Drifting and Meandering of Olive Ridley Sea Turtles in the Bay of Bengal: Role of Oceanic Rossby Waves

Olive Ridley turtles in the Bay of Bengal are previously thought to migrate southward from their nesting ground, along the east coast of India (Orissa coast), towards Sri Lanka. Surprisingly, three of the four Platform Transmitter Terminal (PTT) attached turtles in April-June 2001 meandered off the east coast of India for about two months. It is found that these turtles meandered at the peripherals of cold core cyclonic eddy surrounded by warm core eddies on either side. Concentrations of prey for the turtles in those frontal regions are known to be abundant. Only one of the four PTT attached turtles migrated to the south along the frontal regions in the direction of geostrophic currents. It is found that the locations of these thermal fronts in the Bay of Bengal are primarily determined by the Oceanic Rossby waves and local Ekman pumping.     

Role of Vertical Resolution in Numerical Models Towards the Intensification,Structure and Track of Tropical Cyclones

The impact of vertical resolution on the evolution and movement of tropical cyclones was studied using NCAR MM5 model with a horizontal resolution of 9 km. Four numerical experiments were performed with different vertical resolutions, that is, with 23 vertical levels as control experiment, and 36 vertical levels with high resolution in the lower troposphere, 33 vertical levels with high resolution in the upper troposphere and 46 vertical levels with increased vertical resolution throughout the troposphere as relative to base experiment. The results indicate that increased vertical resolution in the lower troposphere produces efficient intensification and better structure in terms of eye and eyewall. Increased vertical resolution at lower levels improves the prediction of vertical shear of horizontal wind. Experiments with high resolution in the lower troposphere and high resolution throughout the troposphere simulate better track up to 72 hours.     

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.     

Seasonal and interannual variability of oceanic carbon cycling in the western and central tropical-subtropical pacific: A physical-biogeochemical modeling study

The oceanic carbon cycle in the tropical-subtropical Pacific is strongly affected by various physical processes with different temporal and spatial scales, yet the mechanisms that regulate air-sea CO₂ flux are not fully understood due to the paucity of both measurement and modeling. Using a 3-D physical-biogeochemical model, we simulate the partial pressure of CO₂ in surface water (pCO_2sea) and air-sea CO₂ flux in the tropical and subtropical regions from 1990 to 2004. The model reproduces well the observed spatial differences in physical and biogeochemical processes, such as: (1) relatively higher sea surface temperature (SST), and lower dissolved inorganic carbon (DIC) and pCO_2sea in the western than in the central tropical-subtropical Pacific, and (2) predominantly seasonal and interannual variations in the subtropical and tropical Pacific, respectively. Our model results suggest a non-negligible contribution of the wind variability to that of the air-sea CO₂ flux in the central tropical Pacific, but the modeled contribution of 7% is much less than that from a previous modeling study (30%; McKinley et al., 2004). While DIC increases in the entire region SST increases in the subtropical and western tropical Pacific but decreases in the central tropical Pacific from 1990 to 2004. As a result, the interannual pCO_2sea variability is different in different regions. The pCO_2sea temporal variation is found to be primarily controlled by SST and DIC, although the role of salinity and total alkalinity, both of which also control pCO_2sea, need to be elucidated by long-term observations and eddy-permitting models for better estimation of the interannual variability of air-sea CO₂ flux.     

渤海湾西部表层沉积物悬移组分元素特征及物源意义

对渤海湾西部海底表层沉积物样品粒径小于0.063mm的悬移组分进行16种元素测试,分析了各元素特征及分布规律。元素平均丰度与黄土及渤海泥质沉积物基本一致,说明渤海湾西部表层沉积物悬移组分的物源主要与黄河源区黄土高原的黄土有关。研究区16种元素可分为两类,I类是Sc、Co、Fe、V、Al、Ca、Mg、Th、U、Cr;II类是Zr、Hf、Ba、Na、Sr、K。同类元素丰度的平面分布规律相似,呈现正相关性;异类元素丰度的平面分布规律相反且呈负相关性。研究区主要分为两个地球化学分区,两区基本以北纬39°05′线为界,I区位于南部和中部,以高Sc、Co、V、Th、U、Cr、Fe、Al、Mg、Ca等I类元素为特征;而II区位于北部,以高Zr、Hf、Ba、Sr、Na、K等II类元素为特征。渤海湾西部表层沉积物悬移组分的元素特征及分区,可能与研究区内不同季节沿岸环流方向改变,进而导致不同物源母质沉积物输运混合作用有关。     

