The Entrainment and Homogenization of Tracers Within the Cyclonic Gulf Stream Recirculation Gyre

The Entrainment and Homogenization of Tracers Within the Cyclonic Gulf Stream Recirculation Gyre
Author: Robert S. Pickart
Publisher:
Total Pages: 210
Release: 1987
Genre: Gulf Stream
ISBN:

The distributions of tracer associated with the Northern Recirculation Gyre of the Gulf Stream (NRG) are studied to try to obtain information about the flow. An advective-diffusive numerical model is used whose streamlines consist of a gyre situated alongside a boundary current which inputs tracer into the domain. This is meant to simulate the lateral transfer of properties from the Deep Western Boundary Current (DWBC) to the NRG. Tracer is entrained into the model gyre as a plume which spirals across the streamlines, the characteristics of which depend on the flow parameters. Homogenization occurs at steady state, consistent with recently collected tracer data. The presence of vertical mixing is considered in an attempt to explain a difference between salinity and oxygen observed in the data. Comparison of the model results to the oxygen data is favorable, and leads to an estimate of the lateral and vertical diffusivity. The time dependent nature of freon is addressed using a coupled model of the deep water overflow process, advection-mixing in the DWBC, and subsequent entrainment into the NRG. Comparison with the data shows that very little freon has accumulated in the NRG, and that these processes effect the freon-11:freon-12 ratio as well. Keywords: Gulf Stream recirculation. (Theses).

Government Reports Annual Index

Government Reports Annual Index
Author:
Publisher:
Total Pages: 1030
Release: 1987
Genre: Research
ISBN:

Sections 1-2. Keyword Index.--Section 3. Personal author index.--Section 4. Corporate author index.-- Section 5. Contract/grant number index, NTIS order/report number index 1-E.--Section 6. NTIS order/report number index F-Z.

Cities and Their Vital Systems

Cities and Their Vital Systems
Author: Advisory Committee on Technology and Society
Publisher: National Academies Press
Total Pages: 1298
Release: 1989
Genre: Social Science
ISBN: 9780309037860

Cities and Their Vital Systems asks basic questions about the longevity, utility, and nature of urban infrastructures; analyzes how they grow, interact, and change; and asks how, when, and at what cost they should be replaced. Among the topics discussed are problems arising from increasing air travel and airport congestion; the adequacy of water supplies and waste treatment; the impact of new technologies on construction; urban real estate values; and the field of "telematics," the combination of computers and telecommunications that makes money machines and national newspapers possible.

Interpretation of Equatorial Current Meter Data as Internal Waves

Interpretation of Equatorial Current Meter Data as Internal Waves
Author: Martin Benno Blumenthal
Publisher:
Total Pages: 860
Release: 1987
Genre: Internal waves
ISBN:

Garrett and Munk use linear dynamics to synthesize frequency-wavenumber energy spectra for internal waves (GM72, GM75, GM79). The GM internal wave models are horizontally isotropic, vertically symmetric, purely propagating, and universal in both time and space. This set of properties effectively eliminates all the interesting physics, since such models do not allow localized sources and sinks of energy. Thus an important step in understanding internal wave dynamics is to make measurements of deviations from the simple GM models. This thesis continues the search for deviations from the GM models. It has three advantages over earlier work: extensive data from an equatorial region, long time series (2 years), and relatively sophisticated linear internal wave models. Since the GM models are based on mid-latitude data, having data from an equatorial region which has a strong mean current system offers an opportunity to examine a region with a distinctly different basic state. The longer time series mean there is a larger statistical ensemble of realizations, making it possible to detect smaller internal wave signals. The internal wave models include several important extensions to the GM models: horizontal anisotropy and vertical asymmetry, resolution between standing modes and propagating waves, general vertical structure, and kinematic effects of mean shear flow. Also investigated are the effects of scattering on internal waves, effects that are especially strong on the equator because the buoyancy frequency variability is a factor of ten higher than at mid-latitudes. In the high frequency internal wave field considered (frequencies between .125 cph and .458 cph), several features are found that are not included in the GM models. Both the kinematic effects of a mean shear flow and the phase-locking that distinguishes standing modes from propagating waves are observed. There is a seasonal dependence in energy level of roughly 10% of the mean level. At times the wave field is zonally and vertically asymmetric, with resulting energy fluxes that are a small (4% to 10%) fraction of the maximum energy flux the internal wave field could support. The fluxes are, however, as big as many of the postulated sources of energy for the internal wave field.

Exact Reconstruction of Ocean Bottom Velocity Profiles from Monochromatic Scattering Data

Exact Reconstruction of Ocean Bottom Velocity Profiles from Monochromatic Scattering Data
Author: André A. Merab
Publisher:
Total Pages: 712
Release: 1988
Genre: Inverse scattering transform
ISBN:

This thesis presents the theoretical and computational underpinnings of a novel approach to the determination of the acoustic parameters of the ocean bottom using a monochromatic source. The problem is shown to be equivalent to that of the reconstruction of the potential in a Schrodinger equation from the knowledge of the plane-wave reflection coefficient as a function of vertical wavenumber, r(kz) for all real positive k z. First, the reflection coefficient is shown to decay asymptotically at least as fast as (1/kz2) for large kz and is therefore inteqrable. The Gelfand-Levitan inversion procedure is extended to include the case of basement velocity higher than the velocity of sound in water. The neglect of bound states is shown to be justified in both clayey silt and silty clay at the 220 Hz frequency of operation. Three methods for the numerical solution of the integral equation are investigated. The first one is an "Improved Born approximation" wherein the solution is given as a series expansion the first term of which is the Born approximation while the second term represents a substantial and yet easy to implement improvement over Born. The two other methods are based on a discretization of the Gelfand-Levitan integral equation, and both avoid a matrix inversion: one by employing a recursive procedure, and the other by coupling the Gelfand-Levitan equation with a partial differential equation. Bounds are obtained on errors in the solution due either to discretization or to data inaccuracy. These methods are tested on synthetic data obtained from known geoacoustic models of the ocean bottom. Results are found to be very accurate particularly at the top of the sediment layer with resolution of less than the wavelength of the acoustic source in the water. Several effects are investigated, such as sampling, attenuation, and noise. Also examined is the gradual restriction of the reflection coefficient to a finite range of vertical wave numbers and the consequent progressive deterioration of the reconstruction. The analysis shows how to reconstruct velocity profiles in the presence of density variation when the experiment is conducted at two frequencies. Our results provide a good understanding of the issues involved in conducting a monochromatic deep ocean bottom experiment and constitute a promising technique for processing the experimental data when it becomes available.