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. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Meteorology. / Bibliography: leaves 104-107. / by Bruce B. Parker / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1979. / Microfiche copy available in Archives and Science. / Bibliography : leaves 89-90. / by Daniel Golan. / M.S.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2006. / Includes bibliographical references. / Benthic and planktonic foraminiferal [delta]18O ([delta 18Oc) from a suite of well-dated, high-resolution cores spanning the depth and width of the Straits of Florida reveal significant changes in Gulf Stream cross-current density gradient during the last millennium. These data imply that Gulf Stream transport during the Little Ice Age (LIA: 1200-1850 A.D.) was 2-3 Sv lower than today. The timing of reduced flow is consistent with cold conditions in Northern Hemisphere paleoclimate archives, implicating Gulf Stream heat transport in centennial-scale climate variability of the last 1,000 years. The pattern of flow anomalies with depth suggests reduced LIA transport was due to weaker subtropical gyre wind stress curl. The oxygen isotopic composition of Florida Current surface water ([delta]18Ow) near Dry Tortugas increased 0.4%0/ during the course of the Little Ice Age (LIA: -1200-1850 A.D.), equivalent to a salinity increase of 0.8-1.5 psu. On the Great Bahama Bank, where surface waters are influenced by the North Atlantic subtropical gyre, [delta]18Ow increased by 0.3%o during the last 200 years. Although a portion (-O. 1%o) of this shift may be an artifact of anthropogenically-driven changes in surface water [Epsilon]CO2, the remaining [delta]18Ow signal implies a 0.4 to 1 psu increase in salinity after 200 yr BP. / (cont.) The simplest explanation of the [delta]18Ow, data is southward migration of the Atlantic Hadley circulation during the LIA. Scaling of the [delta]18Ow records to salinity using the modern low-latitude 180,w-S slope produces an unrealistic reversal in the salinity gradient between the two sites. Only if [delta]18Ow is scaled to salinity using a high-latitude [delta]18Ow-S slope can the records be reconciled. Changes in atmospheric 14C paralleled shifts in Dry Tortugas [delta]18Ow, suggesting that variable solar irradiance paced centennial-scale Hadley cell migration and changes in Florida Current salinity during the last millennium. / by David C. Lund. / Ph.D.

The global ocean currently absorbs over a third of anthropogenic carbon dioxide (CO₂) emissions, slowing down the growth of atmospheric CO₂, and thus moderating climate change. However, there is significant variability in the strength of the ocean carbon sink on interannual to decadal timescales. There are also uncertainties in the ocean carbon sink, a source of which lies in the coastal ocean. Coastal carbon fluxes are globally relevant and highly variable, but due to the paucity of observations, the coastal ocean remains largely unconstrained. Quantifying and understanding the variability of the ocean carbon sink, and constraining its uncertainties, is essential for supporting climate policy and predicting how the ocean will continue to moderate climate change in the future. This is challenging due to the complex physical and biogeochemical processes in the ocean, as well as the limited observations of ocean carbon. The goal of this thesis is to contribute to the understanding of the ocean carbon cycle and its variability with observations of CO₂ fluxes in the coastal ocean (Chapter 2), a multi-model study of surface carbon interannual variability (Chapter 3), and a mechanistic investigation of decadal variability of air-sea CO₂ fluxes in the global ocean (Chapter 4). (Chapter 2) Jamaica Bay is a hypereutrophic coastal urban estuary within the land-ocean aquatic continuum. Anthropogenic perturbations to the carbon cycle of the continuum are often excluded from global carbon budgets. Studies have shown that not accounting for the lateral transport of anthropogenic carbon through the continuum can lead to an overestimation of land carbon sinks and an underestimation of ocean carbon sinks. In this study, we used the direct covariance method to make direct estimates of CO₂ fluxes