The influence of a steady baroclinic deep ocean on the shelf

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 1988The degree to which a baroclinic deep ocean could be responsible for the mean flow on the shallow continental shelf is examined using steady, boundary forced models which incorporate bottom friction. One set of models, for a vertically well mixed shelf, includes the horizontal advection of density. The second set of models comprises a three-layer model without and a two-layer model with interfacial friction. It is found that near bottom flow has a short cross isobath scale due to the steep continental slope and consequently that the deep oceans lower water column could not be responsible for the observed mean flow. The cross isobath scale of flow in the upper deep ocean is predominantly determined by the oceans velocity profile. In a barotropic or near barotropic flow the upper water column follows the near bottom flow and therefore has little influence on the shelf. A surface intensified deep ocean flow is able to cross isobaths until it encounters the bottom. If deep ocean flow is confined to a surface layer thinner than the depth at the shelf break it could be responsible for the observed flow. The depth scale for velocity and density over the slope in the Mid-Atlantic Bight is generally larger than the shelf break depth and consequently it is concluded that the steep continental slope "insulates" this particular shelf from baroclinic deep ocean influence and therefore that the observed shelf flow is not of oceanic origin. Using oxygen isotope data, Chapman et al. (1986) found that the Scotian shelf is the major source of Mid-Atlantic Bight shelf water. Their barotropic modeling results are extended to show that a baroclinic deep ocean also acts to hold shelf water on the shelf.This Research was carried out with the support of the National Science Foundation, Grant OCE-85-1848

COMPARISON OF WAVE DRAG FOR BOTH THE MALE AND FEMALE FORM

This study measured forces acting male and female mannequins while being towed in a flume in order to quantify the differences in the wave drag contribution to total drag. Substantial differences between the male and female form in terms of the wave drag contribution were found with the female having a substantially lower (by 46.73% at 1.94 ms-1) contribution near the surface while having a greater (by 20.87% at 1.94 ms-1) total drag when deeply submerged. These differences were found despite the smaller frontal area and total surface area of the female. Both the decreased wave drag and increased submerged drag were theorised to be due to the resulting flow field created by the greater curvature of the female torso as compared to the male with the rate of change in curvature of the female being almost double that of the male

Improving Buoy Detection with Deep Transfer Learning for Mussel Farm Automation

The aquaculture sector in New Zealand is experiencing rapid expansion, with a particular emphasis on mussel exports. As the demands of mussel farming operations continue to evolve, the integration of artificial intelligence and computer vision techniques, such as intelligent object detection, is emerging as an effective approach to enhance operational efficiency. This study delves into advancing buoy detection by leveraging deep learning methodologies for intelligent mussel farm monitoring and management. The primary objective centers on improving accuracy and robustness in detecting buoys across a spectrum of real-world scenarios. A diverse dataset sourced from mussel farms is captured and labeled for training, encompassing imagery taken from cameras mounted on both floating platforms and traversing vessels, capturing various lighting and weather conditions. To establish an effective deep learning model for buoy detection with a limited number of labeled data, we employ transfer learning techniques. This involves adapting a pre-trained object detection model to create a specialized deep learning buoy detection model. We explore different pre-trained models, including YOLO and its variants, alongside data diversity to investigate their effects on model performance. Our investigation demonstrates a significant enhancement in buoy detection performance through deep learning, accompanied by improved generalization across diverse weather conditions, highlighting the practical effectiveness of our approach.Comment: 7 pages, 5 figures, submitted to ICVNZ 2023 conference https://ivcnz2023.massey.ac.nz

Developing an Integrated Ocean Observing System for New Zealand

New Zealand (NZ) is an island nation with stewardship of an ocean twenty times larger than its land area. While the challenges facing NZ’s ocean are similar to other maritime countries, no coherent national plan exists that meets the needs of scientists, stakeholders or kaitiakitanga (guardianship) of NZ’s ocean in a changing climate. The NZ marine science community used the OceanObs’19 white paper to establish a framework and implementation plan for a collaborative NZ ocean observing system (NZ-OOS). Co-production of ocean knowledge with Māori will be embedded in this national strategy for growing a sustainable, blue economy for NZ. The strengths of an observing system for a relatively small nation come from direct connections between the science impetus through to users and stakeholders of an NZ-OOS. The community will leverage off existing ocean observations to optimize effort and resources in a system that has historically made limited investment in ocean observing. The goal of the community paper will be achieved by bringing together oceanographers, data scientists and marine stakeholders to develop an NZ-OOS that provides best knowledge and tools to the sectors of society that use or are influenced by the ocean

