Thesis (Ph.D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2009. / Committee Chair: Peter J. Webster; Committee Member: Robert X. Black; Committee Member: John A. Knox; Committee Member: Judith A. Curry; Committee Member: Yi Deng.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (p. 92-96).

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [186]-198).

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. James J. O'Brien, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Sept. 24, 2004). Includes bibliographical references.

A primary goal of paleoclimatology is to extend the instrumental record to capture a wider range of natural variability, documenting the climate system's response to past changes that have no analog in the historical record. Sediment archives of the recent geologic past, both marine and lacustrine, offer the opportunity to study how climate responds to a range of forcings and changing boundary conditions on timescales ranging from years to millennia. In this dissertation I use lacustrine and marine sediment to investigate changes late Quaternary climate, with particular focus on the Last Interglacial period (LIG). First, I use multiple approaches to reconstruct long-term changes in the West African Monsoon by investigating centennial-scale hydrologic variability recorded in Lake Bosumtwi sediments over the past 530,000 years. Over this interval, hydrology in the region is driven by a complex interplay of orbital forcing and glacial-interglacial boundary conditions. Lake level was generally much lower between 50 and 300 ka, likely due to the redistribution of rainfall from the tropics to the subtropics, driven by eccentricity's amplification of precession. Consequently, the Holocene highstand at the lake was both larger and longer lived than the maximum highstand during the LIG.Annual layers were continuously deposited through the LIG in Lake Bosumtwi, and I also present a new, 12,100 year-long, varve record spanning the interval from 128.6 to 116.5 ka. Over the course of the LIG, lake level generally tracks sea surface temperatures (SST) in Gulf of Guinea, including an abrupt drop in lake level that lasted about 500 years ca. 118 ka, coincident with cool SSTs in the North Atlantic and severe aridity in Europe. I find that the despite the generally drier conditions, hydrology varied on similar timescales as the late Holocene, with pronounced multidecadal to centennial-scale variability with non-stationary periodicities. I also investigate the contribution of ocean thermal expansion to sea level rise during the LIG, using a synthesis of paleoceanographic data and a climate model simulation. Globally, LIG SSTs were similar to, or slightly cooler than late Holocene SSTs, with the exception of the North Atlantic, which was several degrees warmer. Consequently, thermal expansion was likely a minor component of sea level rise during the interval, explaining between -0.3 and 0.4 m. of the 6 to 8 m highstand. Lastly, I tested the potential of Raman spectroscopy as a new, non-destructive technique to rapidly measure oxygen isotopic ratios in carbonates at extremely high resolution. Analyses on a suite a synthetic calcites indicate that ¹⁸O/¹⁶O ratios can be measured directly from the Raman spectra and have a 1:1 correspondence with traditional mass-spectrometry measurements. At present, the technique does not have the precision necessary to record natural variability, although there is considerable potential for improving the precision of the technique.

The location of the Inter-Tropical Convergence Zone plays an important role in the climatology of tropical regions. Yet, despite its importance, the basic physics that determine the location of the ITCZ are not fully understood. Observational analyses show that, where the cross-equatorial pressure gradient is strong, the maximum convection is not necessarily associated with the highest sea surface temperature,or correspondingly, the lowest sea level pressure. Tomas and Webster (1997) argue that if a strong enough cross-equatorial pressure gradient exists and the system is inertialy unstable, secondary ameliorating circulations will drive strong off-equatorial convection in regions where ITCZ location is determined by low tropospheric dynamics. The observational record is re-examined to test the inertial instability hypothesis using the new ECMWF reanalysis data set. Composite analyses are performed to study the structure of the summer meridional circulation for the tropical Eastern Pacific Ocean and Atlantic Ocean. In agreement with Tomas and Webster theory, we find that the magnitude of the cross-equatorial pressure difference appears to determine the intensity of convection with low values of outgoing longwave radiation always to the north of the zero absolute vorticity line, and the absolute vorticity advection equatorward of the this line. Also the observed oscillation period of the disturbance for the studied regions coincides with theoretical oscillation period of the inertial flow.

This study has been performed as a pilot study for a project regarding the meridional migration of the Intertropical Convergence Zone (ITCZ) and its relationship with lightning activity in the Eastern Tropical Pacific (ETP). Objectives of this study were to analyze and improve lightning data to be used for such a study and to decide on a method and proper time scale of data analysis and ITCZ index development for this study. Exploratory data analysis has been practiced with World Wide Lightning Location Network (WWLLN) data and ITCZ index data. Results suggest that the most beneficial time-scale to be used for the above study is 15 days and that ITCZ estimations can be obtained via the use of precipitation index and cloud top temperature. Lightning data originated from atmospheric systems not associated with the ITCZ has been analyzed. This report proposes that Uppsala University should become part of the World Wide Lightning Location Network, enabling further work regarding this and similar projects.

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Meteorology. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 320-325. / by Mark A. Cane. / Ph.D.

