• European Marine Science
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A seven level primitive equation equatorial ocean model with temperature and salinity is integrated over a 30 year period to a quasi-steady state. Placement of four of the seven levels of the model in the first 100 meters gives sufficient vertical resolution to resolve most major features of equatorial oceans. The model equivalents of the South Equatorial Current, the Cromwell Current, vertical upwelling in the equatorial area, Ekman divergence of mass toward each pole, and a thermocline were all simulated. A major conclusion was salinity probably has little effect on the general circulation patterns in the equatorial region. Additionally, the use of a vertical eddy diffusion coefficient for momentum that is dependent upon vertical stability, vertical current shear, and depth will probably be required to accurately model the vertical structure of the currents. http://archive.org/details/anoceforecasting1094516273 Lieutenant, United States Navy Approved for public release; distribution is unlimited.

MSc thesis on the extrapolation of AtlantECO-BASE-v1's global microplastics concentrations (Schmiz, 2021) using machine learning models. Contribution to task 2.3.

MSc (Environmental Sciences), North-West University, Potchefstroom Campus Metals have been in our environment since the genesis of the world and are ubiquitous in all environments. We as humans mine, utilize, and release these metals from the environment to a level that may affect chronically or acutely environment and human health. To that sense, information on metal concentrations are valuable in commercially marine species as they are an important food source to many communities. Fish and molluscs are also good bioindicators and biomonitors as they can indicate the health of the environment, they are found in. There is, however, an information gap about metal concentrations in the marine environment off the coast of South Africa. In this study, sardines (Sardinops sagax) and chokka (Loligo reynaudii) from the Indian and the South Atlantic oceans, and hake (Merluccius capensis), kingklip (Genypterus capensis), and monkfish (Lophuis vomerinus) from the South Atlantic Ocean were analysed for metals using an inductively-coupled plasma mass spectrometry. These species, representing two trophic levels, are exploited in large quantities for human consumption. More knowledge on metal composition will shed light on the biological relationships between the species, possible impacts elevated metal concentrations might have on the fish, and on human and predator consumer health. Metal concentrations and compositions of each species were established and compared. Significant differences in metal concentrations were found between sardine, chokka and the demersal species (hake, kingklip, and monkfish). As was expected, higher trophic levels (hake, kingklip and, monkfish) contained significantly higher concentrations of metals than lower trophic levels such as sardines. Chokka contained significantly lower concentrations of vanadium, cobalt, molybdenum, and manganese than sardines, hake kingklip, and monkfish, but significantly higher concentrations were found for boron, titanium, zinc, cadmium, rubidium, and strontium. These patterns could be caused by physiological regulation or lack of regulation of these metals in chokka. Demersal predators’ metal concentrations and compositional patterns did not differ significantly between each other, probably due to a trophic overlap in diet. Metal compositions or fingerprints were distinct between sardines and chokka from different oceans. This indicates metal compositional patterns could be used as a possible stock discrimination tool. Sardines and chokka metal compositions were distinct from the demersal predators. Demersal metal compositions overlapped, once again possibly caused by diet similarity. The effect of physical parameters (length and mass) on metal concentration was assessed for chokka, hake, kingklip, and monkfish. Negative regressions were found for most metals. However, a positive regression was found for chromium with kingklip length that could be cause for consumer (animal and human) concern. Compared with other studies from around the world cadmium, lead, and mercury concentrations were lower or on par in all species. Cadmium, lead, and mercury concentrations in the muscle tissue of all species were assessed for human consumer safety. Concentrations were found to be below the limits set by South Africa and the European Union for these fish. Estimated daily intake and the total hazard quotient (for South African adults) was calculated for cadmium, lead and mercury. All values were below the quotient of unity. Based on my study it can be concluded that the species studied would be safe for human consumption, but data from more fish from more sites would be needed for confirmation. For the first time, sardines, chokka, hake, kingklip, and monkfish metal concentrations and compositions are compared. Also for the first time, metal concentrations and compositions are compared between sardine and chokka sampled from the South Atlantic and Indian oceans. This study provides valuable information on these commercial species and narrows the information gap currently present on commercial marine species off the South African coast. I also stress the need for more samples from more sites, the need to sample more species, the need to sample higher predators such as dolphins Masters

