Algorithm for non-hydrostatic dynamics in the Regional Oceanic Modeling System

A non-hydrostatic algorithm for the Regional Oceanic Modeling System (ROMS) is proposed. It is based on a decomposition technique for hydrostatic and non-hydrostatic pressure. The algorithm has a pressure-correction scheme with split-explicit time-stepping for baroclinic and barotropic vertical modes with a free surface. The algorithm implementation requires solving a Poisson equation for a non-hydrostatic pressure that has a non-symmetric matrix in discrete form. The efficiency of a different class of solvers and preconditioners were tested. The algorithm is successfully implemented with several examples where non-hydrostatic effects are important. These include standing external gravity waves; strongly nonlinear internal wave generation and transformation; stratified shear instability and its associated mixing; and nonlinear internal tidal generation over a ridge. The corresponding changes in the pre-processing and post-processing infrastructure in the existing hydrostatic ROMS code were performed to implement parallel elliptic solvers and a new set of dynamical equations.     

The First Law of Thermodynamics in a salty ocean

The First Law of Thermodynamics is developed from fundamentals for open, non-equilibrium systems of seawater in motion, exchanging salt and freshwater internally and with their surroundings, and varying continuously in temperature, pressure, and salinity. The aim is clarity and consistency of concepts – and precision in the accompanying vocabulary. Particular attention is given to the way in which salinity variation plays out in the logical structures. The arbitrary constants in the thermodynamic potentials and the various First Law equations are highlighted, in order to remove them, and to recover the physically meaningful content. When this is done, it is seen that salinity variations have little consequence in application of the First Law to the ocean, apart from affecting values of coefficients.     

Measurement of DNA single-strand breaks in gill and hemolymph cells of mussels, Mytilus sp., collected on the French Atlantic Coast

DNA single-strand breaks were measured by the comet assay in both gill and hemolymph cells of mussels collected in 3 sampling areas of the French coast (Pointe du Castelli, Pen Bron and Saint-Nazaire Harbour). Whole mussel tissue samples were also collected for the chemical determination of PAH, PCB and heavy metal concentrations. In mussel, a higher level of DNA strand breaks was measured in gill than in hemolymph cells (p < 0.01). Despite a factor of contamination from 2 to 3 between sites, no difference in the extent of mussel DNA strand breaks was shown between sampling locations (p > 0.05), questioning the sensitivity of the assays used in biomonitoring studies.     

Petroleum geochemistry of the Kimmeridge Clay of onshore Southern and Eastern England

The Kimmeridge Clay is considered a major oil source rock for the North Sea hydrocarbon province. The formation is also developed onshore in an organic-rich mudstone facies. This paper examines the possibility of onshore oil generation from the Kimmeridge Clay. Geochemically, onshore basin margin sediments contain rich, potential source horizons with mainly Type l/Type ll oil-prone kerogen, but are immature. Some deeper Cleveland Basin sediments have reached marginal maturity. Burial history reconstruction suggests significant formation palaeoburial depths in central areas of the Cleveland and Wessex Basins. Computed vitrinite isoreflectance contours show the Wealden and Isle of Wight Kimmeridge Clay to be thermally mature. Basin modelling suggests an early Palaeogene onset of oil generation in parts of the Cleveland Basin, while maximum oil generation could have been reached by the formation base in the Isle of Wight area during the late Cretaceous. Although basin subsidence ceased in the Neogene, in the Weald and Isle of Wight, where the formation is still deeply buried, oil generation probably continued for some time during uplift. Thus significant quantities of oil could have been generated. Whether or not this oil is present today however, would depend on the correct timing of suitable migration and trap structures.     

Assessment of the effectiveness of POLYMODE data assimilation by a numerical barotropic model for synoptic motions

This paper considers the results of numerical experiments involving POLYMODE data assimilation by a barotropic model for synoptic ocean dynamics. The model's response the data assimilation for various space-time discretenesses of assimilation is studied. Results derived from the application of optimal interpolation algorithms and modified optimal filtration algorithms are compared. Qualitative similarity to the calculations carried out through the simulation modelling technique is noted. Optimal assimilation algorithms are determined, depending on the space-time discreteness used. An optimal sampling discreteness for the POLYMODE conditions is suggested.Translated by Vladimir A. Puchkin.     

