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Author: Anass El Aouni Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Studying physical processes of an upwelling system is essential to understand its present variability and its past and future changes. This thesis presents an interdisciplinary study of the coastal upwelling system from different satellite acquired data, with the main focus placed on the North West African (NWA) upwelling system. This interdisciplinary study covers (1) the problem of the automatic identification and extraction of the upwelling phenomenon from biological and physical satellite observations. (2) A statistical study of the spatio-temporal variation of the NWA upwelling throughout its extension and different upwelling indices. (3) A Study of the nonlinear relationships between the surface mixing and biological activity in the upwelling regions. (4) Lagrangian studies of coherent eddies; their physical properties and automatic identification. (5) The study of transport made by Lagrangian eddies off the NWA Upwelling and their impact on the open ocean. [...].
Author: Anass El Aouni Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Studying physical processes of an upwelling system is essential to understand its present variability and its past and future changes. This thesis presents an interdisciplinary study of the coastal upwelling system from different satellite acquired data, with the main focus placed on the North West African (NWA) upwelling system. This interdisciplinary study covers (1) the problem of the automatic identification and extraction of the upwelling phenomenon from biological and physical satellite observations. (2) A statistical study of the spatio-temporal variation of the NWA upwelling throughout its extension and different upwelling indices. (3) A Study of the nonlinear relationships between the surface mixing and biological activity in the upwelling regions. (4) Lagrangian studies of coherent eddies; their physical properties and automatic identification. (5) The study of transport made by Lagrangian eddies off the NWA Upwelling and their impact on the open ocean. [...].
Author: Matthew K Gough Publisher: ISBN: Category : Languages : en Pages :
Book Description
Part I: Time evolving 2-D observations of near-surface flow with high frequency (HF) radar are well-suited for calculating Lagrangian Coherent Structures (LCSs) which are a valuable tool for observing turbulent flow. By comparing the evolving HF radar-derived LCS fields with satellite sea surface temperature imagery, the evolving structure of upwelling fronts, filaments, retention zones, and eddy-like recirculation are captured in the upwelling environment off the California coast. Part II: The inertial frequency is nearly diurnal at 30°N latitude which transects the northeastern Gulf of Mexico (NeGoM). At this latitude, near-surface inertial oscillations can amplify due to resonance with diurnal wind forcing. Diurnal oscillations have also been attributed to diurnal tidal forcing in this region. Because tidal forcing, wind forcing, and inertial oscillations are nearly diurnal, a unique series of comparative analyses are required to determine their relative influence on surface circulation. By comparing surface currents obtained by HF radar to predictions of the inertial response to wind forcing and barotropic tidal currents, it is found that diurnal oscillations in the NeGoM were predominantly due to wind-forced inertial oscillations in June 2010. The analyses provide a unique spatiotemporal perspective of inertial oscillations in the NeGoM where there is evidence of propagation, frequency and phase shifts, and amplitude variability. Positive (negative) sub-inertial vorticity [zeta] in the ocean shifts the effective inertial frequency feff of near-inertial oscillations (NIOs) above (below) the local inertial frequency f according to the relationship feff = f + [zeta]/2. It is found that NIO frequencies are consistent with feff determined from the vorticity field over the outer Mississippi Bight shelf and along the northern edge of the DeSoto Canyon during the last week of June 2010. Additionally, spatial NIO phase shifts associated with the frequency field of the NIOs are found to generate oscillatory divergence. In June 2010 oil from the Deepwater Horizon spill traversed through the NeGoM and it is speculated that the oil was exposed to mixing generated by the NIOs.
Author: C. P. Summerhayes Publisher: ISBN: Category : Science Languages : en Pages : 458
Book Description
Upwelling is one of the major physical processes driving the biogeochemistry of the ocean system. It dominates primary productivity in the world?s oceans, accounting for 80?90% of new production. However, because of the physical conditions that have to be met to generate upwelling, this production is concentrated in just a few places, e.g., in the coastal waters of major eastern boundary currents off California, Peru, Mauritania, and Namibia, where productivity leads to major fishing grounds. These areas account for about 50% of the world?s fish catch, underlining the importance of upwelling to humankind. Source rocks for oil formed in ancient coastal upwelling environments, making their study useful for improving oil exploration models. Upwelling also occurs in the open ocean, especially along the equator and beneath the westerly winds in the subarctic Pacific and the Southern Ocean, where the ocean?s silica budget is transformed by the deposition of the remains of siliceous phytoplankton. Because phytoplankton, the grass of the sea, can extract CO2 from the atmosphere, changes in the intensity of upwelling and associated biological productivity through time may have influenced climate. This volume uses an interdisciplinary approach to establish how upwelling systems work, how they vary through time, and whether or not they have a significant influence on the global carbon cycle. An understanding of how these largely wind-driven biogeochemical systems work today, and how they responded to past fluctuations in climate, is essential in predicting how they and their associated living resources may change in the future. One conclusion is that these systems exert a major influence on the global cycle of nutrients, a factor that contributes to making the coastal regions major sinks for organic carbon. This book recommends new strategies for observation, sampling, monitoring, experimentation, and modeling as the basis for improving forecasts of the behavior of upwelling systems. It will be of interest to physical oceanographers, marine biologists, fisheries scientists, marine organic and inorganic chemists, marine geologists, petroleum explorers, paleoceanographers, and paleoclimatologists.
