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The subsurface frontal zone beneath the subtropical convergence in the northeast Pacific OceanBlanton, J. O. 25 January 1968 (has links)
Graduation date: 1968
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Comparison of sea level and currents off the Oregon coast using mean monthly dataMarthaler, James Gordon 06 October 1976 (has links)
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
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Vertical current measurement in the Oregon coastal upwelling regionDeckard, Dennis E. 30 August 1973 (has links)
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
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A mesoscale study of coastal currents and upwelling off PeruEnfield, David B. 01 May 1970 (has links)
Moored instrument records, drogue displacements, and hydrographic
observations are used in describing the coastal currents and
upwelling off Peru. The data were obtained over the continental shelf
near 15°S. during a two week study in late March and early April of
1969.
First order statistics and graphical representations of current
meter time series indicate that the longshore flow was poleward during
most of the study period, interrupted by a three day 'event' of
equatorward flow. The similarity of flow at all current meters indicates that the field of flow as quasi-barotropic. The depth, extent, and transport of poleward flow indicated by current meter time series
and geostrophic sections were similar to those described in the literature
for the Peru-Chile Undercurrent. The observations suggest
that this flow moved further offshore as equatorward flow appeared
over the shelf.
Power spectral analyses performed on current meter records
indicate the existence of semidiurnal tidal currents in the longshore
direction. The magnitude of these currents is estimated at 10% to
15% of period mean speeds.
Ten meter drogue displacements are compared with 25 m recorded
currents and with winds. The observations indicate that: the
drogues were affected by both the 25 m flow and the wind; the depth
of the wind drift layer was between 10 m and 25 m; the drogue displacements were in the sense expected from the Ekman model.
Vertical sections of sigma-t, oxygen, and nitrate indicate the
existence of conditions consistent with upwelling. Surface maps of
temperature, nitrate, and chlorophyll 'a' over the shelf are used to
define the horizontal field of upwelling and its variations in time.
The distributions suggest that upwelling existed throughout the period
and underwent temporal and spatial modulations in intensity. The
possibility of a causal mechanism between observed current and
upwelling variations is examined.
Vertical salinity sections indicated the presence of a weak salinity
minimum between the surface and 100 m. It is suggested that this
minimum manifests the remnants of a tongue of Subantarctic Water
embedded in a much larger mass of Equatorial Subsurface Water.
The occurrence of the minimum only in conjunction with poleward flow
suggests that the water was advected or mixed coastward somewhere
north of the area studied, was entrained in the Peru-Chile Undercurrent,
and was carried south again. / Graduation date: 1970
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The general circulation in the north Pacific Ocean referred to a variable reference surfaceMcAlister, William Bruce 18 May 1962 (has links)
Graduation date: 1962
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Observations and analysis of ocean currents above 250 meters off the Oregon coastMaughan, Paul M. 15 May 1963 (has links)
Graduation date: 1963
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Near-inertial motions off the Oregon coastAnderson, Iain 30 April 1982 (has links)
Nearly three months of current meter records from five moorings off
the Oregon coast taken between October 1977 and January 1978 were analyzed
for near-inertial motions. The moorings were located from the midshelf
out to the foot of the continental slope, spanning the continental
margin. All but two of the eleven current meters were continuously
below the mixed layer. For spectral analysis, the current observation
period was divided into two time periods, one with large amplitude
near-inertial motion (41.1 cm/sec maximum of the band-passed records)
throughout and the other with much less near-inertial energy. The
spectra of the current meter records showed between a 1 and 6% increase
in frequency of the near-inertial peak above f (= 0.0592 cph) in all
but three cases. The exceptions showed spectral peaks about 14% below
f and were linked to a Doppler shift. The period of large amplitude
near-inertial motion had diagonal coherence scales of over 450 meters
vertically and 115 kilometers horizontally. An east-west (cross-shelf)
wavelength of about 50 kilometers was estimated directly from the phase
differences between current meters with roughly horizontal separations.