in Jamaica Bay. Over a 587-day observational study, Jamaica Bay emitted CO₂ to the atmosphere at an average rate of 130 gC/m2/yr. However, we find that the waters within the estuary are a strong CO₂ sink (-170 gC/m2/yr). Thus, on average, air-water CO₂ fluxes damp estuary emissions. We find that the water CO₂ sink is strongest in the summer due to the growth of intense algal blooms which likely drawdown CO₂ via photosynthesis. Although the direction of air-water CO₂ flux is ultimately a function of surface carbon concentrations, we find that in the summer, sea-breeze is a near-daily forcing agent for air-water CO₂ fluxes, contributing up to 43% of the mean summer water CO₂ sink rate. (Chapter 3) The El Nino-Southern Oscillation (ENSO) in the equatorial Pacific is the dominant mode of global air-sea CO₂ flux interannual variability (IAV). Air-sea CO2 fluxes are driven by the difference between atmospheric and surface ocean pCO₂, with variability of the latter driving flux variability. Previous studies found that models in Coupled Model Intercomparison Project Phase 5 (CMIP5) failed to reproduce the observed ENSO-related pattern of CO₂ fluxes and had weak pCO₂ IAV, which were explained by both weak upwelling IAV and weak mean vertical DIC gradients. We assess whether the latest generation of CMIP6 models can reproduce equatorial Pacific pCO₂ IAV by validating models against observations-based data products. We decompose pCO₂ IAV into thermally and non-thermally driven anomalies to examine the balance between these competing anomalies, which explain the total pCO₂ IAV. The majority of CMIP6 models underestimate pCO₂ IAV, while they overestimate SST IAV. Insufficient compensation of non-thermal pCO₂ to thermal pCO₂ IAV in models results in weak total pCO₂ IAV. We compare the relative strengths of the vertical transport of temperature and DIC and evaluate their contributions to thermal and non-thermal pCO₂ anomalies. Model-to-observations-based product comparisons reveal that modeled mean vertical DIC gradients are biased weak relative to their mean vertical temperature gradients, but upwelling acting on these gradients is insufficient to explain the relative magnitudes of thermal and non-thermal pCO₂ anomalies. (Chapter 4) The ocean carbon sink has absorbed about 25% of anthropogenic emissions, thus mitigating the effects of climate change. Over time, the ocean carbon sink has grown almost proportionally with the growth of atmospheric CO₂ concentrations. However, natural variability in the ocean carbon sink combined with large uncertainties, makes it hard to distinguish changes in the ocean sink due to natural variability versus the forced-trend. Thus, there is a need to understand and quantify the variability in the ocean carbon sink. Using the LDEO-Hybrid Physics Data product (1959-2020), we assess the decadal variability of global air-sea CO₂ fluxes. Here, we compare regional contributions to the decadal variability of the global ocean carbon sink and evaluate global patterns of decadal changes to elucidate the mechanisms that drive the dominant mode of global air-sea CO₂ flux decadal variability. We find that the dominant mode of decadal air-sea CO₂ flux variability exhibits strong synchronous signals over the tropical Pacific and Southern Ocean. We suggest that the synchronicity between the tropical Pacific and the Southern Ocean is modulated by the Pacific Decadal Oscillation (PDO) index, which is connected to the Multivariate ENSO Index (MEI). The composite patterns over the tropical Pacific can be explained by ENSO-like mechanisms operating on the decadal timescale, while the composite patterns over the Southern Ocean show a different regime where the westerly winds weakened over the composite period, the mixed layer shoaled, and the Southern Ocean sink weakened. Using a box model, we show that this reduction in mixed layer entrainment drives an accumulation of DIC in the mixed layer, which, when amplified by the high Revelle factor in the Southern Ocean, results in a 14-fold amplification in the surface pCO₂, reducing the ocean's capacity to uptake CO₂.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN. / Vita. / Bibliography : leaves 203-209. / by Douglas Scott Luther. / Ph.D.

