The spectral characteristics and kinematics of short-period internal waves on the Hawaiian shelf

Based on the results of analyzing the characteristics of currents and temperature measured in the water space of the Mamala Bay (the Island of Oahu, Hawaii), we investigate the main properties of the field of short-period internal waves, which is very complex. We focus on analyzing the spectral characteristics and orbit parameters for waves with a period of 20 minutes. The results of investigations reveal two types of short-period internal waves for this area: intense and fast waves propagating predominantly toward the ocean and weaker and slower waves propagating mainly toward the coast. Suppositions are made on how these waves form: the strong and fast waves are likely to be caused by the decay of locally generated internal tides near the shelf edge, while the weak and slow and very short waves seem to result from the specific interaction between the pycnocline and strong tidal currents over a steep slope.     

Mineral associations of the Lost Village and Lost City hydrothethermal fields in the North Atlantic

During the 50th cruise of R/V Akademik Mstislav Keldysh, on the south slope of the Atlantis massif (30°07′N; the Middle Atlantic Ridge), an inactive hydrothermal field named the Lost Village was discovered. This new field was formed of light carbonate rock and was located near the active Lost City hydrothermal field. The mineralogical associations of these fields were studied. A conclusion about the participation the ocean water in the changing of the carbonate composition of the inactive hydrothermal field was reached.     

Tectonics and magmatism of the Hess deep region of the Galapagos rift

The joint analysis of data on the anomalous maganetic field, seismicity, and structures of the Hess deep basalts have allowed us to specify the elongation of zone of spreading and to correct the spatial distribution of the neovolcanic zone. The precise petrogeochemical analysis of various types of basalts composing the uneven-aged oceanic crust of the basin showed that the neovolcanic zone magmatics are related to the primitive type in contrast to rift boards of differential basalts. A model of the Galapagos rift’s deep structure in the area of the western Hess deep has been suggested.     

Bannock Basin,Sirte Abyssal Plain and Conrad Spur: structural relationships between Mediterranean Ridge and its western foreland and implications on the character of the accretionary complex (eastern Mediterranean)

In previous publications, the relationship between the Sirte Abyssal Plain as foreland and the Mediterranean Ridge as accretionary complex was considered to be simple: the foreland is undeformed, the accretionary complex consumes the foreland, the Messinian evaporites control the internal structure of the growing complex. The compilation of our own and published data results in a more complex tectonic pattern and a new geodynamic interpretation. The Sirte Abyssal Plain is imprinted by extensional tectonics which originated independently from and prior to the approaching process of accretion. The structural setting of the pre-Messinian and Messinian Sirte Abyssal Plain is responsible for the highly variable thickness of Messinian evaporites. The foreland setting in the Sirte Abyssal Plain also controls the internal structure of the Mediterranean Ridge, at least between the deformation front and Bannock Basin, following sediment deformation within the accretionary wedge with a dominating inherited SW-NE orientation. The taper angle of the post-Messinian Mediterranean Ridge is unusually small compared with other accretionary wedges. In the studied area, within a distance of about 45 km from the deformation front, there is no appreciable dip in the décollement. Therefore, the slope of the outer 45 km of the Mediterranean Ridge is considered to be caused only by gravitational spreading of Messinian evaporites deposited on the slope of pre-Messinian accretionary wedge. As a consequence, the Mediterranean Ridge underlying such slope is interpreted to belong to the foreland. The allochthonous evaporites overlie autochthonous evaporites of the Sirte Abyssal Plain. The NE-dipping décollement (and thus of the true tectonically driven deformation front) is expected to initiate at about the present position of Bannock Basin. The Sirte Abyssal Plain, the adjacent Cyrene Seamount and neighbouring seafloor relief on the African continental margin are considered to be the product of tectonic segmentation of the continental crust.     

Relationship between environment and the occurrence of the deep-water rose shrimp Aristeus antennatus (Risso, 1816) in the Blanes submarine canyon (NW Mediterranean)

We performed a multidisciplinary study characterizing the relationships between hydrodynamic conditions (currents and water masses) and the presence and abundance of the deep-water rose shrimp Aristeus antennatus in a submarine canyon (Blanes canyon in the NW Mediterranean Sea). This species is heavily commercially exploited and is the main target species of a bottom trawl fishery. Seasonal fluctuations in landings are attributed to spatio-temporal movements by this species associated with submarine canyons in the study area. Despite the economic importance of this species and the decreases in catches in the area in recent years, few studies have provided significant insight into the environmental conditions driving shrimp distribution. We therefore measured daily A. antennatus catches over the course of an entire year and analyzed this time series in terms of daily average temperature, salinity, mean kinetic energy (MKE), and eddy kinetic energy (EKE) values using generalized additive models and decision trees. A. antennatus was captured between 600 and 900 m in the Blanes canyon, depths that include Levantine Intermediate Water (LIW) and the underlying Western Mediterranean Deep Water (WMDW). The greatest catches were associated with relatively salty waters (38.5–38.6), low MKE values (6 and 9 cm² s⁻²) and moderate EKE values (10 and 20 cm² s⁻²). Deep-water rose shrimp occurrence appears to be driven in a non-linear manner by environmental conditions including local temperature. A. antennatus appears to prefer relatively salty (LIW) waters and low currents (MKE) with moderate variability (EKE).     