The observed response of a current meter about 35 meters below
the mixed layer to sharp maxima in the wind stress was similar to that predicted by the Pollard and Millard (1970) model for wind forced
near-inertial motions in the surface mixed layer. The winds associated
with a series of atmospheric fronts were apparently responsible for
generating a 14-day period of large amplitude near-inertial motion
observed below the mixed layer. / Graduation date: 1982
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Theoretical studies of the circulation of the Subarctic Pacific Region and the generation of Kelvin type waves by atmospheric distrubancesThomson, Richard Edward January 1971 (has links)
Theoretical studies of two problems concerned with the surface forced, large-scale motions in bounded oceanic regions are presented. In Part I, such motions are considered for a particular area of the North Pacific Ocean known as the Subarctic Pacific Region. Discussion is based on the assumption that the velocity components may be separated into a time-averaged or quasi-steady flow about which fluctuations occur in the form of transient planetary waves. Some of the characteristics of the latter are briefly outlined. Several aspects of the time-averaged motions are then considered. A simple circulation, driven by the vertical velocity structure, is presented for the interior region of the ocean below the upper frictional layer. Also, using observational data to obtain the depth of the layer between the suface [sic] and the main halocline, this upper layer is found to behave as a geostrophic layer of fluid when averaged over many years. Combination of the above observed depths with the mean calculated Ekman divergences permitted calculation of a mean eddy coefficient of diffusivity for density. The results agree very well with those obtained by Veronis for similar oceanic situations. An explanation for the variations in the intrusion of 'warm' water along the top and bottom of the halocline off the coast of British Columbia is also given.
The two final sections of Part I deal with the overall, quasi-steady circulation of the Subarctic Pacific Region. Here, a theoretical study is combined with the mean-monthly values of the calculated surface forcing. Curvilinear coordinates are used in order to model the northern boundary formed by the Aleutian-Komandorski island chain. The interior quasi-steady flow, which satisfies a Sverdrup-type balance of vorticity, is closed to the north by a frictional boundary layer. Using mean-monthly values for the surface winds over the region, the observed separation of the eastward flowing West Wind Drift into a northern and southern tending flow is found to correspond to the zero of the mean wind-stress curl. In the northern boundary layer, the characteristics of the westward flowing boundary current there, are shown to change downstream
from a Western' to a 'zonal', type boundary current. The stability of the latter is dependent upon vorticity of appropriate sign being added to the boundary layer flow to balance that generated by friction along the coast. Discussion is also given for the effect of passes between the Aleutian islands on the zonal boundary current. Through a type of boundary layer 'suction' or, alternately, by mass transport into the boundary layer, the effect of these passes would seem to be to keep the boundary flow attached to the coast. Finally, spectral analysis of the wind-stress curl data, obtained from the mean-monthly surface pressure, is performed to determine its frequency distribution. A demodulation technique is used to determine the time variations of six of the frequency bands obtained in the spectral analysis. These results are then applied to the circulation in the Subarctic Pacific Region in an attempt to relate variations and spatial distribution in the circulation with the applied winds.
The generation by the atmosphere of a type of long, boundary waves, known as Kelvin waves, is considered in Part II. In particular, it is shown that for a general large-scale distribution of wind and pressure systems that only the longshore component of the wind-stress and pressure can generate such waves. Examples are presented for a semi-infinite wind and moving pressure pattern. Kelvin waves are shown to move away from the force discontinuities at the speed of shallow-water waves. These waves are further found to exhibit a frequency shift, typical of non-dispersive waves from a moving source. Using some observed parameters for the atmospheric forcing terms off the Oregon coast of the United States, numerical values for the wave amplitudes for both examples are given. Part II has been published in the form presented here. Reference: J. Fluid Mech. C1970), 42C4), 657-670. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
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Evaluation of a coastal ocean model for Oahu, HawaiʻiWycklendt, Andrew J January 2005 (has links)
Thesis (M.S.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 62-69). / ix, 69 leaves, bound ill., maps 29 cm
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Upwelling and cross-shelf transport dynamics along the Pacific Eastern BoundaryCombes, Vincent 06 July 2010 (has links)
The upwelling and cross-shelf transport dynamics along the Pacific Eastern Boundary is explored using a high resolution ocean model for the last 60 years. Three ocean circulations have been modeled. From North to South, we investigate the dynamics of the Gulf of Alaska (GOA), the California Current System (CCS) and the Humboldt Current System (HCS, also known as the Peru-Chile Current System). The statistics of coastal waters transport are computed using a model passive tracer, which is continuously released at the coast. By looking at the passive tracer concentration distribution, we find that the Pacific Decadal Oscillation modulates the coastal variability of the GOA, the North Pacific Gyre Oscillation controls the upwelling of the CCS, while the El-Niño Southern Oscillation affects the upwelling of Peru and Chile mainly through coastally trapped Kelvin waves. Results also emphasize the key role of the mesoscale eddies in the offshore transport of coastal waters masses. The passive tracer experiments, performed in this study in the GOA, CCS, and HCS, therefore could provide a dynamical framework to understand the dynamics of the upwelling/downwelling and offshore transport of nutrient rich coastal water and to interpret how it responds to atmospheric forcing. This also could reinforce our interpretation (and therefore predictions) in the changes in vertical and offshore advection of other important biogeochemical quantities, essential in understanding ecosystem variability.
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