Modeling the mesoscale variability in the Adriatic Sea

A new high-resolution (<2 km) version of the DieCAST fourth-accuracy-order model for the ocean circulation is proposed for the study of the general circulation, mesoscale structures, and their variability in the Adriatic Sea. The model uses mean seasonal data on the temperature, salinity, buoyancy fluxes, and wind. The data of the COAMPS system with a 4-km resolution were used for the simulation of the sea response to the effects of various winds: Sirocco, Maestro, and two types of boras. The mean monthly runoffs from 38 rivers and mean daily runoffs from 12 main rivers throughout the year were given in the model. The conditions at the open boundary of the Strait of Otranto were given on the basis of the hierarchy of two coarser models for the Adriatic and Mediterranean seas. Due to the extremely weak dissipation and the high resolution (the mesh size is less than the baroclinic radius of deformation, 5–10 km), the model allows one to trace the development of a baroclinic instability along the Italian coast, to simulate mesoscale structures associated with the instability, and to estimate the scales of the structures. Mesoscale filaments, meanders, mushroom-like currents, fronts, and intrusions known from satellite observations were simulated and explained. The scenario of the anomalous upwelling near the Italian coast observed in the summer of 2003 was also simulated and analyzed.     

Effects of particle migration on the features of their transport by tidal currents in a region of freshwater influence

Using a combined model that couples a three-dimensional ocean circulation model, a model for tidal currents, and a model for particle transport, the structure of the velocity field of the tidal current and the transport of particles migrating over the vertical were studied in the zone of the influence of the riverine runoff in the eastern part of the English Channel. It was found that the interaction between the tidal current and the baroclinic flow formed by the riverine runoff off the northeastern coast of France generates a steady-state intensive (～0.3 m/s) residual current in the zone of the effect of the riverine runoff. In order to assess the influence of different types of particle migration (which simulate ichthyoplankton) on the processes of their transport in the region under consideration, we performed numerical experiments with particle clusters, for which parameterization of their migration was implemented on the basis of the field observations over the proper vertical movements of different types of ichthyoplankton. The experiments showed that the distribution of the fields of the particle concentrations and the velocities of their movements depend not only on the background hydrophysical conditions but also on the character of the vertical migration of the particles. In this paper, a comparison between the results of the modeling and those of the field observations in the region under consideration are presented.     

A regression method for estimating salinity in the Ocean

Specification of salinity is an important problem in initialization of the global ocean circulation models. Unlike the temperature, the salinity data in the World Ocean are irregular and nonuniform; thus, methods for estimating the salinity using pleutiful temperature data are urgently needed. A new regression method for estimating the salinity in the ocean is suggested in this paper. Unlike similar currently known approaches, the method suggested applies a set of polynomials and their powers invariant for the entire ocean, while the latter is divided into a number of study subregions for the estimates. The best-fit regression curves and the minimal errors of the salinity estimates are found for each of the regions. The method uses the World Oceanographic Database (WOD-2001 NODC NOAA) to determine the regression coefficients and the confidence intervals (RCCI). A special RCCI database was organized on the basis of these data. The RCCI database makes possible determination of the salinity at any point in the ocean if the temperature data are provided (measurements, XBT profiles, etc.). A realization of the method suggested is demonstrated by the example of the Atlantic Ocean.     

Estimates of Turbulence Intensity and Power Density of an Asymmetric Tidal Current under Wind Forcing Variability

Izvestiya, Atmospheric and Oceanic Physics - A high-frequency (1.2 MHz) four-beam Acoustic Doppler Current Profiler moored on the seabed has been used for direct turbulence measurements in a tidal...     

Phenomenological Model of Natural Dispersion of an Oil Spill in the Sea and Some Associated Parameterization Processes

Oceanology - The paper proposes a new parameterization of natural dispersion of a marine oil spill due to wind-wave breakup of the oil slick and penetration of oil droplets into the water. The...     

Turbulence investigation in a tidal coastal region

A high-frequency (1.2 MHz) four-beam Acoustic Doppler Current Profiler (ADCP) moored on the sea bottom was used for the direct measurements of the turbulence parameters in the shallow (20 m) coastal zone of the eastern English Channel. The measurements were as long as four tidal cycles during the period of the spring tide development. The measurements in the ocean and estimates showed that the Reynolds stress variability coincided with the semidiurnal tide. Their maximum values during the flood phase were approximately 1.5 Pa, while, during the ebb phase, they reached −1.2 Pa. The variations of the turbulence’s kinetic energy (TKE) and the rate of its production (P) coincided with the period of the tidal harmonic M4. Their maximum values were found during the flood phase near the bottom, and they were approximately equal to 0.03 m²/s² and 0.8 W/m³, respectively. These values decreased rapidly with the distance from the bottom. During the periods of low stagnant water, the values of TKE and P in the water column decreased to the minimum values (2 × 10⁻³ m²/s² and 3 × 10⁻⁵ W/m³, respectively), which coincided with the moment of the current’s reversal flow. The results demonstrated the dominating role of the tidal motion, which controls the structure and intensity of the turbulence in the bottom layer, and revealed the characteristic asymmetry of its distribution related to the nonlinear character of the tidal cycle.     

Modeling processes of the protrusion of near-coastal anticyclonic eddies through the Rim Current in the Black Sea

The eddy-resolving (1/30)° version of the low-dissipative DieCAST [7] ocean circulation model is used for modeling processes of the protrusion of near-coastal anticyclonic eddies (NAEs) through the Rim Current (RC). Under mean climatic forcing, the model realistically reproduces the evolution of the Caucasian NAE (CNAE) from its generation, formation of an attached anticyclonic meander, protrusion through the RC, and, finally, to the formation of an isolated anticyclonic eddy and its dissipation within the Eastern Cyclonic Gyre of the Black Sea. The process of double protrusion of the CNAE and the Kizil-Yirmak NAE into the RC, their passages through the RC, and merging in the eastern part of the Black Sea is also considered. The modeled space-time parameters of NAE evolution agree well with satellite observations [15, 23].