\contentsline {chapter}{\numberline {1}Introduction}{1}
\contentsline {section}{\numberline {1.1}Motivation}{1}
\contentsline {section}{\numberline {1.2}Thesis Outline}{3}
\contentsline {section}{\numberline {1.3}Background}{4}
\contentsline {subsection}{\numberline {1.3.1}Rift-Valley Hydrography and Flow}{4}
\contentsline {subsection}{\numberline {1.3.2}Hydrothermal Plume Dispersal and Fluxes}{6}
\contentsline {subsection}{\numberline {1.3.3}The \emph {AMAR}\xspace Segments}{9}
\contentsline {subsection}{\numberline {1.3.4}The \emph {Rainbow}\xspace Hydrothermal Vent Field}{11}
\contentsline {chapter}{\numberline {2}Data Sets and Methods}{13}
\contentsline {section}{\numberline {2.1}1997 Survey \emph {(FLAME)}\xspace }{13}
\contentsline {section}{\numberline {2.2}1998 Survey \emph {(FLAME-2)}\xspace }{15}
\contentsline {section}{\numberline {2.3}Current-Meter Moorings}{18}
\contentsline {subsection}{\numberline {2.3.1}Sensors and Data}{18}
\contentsline {subsection}{\numberline {2.3.2}Calibrations}{18}
\contentsline {chapter}{\numberline {3}Quasi-Synoptic Hydrographic and Flow Observations}{21}
\contentsline {section}{\numberline {3.1}Introduction}{21}
\contentsline {section}{\numberline {3.2}1997 Survey \emph {(FLAME)}\xspace }{22}
\contentsline {subsection}{\numberline {3.2.1}Regional Hydrography}{22}
\contentsline {subsection}{\numberline {3.2.2}Origin of the Rift-Valley Water}{24}
\contentsline {subsection}{\numberline {3.2.3}Rift-Valley Hydrography and Flow}{26}
\contentsline {subsubsection}{Horizontal Density Distribution}{26}
\contentsline {subsubsection}{Direct Flow Observations}{28}
\contentsline {subsubsection}{Flow Across \emph {Rainbow Sill}\xspace }{31}
\contentsline {subsubsection}{A Topographic Wake}{34}
\contentsline {subsubsection}{Hydrographic Variability on Tidal Time Scales}{35}
\contentsline {section}{\numberline {3.3}1998 Survey \emph {(FLAME-2)}\xspace }{37}
\contentsline {subsection}{\numberline {3.3.1}Changes in the Rift-Valley Hydrography and Flow Regime Between 1997 and 1998}{37}
\contentsline {subsection}{\numberline {3.3.2}Along-Segment Hydrographic Gradients}{41}
\contentsline {subsection}{\numberline {3.3.3}Inflow Into \emph {South AMAR}\xspace }{42}
\contentsline {section}{\numberline {3.4}Discussion}{44}
\contentsline {chapter}{\numberline {4}Current-Meter Observations}{46}
\contentsline {section}{\numberline {4.1}Introduction}{46}
\contentsline {section}{\numberline {4.2}Warming Event}{47}
\contentsline {section}{\numberline {4.3}Energy Partition}{50}
\contentsline {subsection}{\numberline {4.3.1}Flow and Temperature Spectra}{50}
\contentsline {subsection}{\numberline {4.3.2}Bulk Energy Distribution}{55}
\contentsline {section}{\numberline {4.4}High-Frequency Temperature Variability}{57}
\contentsline {section}{\numberline {4.5}Along-Segment Flow and Transport}{59}
\contentsline {subsection}{\numberline {4.5.1}Flow Statistics}{59}
\contentsline {subsection}{\numberline {4.5.2}Volume Flux Across \emph {Rainbow Sill}\xspace }{61}
\contentsline {section}{\numberline {4.6}Discussion}{63}
\contentsline {chapter}{\numberline {5}Hydrothermal Particle-Plume Observations}{65}
\contentsline {section}{\numberline {5.1}Introduction}{65}
\contentsline {section}{\numberline {5.2}1997 Survey \emph {(FLAME)}\xspace }{67}
\contentsline {subsection}{\numberline {5.2.1}Horizontal Particle Distribution}{67}
