Vol 57, No 2 (2017)

To account for tidal variations in the regional climate of a water basin, we propose adding up the vertical eddy diffusivity, determined by wind and thermohaline forcings, and the diapycnal diffusivity, determined from the solution to the problem of the internal tidal wave (ITW) dynamics. This approach agrees with the approximation of “weak interaction” between turbulence of various origins. Then, the hydrothermodynamics equations are integrated with and without regard for ITW-induced diapycnal diffusion until a quasistationary solution is reached. Next we compare these solutions, found by using the 3D finite-element hydrostatic model QUODDY-4. This comparison shows that the contribution of tides to the formation of the Barents Sea climate in summer is not negligible with respect to certain hydrological characteristics. We present the fields of the dynamic topography of a free surface, surface current velocities, and seawater temperature and salinity at the depth of the pycnocline in the sea to illustrate the occurrence of tidal effects.

The work describes the creation of a new global climatology of short-wave radiation incoming to the ocean surface; the climatology is based on a new parameterization of short-wave fluxes. Advantages of the new parameterization are allowance for nonlinearity of the dependence of the atmospheric transmission factor on the height of the Sun under a clear sky and allowance for different morphological types of clouds under the overcast. It is shown that taking into account these factors leads to substantial differences in short-wave radiation fluxes in comparison to existing parameterizations.

The Weather Research and Forecast numerical model (WRF) with the dynamic Advanced Research WRF (ARW) solver was used to simulate the winter (January 2016) and summer (July 2015) atmospheric state over the North Atlantic with a high (15 km) spatial resolution. The quality of precipitation modeling was validated by remote sensing Global Precipitation Measurements (GPM) data and atmospheric ERA-Interim reanalysis. Nonhydrostatic and hydrostatic equations for the vertical velocity were additionally used to investigate their influence on the accuracy of the precipitation modeling results. It was shown that the model in this configuration satisfactorily reproduces the precipitation field. No evidence of hydrostatic approximation was revealed (over a simulation domain with a resolution of 15 km, simplified topography, and parameterizations of convection and microphysical processes).

A new approach to automatic solar disk state detection by all-sky images using machine learning methods is developed and implemented. The efficiency of the most widely used machine learning algorithms is analyzed. The effect of reducing the dimensionality of the feature space on the classification accuracy is estimated. The multilayer artificial neural network model has shown the best accuracy in terms of the true score. The operation result demonstrates the effectiveness of machine learning methods applied to solar disk state detection by all-sky images.

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.

Long-term studies in the Sea of Okhotsk (1986–2012) demonstrated that hyperiids account for a small portion of zooplankton, making up only from 1.0 to 5.3% by weight. The minimum hyperiid biomass was observed in the coastal zone. The hyperiid biomass in the open water shelf community increased from spring to autumn. In the Sea of Okhotsk, hyperiids are represented by ten species, among which the most abundant in the northern regions (mainly in Shelikhov Gulf) is Themisto libellula, while the most abundant in other regions is T. pacifica. The distribution of T. pacifica in different seasons showed that the maximum biomass was concentrated in the deep-water zone. The range of T. libellula in the Sea of Okhotsk is mostly limited to the Shelikhov Gulf, but in certain years its habitation area can expand. In warm years with low ice coverage, the maximum expansion of T. libellula to the west in the shelf zone of the northern part of the Sea of Okhotsk was observed. Since variability of salinity and temperature in the northern part of the Sea of Okhotsk may be fatal for the cryophilic stenohaline T. libellula species, forecasted changes in thermohaline circulation will make it possible to predict the population dynamics of this important species.

This work concerns the trophic web positioning of the alien crab Rhithropanopeus harrisii and other common marine invertebrate species and fishes in the benthic ecosystem of the shallows of Taman Bay, Sea of Azov. The base of the trophic web in this system is composed of phytoplankton, macrophytes (algae and marine grasses), and reeds that use atmospheric carbon for photosynthesis. Analysis of the isotopic composition of nitrogen and carbon has shown that although marine grasses are dominating primary producers in the shallows of the bay, primary consumers (such as Cerastoderma glaucum, Porifera gen. sp., Gammarus aequicauda, Deshayesorchestia deshayesii and Idotea balthica) only partially use this organic source; instead, they use a combination of different sources of primary production. It has been shown that the food source of the alien crab is primarily of animal origin. In Taman Bay, R. harrisii is on the same trophic level as other carnivores/scavengers: benthic fishes Syngnathus nigrolineatus, Gobius spp. and native crab Pilumnus hirtellus and shrimp Palaemon adspersus.

Synchronous measurement of the total suspended organic and mineral particulate matter, together with vertical sedimentary matter flux, carried out in various areas of Yarnyschnaya Inlet (Murmansk coast of the Barents Sea) and Chupa Inlet (Karelian coast of the White Sea) revealed that the seston organic component plays no part in sedimentation, being almost completely utilized in the water column, while the majority of mineral matter is transported out of the bay. The total amount of suspended matter and its components in the water column is estimated, as well as the total flux of sedimentary matter to the bottom of Chupa and Yarnyschnaya inlets.

Integrated geological and geophysical analysis of the anomalous magnetic field along with the previously unpublished profiles of Spanish expeditions onboard the R/V Hesperides and international databases of geomagnetic data processed in the context of the global tectonics concepts made it possible to identify paleomagnetic anomalies C11–C15 and compile the first map of the bottom geochronology of the Scan Basin. Unlike in earlier known publications, the paleoaxis of spreading does extend northeast, but approximately at an angle of 345°. According to calculations, spreading began 35.294‒35.706 Ma ago during chron C15r, and the spreading paleoaxis was abandoned 29.527‒29.970 Ma ago during chron C11n.2n. Thus, the destruction of the American–Antarctic bridge in the region joining the Bruce and Discovery banks with formation of oceanic crust in the Scan Basin started about 36 Ma ago. Regular spreading of the bottom has been continuing for about 6 Ma at a average rate close to 1.8 cm/year.