Seasonal Variability of the California Undercurrent: Statistical Analysis Based on the Trajectories of Floats with Neutral Buoyancy

The seasonal variation of the kinetic energy of the California Undercurrent and the eddy field in the region of this current are reconstructed by analyzing the trajectories of floats with neutral buoyancy (RAFOS) launched by the researchers of the Naval Postgraduate School (Monterey, California, USA) for 10 yr (since 1992). These data are processed by using a mathematical approach based on the combination of a procedure of averaging over cells and a special filtration approach with an aim to improve the statistical reliability of numerical calculations. The analysis of the accumulated data shows that the kinetic energy of the California Undercurrent has a well pronounced seasonal variation with two extrema in late spring and early autumn. The intensification of the California Undercurrent in autumn is accompanied by a decrease in its extension in the direction transverse to the coast. The eddy field of the California Undercurrent is especially intense in autumn. At depths of 300–600 m, the annual average kinetic energy of the eddy field increases with the distance from the coast up to about 127°W. Moreover, in this case, the zonal anisotropy of the eddy field increases.     

Seasonal variability and the types of currents in the upper layer of the Black Sea

Spectral analysis of the climatic circulation in the upper 10 m layer of the Black Sea has been carried out. The current field was calculated from a three-dimensional baroclinic non-linear model. The mode composition of the circulation was derived. It is shown that the surface climatic circulation can be represented as the superposition of a finite number of elementary currents of two types:n- andm-modes. Only 4n-modes are shown to be energy-dominant throughout the year. A relation is established between the different sources of energy supply of currents and the modes which assimilate this energy. Problems concerning the nature of the classical Black Sea currents such as the main Black Sea current (MBSC) and the Knipovich spectacles are discussed. A scenario of the field large-scale experiment is suggested which allows the reconstruction of the amplitudes of the first 10n- and the first 10m-modes from mooring data.Translated by Mikhail M. Trufanov.     

Barite Nodules in the Japan Sea

Although barite nodules are extremely rare in the World Ocean, they are rather widespread in the Japan Sea. They were first discovered by Japanese scientists in the Honshu Island borderland (Okada et al., 1971; Sakai, 1971). They were later reported from the North Yamato Rise (Lipkina and Tsoi, 1980) and Okushiri Ridge (Astakhova et al., 1990) (Fig. 1, Table 1). All barite nodules in the Japan Sea are confined to Miocene marine sediments.     

Determination of Mesoscale Surface Currents in Shallow-Water Regions According to the Data of High-Frequency Radar Measurements

We propose a new method for the evaluation of the velocities of surface currents according to the data of measurements carried out by using high-frequency land-based radars. The method is based on the representation of the velocity fields via two scalar potentials, expansion of these potentials in series in basis functions, and determination of the coefficients of expansion according to the data of radar measurements as solutions of the corresponding variational problems. The errors of the procedure of determination of the coefficients of expansion are removed by using a special regularization procedure based on information theory. The proposed method enables one to fill gaps in the space and time series of radar measurements. We illustrate the method by an example of numerical analysis of mesoscale and submesoscale (10–50 km) surface currents in the Monterey Bay (California, USA) performed on the basis of the data of radar measurements carried out in August 1994. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 24–36, March–April, 2005.