Analysis of volcanogenic perturbations of the subarctic ozonosphere on the basis of space monitoring data

The response of the total ozone (TO) at subarctic latitudes to volcanic eruptions, products of which were injected into the stratosphere, is analyzed. It is established that the behavior of the series of average annual TO values according to the TOMS, SCIAMACHY, and GOME space equipment data averaged for 55°–65° N latitudes agrees with the activity of explosive volcanic eruptions. The series of the TO satellite monitoring instrumental data are extended by 200 years into the past using a reconstruction from the dendro-chronologic data. An analysis of the series of TO reconstructed values indicates that volcanogenic perturbations of the subarctic ozonosphere initiate long-term negative TO deviations. In this case, the TO negative deviation depth depends on the frequency of the ozonosphere volcanogenic perturbations and the phase of quasiperiodic oscillation cycles rather than on the strength of a single volcanic explosion.     

Ionospheric response to submarine earthquake of March 11, 2011, in Japan according to GPS observations

Using available Russian and international Global Positioning System (GPS) network data, we studied the ionospheric response to the M = 8.9 submarine earthquake of March 11, 2011, on the northeastern coast of Honshu Island, Japan, both near and far (about 2000 km away) from the epicenter. In the region over the epicenter, 8.7 min after the event, we detected a characteristic signal of the total electron content (TEC) variations consisting of compression and rarefaction phases and a linear transition zone in between, i.e., in the form of an N-type wave with a steep leading front indicating a rapid uplift of the water surface and, correspondingly, the bottom of the ocean. The shape of the signal can be used for early tsunami warning; i.e., it may indicate the tsunamigenic character of a submarine earthquake. We monitored the subsequent evolution of the ionospheric response as far as 2000 km from the epicenter. It was shown that, besides the wellknown ionospheric N-type wave response to the earthquake, there is also a response in the form of an inverted N-wave, both nearby and far from the epicenter. We detected two more types of ionospheric responses far from the epicenter: a solitary-like wave and an internal gravity wave (IGW). The detected signals have been interpreted.     

Effects of pulsed nutrient inputs on phytoplankton assemblage structure and blooms in an enclosed coastal area

The response of phytoplankton assemblage structure to terrestrial nutrient inputs was examined for the Gulf of Kalloni in the Northern Aegean Sea, a productive semi-enclosed coastal marine ecosystem. The study was focused on a typical annual cycle, and emphasis was placed on the comparative analysis between blooms developing after significant nutrient inputs from the watershed, and naturally occurring blooms. Baseline information was collected on a monthly basis from a network of stations located in the oligotrophic open sea and the interior and more productive part of the embayment. Intensive sampling was also carried out along a gradient in the vicinity of a river which was the most important source of freshwater and nutrient input for the Gulf. Phytoplankton assemblage structure was analyzed from 188 samples using diversity indices (Shannon and Average Taxonomic Distinctness), multivariate plotting methods (NMDS), multivariate statistics (PERMANOVA), and canonical correspondence analysis (CCA). Three characteristic assemblages were recognized: (1) an autumn assemblage developed under nutrient depleted conditions, having low diversity due to the dominance of two small diatoms, (2) a winter bloom of the potentially toxic species Pseudo-nitzschia calliantha occurring immediately after a nutrient peak and characterized by very low diversity, and (3) a naturally occurring early summer bloom of centric diatoms with relatively high diversity. The results of the study support the view that moderate nutrient inputs may have a beneficial effect on the functioning of coastal ecosystems, stimulating the taxonomic diversity through the growth of different taxonomic groups and taxa. On the other hand, a sudden pulse of high nutrient concentrations may greatly affect the natural succession of organisms, have a negative effect on the diversity through the dominance of a single species, and can increase the possibility of a harmful algal bloom development.     

Bathymetric segregation of sea urchins on reefs of the Canarian Archipelago: Role of flow-induced forces

We examined whether adults of three species of sea urchins species (Diadema antillarum, Arbacia lixula, and Paracentrotus lividus) exhibit a consistent depth-dependent partitioning pattern on rocky reefs of the Canarian Archipelago (eastern Atlantic). Hydrodynamic experiments were carried out to quantify the resistance to flow-induced dislodgement in these three species. We tested the model that different morphology can result in habitat partitioning among these sea urchins. Abundances of D. antillarum increased with depth. In contrast, A. lixula and P. lividus showed the opposite zonation pattern, coexisting in high abundances in the shallowest depths (<5 m), and occurring in low densities in the deepest part of reefs (>7 m). Both A. lixula and P. lividus had greater adhesion-surface to body-height ratios than D. antillarum. Similarly, A. lixula and P. lividus showed a greater ability to resist flow-induced dislodgement compared with D. antillarum. The mean “velocity of dislodgement” was 300% and 50% greater for A. lixula and P. lividus, respectively, relative to D. antillarum, for any particular size. As a result, A. lixula and P. lividus are better fitted to life in high-flow environments than D. antillarum. We conclude that the risk of dislodgement by water motion likely play a relevant role in the vertical distribution patterns of these sea urchins in the eastern Atlantic.     

