Direct assimilation of altimetric differences using the Kalman filter

One method that has been proposed for avoiding the effects of geoid error in the use of satellite altimeter data in oceanography is the use of temporal differences of the data, either along repeat tracks or at points where ascending and descending orbital passes cross. Here, the Kalman filter for this special case is derived and its properties examined. The special form of the data does not lead to additional computational workload, as one might expect. The question of observability, i.e., whether temporal differences alone are sufficient to determine the model state uniquely, is discussed, and criteria for observatility are derived in terms of the properties of the dynamical model.     

Tangential velocity profile for pseudoplastic power-law fluids in the hydrocyclone — A theoretical derivation

The tangential velocity profile for pseudoplastic power-law fluids in a hydrocyclone is determined with an analytical solution to a simplified momentum balance equation by the method of perturbation. A numerical solution of the non-linear two-point boundary-value problem by the finite-difference method provides a verification of the perturbation solution. The tangential velocity is found to be controlled by a modified Reynolds number involving the radial velocity at the outer radius of the hydrocyclone and the consistency and flow-behavior indices of the fluid. The radial position of the maximum tangential velocity decreases with an increase in the modified Reynolds number and/or the degree of pseudoplasticity of the fluid. This analysis suggests that improved performance of hydrocyclones may be possible for pseudoplastic fluid systems as the tangential velocity profiles are steeper and the free-vortex zone is extended inwards.     

Mercury-binding proteins in the slipper limpet,Crepidula fornicata,exposed to increased soluble mercury

Crepidula fornicata were held in a flow-through bioassay system and exposed to sand-filtered seawater to which no soluble mercury (control) was added or to which either 5, 25, or 50 μg 1^?1 soluble Hg was added. At specific intervals during the 16-week experiment, a group of limpets was removed from each tank; one subgroup was exposed for 48 h to high concentrations of Hg, and another was analyzed for Hg-binding proteins by gelpermeation chromatography and spectrometry. Mortality from exposure to Hg in the 48-h acute toxicity tests was related to concentrations of Hg experienced both during the long-term exposure period and the 48-h exposure period. Chronic exposure to low levels of Hg resulted in increased amounts of total Hg in the whole body and in the low-molecular-weight Hg-binding proteins. No evidence was found for increased tolerance to Hg with preexposure.     

Effects of a variety of impacts on seagrass restoration in Jamaica

For the first time seagrass rehabilitation was attempted in a tropical nation, Jamaica. Repairs to a variety of developmental impact types were attempted with test plots: dredge and fill, bauxite and oil spills, channelization, urban run-off, urban sewage, river bulkheading, jetty construction and artificial beach, industrial lagoons, saline lagoons, thermal effluents, and cement tailings. Three species were routinely planted (Thalassia testudinum, Halodule wrightii, Syringodium filiforme) plus Ruppia maritima in saline lagoons, each by two planting techniques. Types of damage which were successfully attempted to be restored for the first time were from heated wastes, bauxite spills, jettied river mouths, small scale oil spills, and diluted urban wastes. Types of pollution damage previously repaired in subtropics and temperate zones, which could be successfully repaired in the tropics also were dredge and fill and urban run-off. Erosion seagrass restoration repair was partially successful at some sites. Attempts to repair high salinity lagoons (up to 160‰) and cement tailings were unsuccessful. Functional species were found which could tolerate ongoing pollutant loads in some cases.     

Growth,production, food consumption,and mortality of juvenile spot and croaker: A comparison of tidal and nontidal nursery areas

As the dominant juvenile finfish in southeast and Gulf of Mexico nursery areas, spot and croaker growth, food consumption, production, and mortality are compared in tidal salt marshes and nontidal brackish systems. Growth rates of spot and croaker from 5 studies ranged from 0.021–0.04 g per g per d. Differences in the annual production and food consumption estimates were primarily due to differences in average biomass. Although mean biomass varied widely, the daily production to mean biomass ratios ranged from 0.021–0.037, suggesting that these systems probably could support more juvenile fish than are present. Spot mortality ranged from 0.023–0.041% per d. Despite large hydrographic differences between tidal and nontidal systems and large differences in the amount of detrital input, the secondary production values and many of the fish population parameters are remarkably similar. This is interpreted as confirmation of the basic trophic similarity of the different systems and the highly adaptable and general nature of juvenile fish. The primary consumers are supported by 50–100% of the algal production. But because the dominant fishes consume only 10–35% of that secondary production, at least in some systems, food does not appear to limit juvenile fish production. Predation on the juveniles is implicated as a limiting factor.     