This research involves numerical modeling of acoustic signals through shallow water channels. The sound is computationally modeled in a vertical plane as a dense fan of beams radiating from the transmitter location. The cross section of each 2-dimensional beam is represented as a Gaussian distribution of acoustic energy. The Gaussian beam travels axially along rays governed by Snell's Law, dispersing in width as a function of travel distance. At arbitrary receiver locations in the planar sound field, the intensity of the propagated beams is integrated over time to synthesize the multipath channel response. The influence of the ocean channel is analyzed parametrically, including sensitivity of the eigenray structure and impulse response to water properties, channel boundaries, and source/receiver geometry. Specific maritime environments examined in this study are St. Andrew Bay, Panama City, FL, and Chesapeake Bay, Little Creek, VA. This research supports the possible use of high frequency acoustics (40-70 kHz) for short-range (500 m) through-water communications. Emphasis is on communications between seabed stations. http://archive.org/details/modelingofhighfr109453507 US Navy (USN) author. Approved for public release; distribution is unlimited.

Current practices for modeling the ocean floor in underwater explosion simulations call for application of an inviscid fluid with soil properties. A method for modeling the ocean floor as a Lagrangian solid, vice an Eulerian fluid, was developed in order to determine its effects on underwater explosions in shallow water using the DYSMAS solver. The Lagrangian solid bottom model utilized transmitting boundary segments, exterior nodal forces acting as constraints, and the application of prestress to minimize any distortions into the fluid domain. Elastic materials were used, though multiple constitutive soil models can be applied to improve the accuracy. This method is unable to account for soil cratering effects, however it provides the distinct advantage of modeling contoured ocean floors such as dredged channels and sloped bottoms absent in Eulerian formulations. The dynamic loading effects of the investigated bottom contours were found to be negligible in the analyzed cases as a result of the bulk cavitation zone which dominates the chosen fluid field and serves as a buffer to the target. In addition to its utility in bottom modeling, implementation of the non-reflecting boundary along with realistic material models can be used to drastically reduce the size of current fluid domains. http://archive.org/details/investigationofn109455530 Approved for public release; distribution is unlimited.

The deep ocean is characterized by sound propagation that can support wide-area surveillance throught the use of distributed acoustic sensors near the seabed. Such a deep-water sensor network is potentially enabled by phenomena such as Reliable Acoustic Path (RAP) and Deep Sound Channel (DSC) through which undersea network nodes can transmit and receive data across long distances. To provde a theoretical understanding of system effectiveness, the Bellhop acoustic modeling program is used to predict sensor coverage and communications range. http://archive.org/details/soundpropagation109454334 Outstanding Thesis US Navy (USN) author. Approved for public release; distribution is unlimited.

This doctoral dissertation presents the results from two independent mesocosm studies on naturally present summer plankton communities in the Baltic Sea. The aim was to investigate the impact of ocean acidification (increased CO2 concentration and decreased seawater pH) as well as the combination of ocean acidification and ocean warming (increased seawater temperature) on the abundance and activity of diazotrophic organisms and on N-limited plankton communities.

