The fluvial geochemistry of the rivers of Eastern Siberia and implications for the effect of climate on weathering

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1998.Includes bibliographical references.by Youngsook Huh.Ph.D

Target tracking onboard an autonomous underwater vehicle : determining optimal towed array heading in an anisotropic noise field

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), 2007.Includes bibliographical references (p. 73-76).In order to overcome the challenges that an anisotropic noise field poses for underwater target tracking, we conduct an onboard estimation of the horizontal noise directionality in the real-time processing suite of an autonomous underwater vehicle (AUV) towing a horizontal line array. The estimation of the noise directionality is a precursor to another adaptive behavior: optimizing tracking capability of a towed array by choosing a particular heading that minimizes the detection level in the target's direction. In each distinct simulated anisotropic noise field, the AUV successfully calculates the optimal towed array headings based on the real-time estimation of the horizontal noise directionality. The findings reveal a clear advantage over the conventional broadside beam tracking method, with some limitations due predominantly to the noise field itself.by Maria Alejandra Parra-Orlandoni.S.M

Detection, classification and localization of seabed objects with a virtual time reversal mirror

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), 2009.Includes bibliographical references (p. 88-91).The work presented in this thesis addresses the problem of the detection, classification and localization of seabed objects in shallow water environments using a time reversal approach in a bistatic configuration. The waveguide is insonified at low frequency ('kHz) with an omnidirectional source and the resulting scattered field is sampled by a receiving array towed behind an Autonomous Underwater Vehicle (AUV). The recorded signals are then processed to simulate onboard the AUV, the time reversed transmissions which serve to localize the origin of the scattered field on the seabed and estimate the position of the targets present. The clutter rejection based upon the analysis of the singular values of the Time Reversal operator is investigated with simulated data and field measurements collected off the coast of Palmaria (Italy) in January 2008.by Alexis J. Dumortier.S.M

The evolution of upper ocean thermal structure at 10⁰N, 125⁰W during 1997-1998

Thesis (M.S.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences and the Woods Hole Oceanographic Institution), 2003.Includes bibliographical references (p. 181-191).In this thesis I have endeavored to determine the factors and physical processes that controlled SST and thermocline depth at 10⁰N, 125⁰W during the Pan Amer- ican Climate Study (PACS) field program. Analysis based on the PACS data set, TOPEX/Poseidon sea surface height data, European Remote Sensing satellite wind data, and model simulations and experiments reveals that the dominant mechanisms affecting the thermocline depth and SST at the mooring site during the measurement period were local surface fluxes, Ekman pumping, and vertical mixing associated with enhancement of the vertical shear by strong near-inertial waves in the upper ocean superimposed upon intra-seasonal baroclinic Rossby waves and the large scale zonal flow.by J. Thomas Farrar.M.S

Bibliography of technical reports, 1993

The technical reports prepared by the Woods Hole Oceanographic Institution in 1993 are listed in this bibliography. Inquiries about availability of extra copies wil be handled on an individual basis. Initial distribution of the reports is controlled by the funding agencies. Reports listed in this bibliography are available from the: National Technical Information Service, NTIS Order Desk, 5285 Port Royal Road, Springfield, V A 22161 USA. When available, NTIS order numbers are included with each report listed

The feasibility of sodar wind profile measurements from an oceanographic buoy

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), 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 (leaf 75).This thesis explores the feasibility of making wind speed profile measurements from an oceanographic buoy using a Doppler sodar. In the fall of 2005, we deployed a Scintec SFAS sodar on an ASIS buoy. Roughly one week of buoy motion data and one day of sodar observations were collected. Data from both this deployment, and the Martha's Vineyard Coastal Observatory, were used in conjunction with models to predict sodar performance. Results are compared for an ASIS and a 3-meter discus buoy. We also predict the yearly average probability of sodar data availability in the presence of buoy motion. We show that buoy tilting in response to wave forcing is the main factor affecting sodar performance. Our results strongly suggest that ASIS is a suitable platform for sodar measurements at sea.by Allison M. Berg.S.M

Examining the effects of mid ocean ridge topography on 3D marine magnetometric resistivity model responses

Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2004.Includes bibliographical references (leaves 68-69).Methods which measure seafloor resistivity are uniquely suited to studying hydrothermal circulation in the crust. The magnetometric resistivity (MMR) technique is a galvanic method which uses a bipole current source with a magnetometer receiver. The resistivity of the subsurface can be estimated from the magnetic field read in MMR. In order to analyze and invert MMR data taken near Mid Ocean Ridges, it is important to understand the effects of ridge topography on MMR models. To analyze these effects a 3D MMR forward modeling program MMR3Df̲wd is used to model Mid Ocean Ridges with varying slopes, resistivities, and source/receiver geometries. The modeled magnetic fields are compared with models with a flat seafloor to determine the impact of the ridge topography. Results show that for some of the ridges modeled, the effects of the topography were significant, suggesting that in some instances it is important to include ridge topography in forward models to obtain accurate results from data inversion.by Lisa A. Lassner.S.M

Construction and phenotypic screening of mid-size insert marine microbial environmental genomic libraries

Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering; and the Woods Hole Oceanographic Institution), 2008.Includes bibliographical references (leaves 52-56).Functional screening of environmental genomic libraries permits the identification of clones expressing activities of interest without requiring prior knowledge of the genes responsible. In this study, protocols were optimized for the construction of mid-size DNA insert, inducible expression environmental genomic plasmid libraries for this purpose. A library with a mean insert size of 5.2 kilobases was constructed with environmental DNA isolated from surface ocean water collected at Hawaii Ocean Time-series station ALOHA in plasmid cloning vector pMCL200 under the inducible control of the PLAC promoter. To begin to evaluate the utility of such libraries for gene expression-based screens, this library was screened phenotypically for clones expressing genes that confer fluorescence or distinctive coloration on colonies of host Escherichia coli cells, and results were compared to those for a fosmid library constructed from the same marine microbial DNA sample. Ecologically relevant sequences were identified in both libraries, and each was observed to offer both advantages and disadvantages. Results of this study suggest that mid-size insert plasmid libraries under the control of inducible promoters can provide a useful and complementary approach for both functional screening and shotgun sequencing of environmental genomic libraries.by Jennifer C. Braff.S.M

Petrologic and microstructural constraints on focused melt transport in dunites and the rheology of the shallow mantle

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2004.Includes bibliographical references.Observations at mid-ocean ridges indicate that magmas are focused to the ridge axis by a network of porous dunites in near chemical isolation. This thesis investigates several of the outstanding questions regarding the mechanisms of melt transport and its effects on the shallow mantle. Chapter 1 details the current understanding of melt migration from observations at mid-ocean ridges and ophiolites. Chapter 2 uses the size distribution and abundance of dunites measured in the Oman ophiolite to place limits on the potential mechanisms by which dunites form and subsequently estimate the flux of chemically unequilibrated melt which a network of dunites can supply. Chapter 3 characterizes the chemical composition of dunites and harzburgites from Oman to further constrain the process by which dunites form and relates the observed trends within dunites to variations in the time-integrated melt/rock ratio. Chapter 4 examines the microstructures of peridotites in Oman to constrain the deformation mechanisms which determine the viscosity of shallow mantle. Chapter 5 is a numerical investigation of advection beneath ridges incorporating the rheology inferred from the observed microstructures. Chapter 6 integrates the conclusions of the previous chapters, reevaluating the potential melt flux through dunites and constraining the permeability of the shallow mantle.by Michael Geoffrey Braun.Ph.D

Evolution of oceanic margins : rifting in the Gulf of California and sediment diapirism and mantle hydration during subduction

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2013.Cataloged from PDF version of thesis.Includes bibliographical references.This thesis investigates three processes that control the evolution of oceanic margins. Chapter 2 presents seismic images of a ~2-km-thick evaporite body in Guaymas Basin, central Gulf of California. In rifts, evaporites form under conditions unique to the latest stages of continental rupture, and the presence, age, thickness, and shape place new constraints on the history of early rifting there. Chapter 3 presents numerical experiments that show that diapirs can form in sediments on the down-going plate in subduction zones and rise into the mantle wedge, delivering the sedimentary component widely observed in arc magmas. Chapter 4 presents measurements of seismic anisotropy from wide-angle, active-source data from the Middle America Trench that address the hypothesis that the upper mantle is hydrated by seawater flowing along outer-rise normal faults. These measurements indicate that the upper mantle is ~1.57 to 6.89% anisotropic, and this anisotropy can be attributed to bending-related faulting and an inherited mantle fabric. Accounting for anisotropy reduces previous estimates for the amount of water stored in the upper mantle of the down-going plate from ~2.5 to 1.5 wt%, a significant change in subduction zone water budgets.by Nathaniel Clark Miller.Ph.D