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  • Massachusetts Institute of Technology and Woods Hole Oceanographic Institution  (1)
  • thesis  (1)
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  • 1
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    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Publication Date: 2022-05-25
    Description: 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 October 1987
    Description: A two-layer shallow water equation model is used to investigate the linear stability of a coastal upwelling front. The model features a surface front near a coastal boundary and bottom topography which is an arbitrary function of the cross-shelf coordinate. By combining the various conservation statements for the global properties of the system, a general stability theorem is established which allows the a priori determination of the stability of a coastal upwelling front. Unstable waves are found for the modelled coastal upwelling front. The unstable wave motions are frontally-trapped and dominant in the upper layer. The wave propagates phase in the direction of the basic state flow and the primary energy conversion is via baroclinic instability. The effect of varying the model parameters is presented. Moving the front closer than ~ 2 Rossby radii to the coastal boundary results in a decrease in the growth rate of the fastest growing wave. Increasing the overall vertical shear of the basic state flow, by either decreasing the lower layer depth or increasing the steepness of the interface, results in an increase in the growth of the fastest growing wave. A bottom sloping in the same sense as the interface results in a decrease of the growth rates and alongfront wavenumbers of the unstable waves in the system. Linearized bottom friction is included in the stability model and results in a decrease in the growth rates of the unstable waves by extracting energy from the system. Since the unstable mode is strongest in the upper layer, bottom friction will not stabilize the upwelling front. A comparison between the predictions from the simple two-layer model and observed alongfront variability for three areas of active upwelling is presented. Reasonable agreement is found, suggesting that observed alongfront variability can be interpreted in terms of the instability of a coastal upwelling front.
    Description: This study was supported by the National Science Foundation Grant OCE 84-08563 and the Office of Naval Research Coastal Ocean Sciences Program 10/1984.37.
    Keywords: Upwelling ; Waves
    Repository Name: Woods Hole Open Access Server
    Type: Thesis
    Format: application/pdf
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  • 2
    Publication Date: 2022-01-31
    Description: Advances in ocean observing technologies and modeling provide the capacity to revolutionize the management of living marine resources. While traditional fisheries management approaches like single-species stock assessments are still common, a global effort is underway to adopt ecosystem-based fisheries management (EBFM) approaches. These approaches consider changes in the physical environment and interactions between ecosystem elements, including human uses, holistically. For example, integrated ecosystem assessments aim to synthesize a suite of observations (physical, biological, socioeconomic) and modeling platforms [ocean circulation models, ecological models, short-term forecasts, management strategy evaluations (MSEs)] to assess the current status and recent and future trends of ecosystem components. This information provides guidance for better management strategies. A common thread in EBFM approaches is the need for high-quality observations of ocean conditions, at scales that resolve critical physical-biological processes and are timely for management needs. Here we explore options for a future observing system that meets the needs of EBFM by (i) identifying observing needs for different user groups, (ii) reviewing relevant datasets and existing technologies, (iii) showcasing regional case studies, and (iv) recommending observational approaches required to implement EBFM. We recommend linking ocean observing within the context of Global Ocean Observing System (GOOS) and other regional ocean observing efforts with fisheries observations, new forecasting methods, and capacity development, in a comprehensive ocean observing framework.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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