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The methodical principles of the analysis of biogenic silica accumulation in the pelagic zones of the Pacific and Indian oceans are considered. Two quantitative approaches of lithological analysis are compared: method of absolute mass by A.D. Arkhangel'skii and volumetric method by A.B. Ronov. It is established that the concept of 'two oceans' ('ice' and 'non-ice') may be applied to both the oceans. Differences in the evolution of the silica accumulation rate in the Pleistocene between high- and low-latitude oceans are revealed. [ABSTRACT FROM AUTHOR]

Abstract: We test the feasibility of two scenarios that may drive the broad, prograde, equatorial jets in the Jovian atmosphere within the shallow “weather layer”. The first idea attempts to explain the flat-headed jet as a consequence of a hydrodynamic instability along an equatorially trapped primarily jet. The strong primary jet is induced by a 300ms−1 Kelvin wave. The second idea is a bridging of a pair of off-equatorial jets due to horizontal eddy diffusion (the so-called Gierasch mechanism). The primary jets can be induced by a Hadley circulation, and might then be interconnected by subsequent hydrodynamic instabilities between them. We test the two scenarios using a general circulation model, but have so far been unable to obtain an equatorial jet that resembles observations. It appears, therefore, that the previously proposed model of combining Kelvin and Hadley forcing, is more plausible under the shallow hypothesis. [Copyright &y& Elsevier]

The structure of the copepod community from the San Lorenzo Channel,Gulf of California, is described for 1990 and the 1992- 93 ENSO. Themain difference between sampling periods was the decrease of the calanoid Nannocalanus minor. This ocean species, distributed mainly in the equatorial zone, was one of the dominant in the plankton of the channel from February to August 1990. During the 1992-93 ENSO it appeared to be partially displaced by another equatorial but smaller species, Clausocalanus arcuicornis, and the tropical coastal species, Undinula vulgaris. Among the carnivores, Euchaeta marina decreased during ENSO, while the incidence of Candacia truncata and Candacia catula was observed. The mesh size of the net used noticeably affected the community structure observed, due to the escape of organisms through thenet. With the net of 300 pm mesh size, 30% more species were collected than with the net of 500 pm, and the abundances of the smaller species presented high escape percentages with the latter. [ABSTRACT FROM AUTHOR]