hydrogen sulphide co-existence zone in the open part of the Black Sea

This paper focuses on the impact of periodic internal waves on the oxygen/hydrogen sulphide co-existence zone in the open Black Sea. The numerical model is based on a set of transport/diffusion equations governing the evolution of oxygen/hydrogen sulphide concentrations and considering the reaction between them. The wave velocity field is determined by solving a spectrum problem for preinertial period internal waves, using the characteristic vertical density profile for summertime. Via analysis of the model data, the influence of wave characteristics on the parameters of the O₂/H₂S co-existence zone has been assessed.Translated by Vladimir A. Puchkin.     

Approach to the geostrategy of the oceans: The case of the mediterranean

It is known that by the general ‘geostrategy’ for the oceans we mean the behaviour of countries of the world in defending their own vital economic interests as projected on different oceans. The means for protecting national interests can be economic, political, diplomatic or military. This paper dwells in particular on these last aspects, offering in the first part some useful reflections on the analysis of regional seas. The second part gives elements for the understanding of the complex Mediterranean situation where the East-West confrontation is accentuated by widespread economic, political, ideological and ethnic contrasts between coastal states. For these reasons this sea can be defined as one of the most unstable and belligerent regions in the world.     

Dynamics of the ice cover and peculiarities of the ice transportation of the sediments at the tidal flats of the Kandalaksha Gulf of the White Sea

Ten years of semistationary studies of the interaction of the ice cover and the coastal relief of the Kandalakhsa Gulf in the White Sea allowed us to reveal the peculiarities of these processes in the warm and cold years and the mechanisms of the origination of ice forms, including ice tents, which govern the character of the tidal flats. Three dynamic fast ice zones are distinguished by their geomorphological location, morphology, and ice dynamics. The dependence of the mechanisms and volumes of the enrichment of the fast ice in the sediments on the coastal zone??s relief was established. At the coast of the Kindo Peninsula (Velikaya Salma Strait), the ice mostly contains fine-sandy sediments. Coarser sediments, including boulders, are occasional and frozen into the ice at the contact of the fast ice and the bottom. At the expense of the ice??s spreading by 4?C6 times in the warm years and 2?C4 times in the cold years, several thousand tons of sediments mostly from the tidal flat??s surface (100?C700 m³ from 1 km of coast in the wide tidal flats and <50 m³ on the steep coasts) are delivered to the water area.     

The influence of geochemical processes in the near-bottom layer on the hydrochemical characteristics of the waters of the Sea of Japan

According to the results of the international expedition aboard the R/Vs Roger Revelle and Professor Khromov in the summer 1999, areas with low oxygen contents (below 210 μM/kg) and those with increased contents of dissolved inorganic carbon and phosphates were found that roughly coincided with one another. These areas are located near the bottom on the southwestern slope of the Tsushima Basin in the region of the Korea Strait and on the continental slope in the region of the Tatar Strait in the northern part of the sea at about 46° N. The set of hydrochemical data points to a high geochemical activity in the near-bottom layer of the areas noted. This activity is confirmed by direct observations of the composition of the interstitial water in the sediments collected in the northern part of the sea during the expedition of R/V Akademik M.A. Lavrent’ev in 2003. It was supposed that the main cause of the increased geochemical activity is the runoff of suspended and dissolved matter from the Korea and Tatar straits. In the areas mentioned, the near-bottom waters are characterized by low values of the nitrogen-phosphorus ratio (below 10), which is geochemical proof of the denitrification process occurring under the conditions of high oxygen concentrations characteristic of the Sea of Japan. Based on the value of the annual production in the Sea of Japan, a rate of denitrification equal to 3.4 × 10¹² gN/year was calculated. Hence, it is confirmed that the geochemical processes in the near-bottom layer have a direct influence on the spatiotemporal characteristics of the hydrochemical properties of the waters of the Sea of Japan.     

Modelling of the ecosystem on the shelf of the Republic of Guinea

Three mathematical models are considered: a two-dimensional model for calculating the concentration fields of the ecosystem components on the shelf of the Republic of Guinea, a pointwise model for the annual variation of the components, and a two predators-prey model. These models are used to study the effect of hydrodynamic conditions on the state of the shelf ecosystem and for research into the causes which distort the balance between marketable and unmarketable fish.Translated by Mikhail M. Trufanov.     

Analysis of the experimental compressibility of deep water marine sediments from the Gulf of Guinea

This study strives to analyze the compressibility of deep water marine sediments originating from the Gulf of Guinea. Our approach is multi-scaled and, on the macroscopic level, based on two equations which link the overburden effective stress with the liquidity index, the Biarez & Favre equation on the one hand, and the Burland equation on the other hand (after calculation of the ICL expression as a function of the I_L parameter). On the local level, the evolution of the microstructures is analysed and compared with GoG remoulded clay. Two additional observation techniques have been used, the scanning electron microscope and the mercury intrusion porosimetry.     

The effect of the vertical density structure on internal waves in the neighbourhood of the intertial period

With the latitudinal variability of the Coriolis parameter considered, the influence of the vertical density structure on the parameters of free internal waves is stuided. Numerical calculations are performed for Brunt-Väisälä frequency profiles characteristic of the four seasons of the year in the deep section of the Black Sea. Results of the analysis of the dependences of the wavenumber and group velocity on the frequency are presented, and the domain of application of thef-plane approximation is defined.Translated by V. Puchkin.