A Multi Dimensional Spectral Description Of Ocean Variability With Applications
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A Multi-dimensional Spectral Description of Ocean Variability with Applications
Efforts to monitor the ocean for signs of climate change are hampered by ever-present noise, in the form of stochastic ocean variability, and detailed knowledge of the character of this noise is necessary for estimating the significance of apparent trends. Typically, uncertainty estimates are made by a variety of ad hoc methods, often based on numerical model results or the variability of the data set being analyzed. We provide a systematic approach based on the four-dimensional frequency-wavenumber spectrum of low-frequency ocean variability. This thesis presents an empirical model of the spectrum of ocean variability for periods between about 20 days and 15 years and wavelengths of about 200-10,000 km, and describes applications to ocean circulation trend detection, observing system design, and satellite data processing. The horizontal wavenumber-frequency part of the model spectrum is based on satellite altimetry, current meter data, moored temperature records, and shipboard ADCP data. The spectrum is dominated by motions along a "nondispersive line". The observations considered are consistent with a universal [omega] -2 power law at the high end of the frequency range, but inconsistent with a universal wavenumber power law. The model spectrum is globally varying and accounts for changes in dominant phase speed, period, and wavelength with location. The vertical structure of the model spectrum is based on numerical model results, current meter data, and theoretical considerations. We find that the vertical structure of kinetic energy is surface intensified relative to the simplest theoretical predictions. We present a theory for the interaction of linear Rossby waves with rough topography; rough topography can explain both the observed phase speeds and vertical structure of variability. The improved description of low-frequency ocean variability presented here will serve as a useful tool for future oceanographic studies.
Modern Observational Physical Oceanography
Author: Carl Wunsch
language: en
Publisher: Princeton University Press
Release Date: 2015-05-04
The essential introduction to modern physical oceanography With the advent of computers, novel instruments, satellite technology, and increasingly powerful modeling tools, we know more about the ocean than ever before. Yet we also have a new generation of oceanographers who have become increasingly distanced from the object of their study. Ever fewer scientists collect the observational data on which they base their research. Instead, many download information without always fully understanding how far removed it is from the original data, with opportunity for great misinterpretation. This textbook introduces modern physical oceanography to beginning graduate students in marine sciences and experienced practitioners in allied fields. Real observations are strongly emphasized, as are their implications for understanding the behavior of the global ocean. Written by a leading physical oceanographer, Modern Observational Physical Oceanography explains what the observational revolution of the past twenty-five years has taught us about the real, changing fluid ocean. Unlike any other book, it provides a broad and accessible treatment of the subject, covering everything from modern methods of observation and data analysis to the fluid dynamics and modeling of ocean processes and variability. Fully illustrated in color throughout, the book describes the fundamental concepts that are needed before delving into more advanced topics, including internal-inertial waves, tides, balanced motions, and large-scale circulation physics. Provides an accessible introduction to modern physical oceanography Written by a leading physical oceanographer Emphasizes real observations of the fluid ocean Features hundreds of color illustrations An online illustration package is available to professors
Ocean Circulation and Climate
Author: Carl Wunsch
language: en
Publisher: Elsevier Inc. Chapters
Release Date: 2013-10-22
The World Ocean Circulation Experiment drove the development of estimates of the decadal scale time evolving general circulation that are dynamically and kinematically consistent. A long timescale, and a goal of estimation rather than prediction, preclude the use of meteorological methods called “data assimilation (DA).” Instead, “state estimation” methods are reviewed here and distinguished from DA. Results from the dynamically consistent family of solutions from the project Estimating the Circulation and Climate of the Ocean based upon least-squares Lagrange multipliers (adjoints) are used to discuss the determination of the dominant elements of the circulation in the period since 1992—which marked the beginning of the satellite altimetric record. Significant changes documented in the Arctic in recent decades now mandate consideration of the coupled ocean-cryospheric state.