Wave breaking at the ocean surface is an important process for air-sea exchange. Whitecaps are visual sea surface signatures of breaking waves. By measuring the fractional coverage of whitecaps on the sea surface, it is possible to quantify wave breaking. This thesis comprises of three distinctive pieces of research. I compare model simulations of sea surface temperature to high resolution observations for three unique cases. The model runs over a daily cycle using a 1-dimensional 2nd moment closure turbulence scheme with the inclusion of a wave breaking model. The comparisons reveal poor performance when the wave breaking model is included. Subsequently, attempts to improve on our understanding of wave breaking were made. I developed a technique for estimating whitecap coverage estimates of both actively breaking (stage A) waves, and maturing (stage B) foam. The Spatial Separation of Whitecap Pixels (SSWP) allows for accurate distinguishing of stage A and stage B whitecap regions by manually evaluating the pixel intensity, location (with respect to the crest of the wave), texture and shape of a given whitecap region. Finally, measured WA and overall whitecap coverage (WT = WA +WB) for the North Atlantic dataset were then compared with modeled estimates of whitecap coverage, derived using a semi empirical formula and various wave-field model parameters. High resolution model estimates of the wave-field are provided by the European Center for Medium Range Weather Forecasting (ECMWF) Wave Model (WAM). Results reveal good performance between WA and modeled generated WT for specific tuning values, which are provided.

5km) communications in the 9-14 kHz band. The proposed scheme exploits a higher carrier frequency at 45 kHz and increased spectral bandwidth compatible with the short-range link, thus achieving an increased channel capacity. Analytical expressions are provided for the scheme, which combines principles of M-ary frequency-shift keying (MFSK) and orthogonal frequencydivision multiplexing (OFDM) in a modulation referred to as multi-channel MFSK. The proposed scheme consists of 32 orthogonally spaced channels, each of which contains a 4-ary FSK pulse train. Existing medium-range modem algorithms are adapted for the higher carrier frequency and candidate variations are implemented with bandwidths of 10 and 20 kHz. The variations involve bandwidth scaling or multiplexing the original 5 kHz spectral bandwidth. Of concern for short-range links in shallow water is multipath interference, which causes time-spreading and significant intersymbol interference (ISI). Dominant eigenray paths are determined in order to estimate the amount of time-spread expected in various shallow water environments. These are analyzed with respect to the time/frequency relationships of multi-channel MFSK to comparatively evaluate the candidate variations in terms of protection against ISI. On this basis, we propose multiplexing the 5 kHz MFSK modulation across the larger operating band. http://archive.org/details/timefrequencyrel109455205 US Navy (USN) author Approved for public release; distribution is unlimited.

In August of 2006 the Adaptive Sampling and Prediction (ASAP) experiment was conducted near the northern Monterey Bay. Multiple assets including aircraft, autonomous vehicles, moorings, and numerical models were used to gain a better understanding of three-dimensional upwelling centers. Data were collected at two separate mooring locations using Acoustic Doppler Current Profilers (ADCPs) during the experiment. The focus of this thesis is to determine the effects of local wind forcing on the ocean circulation and provide a comparison between the data collected at the mooring locations and numerical predictions for the region. Upwelling and relaxation events are used as the basis for understanding the local wind forcing. Upwelling typically results in equatorward flow while relaxation events typically result in poleward flow. Several different types of analyses were used to determine the effects of the local wind forcing. A visual analysis was performed with stick vector plots and component plots of the rotated time series that compared the wind with the data from the water column. Two methods of cross correlation, component correlations and vector correlations, were exploited as well as a spectral analysis of the wind and ADCP data. Finally the coherence and phase between the wind and currents were examined. Based on the analysis it became evident that the currents were forced by both wind and non-local events such as eddies, meanders, and the large-scale alongshelf pressure gradient. Associated with the ASAP experiment, the Harvard Ocean Prediction System (HOPS), the Regional Ocean Modeling System (ROMS), and the Navy Coastal Ocean Model (NCOM) provided nowcasts that were compared with the mooring data to determine their accuracy and precision. Overall, in the beginning of August the models provided reasonable representations of the flow patterns at the mooring locations. The prediction error increased towards the end of August which was possibly related to data assimilation techniques and more non-local forcing at that time. The military application of this thesis is that accurate current prediction by ocean models will benefit amphibious operations, special warfare operations, and mine warfare in the littoral zone. http://archive.org/details/observationsndmo109453469 US Navy (USN) author. Approved for public release; distribution is unlimited.