This investigation focuses on gaining a better understanding of the complex relationship between melt generation, source variability and mid-ocean ridge morphology. The approach adopted here uses a variety of geochemical techniques to evaluate the ability of 'global' models to predict regional scale geochemical variability associated with axial depth and axial...
In an attempt to understand the phase equilibria and petrogenesis of MORB anorthitic plagioclase, Cr-spinel commonly hosted within anorthitic plagioclase has been investigated petrographically and compositionally. Based on spinel-anorthite relationships from three samples of plagioclase ultra-phyric basalt (PUB; Southeast Indian Ridge, Axial Seamount and West Valley Segment, Juan de Fuca...
Prior to eruption at mid-ocean ridges, melts must travel through >6 km of crust from their origin in the mantle. The final composition of the melts is dependent on both the melting conditions and magmatic processes within the crust. While mid-ocean ridge basalt (MORB) glasses are commonly used to infer...
Magmatic processes control the chemical compositions of all lavas erupted at
mid-ocean ridges. In this thesis, I present studies of magmatic processes on three
different mid-ocean ridges to determine which processes are in action and to what extent
each has affected the chemistry of mid-ocean ridge basalts at each location....
The Kane Oceanic Core Complex (OCC) is a valuable window into crustal architecture and chemical composition of the lithosphere beneath a slow-spreading ocean ridge. A suite of > 30 samples (comprised of whole rocks, mineral separates and basalt glasses) has been analyzed for ³He/⁴He isotope ratios and He concentrations. Gas...
The seismicity at the northern section of the Gorda Ridge has been
studied with Ocean Bottom Seismographs. Nearly one hundred earthquakes
were located with RMS travel time residuals less than 0.5 seconds.
Most of these events lie within or near the array and they are probably
associated with the dynamics...
We have determined the seismic crustal structure of the
northern part of the Gorda Ridge using signals generated by
explosive charges and recorded on Ocean Bottom Seismometers. The
shot pattern forms two parallel lines, one on the east flank and the
other along the median valley. Inversion of the travel...
Thorough understanding of the mechanisms controlling the temperature structure in the surface mixed layer of the ocean and, in particular, accurate values of sea surface temperature are critical for properly parameterizing air-sea heat exchange and quantifying the amount of heat redistributed below the surface. It is however difficult to obtain...
The importance of wind-driven latent heat fluxes for supporting tropical intraseasonal precipitation variability is analyzed. Tropical
intraseasonal variability in the west pacific and Indian ocean is analyzed for northern and southern hemisphere summer during 1999-2005 using
satellite and buoy observations. A composite analysis of QuikSCAT ocean vector winds and TRMM...
In this thesis, data collected during the Dynamics of the Madden Julian Oscillation (DYNAMO) field campaign, conducted in the Indian Ocean in Fall of 2011, is used to compute heat fluxes at the air-sea interface by evaluating eddy covariances and bulk aerodynamic formulae. Errors in daily average gridded fluxes computed...
A Regional Ocean Modeling System (ROMS) application for the coastal region of Kenya and Tanzania (0-10° S, 38.7-46.98° E) was developed with the aim of better resolving the circulation patterns in the coastal region that is poorly represented in global models. The model has a horizontal resolution of 4 km,...
Recent studies have found that equatorial Atlantic sea surface temperature (SST) variability may be influencing tropical Indian Ocean climate (Kucharski 2009, Wang 2009). Due to the economic and social impact of tropical cyclones, it is important to investigate how an Atlantic-Indian Ocean connection may be affecting tropical cyclone behavior in...
Oceanic crust covers nearly 70% of the Earth's surface, of which, the upper,
sediment layer is estimated to harbor substantial microbial biomass. Marine crust;
however, extends several kilometers beyond this surficial layer, and includes the
basalt and gabbro layers. In particular, the basalt layer has high permeabilities which
allows for...
Tropical coral reef ecosystems are very important from both the ecological and economical
points of view. However, they are also particularly fragile, and have been
declining in recent years in most regions of the world, since they are highly susceptible
to anthropogenic stressors operating at global scales (e.g., global warming...
The 2004 Indian Ocean tsunami raised concern among marine park managers and
hazard mitigation professionals about the significant impact of major coastal hazards
on marine park natural resources and ecosystems. The main reason for this concern is
the strong linkage of marine parks and their rich assortment of ecosystem services...
Subduction zone earthquake and tsunami hazards affect tens of millions worldwide and the recurrence of these disasters can be evaluated with paleoseismic techniques, because earthquake cycles (and their supercycles) typically span many millennia. In these three chapters, I discuss a suite of analyses I use to evaluate the sedimentary record...