On the optimal siting of cubic kilometre scale neutrino telescope infrastructure on the deep-sea floor

The aim of this paper is to propose an approach for optimal siting of the KM3NeT neutrino telescope on the sea floor. The method is based on Geographic Information System (GIS) spatial analyses and cost assessment. GIS techniques initially aim to derive depth and slope characteristics of the sea floor, and estimate the distance from shore. Subsequently, GIS methods are used to pre-select sites meeting the KM3NeT infrastructure criteria. Finally, the candidate locations are evaluated in terms of cost estimation. A convex combination of instantaneous cost functions (ICFs) is applied and different weighting factors are allowed to account for dissimilar importance of the considered variables. The ICFs are indexed by a parameter β to assign different cost characteristics to different variables. The overall assessment is based on the comparison of costs computed for the candidate sites assuming many configurations of weights and β values. Our exercise uses a simulated numerical bathymetry to avoid a site-specific evaluation at the initial stage of the KM3NeT project. Hence, no recommendations as to the real locations of the neutrino telescope in the Mediterranean Sea are addressed. Our approach is found to serve well in the process of comparing costs between different candidate sites.     

A study of the spatial structure of the atmospheric boundary layer with a Doppler-Sodar network

The studies conducted in 1991–2004 by scientists of the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, and the Karpov Institute of Physical Chemistry yielded data on the structures of the surface air layer (to a height of 20 m) and both subinversion and inversion layers (to heights of from 800 m to 1 km), where arid aerosol is transported. One of the main objectives of the 2007 experiment was to record the space-vortex structures within a layer of 30–700 m that directly provide the removal and long-range transport of fine-dispersed (<5 µm) desert aerosol. This paper describes the organization of the Khar-Gzyr 2007 experiment (Black Lands, 2007) to study the convective removal of arid aerosol from desertificated lands, and it presents some data obtained from the remote sensing of the atmospheric boundary layer with a sodar network in the course of this experiment. The sodar network, which was developed to study a spatial structure of coherent vortices, included three identical minisodars (with carrier frequencies of 3.8 kHz) located at the apices of a triangle, each side of which was about 3.5 km, and a sodar (with a carrier frequency of 1.7 kHz). The vertical profiles of the three wind-velocity components and the characteristics of air temperature fluctuations were determined. The procedure of identifying coherent vortex structures is described. The variations in the vertical and horizontal wind-velocity components and the scales characteristic of such structures are estimated.     

The thermal structure of the Dvurechenskii mud volcano and its implications for gas hydrate stability and eruption dynamics

The sediment temperature distribution at mud volcanoes provides insights into their activity and into the occurrence of gas hydrates. If ambient pressure and temperature conditions are close to the limits of the gas hydrate stability field, the sediment temperature distribution not only limits the occurrence of gas hydrates, but is itself influenced by heat production and consumption related to the formation and dissociation of gas hydrates. Located in the Sorokin Trough in the northern Black Sea, the Dvurechenskii mud volcano (DMV) was in the focus of detailed investigations during the M72/2 and M73/3a cruises of the German R/V Meteor and the ROV Quest 4000 m in February and March 2007. A large number of in-situ sediment temperature measurements were conducted from the ROV and with a sensor-equipped gravity corer. Gas hydrates were sampled in pressurized cores using a dynamic autoclave piston corer (DAPC). The thermal structure of the DMV suggests a regime of fluid flow at rates decreasing from the summit towards the edges of the mud volcano, accompanied by intermittent mud expulsion at the summit. Modeled gas hydrate dissociation temperatures reveal that the gas hydrates at the DMV are very close to the stability limits. Changes in heat flow due to variable seepage rates probably do not result in changes in sediment temperature but are compensated by gas hydrate dissociation and formation.     

Reproduction in the sea pen Funiculina quadrangularis (Anthozoa: Pennatulacea) from the west coast of Scotland

The sea pen Funiculina quadrangularis (Pallas, 1766) is a species of conservation concern in Scottish coastal waters, due to its restricted geographical distribution and high sensitivity to demersal fishing activities. Reproduction in F. quadrangularis was investigated in a population located in southern Loch Linnhe, west Scotland. This was accomplished through the analysis of trends in oocyte size-frequency distribution and relative fecundity over a 12-month period. Funiculina quadrangularis is dioecious and the study population exhibited a sex ratio of 1:1. Oogenesis in female F. quadrangularis is characterised by the maintenance of a large pool of asynchronously developing oocytes throughout the year, of which a small proportion (<10%) mature with increasing sychronicity and are spawned in midwinter. The reasons for this distinct pattern of oogenesis and winter spawning remain unclear, although the potential influence of environmental cues and the role of endogenous factors in relation to this sea pen's deep-sea habit are discussed. Whilst the duration of oogenesis is prolonged (>12 months), it is proposed that spawning is a brief and synchronous annual event. Relative fecundity is high and is independent of colony size, varying between approximately 500–2000 oocytes per 1 cm rachial midsection. This measure of fecundity exhibited pronounced seasonality and was significantly lower during the post-spawning winter months. Total fecundity in F. quadrangularis is considered to be high; although a small proportion of the total number of oocytes is spawned annually, this is compensated for by large colony size. Funiculina quadrangularis produces large oocytes (>800 μm), indicative of the production of lecithotrophic larvae.     

Estimating the economic impact of the Prestige oil spill on the Death Coast (NW Spain) fisheries

This paper presents an estimation of the economic effects of the Prestige oil spill in Galicia, focusing on the Death Coast fisheries and using fish landings as a market technique. Examining the evolution of landings in the Death Coast before and after the accident, the analysis reveals two opposing trends, with landings of some species increasing and those of other species diminishing.