The fall-winter surface current field off Oregon was determined by analysis of ten years of drift bottle data. Computer programs were developed for generating bottle tracks on a numerical grid, for interpolating bottle velocity components to fill void grid points and for smoothing irregularities in the velocity fields. Charts are presented showing the spatial distribution of surface currents determined in the study area of 5° latitude by 2-1/2° longitude. The mean currents for the fall-winter season have a predominantly northerly flow with speeds increasing from the south to the north (from 0.01 to 0.35 knots). This probably is a consequence of the increase in speed of southerly winds from south to north in the study area during the fall-winter season. The northly flow in October during the years 1961-70, when compared with the dominant southerly flow during this month from measurements prior to 1935, may indicate a major change of Davidson-California Current System within the past forty years. Apparent onshore flow may be introduced by bottle diffusion; this flow is prominant at all latitudes along which bottle releases are concentrated. An offshore flow component north of 46°30'N may be related to the Columbia River discharge and the westward extension of land. / Graduation date: 1973

The physical characteristics of continental shelf waters off Oregon during late winter and spring of 1975 are described and compared with observations taken previously during summer. The currents in winter are barotropic in the monthly means while in summer the currents are baroclinic. Alongshore current fluctuations on the time scale of a few days are depth dependent in winter but become depth independent in summer. The current shear changes sign on the several day time scale in winter while in summer the deeper currents are always northward with respect to the near surface currents. Alongshore coherences of sea level and currents indicate that winter fluctuations generally propagate southward rather than northward as previously observed in summer. These winter fluctuations in alongshore currents also have onshore/offshore phase speeds that are comparable in magnitude to their alongshore phase speeds. There is no evidence for free continental shelf wave activity in winter although forced waves (travelling predominately southward, as do the meteorological disturbances) may exist. The Gill and Schumann (1974) model, which predicts sea level from a knowledge of the alongshore components of winds along the coastline, is tested for winter and summer in 1975 and found to have some predictive ability for fluctuations on the time scale of several days. The transition from winter to summer is initiated in a dramatic barotropic event and continues as a longer period baroclinic adjustment. The former is marked by a sudden reversal of currents and a lowering of sea level while the latter is marked by a slow rising of the pycnocline and with it the layer of maximum vertical shear. Both the barotropic changes at the transition event and the adjustment of the density field, which occurs after the transition event, are directly forced by the local wind. / Graduation date: 1977

The geopotential anomalies and the average meridional geostrophic flow off Newport, Oregon, were computed from the data taken during twenty-one hydrographic cruises. The annual average of geopotential anomaly was 1.31 dynamic meters with a seasonal variation of the order of 14 dynamic centimeters. Highest values of geopotential anomaly occurred in September; lowest values occurred in April. Both the highest and lowest value of geopotential anomaly occurred at 105 nautical miles offshore. The currents found by dynamic computation were weak and irregular, generally 5 cm/sec or less. The direction of the average meridional geostrophic flow varied with season. Within 105 nautical miles of the coast, flow was southward in summer, northward in winter. Beyond 105 nautical miles from the coast, flow directions reversed, that is, flow was northward in summer and southward in winter. / Graduation date: 1967

Typescript. / Bibliography: leaves 144-147. / Photocopy. / xvi, 147 leaves ill

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

Graduation date: 1968

Using the hydrographic data collected by the ACONA from June 1961 to May 1963, the Oregon coastal front has been examined. Representative sigma-t surfaces were chosen to delineate the front, and changes in position of these surfaces with time were used to obtain zonal flow rates for the frontal and surface layers. From May to early October upwelling resulted in offshore flow. Onshore flow was indicated from late October to January, and indeterminate zonal flow occurred during the remainder of the year. Flow within the front agreed with these surface flows in ten of the fourteen observational periods. / Graduation date: 1964

Sea level and current observations made over the Oregon continental shelf exhibit wavelike characteristics in a frequency band from approximately 0.15 to 0.45 cpd. In a narrow band around 0.22 cpd the current-sea level relationship is consistent with the predicted values for the first mode of Robinson's continental shelf waves. In addition, an interesting relationship exists between the form of the sea level-current coherency spectra and the arrangement of the maximum frequencies for the first three shelf wave modes. The currents were measured in 100 m of water about seven nautical miles off Depoe Bay, Oregon. Current meters were placed at 25, 50 and 75 m depth. The duration of the experiment was from 18 April 1968 until 11 September 1968. Due to some instrument failures a complete current data set for this period was not obtained. Simultaneous and continuous measurements of surface elevation and atmospheric pressure were also obtained at Newport, Oregon, a nearby coastal station. Shelf wave dispersion curves and eigenfunctions for the Oregon coastal profile are computed using a new numerical technique. These are compared with a low frequency (about 0.03 cpd to 0.75 cpd) spectral analysis of the current, sea level and atmospheric pressure records. The relative vertical uniformity of the currents, as a function of frequency, is examined. The longshore component of the current appears to be substantially more barotropic than the onshore-offshore component. / Graduation date: 1972

Graduation date: 1963