\contentsline {subsection}{\numberline {5.2.2}Individual Nephelometry Profiles}{69}
\contentsline {subsection}{\numberline {5.2.3}Mean Particle Plume}{70}
\contentsline {section}{\numberline {5.3}1998 Survey \emph {(FLAME-2)}\xspace }{71}
\contentsline {section}{\numberline {5.4}Discussion}{74}
\contentsline {chapter}{\numberline {6}Geothermal Hydrographic Anomalies}{76}
\contentsline {section}{\numberline {6.1}Introduction}{76}
\contentsline {section}{\numberline {6.2}Isopycnal Hydrographic Anomalies}{78}
\contentsline {section}{\numberline {6.3}Relationship Between Isopycnal and Isohaline Anomalies}{81}
\contentsline {section}{\numberline {6.4}Plume-Bracketing Method}{83}
\contentsline {section}{\numberline {6.5}Bilinear Method}{86}
\contentsline {section}{\numberline {6.6}Spice Anomalies of the \emph {Rainbow}\xspace Hydrothermal Plume}{88}
\contentsline {subsection}{\numberline {6.6.1}1997 Survey \emph {(FLAME)}\xspace }{88}
\contentsline {subsection}{\numberline {6.6.2}1998 Survey \emph {(FLAME-2)}\xspace }{91}
\contentsline {section}{\numberline {6.7}Spice Anomalies of Pacific Hydrothermal Plumes}{92}
\contentsline {section}{\numberline {6.8}Discussion}{95}
\contentsline {chapter}{\numberline {7}Convective Heat Flux from the \emph {Rainbow}\xspace Hydrothermal Vent Field}{98}
\contentsline {section}{\numberline {7.1}Introduction}{98}
\contentsline {section}{\numberline {7.2}Height-Of-Rise Method}{98}
\contentsline {section}{\numberline {7.3}Advective Flux in the 1997 Particle Plume}{101}
\contentsline {section}{\numberline {7.4}Discussion}{102}
\contentsline {chapter}{\numberline {8}Mass and Heat Budgets of the \emph {AMAR}\xspace Segments}{104}
\contentsline {section}{\numberline {8.1}Introduction}{104}
\contentsline {section}{\numberline {8.2}Heat Budget Beneath a Grounding Isopycnal}{105}
\contentsline {section}{\numberline {8.3}Rift-Valley Mass and Heat Budgets}{108}
\contentsline {section}{\numberline {8.4}Discussion}{111}
\contentsline {chapter}{\numberline {9}A Simple Basin/Sill Model}{113}
\contentsline {section}{\numberline {9.1}Introduction}{113}
\contentsline {section}{\numberline {9.2}Model Formulation}{113}
\contentsline {section}{\numberline {9.3}Steady Forcing}{115}
\contentsline {section}{\numberline {9.4}Non-Steady Forcing}{117}
\contentsline {section}{\numberline {9.5}Discussion}{118}
\contentsline {chapter}{\numberline {10}Findings, Implications and Speculation}{120}
\contentsline {section}{\numberline {10.1}Main Observations and Conclusions}{120}
\contentsline {subsection}{\numberline {10.1.1}Observations}{120}
\contentsline {subsubsection}{Rift-Valley Flow and Hydrography}{120}
\contentsline {subsubsection}{Basin/Sill Systems}{121}
\contentsline {subsubsection}{\emph {Rainbow}\xspace Hydrothermal Plume}{121}
\contentsline {subsection}{\numberline {10.1.2}Conclusions}{121}
\contentsline {subsubsection}{Rift-Valley Hydrography and Flow}{121}
\contentsline {subsubsection}{Hydrothermal Hydrographic Anomalies}{122}
\contentsline {subsubsection}{\emph {Rainbow}\xspace Hydrothermal Plume}{122}
\contentsline {section}{\numberline {10.2}Implications and Speculation}{122}
\contentsline {subsection}{\numberline {10.2.1}Geothermal Fluxes}{122}
\contentsline {subsection}{\numberline {10.2.2}Rift-Valley Hydrography and Flow}{123}
\contentsline {subsection}{\numberline {10.2.3}Dispersal of Hydrothermal Tracers and Biota}{125}
\contentsline {chapter}{Bibliography}{126}