Vol 57, No 5 (2017)

The paper discusses mathematical simulation of intensive coastal upwelling observed in the northeastern part of the Black Sea in the water area of the hydrophysical test site of the Shirshov Institute of Oceanology, Russian Academy of Sciences, in September 2013. The simulation was carried out with the MIKE 21/3 Coupled Model FM combined hydrodynamic model of the Danish Hydraulics Institute (DHI). The calculation results are compared with the data of direct instrumental observations carried out in the IO RAS hydrophysical survey area. The essential role of surface wind waves in the formation of the observed temperature profiles is demonstrated, as well as the necessity of taking it into account when considering peculiarities in the vertical circulation of coastal waters.

The transition from winter vertical mixing to the formation of the spring thermocline in the southeastern Baltic Sea is studied based on data from the hydrophysical measurements program (11 expeditions) in the Russian part of Gdansk Bay in March–June 2010, 2011, and 2013. CTD measurements were taken along the standard 18-km transect across the isobaths with a 500-m step abeam the city of Baltiysk. A set of frequently measured data was collected in a 1–2 week interval from the end of March to the beginning of May, which made it possible to analyze the transformation of the vertical thermal structure of water from inverse winter type to the summer stratification with the transition of temperature over the temperature of the density maximum. Series of repeated measurements at the deep and coastal stations as well as surface and subsurface towed measurements were carried out. The fact that lenses of freshened warmer water appear at the surface almost simultaneously with intensification of cold intrusions in intermediate (10–40 m) layers makes it possible not only to confirm the advective nature of the formation of the spring thermocline in the Baltic Sea, but also to hypothesize about the intensification of intrabasin exchange when winter-time vertical mixing ceases: the potential energy excess supported by vertical mixing in the 60-m upper quasi-homogeneous layer (UQL) of the Baltic Proper, in which the horizontal estuarine salinity gradient is significant, is converted to kinetic energy of exchange currents as the mixing process terminates. Such water dynamics makes it possible to explain the intensification of intrusions in the Baltic in spring and the formation of the cold intermediate layer due to the fast propagation of late-winter UQL water from the Bornholm Basin to the Baltic Proper. The results agree well with earlier published studies of other authors.

Based on the AVISO velocity field, we compute daily synoptic Lagrangian maps in the South Kuril area for the fishery seasons of 1998, 1999, and 2001–2005 from available catching data on neon flying squid (NFS). With the help of drift maps for artificial particles, we found that the majority of NFS fishing grounds featuring maximum catches are situated near large-scale Lagrangian intrusions: tongues of water penetrating the surrounding water of other Lagrangian properties. It is shown that the NFS catch locations tend to accumulate at places where waters with different magnitudes of certain Lagrangian indicators converge, mix, and produce filaments, swirls, and tendrils typical of chaotic advection. Potential NFS fishing grounds are mainly located near (1) Lagrangian intrusions of the Subarctic front, (2) intrusions of Okhotsk Sea and Oyashio waters around mesoscale anticyclones east of Hokkaido with subsequent penetration of catch locations inside eddies and (3) intrusions of subtropical waters into the central part of the South Kuril area due to interaction with eddies of different size and polarity. Possible reasons for increased biological production and fishery in the vicinity of Lagrangian intrusions are discussed.

Jurassic–Cretaceous siliceous–volcanogenic rocks from nappes of tectonostratigraphic sequences of the East Asia Middle Cretaceous Okhotsk–Koryak orogenic belt are represented by a wide range of geodynamic sedimentation settings: oceanic (near-spreading zones, seamounts, and deep-water basins), marginal seas, and island arcs. The taxonomic compositions of radiolarian communities are used as paleolatitude indicators in the Northern Pacific. In addition, a tendency toward climate change in the Mesozoic is revealed based on these communities: from the warm Triassic to the cold Jurassic with intense warming from the Late Jurassic to the Early Cretaceous. Cretaceous warming led to heating of ocean waters even at moderately high latitudes and to the development of Tethyan radiolarians there. These data are confirmed by a global Cretaceous temperature peak coinciding with a high-activity pulse of the planetary mantle superplume system, which created thermal anomalies and the greenhouse effect. In addition, the Pacific superplume attributed to this system caused accelerated movement of oceanic plates, which resulted in a compression setting on the periphery of the Pacific and the formation of the Okhotsk–Koryak orogenic belt on its northwestern framing in the Middle Cretaceous, where Mesozoic rocks of different geodynamic and latitudinal–climate settings were juxtaposed into allochthonous units.

Ferromanganese nodules recovered from the bottom of the East Siberian Sea near Bennett Island are studied by coupled ultramicroscopic and ICP-MS methods. The majority of nodules are flattened dense formations 2.5 to 10 cm in cross section and circled by a thick rim, which is common in nodules from other Arctic basins. The major components of nodules are iron and manganese oxides in the form of ferruginous vernadite and magnetite, as well as accessory minerals, including apatite and titanomagnetite. The major and trace element compositions of nodules are comparable to Arctic nodules from other Arctic seas, but somewhat different compared to those from the Mendeleev Rise. A specific feature of these nodules is that they contain high amounts of mercury in all samples and a positive europium anomaly in one sample, along with gold; this may be related to the influence of endogenous gas-and-vapor exhalations.

The structure of the Caribbean region testifies to the extremely unstable condition of the terrestrial crust of this intercontinental and simultaneously interoceanic area. In the recent geological epoch, the Caribbean region is represented by a series of structural elements, the main of which are the Venezuelan and Colombian deep-sea suboceanic depressions, the Nicaraguan Rise, and the Greater and Lesser Antilles bordering the Caribbean Sea in the north and east. There are 63 sedimentary basins in the entire Caribbean region. However, only the Venezuelan and Colombian basins, the Miskito Basin in Nicaragua, and the northern and eastern shelves of the Antilles, Paria Bay, Barbodos-Tobago, and Grenada basins are promising in terms of oil-and-gas bearig. In the Colombian Basin, the southwestern part, located in the rift zone of the Gulf of Uraba, is the most promising. In the Venezuelan Basin, possible oil-and-gas-bearing basins showing little promise are assumed to be in the northern and eastern margins. The main potential of the eastern Caribbean region is attributed to the southern margin, at the shelf zone of which are the Tokuyo-Bonaire, Tuy-Cariaco, Margarita, Paria Bay, Barbados–Tobago, and Grenada oil-and-gas-bearing basins. The rest of the deepwater depressions of the Caribbean Sea show little promise for hydrocarbon research due to the small thickness of the deposits, their flat bedding, and probably a lack of fluid seals.