Deep-ocean pressure measurements are a necessary component for ocean characterization and oceanographic monitoring. Some principle applications such as tsunami detection and ocean floor subsidence are reliant on deep-ocean pressure measurement data. The deep ocean is a challenging environment especially for pressure measurements; discerning pressure changes that are a small fraction of the ambient pressure calls for intelligent engineering solutions. An ocean-deployable concept model of a pressure sensor is developed. The design is based on a diaphragm transducer intended for measuring hydrostatic pressure changes on the order of 1 centimeter of water (cmH2O) while exposed to ambient pressures several orders of magnitude greater for up to 2500 meters of water (mH2O). Two laboratory-scale pressure sensors are fabricated to test the fundamental principle of the proposed concept at lab-safe pressures. One is a single-sided sensor exposed to atmospheric pressure. The second sensor is a two-sided design that operates at a defined target depth pressure and measures the differential pressure across both faces of the diaphragm. The sensor design built for atmospheric pressure testing observed a mean experimental sensitivity of 6.05 pm/cmH2O in contrast to 6 pm/cmH2O determined theoretically. The percent error between the experimental and theoretical values is 0.83%. The second design was tested at target depth pressures of 10, 20, 40, and 60 psi (7, 14, 28, and 42 mH2O) and performance was within 5.8%, 2.8%, 0.7%, 4.0% respectively when considering percent error of the mean experimental and theoretical. The repeatability was sufficient for a given sample and pressure response within the range proposed in theory when a pressure preload was present to the diaphragm. Future work will aim at developing a design concept that incorporates a piston and is tested at a higher hydrostatic pressure system, and within ocean waters. A deployment plan and consideration of challenges associated with ocean testing will be accounted for. / Graduate

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2006. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references. / Ocean surface infragravity waves (periods from 20 to 200 s) observed along the southern California coast are shown to be sensitive to the bottom topography of the shelf region, where propagation is linear, and of the nearshore region, where nonlinearity is important. Infragravity waves exchange energy with swell and wind waves (periods from 5 to 200 s) via conservative nonlinear interactions that approach resonance with decreasing water depth. Consistent with previous results, it is shown here that as waves shoal into water less than a few meters deep, energy is transfered from swell to infragravity waves. In addition, it is shown here that the apparent dissipation of infragravity energy observed in the surfzone is the result of nonlinear energy transfers from infragravity waves back to swell and wind waves. The energy transfers are sensitive to the shallow water bottom topography. On nonplanar beach profiles the transfers, and thus the amount of infragravity energy available for reflection from the shoreline, change with the tide, resulting in the tidal modulation of infragravity energy observed in bottom-pressure records on the continental shelf. The observed wave propagation over the shelf topography is dominated by refraction, and the observed partial reflection from, and transmission across, a steep-walled submarine canyon is consistent with long-wave theory. A generalized regional model incorporating these results predicts the observed infragravity wave amplitudes over variable bottom topography. / by James M. Thomson. / Ph.D.

