The objective of this study was to ascertain the magnitude and distribution of rainfall over coastal waters of the northwestern United States and to compare values with those at nearby land stations. Precipitation was measured with gauges at Totem, rainfall amounts were assessed from weather reports at lightships off the coast, and precipitation frequencies at lightships and land stations were examined. Results from the three methods were quite consistent; precipitation. on at sea was only about one-third that at coastal land stations. These values are appreciably less than previous estimates of oceanic rainfall in this area, and they support the view that a significant horizontal gradient of precipitation may exist between the coast and open sea. Rainfall typically occurs both at sea and ashore on the same day, but it rains fewer hours at sea. The relative amount of rain at sea varies with the type of atmospheric system, and rainfall at the coast appears to be intensified by frictional processes. Estimates of evaporation minus precipitation are less negative than earlier ones; consideration of their relation to surface salinity leads to distributions that are in good agreement with oceanographic knowledge. The newer values suggest that in this region the heat gain by the atmosphere may be less (but moisture entrainment may be greater) than was thought. / Graduation date: 1973

Graduation date: 1973

Graduation date: 1969

Graduation date: 1968

Graduation date: 1966

Holocene hemipelagic deposition of terrigenous silts and clays dominates sedimentation on most of the Oregon and Washington continental slope. The sources of these sediments, the mechanisms causing sediment dispersal, and the relative contributions of the various continental sources to the marine deposits have been investigated using quantitative mineral and geochemical data for the 2-20 μm and the <2 μm size fractions. In the 2-20 μm size fraction, material derived from the Klamath Mountains and the California and Washington Coast Ranges contains chlorite and illite, but only Klamath material contains hornblende. Columbia River material lacks chlorite, and the Oregon Coast Range source is dominated by smectite. In the <2 μm fraction, source area compositions are less distinctive due to the ubiquity of smectite, but the northern and southern sources again contain both chlorite and illite. Regional and local mineralogic and textural variations in the fluvial sediments reflect geologic and geographic changes between drainage basins. Amorphous material is a minor component in the 2-20 μm fraction of the fluvial sediments, but may form 25-50% of the <2 μm fraction in some source areas. Sediments derived from all source areas are transported north and northwestward across the margin, either by a poleward-flowing undercurrent along the slope, by wind-driven surface currents on the shelf and associated turbid layers on the slope, or by a combination of the two processes. Columbia River <2 μm material may also be carried southward along the shelf and upper slope by summer surface currents. The poleward undercurrent (an eastern boundary undercurrent) appears to have limited sedimentological significance when compared to the role of the western boundary undercurrent in sediment transport and deposition on the continental slope and rise of the eastern United States. Linear programming has been applied successfully to estimate source area contributions to the 2-20 μm marine sediments. The influence of each source is largest in proximal environments, and the contribution estimates indicate that material derived from each source area is transported northward along the margin. Similar estimates for the <2 μm material are considered unreliable because of internal inconsistencies and the uniform nature of the <2 μm compositions used in the modelling. The contributions have been used to calculate a sediment budget for the 2-20 μm fraction. This budget indicates that the mass accumulating on the entire slope within the study area contains 47% Columbia River, 32% Klamath Mountain, and 21% California Coast Range material in the 2-20 μm fraction, and demonstrates the importance of multiple sediment sources and sediment mixing in the formation of hemipelagic sediments on the continental margin. / Graduation date: 1982

Changes in sea level during the past 20,000 years are recorded in sediments taken from the continental shelf off the Rogue River, Oregon. Sea level has risen approximately 125 m. during the Holocene (Curray, 1965) and the general transgression has been interrupted by several stillstands and minor regressions. Box core samples taken in the area of investigation depict the nature of sedimentation during the last rise of sea level as well as present-day equilibrium sediment relationships. Three sediment facies, a recent fine-grained mud, a basal transgressive sand, and an intermediate sediment, believed to be a mixture of the other two, are defined on the shelf on the basis of textural parameters. The mud facies dominates surface sediment on the central shelf while the sand facies is the most commonly exposed on both the inner and outer shelf. The percentage of sand generally increases with depth in the box cores, often producing a change in sediment facies with depth and demonstrating the transgressive nature of the sediments. Grain-size analysis of the sand fraction of the offshore sediments reveals that offshore sands are finer-grained and better sorted than those occurring on the present beaches. The offshore sands most likely represent relict nearshore deposits and not ancient beach sands which would occur lower in the sediment sequence. High concentrations of heavy minerals are found in the sand fraction of the offshore sediments as well as in beach sands in the area. Brief stillstands of sea level may be reflected in depths where the offshore sands contain anomalously high percentages of heavy minerals. Opaque minerals, chiefly magnetite, occur in placer accumulations on the present beaches and high percentages of these minerals in the offshore sands may be indicative of submerged beach environments associated with stillstands of sea level. The magnetite may be concentrated in sufficient quantity in the placers to produce detectable magnetic anomalies, several of which have been recorded in the area. Other lines of evidence used to determine the depths of probable stillstands of sea level are bathymetric relief, the distribution of shallow water fauna in sediments from deep water, and the distribution of rounded gravels on the shelf. A compilation of the several lines of evidence suggests several stillstands of sea level associated with the Holocene transgression occurring at depths of 18, 29, 47, 71, 84, 102, and 150 meters. / Graduation date: 1969

Sea level and current data collected near Newport, Oregon are compared to determine an empirical relationship from which the low frequency (f < .1 cpd) alongshore current field over the continental shelf is estimated from observed sea level measurements at the coast. Regression analysis of the near-surface (20-25 m) currents with sea level indicates the surface currents are in geostrophic balance with the sea surface slope. Analysis of the alongshore shear between the near-surface and deep (75-80 m) layers with sea level shows the thermal wind relationship holds. A near-surface regression model is developed from which the mean monthly alongshore current 20-25 m below the surface can be estimated with a standard estimate of error (σ[subscript ER]) less than six cm/sec. The annual range at this depth is nearly 60 cm/sec. A regression model for the alongshore shear is formed from which the mean vertical shear is estimated with a σ[subscript ER] of .07-.10 cm/sec/m. The annual range is approximately .8 cm/sec/m. The surface currents are found to be predominantly driven by the local meteorological conditions. Deep and near-bottom current observations suggest the deep layer currents are primarily influenced by the thermal wind relationship and the location of the California Undercurrent. / Graduation date: 1977

Graduation date: 1974

Direct measurements of vertical water motions were made in the Oregon coastal region during the 1972 summer upwelling season. The instruments used were the Webb-Voorhis vertical current meters which are freely drifting neutrally buoyant floats capable of sensing vertical motion. It was found that in the region studied, water tended to sink at depths of 40 to 60 meters under the influence of strong northward and southward winds but that water tended to rise during the slackening periods of a southward wind. Techniques used in processing the data, some problems encountered, and the results of four good dives are presented along with possible correlations of vertical water movements with wind, sea Level, and isopycnal movements. / Graduation date: 1974