The time-averaged velocity field in the North Pacific was estimated in two sets of inverse calculations. The planetary geostrophic equations were the basis for dynamical models of the flow in each case. The inverse estimates of the circulation were obtained by minimizing a positive-definite cost function, which measured the inconsistency of the model's predictions against a set of observations comprised of a large, high-quality hydrographic data set, and surface fluxes of heat, fresh water, and momentum. In the first part of this work, four solution methods for the generalized inverse of a linear planetary geostrophic model of the North Pacific are compared. A conjugate gradient solver applied to the equation for the generalized inverse, expressed in terms of a representer expansion, was the most computationally efficient solution method. The other methods, in order of decreasing efficiency, were, a conjugate gradient descent solver (preconditioned with the inverse of the model operators), a direct solver for the representer coefficients, and a second conjugate gradient descent solver (preconditioned so that the diagonal elements of the cost Redacted for Privacy function Hessian were unity). All but the last method were successful at minimizing the penalty function. Inverse estimates of the circulation based on the linear planetary geostrophic model were stable to perturbations in the data, and insensitive to assumptions regarding the model forcing and boundary condition uncertainties. A large calculation, which involved approximately 18,000 observations and 60,000 state variables, indicated that the linear model is remarkably consistent with the observations. The second part of this work describes an attempt to use a nonlinear planetary geostrophic model (which included realistic bottom topography, lateral momentum mixing, out-cropping layers, and air-sea fluxes of heat, freshwater, and momentum) to assimilate the same hydrographic data set as above. Because of the nonlinearity in the model, descent methods (rather than a representer-based method) were used to solve the inverse problem. The nonlinearity of the model and the poor conditioning of the cost function Hessian confounded the minimization process. A solver for the tangent-linearization of the planetary geostrophic system should be used as a preconditioner if calculations of this type are attempted in the future. / Graduation date: 1996

During the North Pacific cruise of the R/V Yaquina in 1966, total magnetic field intensity was measured in the Andreanof group of the Aleutian Islands. Three north-south track lines were made across the Aleutian Trench and ridge between longitudes 175° W and 180°. Three small scale magnetic profiles across the trench and ridge and one large scale profile over the crest of the ridge were constructed from the data. Total field and anomaly contour maps were drawn from the profiles. The data reveal: 1. A strong east-west trend of the contours present south of the ridge but absent north of the ridge which suggests that the Aleutian ridge is the boundary of two different magnetic provinces. 2. Large anomalies south of the trench which appear to be continuous for a distance of about 500 miles. The anomalies result from shallow structures and are considered to be ocean floor magnetic lineations. 3. Large anomalies north of the trench which result from deep-seated structures, probably strongly magnetic intrusions. 4. Short wavelength anomalies on the crest of the ridge which may result from dike intrusions parallel to the trend of the ridge. 5. A local magnetic gradient of about 800 gammas after removal of the regional geomagnetic field. The residual gradient is "low" over the trench and "high" over the ridge. The magnetic variation may be related to changes in the depth of the Curie temperature isotherm. / Graduation date: 1968

Graduation date: 1993

Graduation date: 1971

Graduation date: 1987

Graduation date: 1987

Graduation date: 1983

Graduation date: 1999 / Best scan available for figures. Original has a moray pattern.

East Pacific green sea turtles, Chelonia mydas, play ecologically important roles in marine habitats which range from grazing (and thus regularly "mowing") algae and seagrass beds to cycling nutrients between the ocean and land. However, these important grazers have been hunted to ecological extinction in some places for their eggs, meat, and skin. The conservation initiative for the survival of sea turtles requires the protection of their primary habitats in conjunction with a decrease in their interaction with humans. One way these objectives can be met is through the creation of species distribution maps (SDMs). For this thesis, a SDM was created from a generalized additive model used to identify major feeding areas for East Pacific green turtles residing in the Galapagos Islands. The input for the model was green turtle sighting locations during a June 2010 marine life observation survey and remotely sensed values of four oceanographic parameters obtained from satellite sensors (Bathymetry, Sea Surface Temperature, Chlorophyll a, and Current Speed). Line transects of intertidal and subtidal shoreline regions of the islands of Isabela, San Cristobal, and Floreana were also completed, to describe similarities and differences in macroalgal abundance between the locations. A generalized additive model (GAM) explained 56% of the data's null deviance and had a true positive rate of 0.83. The corresponding species distribution map indicated that East Pacific green sea turtles prefer to forage in warm, low chlorophyll a, slow moving waters at depths mostly less than 250m throughout the archipelago. ANOVA analyses showed that macroalgal abundance was statistically different (p-value < 0.01) between the islands of San Cristobal and Isabela. The line transects analysis also documented that red algae was the most prominent phyla at the sites and that the macroalgal abundance did not vary much between months June 2010 and April/May 2011. With these results, potential foraging areas for East Pacific green turtles can be identified and protected. Future studies will be focused on the collection of macroalgae from coastal areas outlined in the SDM and the interactions between green turtles and their competitors and/or predators. This information can be used to validate the areas delineated by the model and to further the understanding of the spatial-temporal effects on macroalgal abundance.

Thesis (Ph.D.)--University of Hawaii at Manoa, 1991 / Includes bibliographical references (leaves 177-195) / Microfiche. / xxii, 195 leaves, bound ill., maps 29 cm