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A motion compensated ADV system was evaluated to determine its ability to make measurements necessary for characterizing the variability of the ambient current in the Gulf Stream. The impact of IMU error relative to predicted turbulence spectra was quantified, as well as and the ability of the motion compensation approach to remove sensor motion from the ADV measurements. The presented data processing techniques are shown to allow the evaluated ADV to be effectively utilized for quantifying ambient current fluctuations from 0.02 to 1 Hz (50 to 1 seconds) for dissipation rates as low as 3x10-7. This measurement range is limited on the low frequency end by IMU error, primarily by the calculated transformation matrix, and on the high end by Doppler noise. Inshore testing has revealed a 0.37 Hz oscillation inherent in the towfish designed and manufactured as part of this project, which can nearly be removed using the IMU. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

The concept of Intensity Duration Frequency (IDF) relationship curve presents crucial design contribution for several decades under the assumption of a stationary climate, the frequency and intensity of extreme rainfall nonetheless seemingly increase worldwide. Based on the research conducted in recent years, the greatest increases are likely to occur in short-duration storms lasting less than a day, potentially leading to an increase in the magnitude and frequency of flash floods. The trend analysis of the precipitation influencing the climate variability and extreme rainfall in the state of Florida is conducted in this study. Since these local changes are potentially or directly related to the surrounding oceanic-atmospheric oscillations, the following oscillations are analyzed or highlighted in this study: Atlantic Multi-Decadal Oscillation (AMO), El Niño Southern Oscillation (ENSO), and Pacific Decadal Oscillations (PDO). Collected throughout the state of Florida, the precipitation data from rainfall gages are grouped and analyzed based on type of duration such as short-term duration or minute, in hourly and in daily period. To assess statistical associations based on the ranks of the data, the non-parametric tests Kendall’s tau and Spearman’s rho correlation coefficient are used to determine the orientation of the trend and ultimately utilize the testing results to determine the statistical significance of the analyzed data. The outcome of the latter confirms with confidence whether there is an increasing or decreasing trend in precipitation depth in the State of Florida. The main emphasis is on the influence of rainfall extremes of short-term duration over a period of about 50 years. Results from both Spearman and Mann-Kendall tests show that the greatest percentage of increase occurs during the short rainfall duration period. The result highlights a tendency of increasing trends in three different regions, two of which are more into the central and peninsula region of Florida and one in the continental region. Given its topography and the nature of its water surface such as the everglades and the Lake Okeechobee, Florida experience a wide range of weather patterns resulting in frequent flooding during wet season and drought in the dry season. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 148-152). / Wind waves in the ocean are a product of complex interaction of turbulent air flow with gravity driven water surface. The coupling is strong and the waves are non-stationary, irregular and highly nonlinear, which restricts the ability of traditional phase averaged models to simulate their complex dynamics. We develop a novel phase resolving model for direct simulation of nonlinear broadband wind waves based on the High Order Spectral (HOS) method (Dommermuth and Yue 1987). The original HOS method, which is a nonlinear pseudo-spectral numerical technique for phase resolving simulation of free regular waves, is extended to simulation of wind forced irregular broadband wave fields. Wind forcing is modeled phenomenologically in a linearized framework of weakly interacting spectral components of the wave field. The mechanism of wind forcing is assumed to be primarily form drag acting on the surface through wave-induced distribution of normal stress. The mechanism is parameterized in terms of wave age and its magnitude is adjusted by the observed growth rates. Linear formulation of the forcing is adopted and applied directly to the nonlinear evolution equations. Development of realistic nonlinear wind wave simulation with HOS method required its extension to broadband irregular wave fields. Another challenge was application of the conservative HOS technique to the intermittent non-conservative dynamics of wind waves. These challenges encountered the fundamental limitations of the original method. Apparent deterioration of wind forced simulations and their inevitable crash raised concerns regarding the validity of the proposed modeling approach. The major question involved application of the original HOS low-pass filtering technique to account for the effect of wave breaking. It was found that growing wind waves break more frequently and violently than free waves. / (cont.) Stronger filtering was required for stabilization of wind wave simulations for duration on the time scale of observed ocean evolution. Successful simulations were produced only after significant sacrifice of resolution bandwidth. Despite the difficulties our modeling approach appears to suffice for reproduction of the essential physics of nonlinear wind waves. Phase resolving simulations are shown to capture both - the characteristic irregularity and the observed similarity that emerges from the chaotic motions. Energy growth and frequency downshift satisfy duration limited evolution parameterizations and asymptote Toba similarity law. Our simulations resolve the detailed kinematics and the nonlinear energetics of swell, windsea and their fast transition under wind forcing. We explain the difference between measurements of initial growth driven by a linear instability mechanism and the balanced nonlinear growth. The simulations validate Toba hypothesis of wind-wave nonlinear quasi-equilibrium and confirm its function as a universal bound on combined windsea and swell evolution under steady wind. / by Alexander G. Kalmikov. / S.M.