Thesis (M.S.)--Naval Postgraduate School, 1993. / "December, 1993." Includes bibliographical references (p. 106-111).

This research describes the position, strength and variability of the mixing front along the East Shetland coast and the geostrophic current associated with the front. Between 2004 and 2010, new current meter measurements have been made at two mooring sites on the East Shetland shelf. By combining the current meter datasets with other surface temperature and salinity observations, such as surface underway data from the ferry MV “Norröna” and existing hydrographic datasets, this research provides new insights into the seasonal variability of the currents on the east Shetland shelf. The results show that in this region of the northern North Sea the balance of heating-stirring results in a tidal mixing front close to a (log10( h/u3)) of 3.4. Along the steeply sloping shelf to the east of Shetland a mixing front is found in water around 100m depth and results in significant geostrophic currents of up to 20 cm/sec between June and August each year. Monthly volume transports associated with broad scale wind forcing are estimated to be between -0.27 and -0.51 Sv during the well mixed periods (December to March). During the summer months (June, July and August) wind driven transport reduced to an average of -0.27 Sv, at the same time the persistent southerly flow associated with the geostrophic transport contributes an equivalent transport (-0.24 Sv). Taking the east Shetland shelf as a whole (coast to 1.5°E) the maximum volume transport is estimated to occur in Autumn (September to October) when density driven currents remain significant and wind speeds begin to increase. In the narrow region close to the coast, however, monthly mean volume transport is observed to be highest during the summer months as a result of the strong jet-like currents that flow along the density front.

No description available.

Thesis (M.S.) in Marine Biology--University of Maine, 2001. / Includes vita. Includes bibliographical references (leaves 91-98).

Thesis (M.S.)--Naval Postgraduate School, 1996. / "September, 1996." Includes bibliographical references (p. 169-177).

Thesis (M. S.)--Florida State University, 2006. / Advisor: Sergio Fagherazzi, Florida State University, College of Arts and Sciences, Dept. of Geology. Title and description from dissertation home page (viewed June 12, 2006). Document formatted into pages; contains ix, 83 pages. Includes bibliographical references.

An acoustic Doppler current profiler (ADCP) has been tried and found suitable for taking profiles of the time-mean three-dimensional velocity, vertical shear. Reynolds stress and turbulent kinetic energy (TKE) density in a coastal tidal channel. The velocity profiles have been used to reveal the existence of a log-layer. The data collected with the ADCP have been combined with fine- and microstructure data collected with a moored instrument (TAMI) to examine the TKE budget and turbulence characteristics in tidal flows. The ADCP was rigidly mounted to the bottom of the channel and the instrument was set to rapidly collect samples of along-beam velocities. In the derivation of the mean flow vector and the second-order turbulent moments, one must assume that the mean flow and turbulence statistics are homogeneous over the distance separating beam pairs. A comparison of the estimated mean velocity against the “error” velocity provides an explicit test for the assumption of homogeneity of the mean flow. The number of horizontal velocity estimates that pass a simple test for homogeneity increases rapidly with increasing averaging distance, exceeding 95% for distances longer than 55 beam separations. The Reynolds stress and TKE density are estimated from the variances of the along-beam velocities. Doppler noise causes a systematic bias in the estimates of the TKE density but not in the Reynolds stress. With increasing TKE density, the statistical uncertainty of the Reynolds stress estimates increases, whereas the relative uncertainty decreases. The spectra of the Reynolds stress and the TKE density are usually resolved; velocity fluctuations with periods longer than 20 minutes contribute little to the estimates. Stratification in the channel varies with the strength of the tidal flow and is weak below mid- depth. The ADCP measurements provide clear examples of secondary circulation, intense up/down- welling events, shear reversals, and transverse velocity shear. Profiles of the streamwise velocity are fitted to a logarithmic form with 1% accuracy up to a height, defined as the height of the log-layer, that varies tidally and reaches 20 m above the bottom during peak flows of 1 m s ⁻¹. The height is well predicted by 0.04u*/ω, where u * is the friction velocity and ω is the angular frequency of the dominant tidal constituent. The mean non-dimensional shear, [special characters omitted],is within 1% of unity at the 95% level of confidence inside the log-layer. Estimates of the rates of the TKE production and dissipation, eddy viscosity and diffusivity coefficients and mixing length, are derived by combining measurements with the ADCP and TAMI located at mid-depth. Near the bottom (z = 3.6 m), the production rate is 100 times larger than all other measurable terms in the TKE equation. Hence, the rate of production of TKE must be balanced by dissipation. The observed rate of production is proportional to the rate of dissipation calculated using the observed TKE density and mixing length, following the closure scheme of Mellor and Yamada (1974). This proportionality holds for the entire 3 decades of the observed variations in the rate of TKE production. At mid-depth, the eddy diffusivity of density and heat, deduced from microstructure measurements, agrees with the eddy viscosity derived from measurements with the ADCP. The scaling of the log-layer height with tidal frequency in the channel is comparable to the scaling with Coriolis parameter for the log-layer in steady planetary boundary layer. However, some results are inconsistent with those from boundary layers over horizontal homogeneous bottoms. The Reynolds stress is not constant within the log-layer, and its magnitude at 3.6 m above the bottom is 3 times smaller than the shear velocity squared [special characters omitted] derived from log-layer fitting. The peak of the non-dimensional spectrum for the Reynolds stress, when compared to measurements from atmospheric boundary layer, is shifted to higher wavenumbers by a factor of 2.5. One possible explanation for these discrepancies is the influence of horizontal inhomogeneity caused by bed forms. / Graduate