Growth and Production in Posidonia Oceanica (L.) Delile*

Abstract. In situ investigations of growth and production in a stand of Posidonia oceanica (L.) DELILE at a depth of 4 m at Ischia (Gulf of Naples) were carried out over two growing seasons. Posidonia starts to grow in August and an average bundle produces ten leaves in increasing time intervals until May. Growth curves for the leaves are given. Maximum leaf standing crop is in May with 1300 g dry weight per m^-2, leaf area index at this time reaches 22 m² m^-2. Leaf net productivity is highest in March with 12 g dry weight per m² per day. Annual leaf production is estimated as 3110 g dry weight per m², “underground” production as 115 g dry weight per m². About half the leaf production is exported from the system. Adaptive strategies of the growth and production pattern are discussed.     

Patterns of biomass-size spectra from oligotrophic waters of the Northwest Atlantic

The study of the distribution of biomass by size provides an ataxonomic approach for analyzing the structure of the pelagic ecosystem. However, empirical data regarding planktonic size-structure in offshore areas are scarce. Here, we report the results of a study of the planktonic biomass size-distribution at several stations located within two regions (Sargasso Sea and New England Seamounts Area) of the Northwest Atlantic. The biomass size-spectra covered a body-size range from bacteria to mesozooplankton and a depth range from the surface to 400 m. It is shown that the slope of the normalized biomass size-spectrum (NBS-spectrum) varies depending on whether volume or carbon units are used. The transformation from volume to carbon units makes the slope of the NBS-spectrum approximately 0.15 units more negative. The distribution of normalized-biomass by size was linear (plotted on a log–log scale) at all stations. The slopes of the NBS-spectra (volume scale) ranged from −0.96 to −1.01. There were no significant differences among the slopes of the NBS-spectra within either of the two areas studied. In addition, no significant differences were detected between the stations in the Sargasso Sea and those located in the New England Seamounts area. Apart from a tendency towards a decrease in the intercept of the normalized-biomass axis of the size-spectra in deeper waters, the NBS-spectra were also very similar through depth. The slopes of the NBS-spectra in biovolume units are not significantly different from −1.0 (p<0.01), and therefore are in agreement with Sheldon’s Linear Biomass Hypothesis. By contrast, the slopes of the NBS-spectra in carbon units are significantly different (p<0.01) from −1.0 (range=–1.09 to –1.17; all stations TOGETHER=–1.14) and their numerical values are in close agreement with Platt and Denman’s model and with the findings of [Rodríguez and Mullin, 1986a]) for the North Pacific Central Gyre. The results of this study support the hypothesis that the planktonic size-structure of offshore oligotrophic systems is a conservative property.     

Horizontal and Vertical Structure of Geostrophic Currents in the Black Sea According to the Data of the Summer Survey Performed as a Part of the ComSBlack-92 Program

We describe the methodology and software developed for the numerical analysis of the characteristics of the horizontal and vertical structure of geostrophic currents. We present the results of computation of these characteristics according to the data of the summer survey of the Black Sea carried out as a part of the ComSBlack-92 program. The distinctive features of the space structure of geostrophic currents discovered as a result and the established parameters of their variability may supplement the existing data on the current field in the Black Sea.     

Analysis of solutions to the inverse problem on the retrieval of the microstructure of stratospheric aerosol from satellite measurements

A statistical ensemble of microphysical parameters of the background stratospheric aerosol at altitudes of 15 to 30 km is modeled on the basis of experimental data. The aerosol attenuation coefficients (AACs) in the wavelength range 0.38–16.3 μm are calculated for all realizations of the ensemble by algorithms of the Mie theory. Analysis of correlations between the AACs and the microphysical parameters indicate that the AAC correlates most strongly with the total volume V and area S of all particles. The errors of determining the microphysical parameters from AAC measurements are analyzed via the method of linear regression. It is shown that, if the AAC is measured with an error of 5%, the errors of determining both the particle size distribution (PSD) for particles with sizes of 0.4 to 4 μm and the parameter S are an order of magnitude smaller than the prior uncertainty, whereas the error of determining V is two orders of magnitude smaller than the prior uncertainty. Schemes of AAC measurements with the SAGE III, ISAMS, CLAES, HALOE instruments and an IR interferometer in the visible and IR regions are discussed. It is shown that combining the schemes makes it possible to extend the range of particle sizes for which the PSD is retrieved with a satisfactory accuracy and to increase the accuracy of determining S and V substantially and the accuracy of determining the total number of particles N _opt to a lesser extent. Examples of interpreting AAC measurements carried out simultaneously with the SAGE III and HALOE instruments within the same spatial region are presented. A systematic discrepancy between vertical profiles of S and V obtained from SAGE III and HALOE measurements is revealed.