Graduation date: 1981

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Meteorology. / Microfiche copy available in Archives and Science. / Bibliography: p. 239-241. / Ph.D.

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Meteorology. / Microfiche copy available in Archives and Science. / Vita. / Bibliography : p. [323-328]. / Ph.D.

Currents and sea level fluctuations in the Avalon Channel, driven over a broad range of time scales by buoyancy forces, atmospheric pressure, and wind stress, are described and compared with dynamical theory. / Seasonal fluctuations in adjusted coastal sea level at St. John's are shown to be consistent with steric height and bottom pressure variations 3 km offshore in a depth of 180 m. / Low frequency fluctuations (periods of 7-50 d) in observed Avalon Channel currents and water properties suggest the presence of a baroclinically-unstable, buoyancy-driven coastal current. A kinematic analysis of the current fluctuations reveals an eddy structure resembling that predicted for baroclinically-unstable waves on a longshore current with the density stratification and vertical shear observed in the fall. / Cross-spectral analysis of St. John's sea level and meteorological records, and Avalon Channel steric height estimates, shows that sea level responds isostatically to atmospheric pressure forcing at periods longer than 2 days, and to seasonal changes in steric height. Adjusted sea level responds 180 degrees out-of-phase to forcing by longshore wind stress at periods longer than 2 days. Longshore current responds in-phase to longshore wind stress forcing, with surface intensification of the response close to shore. / Frequency response functions are derived from the shallow water equations of motion for the response of sea level and current to atmospheric pressure and wind stress forcing in homogeneous and two-layer, uniform-depth coastal ocean models, and in a homogeneous, step-shelf model. Linear bottom friction is assumed in the homogeneous ocean models. The phases of the observed sea level and current responses to wind stress suggest that the response is due to the existence of continental shelf waves originating at the northern edge of the Grand Banks, about 150 km away from the study site. The near-shore surface intensification of the current and sea level responses are consistent with the predictions of the two-layer uniform-depth model.

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Meteorology. / Microfiche copy available in Archives and Science. / Vita. / Bibliography : p. 194-197. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1980. / Microfiche copy available in Archives and Science. / Bibliography: leaves 206-211. / by Alexander N. Shor. / Ph.D.

Thesis: Ph. D., Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 163-174). / The Gulf Stream and Deep Western Boundary Current (DWBC) shape the distribution of heat and carbon in the North Atlantic, with consequences for global climate. This thesis employs a combination of theory, observations and models to probe the dynamics of these two western boundary currents. First, to diagnose the dynamical balance of the Gulf Stream, a depth-averaged vorticity budget framework is developed. This framework is applied to observations and a state estimate in the subtropical North Atlantic. Budget terms indicate a primary balance of vorticity between wind stress forcing and dissipation, and that the Gulf Stream has a significant inertial component. The next chapter weighs in on an ongoing debate over how the deep ocean is filled with water from high latitude sources. Measurements of the DWBC at Line W, on the continental slope southeast of New England, reveal water mass changes that are consistent with changes in the Labrador Sea, one of the sources of deep water thousands of kilometers upstream. Coherent patterns of change are also found along the path of the DWBC. These changes are consistent with an advective-diffusive model, which is used to quantify transit time distributions between the Labrador Sea and Line W. Advection and stirring are both found to play leading order roles in the propagation of water mass anomalies in the DWBC. The final study brings the two currents together in a quasi-geostrophic process model, focusing on the interaction between the Gulf Stream's northern recirculation gyre and the continental slope along which the DWBC travels. We demonstrate that the continental slope restricts the extent of the recirculation gyre and alters its forcing mechanisms. The recirculation gyre can also merge with the DWBC at depth, and its adjustment is associated with eddy fluxes that stir the DWBC with the interior. This thesis provides a quantitative description of the structure of the overturning circulation in the western North Atlantic, which is an important step towards understanding its role in the climate system. / by Isabela Astiz Le Bras. / Ph. D.

No description available.

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), 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 165-174). / The variability in the DWBC, its connection to the forcing in the northern North Atlantic and interaction with the Gulf Stream were explored from a combination of remote sensing and in-situ measurements in the western North Atlantic. Using satellite altimetry and Sea Surface Temperature (SST) we found evidence of the relation between changes in the Gulf Stream path and the variability in the temperature and velocity fields in the Slope Water. This relation was such that southward shifts of the main axis of the Gulf Stream were preceded by cold temperature anomalies and intensification of the southwestward flow. The analysis of 5.5 years of moored CTD and horizontal velocity data in the DWBC at 69 0W recorded during the period 2002-2008, showed that the variability along the DWBC is linked to changes in the dense water formation regions. The evolution of potential vorticity (PV) at the mooring site, characterized by a transition from deep to upper Labrador Sea Water (LSW), was similar to that observed in the Labrador Sea 6 to 9 years earlier, and imply spreading rates for the LSW that varied over time from 1.5 to 2.5cm/s. The time dependence of the spreading rates was in good agreement with changes in the strength of the DWBC at the mooring site. The evolution of the DWBC transport was explored in more detail from a 5- element moored array, also at 69'W. The results, for the period of 2004-2008, were consistent with the single mooring analysis. The variability measured from the array showed that upper, intermediate and deep water mass layers expand and contract at each other's expense, leading to alternating positive and negative PV anomalies at the upper-LSW, deep-LSW and Overflow Water (OW). Larger DWBC transports were associated with enhanced presence of recently ventilated upper-LSW and OW, rather than deep-LSW. The relative contribution of the different water masses to the observed circulation was investigated by inverting individual PV anomalies isolated from the observations. We found that changes in the depth-integrated circulation were mostly driven by changes in the OW. / by Beatriz Peña-Molino. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1982. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 221-225. / by Ping-Tung Peter Shaw. / Ph.D.