Reply to A. S. Dyke's discussion

In our opinion the amino acid data are consistent with the till/nonglacial stratigraphy. We reject Dyke's proposal that the plotting of data in 0.04 increments is appropriate as an unwarranted interpretation that errors are cumulative. We also see no grounds for accepting his alternative interpretation that the groups of amino acid ratios reflect various transport (read temperature) histories of a single population of Bell Sea shells. It is our opinion that the relative sequence of marine incursions in Hudson Bay is reliable and we repeat that the evidence favors one or more deglacial events. We stress that the ages of the units between the Tyrrell Sea and Bell sea end membrers are interpolated and that the chronology of events is currently based on the assumption that the Bell Sea represents marine incursion at the onset of marine isotope stage 5.Dyke has raised a number of points which have concerned us since we started our joint research on the aminostratigraphy of the Hudson Bay Lowlands. The answer to many questions will come, not from the amino acid results per se, but from detailed litho-, and biostratigraphic logging of the thousands of kilometers exposed along the large rivers that drain into James Bay and southwestern Hudson Bay. This work is presently going on. Let us say in conclusion that analysis of a further 63 shells and shell fragments resulted in a virtually identical frequency distribution to that discussed in our paper. We are currently evaluating the stratigraphic integrity of these results. Field expeditions by the Geological Survey of Canada in 1982 and 1983 into the Hudson Bay Lowlands were specifically designed to log new sections and make additional shell collections. We hope to report on these new data in due course.     

Multichannel analysis of surface wave method with the autojuggie

The shear (S)-wave velocity of near-surface materials and its effect on seismic-wave propagation are of fundamental interest in many engineering, environmental, and groundwater studies. The multichannel analysis of surface wave (MASW) method provides a robust, efficient, and accurate tool to observe near-surface S-wave velocity. A recently developed device used to place large numbers of closely spaced geophones simultaneously and automatically (the ‘autojuggie’) is shown here to be applicable to the collection of MASW data. In order to demonstrate the use of the autojuggie in the MASW method, we compared high-frequency surface-wave data acquired from conventionally planted geophones (control line) to data collected in parallel with the automatically planted geophones attached to steel bars (test line). The results demonstrate that the autojuggie can be applied in the MASW method. Implementation of the autojuggie in very shallow MASW surveys could drastically reduce the time required and costs incurred in such surveys.     

A fluid-pressure feedback model of dehydration reactions: experiments, modelling, and application to subduction zones

Dehydration and melting reactions generate large volumes of fluid in the crust and upper mantle, and play an important role in subduction zone seismicity. The fluid pathway must evolve from isolated pockets in low porosity, low permeability rock, coalescing to interconnected permeable pathways to the surface. When fluid pressures generated from a dehydration or melting reaction are sufficient to induce hydrofracture, then hydrofracture significantly influences the porosity–permeability structure within the dehydrating/melting horizon. If a low fluid-pressure boundary is introduced to the dehydrating rock, then fluid will be driven from the rock along the evolved permeable network toward that boundary. The resulting pressure reduction can then accelerate the dehydration reaction and further drive the flow. The sudden introduction of a low fluid-pressure boundary may occur by the co-seismic (dilatant) rupturing of a pressure seal that connects different fluid pressure states. This mechanism is invoked to explain the observed post-seismic evolution of wave velocities (V_p/V_s) following the 1995 Antofagasta, Chile earthquake. We show experimental results and introduce a conceptual and numerical model that reflects this scenario. The model couples the mechanical and thermodynamic effects of fluid pressure with devolitization kinetics, and is quantitatively consistent with experimental studies of the dehydration of gypsum and serpentine. The experimental results show that dehydration is controlled by access to a free (drained) boundary. The model provides a mechanistic explanation for the experimental observations and has applications in understanding the role of transient transport networks on the large-scale behavior of dehydrating and melting systems.     

Successful Use of an Innovative Horizontal/Vertical Well Couplet in Fractured Bedrock to Intercept a Mobile Gasoline Plume

The horizontal directional drilling (HDD) technology was successfully used in a fracture-controlled sandstone matrix to intercept a gasoline plume and create a 150-foot-long hydrodynamic barrier preventing seepage of gasoline and contaminated ground water into a salmon-bearing stream within a public park. A 36-foot-deep vertical recovery well (VW) intercepts the central low point of the 420-foot-long HDD borehole to pump recovered fluids. Contaminant seepage into the creek ceased within hours of starting up the HDD/VW interceptor system in August 1999. Approximately 325 gallons of gasoline and 2 million gallons of contaminated ground water have been recovered to date.