A residual analysis method for quantitative comparison of spatial data from the Iceland-Faeroes Front

A spatial statistical method has been developed from the well-known Kriging technique in geostatistics, as a way of providing quantitative comparison between a pair of spatial data sets, and a measure for such a comparison. This residual analysis method is applied to oceanographic data in order to compare Iceland-Faeroes Front (IFF) model predictions against appropriate field observations, with an aim to assess the IFF model performance and its prediction accuracy. The method is also used to evaluate the model-generated dynamical variability within the model predictions, as well as the natural variability within the frontal observations. From the results, it has been found that the IFF model is highly robust, and gives better predictions at depth 150–350 m than elsewhere. Within such a depth (i.e. 250–350 m), there is also evidence to suggest that the main frontal region is most active above the IF Ridge. The natural variability obtained from the observations appears to be comparable to the model-generated dynamical variability after 20 days of integration, indicating a certain degree of accuracy in the model predictions. The method reported in this paper could also be extended for further use in model data assimilation. Thus, the work not only demonstrates how spatial statistics can be applied to oceanographic data, but also opens up new statistical tools for data handling in ocean modelling.     

Video observations of marine gravel transport

In an analysis of video observations of gravel transport in the West Slent, UK, collective and individual characteristics of 458 bursts of bedload have been examined and the transport velocity and distance of 1680 individual particles in a consecutive succession of burst events determined. Infrequent, long duration, high stress events account for 60% of total transport in only 24% of the total time with the mean free path and transport velocity for particles being 0.16 m and 0.22 m/s, respectively. Clear links between intense intermittent turbulence and bedload transport revealed in this study, suggest progress in modelling requires a clearer understanding of near bed flow structure.     

Modern swathe sounding and sub-bottom profiling technology for research applications: The Atlas Hydrosweep and Parasound Systems

This chapter describes two separate but complementary research echosounder systems originally developed by Krupp Atlas Elektronik GmbH for the new German oceanographic research vessel Meteor.The Hydrosweep is a Hydrographic wide-swathe sweep survey echosounder for both shallow and deep water applications providing accurate bathymetric surveys and terrain-following navigation capabilities.The Parasound system is a hull-mounted dual channel parametric narrow-beam deep sea survey and sub-bottom profiling echosounder enabling particularly high vertical and horizontal resolution of seabed features.     

Three-dimensional visualization of mission planning and control forthe NPS autonomous underwater vehicle

The Naval Postgraduate School (NPS) is constructing a small autonomous underwater vehicle (AUV) with an onboard mission control computer. The mission controller software for this vehicle is a knowledge-based artificial intelligence (AI) system requiring thorough analysis and testing before the AUV is operational. The manner in which rapid prototyping of this software has been demonstrated by developing a controller code on a LISP machine and using an Ethernet link with a graphics workstation to simulate the controller's environment is discussed. The development of a testing simulator using a knowledge engineering environment (KEE) expert system shell that examines AUV controller subsystems and vehicle models before integrating them with the full AUV for its test environment missions is discussed. This AUV simulator utilizes an interactive mission planning control console and is fully autonomous once initial parameters are selected     

Numerical simulation of unsteady free-surface motions using a boundary integral formulation

A numerical time simulation method is described to solve fluid flow problems including unsteady free surface motion. The method is based on potential flow theory. At every time step, the problem is solved using a boundary integral formulation of the fluid domain. The linearized free surface conditions are integrated in time and the solution is marched forward. Computational results simulating the free surface motion for the cases of a linear progressive wave, wave propagating into a region of calm water and the wave maker motion are presented. Comparison with theoretical results demonstrate the feasibility of the proposed simulation scheme.     

Histopathological changes in the liver of dab (Limanda limanda) from a contamination gradient in the North sea

As part of a joint workshop organised by the International Council for the Exploration of the Sea (ICES) and the Intergovernmental Oceanographic Commission (IOC) on biological effects monitoring techniques. dad (Limanda limanda) were examined from six spaced stations along a 200 km transect extending from near the mouth of the Elbe River out to the Dogger Bank in the North Sea. Based on historical data, differences in contaminant concentrations in sediments exist along the transect (lipophilic organic xenobiotics at the inshore sites and heavy metals offshore over the Dogger Bank). The most contaminated site sampled was the most inshore, the least contaminated was approximately midway along the transect, with contamination building up again over the farthest point along the transect, over the Dogger Bank. Multiple organs and tissues were examined for full pathology from each fish sampled. Only liver data are presented here (11–20 livers per station). The most significant lesions were considered to be well-developed foci of cellular alteration, high mitotic activity and high neutral lipid accumulation in livers from dab sampled from the most inshore site examined. Livers from the least-contaminated station showed minimal evidence of such changes. Foci of cellular alteration and neutral lipid accumulation were also seen in dab liver sampled from fish from the Dogger Bank site. Thus far, the hepatic changes seen correlate well with the most contaminated sites along the transect. The value of comprehensively examining the histopathology of an organ of toxicological significance, such as the liver in a European species of flatfish, is demonstrated.     

Trace metal concentrations in sediments of the Eastern Mississippi Bight

Sediments collected from 3 onshore-offshore transects (12 stations total) in the Eastern Mississippi Bight at 5 different times during 1987–1988 have been analyzed for total Ag, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Se, Sn, Th and Zn. The data show considerable variation both spatially and temporally, largely as a result of natural variability in grain size and mineralogy. Clay-rich samples from deep water were always more metal-rich than sandy samples from shallow areas. Many samples from near the Mississippi River Delta appeared to be enriched in Ba by about a factor of two, probably as a result of contamination from oil well drilling mud, but there were few other indications of pollution influences. Many samples from throughout the area gave Mn/Fe and Cd/Fe ratios a factor of two or more lower than their Mississippi River source material. This shows that biochemical activity in the sediment is capable of solubilizing reducible and adsorbed metals.