Parameterization of the depth of the upper quasi-homogeneous layer based on measurements in the North Atlantic (Section along 53° N)

The dependence of the variation in the depth of the upper mixed layer (MLD) on the governing parameters (the momentum flux, the buoyancy fluxes at the ocean surface, and the density gradient in the pycnocline) is considered. It is shown that, in the spring storm season, wind mixing dominates over convective mixing. In this case, the MLD is linearly correlated with the Ekman scale calculated from the friction velocity observed approximately 12 h before the measurement of the MLD.     

Primary production in the eastern tropical Pacific: A review

The eastern tropical Pacific includes 28 million km² of ocean between 23.5°N and S and Central/South America and 140°W, and contains the eastern and equatorial branches of the north and South Pacific subtropical gyres plus two equatorial and two coastal countercurrents. Spatial patterns of primary production are in general determined by supply of macronutrients (nitrate, phosphate) from below the thermocline. Where the thermocline is shallow and intersects the lighted euphotic zone, biological production is enhanced. In the eastern tropical Pacific thermocline depth is controlled by three interrelated processes: a basin-scale east/west thermocline tilt, a basin-scale thermocline shoaling at the gyre margins, and local wind-driven upwelling. These processes regulate supply of nutrient-rich subsurface waters to the euphotic zone, and on their basis we have divided the eastern tropical Pacific into seven main regions. Primary production and its physical and chemical controls are described for each.Enhanced rates of macronutrient supply maintains levels of primary production in the eastern tropical Pacific above those of the oligotrophic subtropical gyres to the north and south. On the other hand lack of the micronutrient iron limits phytoplankton growth (and nitrogen fixation) over large portions of the open-ocean eastern tropical Pacific, depressing rates of primary production and resulting in the so-called high nitrate-low chlorophyll condition. Very high rates of primary production can occur in those coastal areas where both macronutrients and iron are supplied in abundance to surface waters. In these eutrophic coastal areas large phytoplankton cells dominate; conversely, in the open-ocean small cells are dominant. In a ‘shadow zone’ between the subtropical gyres with limited subsurface ventilation, enough production sinks and decays to produce anoxic and denitrified waters which spread beneath very large parts of the eastern tropical Pacific.Seasonal cycles are weak over much of the open-ocean eastern tropical Pacific, although several eutrophic coastal areas do exhibit substantial seasonality. The ENSO fluctuation, however, is an exceedingly important source of interannual variability in this region. El Niño in general results in a depressed thermocline and thus reduced rates of macronutrient supply and primary production. The multi-decadal PDO is likely also an important source of variability, with the ‘El Viejo’ phase of the PDO resulting in warmer and lower nutrient and productivity conditions similar to El Niño.On average the eastern tropical Pacific is moderately productive and, relative to Pacific and global means, its productivity and area are roughly equivalent. For example, it occupies about 18% of the Pacific Ocean by area and accounts for 22–23% of its productivity. Similarly, it occupies about 9% of the global ocean and accounts for 10% of its productivity. While representative, these average values obscure very substantial spatial and temporal variability that characterizes the dynamics of this tropical ocean.     

Nutrients and zooplankton composition and dynamics in relation to the hydrological pattern in a confined Mediterranean salt marsh (NE Iberian Peninsula)

The role of the hydrological regime in the nutrients and zooplankton composition and dynamics has been analysed in five lagoons of La Pletera salt marshes (NE Iberian Peninsula) during a complete hydrological cycle (2002–2003). Two of the lagoons have their origin in the old river mouths while the other three were recently created in the framework of a Life Restoration project. This fact has also allowed us to study the effect of the lagoon age on nutrient and zooplankton composition and dynamics. The salt marsh hydrology is determined by a prolonged period of confinement without water inputs, irregularly interrupted by sudden water inputs due to flooding events (sea storms or intense rainfalls). While the dynamics of oxidized nitrogen compounds in the lagoons depends on the water inputs variability within each hydrological cycle, the internal load of phosphorus, total nitrogen and organic matter is related more to the cumulative mechanisms during the confinement periods. Accumulation processes may be easily related to lagoon age, since old lagoons have higher content of nutrients and organic matter, suggesting that these lagoons progressively accumulate nutrients during the successive confinement events. This is the usual case for most Mediterranean salt marshes without an artificially manipulated water regime. The zooplankton community in La Pletera integrates the effects of both the hydrological regime and the lagoon age since the former determines the temporal pattern of the main zooplankton species and the latter explains differences in composition and structure between old and new lagoons.     