Author: Christian E. Vincenot Publisher: Frontiers Media SA ISBN: 2889450554 Category : Languages : en Pages : 186
Book Description
Systems studied in environmental science, due to their structure and the heterogeneity of the entities composing them, often exhibit complex dynamics that can only be captured by hybrid modeling approaches. While several concurrent definitions of “hybrid modeling” can be found in the literature, it is defined here broadly as the approach consisting in coupling existing modelling paradigms to achieve a more accurate or efficient representation of systems. The need for hybrid models generally arises from the necessity to overcome the limitation of a single modeling technique in terms of structural flexibility, capabilities, or computational efficiency. This book brings together experts in the field of hybrid modelling to demonstrate how this approach can address the challenge of representing the complexity of natural systems. Chapters cover applied examples as well as modeling methodology.
Author: Annalisa Griffa Publisher: Cambridge University Press ISBN: 113946308X Category : Science Languages : en Pages : 479
Book Description
Written by a group of international experts in their field, this book is a review of Lagrangian observation, analysis and assimilation methods in physical and biological oceanography. This multidisciplinary text presents new results on nonlinear analysis of Lagrangian dynamics, the prediction of particle trajectories, and Lagrangian stochastic models. It includes historical information, up-to-date developments, and speculation on future developments in Lagrangian-based observations, analysis, and modeling of physical and biological systems. Containing contributions from experimentalists, theoreticians, and modelers in the fields of physical oceanography, marine biology, mathematics, and meteorology, this book will be of great interest to researchers and graduate students looking for both practical applications and information on the theory of transport and dispersion in physical systems, biological modeling, and data assimilation.
Author: Timothy Getscher Publisher: ISBN: Category : Dissertations, Academic Languages : en Pages : 99
Book Description
This thesis analyzes data from two types of unique drifter experiments in order to characterize two aspects of ocean flows that are often difficult to study. First, vertical velocities and their associated transport processes are often challenging to observe in the real ocean since vertical velocities are typically orders of magnitude smaller than horizontal velocities in mesoscale and submesoscale flows. Second, Lagrangian coherent structures (LCS) are features which categorize ocean flows into regimes of distinct behavior. These structures are also difficult to quantify in the real ocean, since sets of gridded trajectories from real ocean data (rather than model fields) are rarely available. The first experiment uses drifters drogued at multiple depths in the Alboran Sea to observe and characterize the ocean’s vertical structure, particularly near a strong front where vertical velocities are expected to be much stronger than other regions of the Ocean. The second experiment uses a roughly gridded pattern of surface drifters in the Gulf of Mexico to study LCSs as quantified by methods from dynamical systems such as finitetime Lyapunov exponents (FTLEs), trajectory arc-length, correlation dimension, dilation, Lagrangian-averaged vorticity deviation (LAVD), and spectral clustering. This thesis includes the first attempt to apply these dynamical systems techniques to real drifters for LCS detection. Overall, these experiments and the methods used in this paper are shown to be promising new techniques for quantifying both the vertical structure of ocean flows and Lagrangian Coherent Structures of flows using real drifter data. Future work may involve modified versions of the experiments, with denser sets of ocean drifters in the horizontal and/or vertical directions.
Author: Irina I. Rypina Publisher: ISBN: Category : Languages : en Pages :
Book Description
The Lagrangian dynamics of two-dimensional incompressible fluid flows is considered, with emphasis on transport processes in atmospheric and oceanic flows. The dynamical-systems-based approach is adopted; the Lagrangian motion in such systems is studied with the aid of Kolmogorov-Arnold-Moser (KAM) theory, and results relating to stable and unstable manifolds and lobe dynamics. Some nontrivial extensions of well-known results are discussed, and some extensions of the theory are developed. In problems for which the flow field consists of a steady background on which a time-dependent perturbation is superimposed, it is shown that transport barriers arise naturally and play a critical role in transport processes. Theoretical results are applied to the study of transport in measured and simulated oceanographic and atmospheric flows. Two particular problems are considered. First, we study the Lagrangian dynamics of the zonal jet at the perimeter of the Antarctic Stratospheric Polar Vortex during late winter/early spring within which lies the 3ozone hole4. In this system, a robust transport barrier is found near the core of a zonal jet under typical conditions, which is responsible for trapping of the ozone-depleted air within the ozone hole. The existence of such a barrier is predicted theoretically and tested numerically with use of a dynamically-motivated analytically-prescribed model. The second, oceanographic, application considered is the study of the surface transport in the Adriatic Sea. The surface flow in the Adriatic is characterized by a robust threegyre background circulation pattern. Motivated by this observation, the Lagrangian dynamics of a perturbed three-gyre system is studied, with emphasis on intergyre transport and the role of transport barriers. It is shown that a qualitative change in transport properties, accompanied by a qualitative change in the structure of stable and unstable manifolds occurs in the perturbed three-gyre system when the perturbation strength exceeds a certain threshold. This behavior is predicted theoretically, simulated numerically with use of an analytically prescribed model, and shown to be consistent with a fully observationally-based model.
Author: Anass El Aouni
Author: Anass El Aouni
Author: Matthew K Gough
Author: C. P. Summerhayes
Author: Christian E. Vincenot
Author: Robert L. Smith
Author: Kuoping Chiang
Author: Annalisa Griffa
Author: Marie-Hélène Durand
Author: Timothy Getscher
Author: Irina I. Rypina