Use of late ovarian atresia in describing spawning history of sardine, Sardina pilchardus

We investigated and compared the pattern of accumulation of recent and late atretic follicles in the ovaries of Iberian sardine, Sardina pilchardus, in relation to body size with the aim to examine whether late atresia can be used in back-calculations of individual spawning history. Oppositely to earlier stages, late atresia in sardine was shown to accumulate even at peak spawning periods in fish of larger size/age indicating a relationship between atretic intensity and the distant reproductive performance of the individuals. Despite the fact that intensity of late atresia was very high in some occasions, its accumulation was not shown to impede imminent spawning activity. Lack of dependence between imminent spawning activity and the intensity of late atresia was related to the differential pattern with which postovulatory and atretic follicles are associated to the lamellar epithelium of the ovary. Finally, the effect of the ‘reference trap’ which is a major source of bias when quantifying structures in stereological measurements, could be mediated or even completely removed by using a measure of ovarian growth, such as gonosomatic index in the present study, as a covariate when modeling variability in the intensity of atresia.     

Marine reserve phenomenon in the Pacific islands

Coinciding with increased numbers of global marine reserves, communities in the Pacific islands are establishing unprecedented number of periodically-harvested and indefinitely-closed marine reserves. An integrated ecological and social comparative methodology is used to examine the motivations and outcomes of reserves in Vanuatu. Communities establish permanent reserves due to concerns about human impacts on reefs, while others establish periodic reserves in response to declining resources. Local knowledge suggests that both reserve types are effective, although validation by underwater surveys was inconclusive. Community support for both reserve types is strong, suggesting that the marine reserve phenomenon in Pacific will continue.     

An early Miocene reefal platform in the Rama Ridge (Banda Sea, Indonesia)

 In December 1995 we dredged early Miocene coral-reef carbonates and early/middle Pliocene slope carbonates outcropping on the submerged Rama Ridge. This indicates that some of the Banda Sea Ridges were present during early Miocene times. Subsequent major tectonic subsidence occurred between middle Miocene and early Pliocene times. These results concur with the hypothesis of a relatively recent age for the North Banda Sea basement. Received: 5 March 1997 / Revision received: 23 October 1997     

Analytical solutions of the diffraction problem of a group of truncated vertical cylinders

An exact analytical method is described to solve the diffraction problem of a group of truncated vertical cylinders. In order to account for the interaction between the cylinders, Kagemoto and Yue's exact algebraic method is utilised. The isolated cylinder diffraction potential due to incident waves is obtained using Garret's solution and evanescent mode solutions are derived in a similar manner.Numerical results are presented for arrays of two and four cylinders. Comparisons between the results obtained from the method presented here and those obtained from numerical methods show excellent agreement.     

An iterative method for boundary element solution of large offshore structures using the GMRES solver

The GMRES approach is used to solve complex matrix solution arising from boundary element analysis of large offshore structures. This makes it possible to solve problems with large numbers of panels on a workstation with a much smaller memory than typical high performance computers. The speed of the solver is compatible with direct solvers when the enough RAM is available. Otherwise, an iteration procedure can be used. By using an out-of-core treatment, typical RAM requirement is reduced to a size approximately linearly proportional to the panel number n instead of being proportional to n². The code is first verified with direct solver for cases with small number of panels. The applicability to large offshore structure of the model is demonstrated for a TLP case.