The steep continental slopes of the southern Celtic shelf have long been thought to be a major export region for the flux of sediment from the south west approaches to the deep ocean (47-49°). Recent studies have suggested that the transfer of energy from the large barotropic tidal currents to internal tides, and higher frequency internal waves is locally enhanced, and provides a mechanism for the re-suspension and downslope transport of bed material on the upper slope region. This material is thought to be preferentially transported at the head of the many submarine canyons that exist along these ocean margins, where the barotropic tidal currents are locally amplified and internal wave energy focused. A unique 23 day deployment of the benthic lander STABLE (Sediment Transport and Boundary Layer Equipment) in July 1990, was at a depth of 388m on La Chapelle Bank continental slope. The site was at the head of a canyon, and at a depth thought to be critical for the generation of internal tidal energy. It was also at the deep water end of a transect of two current meter moorings across the slope. These measurements have shown that during summer stratified conditions the barotropic and baroclinic tides are sufficiently energetic near to the bed to mobilise the sand/gravel sized sediment on the upper slopes and at the shelf break. Eulerian residual bottom currents and maximum tidal currents are orientated cross-slope and this has important implications for sediment transport. The shelf break is predicted to be a region of bed load parting with bedload transport shelfwards at the shelf break and downslope immediately oceanward. On the critical slope region peaks in suspended sediment concentration occur at times of locally enhanced maximum down-slope flow (40cmsˉ¹) and maximum current shear. This suggests that sediment is being eroded from the bed locally and confirms a net flux of material downslope. Above the boundary layer suspended particulate matter will be transported with the net flow of water which is predominantly along-shelf and polewards. A second 10.4 day deployment of STABLE (II) in January 1994 was at a depth of 879m on the Goban Spur. These observations demonstrated the variability of continental slope processes on the margins of the Celtic shelf. During the deployment, weaker tidal currents (maximum of 24cmsˉ¹) were orientated along-slope and there was no evidence to suggest that the fine cohesive sand/mud sized sediment was mobile. Current meter measurements show that any suspended material will be predominantly transported along-slope and poleward. This will be periodically reversed and the net flux will be equatorward. The two studies have highlighted the temporal and alongslope variability of geological and hydrodynamical conditions near to the bed and highlight the difficulties in estimating shelf-ocean fluxes of material across the whole of the north-west European continental margin.

Thesis (Ph.D.)--University of Adelaide, Dept. of Applied Mathematics, 1998? / Errata pasted onto front end paper. Bibliography: leaves 131-136.

Thesis (M.S.)--University of Delaware, 2008. / Principal faculty advisor: Kuo-Chuin Wong, College of Marine and Earth Studies. Includes bibliographical references.