Thesis: S.M., Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 97-103). / The presence of superimposed bedforms, where smaller bedforms exist on larger bedforms, is ubiquitous to energetic tidal environments. Due to their wide range in scale, it is difficult to simultaneously observe these features over tidal timescales. This thesis examines the morphological response of superimposed bedforms to a tidally reversing flow using novel instrumentation and platform systems. A method is outlined in chapter 2 to expand the functionality of low-mounted sidescan sonars by utilizing sonar shadows to estimate bedform height and asymmetry. Empirical models are generated to account for realistic variability in the seabed and the method is validated with bathymetric observations of wave-orbital ripples and tidally reversing megaripples. Given the high temporal and spatial resolution of seafloor frame mounted rotary sidescan sonars, the dynamics and evolution of the bedforms over an approximately 40 m x 40 m area can be resolved. In chapter 3 the method is applied to data of superimposed bedforms at Wasque Shoals, an ebb delta off the southeast corner of Martha's Vineyard, MA. These data reveal the small, superimposed bedforms reversing their asymmetry with the flow while the larger bedforms on which they reside remain oriented in the direction of the dominant flow. Similar bedform dynamics are observed at Nauset Inlet, a dynamic inlet system, on Cape Cod, MA using an autonomous jet-powered kayak, the Jetyak, equipped with a bathymetric swath sonar. The time needed for bedform asymmetry to reverse in the presence of a tidal flow was estimated with a geometric bedform model that incorporates an empirical sediment transport rate. The morphological lag time from the observations agree well with the geometric model with larger bedforms and slower flows resulting in a longer lag time. Finally, the migration of these superimposed bedforms is considered in chapter 4. Data from the rotary sidescan sonar at Wasque Shoals capture the interaction of smaller bedforms, or megaripples, with a dune. The net convergence of megaripples on the tidally dominate lee face of the dune suggests that the smaller bedforms serve as an intermediate step between grain-scale transport processes and larger scale dune migration. / by Katie Renae Jones. / S.M.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), June 1990. / "April 1990." / At scale lengths less than 100 km or so, statistical descriptions of seafloor morphology can be usefully employed to characterize processes which form and reshape abyssal hills, including ridge crest volcanism, off-axis tectonics and volcanism, mass wasting, sedimentation, and post-depositional transport. The objectives of this thesis are threefold: (1) to identify stochastic parameterizations of small-scale topography that are geologically useful, (2) to implement procedures for estimating these parameters from multibeam and side-scan sonar surveys that take into account the finite precision, resolution, and sampling of real data sets, and (3) to apply these techniques to the study of marine geological problems. The seafloor is initially modeled as a stationary, zero-mean, Gaussian random field completely specified by its two-point covariance function. An anisotropic two-point covariance function is introduced that has five free parameters describing the amplitude, orientation, characteristic width and length, and Hausdorff (fractal) dimension of seafloor topography. The general forward problem is then formulated relating this model to the statistics of an ideal multibeam echo sounder, in particular the along-track auto-covariance functions of individual beams and the cross-covariance functions between beams of arbitrary separation. Using these second moments as data functionals, we then pose the inverse problem of estimating the seafloor parameters from realistic, noisy data sets with finite sampling and beamwidth, and we solve this inverse problem by an iterative, linearized, least squares method. Resolution of this algorithm is tested against ship variables such as length of data, the orientation of ship track with respect to topographic grain, and the beamwidth. This analysis is conducted by inverting sets of synthetic data with known statistics. The mean and standard deviation of the inverted parameters can be directly compared with the input parameters and the standard errors output from the inversion. The experiments conducted in this study show that the rms seafloor height can be estimated to within -15% and anisotropic orientation to within ~5* (for a strong lineation) using very short track lengths (down to 3 characteristic lengths, or -10 to 100 km), and characteristic lengths of seafloor topography can be estimated to within -25% using fairly short track lengths (down to 5 or 6 characteristic lengths, or 10's of km to -200 kin). The number of characteristic lengths sampled by a ship track, and hence the accuracy of the estimation, is maximized when the ship track runs perpendicular to abyssal hill lineation. Using the assumed beamwidth, the measured noise values, and the seafloor parameters recovered from the inversion, Sea Beam "synthetics" are generated whose statistical character can be directly compared with raw Sea Beam data. However, these comparisons are spatially limited in the athwart ship direction. A recent SeaMARC II survey along the flanks and crest of the East Pacific Rise between 130 and 15* N included sufficient off-axis topography to permit a comparison of a complete 2-D synthetic topographic field with a region of abyssal-hill terrain that has close to 100% data coverage. Synthetic data is compared to both Sea Beam swaths and SeaMARC II survey data. These comparisons generally indicate that we are successful in characterizing the second order properties of the seafloor. They also indicate the directions we will need to take to improve our modeling, including generalization of the second-order model and characterization of higher moments. The inversion procedure is applied to a data set of 64 near-ridge Sea Beam swaths to characterize near ridge abyssal hill morphology and its relationship to ridge properties. Much of the data (27 swaths) comes from cruises to the Pacific-Cocos spreading section of the East Pacific Rise between 9* and 15* N. These data provide very good abyssal hill coverage of this well-mapped and studied ridge section and form the basis of a regional analysis of the correlation between ridge morphology and stochastic abyssal hill parameters. This regional analysis suggests a strong relationship between magma supply and the character of abyssal hills. We also have data from near the Rivera (9) and Nazca (7) spreading sections of the East Pacific Rise, the Mid-Atlantic Ridge (18), and the Indian- African Ridge (3). Though spotty, this constitutes a good initial data set for the analysis of correlations among covariance parameters and between parameters and ridge characteristics, especially spreading rate. A working hypothesis is introduced to explain the observations within a geological framework. This hypothesis contends 1) that the maximum size of abyssal hills is related to the lithosphere's ability to elastically support the load, 2) that fissuring and horst and graben formation dominate abyssal hill formation at fast spreading ridges, and 3) that volcanic edifice formation, modified by faulting driven by lithospheric necking, dominates abyssal hill formation at slow spreading ridges. To quantify abyssal hill characteristics such as vertical and lateral asymmetry and "peakiness" we must appeal to higher statistical moments than order two. A mathematical framework is introduced for the study of higher moments of a topographic field. This framework is built upon the concept that lower-order moment provide the groundwork for studying the higher-order moments. A simple 1-D parameterized model is proposed for moments up to order 4. This model includes two parameters for the third moment, describing vertical and lateral asymmetries, and one for the fourth moment, which describes the peakiness of topography. Initial methods are developed for estimating these parameters from bathymetric profiles. Results from the near ridge data set are presented and interpreted with regard to abyssal hill forming processes. / by John Anson Goff. / Ph.D.

The subject area of this thesis is the proposed international sea regime. The regime in this context refers to the proposed international organization to control the resources of the sea-bed beyond the limits of national jurisdiction. Regime in the above context has a specific meaning and should not be confused with the more general meaning of a regime of the sea. In the more general sense a regime of the sea would encompass the entire law of the sea. Such a broad scope is not intended, therefore no treatment of fishing rights, limitation of nuclear arms, extensive oil deposits at centers are attempted except as they specifically relate to the proposed ocean regime and its jurisdiction.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24423号 / 理博第4922号 / 新制||理||1703(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)准教授 伊藤 喜宏, 准教授 西村 卓也, 教授 王 功輝 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1980. / Microfiche copy available in Archives and Science. / Vita. / Bibliography : leaves 206-213. / by John Shai-Fu Shih. / Ph.D.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Science. / Microfiche copy available in Archives and Science. / Vita. / Includes bibliographies. / by Robert Sherman Detrick, Jr. / Ph.D.

Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Bibliography: leaves 154-158. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1982. / Microfiche copy available in Archives and Science / Vita. / Bibliography: leaves 312-321. / by Anne Martine Tréhu. / Ph.D.