The STRATAGEM project: Stratigraphic development of the glaciated European margin

The EC-funded STRATAGEM project ran from 2000 to 2003 and was a study of the Neogene evolution of the glaciated northeast Atlantic margin from Lofoten to Porcupine, an area extending over nearly 20 degrees of latitude. An extensive seismic, borehole and sample database has been used, much of it supplied by the oil industry. The main products of STRATAGEM have been an integrated, unified stratigraphic framework in the form of an atlas documenting and illustrating the detailed stratigraphy of the entire margin, and a detailed evolution model for this margin. A brief summary of the background to, and organisation of, the project is presented, together with an outline of the main objectives, the physiographic setting of the area and the database.     

Stress and deformation of offshore piles under structural and wave loading

Various offshore structures, especially large structures such as Tension Leg Platforms (TLP), are usually supported by concrete piles as the foundation elements. The stress distribution within such a large structure is a dominant factor in the design procedure of an offshore pile. To provide a more accurate and effective design for offshore foundation systems under axial and lateral wave loads, a finite element model is employed herein to determine the stresses and displacements in a concrete pile under similar loading conditions. A parametric study is also performed to examine the effects of the stress distribution due to the changing loading conditions.     

基于GIS数据仓库的激光单分子海洋油气化探数据可视化处理

采用基于地理信息系统(GIS)的数据仓库技术,以激光单分子海洋油气化探数据处理与评价作为数据仓库主题,实现了激光单分子海洋油气化探数据的可视化处理。将可视化处理分为4个步骤:数据预处理、异常背景分析、异常分析、异常综合评价;使用MAPX、DELPHI等软件研制开发了相应的可视化软件模块。通过对渤海湾盆地某测区实测的甲苯化探数据的处理,验证了所开发技术的实用性。     

海浪周期关系的研究

本文利用现场观测数据、实验室风浪槽观测数据和由文氏谱及JONSWAP谱生成的模拟数据,研究了有效周期与谱平均周期、谱峰周期与谱平均周期以及有效周期与谱峰周期的关系,通过数据拟合给出了相应的关系式.研究发现,有效周期与由谱的负阶矩计算的平均周期之间的关系更加稳定,并且有效周期与负2阶矩计算的平均周期几乎相等,均代表了海浪主导波对海浪平均周期的贡献.     

6-DMAP诱导缢蛏三倍体的研究

用6-DMAP抑制受精卵第二极体排放的方法诱导缢蛏三倍体的试验．结果表明：6-DMAP在100～500μmol／dm^3处理浓度范围内均可以诱导出三倍体，随着药物处理浓度和处理时间的提高，三倍体倍化率和D形幼虫畸形率有不同程度的提高，而D形幼虫孵化率会随之下降．综合来看，在30％卵子受精并出现第一极体，6-DMAP浓度为300μmol／dm^3和处理持续时间为20min时的处理组的处理效果优于其他处理组组合．     

Thermohydrodynamics of the ocean decay of nonlinear oscillations in a bounded basin of variable depth

We study the time decay of surges of a liquid in a round shallow-water basin of variable depth. The dependence of the logarithmic decrement of oscillations on the bottom topography and wind velocity is analyzed. The role of convective acceleration and bottom friction in the formation of both the level of vertical displacement of the surface of the basin and the velocity field of horizontal wave currents is estimated. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 3–11, March–April, 2006.