MultiRow from An optimal tuning strategy for tidal turbines

Additional examples with multiple rows of turbine

Photoprotection in Southern Ocean phytoplankton: missing key to low primary productivity

The Southern Ocean is considered a zone of high nutrients and low chlorophyll (HNLC). Despite the year round availability of nutrients, phytoplankton biomass remains low. Key modes of control are now thought to be light, grazing, iron and supply of silicic acid^1^. Physiological photoprotective mechanisms used by phytoplankton to regulate photosynthesis versus rapid light fluctuations have not been considered important. In diatoms and haptophytes, which are the major component of phytoplankton biodiversity in the Southern Ocean, the one step de-epoxidation of diadinoxanthin (Dd) into diatoxanthin (Dt) of the Dd-cycle constitutes the main photoprotective mechanism^2,3^. Here we show that Southern Ocean diatoms and haptophytes have higher concentrations of cellular Dd-cycle pigments than other oceanic regions. The Dd-cycle is activated under low irradiance conditions and the pool of photoprotective pigments increases under intermittent light conditions. The high cellular concentration of Dd-cycle pigments and our observations of an increase of the pool size of Dd-cycle pigments towards the surface implies that the Dd-cycle pigments bind to light harvesting proteins other than with fucoxanthin and chlorophyll c. Within photosystem II, enrichment of Dd and the physiological acclimation to light changes constrains photosynthetic activity, efficiency and potentially growth rates^3-7^. These results raise important questions about the role of photoprotective mechanisms in limiting Southern Ocean primary productivity and how these mechanisms will respond to predicted climate change impacts^8^

Wave drag on human swimmers

Mesures de la trainée passive de vague chez les nageurs, notamment lors des phases immergées du départ et du virage

Inferring parental areas of juvenile mussels using hydrodynamic modelling

Mussel aquaculture is heavily reliant on wild mussel populations that supply juveniles (spat) for seeding farms. However, little is often known about parent populations, representing a risk for the sustainability of the industry. We used hydrodynamic back-tracking models to identify potential parental areas that provision green-lipped mussel (Perna canaliculus) spat across a range of settlement sites in New Zealand's largest aquaculture area. Median parental area varied considerably between 19 km2 for sites located in enclosed bays and a maximum of >1150 km2 for sites located in open bays. Median distance to parent populations ranged between 1.8 and 21.4 km, with a maximum larval dispersal estimated to be ca. 100 km. Small seasonal variations in parental area and dispersal distance were detected in some regions, whereas inter-annual variability was relatively minor. Regional connectivity between settlement and parental regions ranged between a minimum of 45% of larvae originating in the same parental region, to maximum retention rates of 99.9% for sites in enclosed bays, implying a considerable regional variation in the potential for self-seeding and exporting mussel larvae other areas. Our results also delineate areas that support spatfall by identifying likely locations for wild or farmed parental populations, and by establishing the spatial extent where mussel reproduction and larval development through to settlement take place. These dispersal and connectivity patterns are crucial to support management decisions for the conservation and restoration of parental populations, and other environmental constraints, such as water quality, which are necessary to ensure the sustainability of spat catching operations that enable shellfish farming

Designing large arrays of tidal turbines: A synthesis and review

Abstract Much of the global tidal current energy resource lies in the accelerated flows along narrow channels. These channels have the potential to produce 10–1000 s of MW of electricity. However, realizing 100 MW of a channel׳s potential is much more complex than installing 100 1-MW turbines because large scale power extraction reduces tidal currents throughout the channel, changing the resource. This synthesis and review gives an overview of the issues and compromises in designing the layout of the large tidal turbine arrays required to realize this potential. The paper focuses on macro- and micro-design of arrays. Macro-design relates to the total number of turbines and their gross arrangement into rows, while micro-design adjusts the relative positions of the turbines within a grid and the spacing between rows. Interdependent macro-design compromises balance the total number of turbines, array power output, the power output of each turbine, the loads the turbines experience, turbine construction costs, maintaining navigability along the channel and any environmental impacts due to flow reduction. A strong emphasis is placed on providing physical insights about how “channel-scale dynamics” and the “duct-effect” impact on the compromises in array design. This work is relevant to the design of any “large” array which blocks more than 2–5% of a channel׳s cross-section, be it 2 turbines in a small channel or 100 turbines in a large channel