Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2005. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 44). / The oceanic circulation plays a significant role in earth's climate by transporting heat polewards. Here the ocean's thermohaline circulation is studied using the Marotzke and Stone four box ocean-atmosphere model under both the buoyancy constraint proposed by Stommel and the energy constraint proposed by Huang. Both a sensitivity study and stability analysis is performed. In the sensitivity study it is evident that the model under the buoyancy constraint reacted to variations in flow between ocean boxes, net incoming radiation gradient and longwave radiation reflection coefficient in the same manner regardless of whether it was in thermal mode or haline mode. Under the energy constraint the study yielded similar results in both modes, with the exception of the equilibrium temperature and salinity having opposite relationships to the energy parameter in the thermal and haline modes. The model under the buoyancy constraint under both limits becomes more sensitive to changes in both the net incoming radiation gradient and the longwave radiation reflection coefficient as the rate of flow between the two ocean boxes decreases. The model under the energy constraint, in contrast, becomes more sensitive to changes in the longwave radiation reflection coefficient as the energy parameter decreases but the model's sensitivity to changes in the net incoming radiation gradient is unaltered by changes in the energy parameter. This suggests that the model under the energy constraint is less sensitive to global climate changes. The stability analysis shows that the model under both the buoyancy and energy constraint is stable to realistic perturbations in temperature and salinity. / by Christie Wood. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2004. / "June 2004." / Includes bibliographical references (leaves 41-42). / I present 1.2 mm observations of the HII regions RCW 38, RCW 36, and RCW 108 which reveal the distributions of dust associated with the three regions. The dust emission in RCW 38 exhibits a ring like structure centered around an O-star. A bright knot in the ring was determined to contain 15% of the total dust by mass in the region and roughly coincided with regions of high emission at various infrared wavelengths as well as 6 cm continuum emission. The dust emission in RCW 36 extended along a ridge with a bright clump in the north of the ridge containing 70% of the mass of the entire cluster. The dust emission in RCW 108 is concentrated in a single tight knot with a faint extension to the south. The dust emission is compared to the infrared and radio emissions to attempt to describe the characteristics of possible areas of active star formation. / Miquela Vigil. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997. / Includes bibliographical references (leaves 192-195). / by Igor V. Kamenkovich. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1987. / Microfiche copy available in Archives and Science. / Vita. / Includes bibliographies. / by Adam Paul Freedman. / Ph.D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 50-56). / Stromatolites, columnar rock-like structures, are potentially some of the oldest, microbially mediated fossils visible in the rock record; if biogenesis is able to be confirmed for these ancient stromatolites, some being greater than 3 billion years old, these ancient stromatolites could be used to demonstrate the microbial community assemblages throughout ancient time. Hamelin Pool, Shark Bay, Australia is an ideal field site for this task, as stromtolites and modem microbial mats coexist and the microbial mats have been shown to contribute to the formation of the stromatolites. Comprehensive lipid biomarker profiles were determined in this study for non-lithified smooth, pustular, and colloform microbial mats, as well as for smooth and colloform stromatolites. Intact polar lipids, glycerol dialkyl glycerol tetraethers, and bacteriohopanepolyols were analyzed via liquid chromatography-mass spectrometry (LC-MS) coupled to a Quadropole Time-of-Flight (QTOF) mass spectrometer, while the previously studied fatty acids (Allen et al., 2010) were analyzed using gas chromatography-mass spectrometry (GC-MS) to prove consistent signatures. From the lipid profiles, sulfate-reducing bacteria and anoxygenic phototrophic bacteria and archaea could be inferred. The presence of the rare 3- methylhopanoids (3 Me-BHPs) was discovered in a significant portion of the samples, which could add to the characterization of this molecule, which has only been concretely linked to oxygenic conditions for formation. In accordance with Allen et al. in 2010, 2- methyhopanoids were detected, as well as limited signals from higher (vascular) plants. While the lipid profiles for all sediment types were similar, there were some differences that are likely attributable to morphological differences. However, the overall similarities suggest microbial communities can be similar between non-lithified microbial mats and stromatolites. 2 / by Elise McKenna Myers. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1993. / Includes bibliographical references (p. 208-214). / by D'Arcy Winston Straub. / Ph.D.