长江口渔场、舟山渔场硅酸盐浓度分布与生物量关系的研究

根据1998年和2000年东海北部的营养盐调查资料和相应的历史资料,以及同期开展的虾类资源调查资料,研究了冬、夏季长江冲淡水的流向以及它对长江口渔场、舟山渔场硅酸盐分布规律和虾类生物量分布规律的影响。结果表明,长江冲淡水转向的原因可以归纳为4类,夏季长江冲淡水的流动界限由123°E,30．3°N到127．3°E,33°N的直线和由123°E,31．8°N到127．3°E,34．5°N的直线所围的区域。长江冲淡水给长江口渔场、舟山渔场提供了大量的硅酸盐,对提高该海区的初级生产力起到了积极的作用,有利于生物的繁衍生息,提高了生物量。最后,用该海区虾类的分布密度证实了由该水团所做出的对生物量的推论。     

Three Kings Ridge: a west-facing arc

The Three Kings Ridge has been described as a remnant arc or an east-facing arc on the western side of the South Fiji Basin under which symmetric South Fiji Basin magnetic anomaly lineations have been lost. We find evidence of neither arc-trench morphology on the eastern flank of the ridge nor collision tectonism within the adjacent South Fiji Basin that might have obliterated it. We believe there is room for the missing magnetic lineations within the South Fiji Basin and we recognize the distinctive island-arc morphology characteristic of a west-facing arc on the western flank of the Three Kings Ridge. Our interpretation requires that arc volcanism postdated formation of much of the South Fiji Basin and that oceanic lithosphere from the adjacent Norfolk Basin must have been subducted beneath the west-facing Three Kings Arc.     

A low level supplementary heating system for free divers

A simple and effective method of heating divers in extreme cold water has been developed. The local heating concept utilizes a uniformly distributed granular mixture of magnesium and iron particles packed in small sachets. Upon activation by sea water, the two metal mixture behaves as a multitude of short-circuited electrolytic cells, producing thermal energy rather than electrical energy. The 45 mm-square sachets may be placed where heating is required on the diver's body, thus giving rise to the term “local heating”, obviously, the heating system requires no pumping device, or distribution network. Heating rate and duration of output of the sachets are controlled by particle size, and mixture ratio of the constituent Mg and Fe particles.This paper described the development, testing and performance of the heating sachets. Results of live tests in different dive situations are also presented and discussed.     

Dynamics of an elastically moored floating body by the three-dimensional infinite element method

The three-dimensional problem of the dynamics of a moored floating object under the action of regular waves is solved numerically as a boundary value problem by use of the finite-infinite element method. The cross-sectional shape of the floating body and the mooring arrangements may all be arbitrary. The mathematical formulations of the problem and procedures of the numerical method are presented in this paper. A corresponding computer program WALOAD has been developed, which is capable of computing wave forces on fixed and floating structures. Numerical computations using this program could give very accurate results, even though rather coarse meshes were used. The program is easy to use and is readily applicable in many practical situations.     

Imaging of Buried Archaeological Materials: The Reflection Properties of Archaeological Wood

Effective marine archaeological site management demands detailed information on not only the spatial distribution of artefacts but also the degradation state of the materials present. Although sonar methods have frequently been used in an attempt to detect buried wooden shipwrecks they are currently unable to indicate their degradation state. To assess the sensitivity of acoustic measurements to changes in the degradation state of such material, and hence the potential for sonars to quantify degradation, laboratory measurements of compressional wave velocity, as well as bulk density for oak and pine samples, in varying states of decay, were undertaken. These data enabled the calculation of theoretical reflection coefficients for such materials buried in various marine sediments. As wood degrades, the reflection coefficients become more negative, resulting in the hypothesis that the more degraded wood becomes, the easier it should be to detect. Typical reflection coefficients of the order of −0.43 and −0.52 for the most degraded oak and pine samples in sand are predicted. Conversely, for wood exposed to seawater the predicted reflection coefficients are large and positive for undegraded material (0.35 for oak, 0.18 for pine) and decrease to zero or slightly below for the most degraded samples. This indicates that exposed timbers, when heavily degraded, can be acoustically transparent and so undetectable by acoustic methods. Corroboration of these experimental results was provided through comparison with high resolution seismic reflection data that has been acquired over two shipwrecks.