Thesis: S.M. in Geophysics, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 115-116). / Being valid for single-phase flow, Darcy's law is adapted to two-phase flow through the standard approach of relative permeability, in which permeability, rather than being a unique property of the porous medium, becomes a joint property of the porous medium and each fluid phase. The goal of this study is to find a proper, alternate approach to relative permeability that can describe two-phase flow in porous media while maintaining sound physical concepts, specifically that of a unique permeability exclusive to the porous medium. The suggested approach uses the concept of an average viscosity of the two-phase fluid mixture. Viscosity, the only fluid-characterizing term in Darcy's law, should -at least partially- explain two-phase flow behavior by becoming the two-phase flow property that varies with the saturation ratio of the two fluid phases. Three common mathematical averages are tested as potential viscosity averages. Aspects of two-phase flow in pipes are then considered to see whether two-phase flow behavior in porous media can be attributed to the fluid mixture alone. Total flow rate of the two-phase fluid mixture is modeled by using the fluid mixture average viscosity in Darcy's law. Using two-phase flow data from Oak et al. (1990a, 1990b), the harmonic average weighted by the reduced fluid saturations represents the average viscosity of liquid-gas mixtures in steady-state flow in imbibition. Extracting flow rates of the individual phases from the total flow rate of the fluid mixture is the next, but crucial, step that determines whether the average viscosity approach can replace that of relative permeability in solving common reservoir engineering problems. Liquid-liquid flow in both drainage and imbibition, and liquid-gas flow in drainage are not represented by a simple viscosity average, which indicates the need for further study into more complex viscosity averages. / by Lubna Khalid Albarghouty. / S.M. in Geophysics

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995. / Includes bibliographical references (leaves 55-57). / by Wenjie Hu. / M.S.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 53-56). / Elevated concentrations of CO₂ have been proposed as the reason that the Cretaceous climate was 6-14°C warmer than the present, however the source of Cretaceous CO₂ is unknown [Barron, 1983]. This study examines the possibility of continental arc magmatism as a mechanism for CO2 release, specifically as a volatile produced during crustal assimilation and contact metamorphism of carbonates around plutons. Bedrock maps of the North American Cordillera (a region of active continental arc magmatism during the Cretaceous), the relative locations of the carbonates, the Cretaceous plutons, and the calculated "decarbonation zones"around the plutons. These measurements were then input in a thermal and petrologoical model in order to estimate the quantity of CO₂ released by continental arc magmatism. Testing a number of cases with varying parameters, the model found the arc-magmatism-induced temperature difference between the present and Cretaceous global climates to have a lower limit of [Delta]T < 1°C and an upper limit of 5.1 < [Delta]T < 12.3°C. Decarbonation from continental arc magmatism is shown to be a possible mechanism of paleoclimatic warming, and more work is required to either confirm or refute the hypothesis. / by Anna Elizabeth Brunner. / S.B.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2008. / Cataloged from PDF version of thesis. "May 5, 2008." "This thesis was submitted to the Institute Archives without all the required signatures"--Disclaimer Notice page. / Includes bibliographical references (page 33). / The mineralogical composition of asteroids can be constrained using visible and near-infrared (VNIR) spectroscopy. The most prominent spectral features observed over this wavelength range are due to olivine and pyroxene, the two most abundant minerals in both chondritic and achondritic meteorites. The observed ratio of these two minerals is highly dependent on the amount of heating that an asteroid has undergone. The 1-micron band center wavelength and the band area ratio (BAR) between the 2- and 1-micron bands reveal relative abundances of olivine and/or pyroxene on an asteroid surface (Gaffey, 1993). A large sample of S-, A-, V-, and R-type asteroid spectra was collected over the visible and near-IR wavelengths during the second phase of the Small Main-belt Asteroid Spectroscopic Survey (Bus and Binzel, 2002) and using the low-resolution SpeX spectrograph (Rayner, 2003) at NASA's Infrared Telescope Facility (IRTF). Here we present a methodology for calculating the location of the 1-micron band center wavelength and BAR with appropriate 1- sigma uncertainties. This method was used to characterize 188 S-type asteroids throughout the inner main belt. We will also present the distribution of olivine / pyroxene throughout the main belt by measuring how the S-type mineralogy varies with heliocentric distance. This will provide a better understanding of both the thermal processing across the main belt and subsequent mixing of asteroids through collisional and dynamical processes. / by Shaye Perry Storm. / S.B.