A Zona de Convergência Intertropical (ITCZ) marca a área de ar ascendente nos trópicos, associada com altas pluviosidades e característica chave da circulação tropical da célula de Hadley, dominando o ciclo hidrológico sazonalmente sobre os trópicos, com precipitação máxima associada ao hemisfério com as maiores temperaturas da superfície do mar. As alterações de longo prazo na posição ITCZ tem sido considerada como um importante fator de controle da paleo-precipitação na área equatorial para avaliar as alterações relativas na sua posição e intensidade em escalas de tempo orbitais e milenar. A este respeito, há uma necessidade de registros de precipitação com amplia profundida temporal, alta resolução e bem datados no norte da América do Sul para avaliar como o deslocamento da ITCZ influenciou a paleo-precipitação na região e sua relação com o Sistema da Monção Sul-Americana (SASM). Nosso registro de \'delta\' \'ANTPOT.\'18 O em espeleotema da caverna de Carracos, localizada no município de El Peñon na região centre leste da Colombia e situado na posição média atual da ITCZ no norte da América do Sul, exibiu mudanças na precipitação durante os últimos 103 ky BP até o presente, com uma curva isotópica continua para o último período deglacial. O registro de El Peñon é composto por nove espeleotemas individuais com um total de 6857 amostras de \'delta\' \'ANTPOT.\'18 O e um modelo de idade com 132 datações, precisamente datadas pelo método U/Th. Documentamos pela primeira vez como as mudanças de longo prazo na atividade da ITCZ estão associadas a mudanças na circulação do Atlântico Meridional Overturning na escala orbital. Nos eventos GI, GS e HS, há uma mudança relativa na posição e intensidade da ITCZ na região norte da América do Sul, expondo a área de El Peñon como um setor sensível a essas variações, o que gera relações de fase/antifase com registros do Caribe e a área de influência sul daITCZ. Igualmente, é sugerida uma assimetria zonal durante o LGM caracterizada pela posição da ITCZ, levando aumento do fluxo de umidade em Centro America e Colômbia, enquanto condições climáticas contrastantes são observadas do lado leste do continente o sem uma resposta forte nos outros registros de América do Sul. Apesar que as condições nas mudanças oceânicas sejam o fator climático dominante para a variabilidade da ITCZ durante o último período glacial, a forçante de insolação no verão austral ainda é muito evidente durante o Holoceno, levando a um deslocamento para o sul da ITCZ em poucos graus alcançando, sua posição mais meridional no presente. / The Intertropical Convergence Zone (ITCZ) marks the area of ascending air in the tropics, which is associated with generally high rainfall and is a key feature of the tropical Hadley circulation. This ITCZ dominates the hydrological cycle seasonally over the tropics with maximum rainfall associated with warmer sea surface temperatures in each). Although long-term changes in the ITCZ position have been considered as a major factor controlling paleo-precipitation in the equatorial area to evaluate the relative changes in its position and intensity on both orbital and millennial time scales. In this regard, there is a need for long, high resolution and well-dated records of precipitation in Northern South America to evaluate how the ITCZ has influenced the paleo-precipitation over the SASM domain. Our composite speleothem \'delta\' \'ANTPOT.\'18 O record from Carracos cave inferring past precipitation changes during the last 103 ky B.P., it is located in the El Peñon municipality in the eastern Colombian Cordillera and the latitude of the study site coincides with the mean modern position of the ITCZ in northern South America. The El Peñon speleothem \'delta\' \'ANTPOT.\'18 O record is composed of nine individual speleothems with 6857 \'delta\' \'ANTPOT.\'18 O measurements and the chronology of the CAR speleothem record is based on 132 very precise U/Th dates. We document for the first time how long-term changes in ITCZ activity are associated with changes in the Atlantic Meridional Overturning circulation. In the GI and HS events, there is a relative change in the position and intensity of the ITCZ in the northern region of South America, exposing the El Peñon area as a sector sensitive to these variations, which generates phase/antiphase relationships with records from the Caribbean and the southern area of influence of the ITCZ. The El Peñon speleothem record also suggests that the ITCZ was characterized by a large zonal asymmetry during the LGM, leading to enhanced moisture influx from the Caribbean toward Colombia, intensifying the monsoon over the SASM region of western and southern Brazil and the tropical Andes, while contrasting climate conditions are observed from the eastern side of continent. Although the changing oceanic conditions are notably the dominant climate driver for ITCZ variability during the last glacial period, austral summer insolation forcing is still very evident during the Holocene, leading to a southward displacement of the ITCZ by a few degrees reaching its southernmost position at present-day.

Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-09-12T22:15:43Z No. of bitstreams: 1 FábioCGL_DDISERT.pdf: 2278528 bytes, checksum: 896534b24761eed81c350463209426cc (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-10-27T13:04:36Z (GMT) No. of bitstreams: 1 FábioCGL_DDISERT.pdf: 2278528 bytes, checksum: 896534b24761eed81c350463209426cc (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-10-27T13:04:56Z (GMT) No. of bitstreams: 1 FábioCGL_DDISERT.pdf: 2278528 bytes, checksum: 896534b24761eed81c350463209426cc (MD5) / Made available in DSpace on 2017-10-27T13:08:17Z (GMT). No. of bitstreams: 1 FábioCGL_DDISERT.pdf: 2278528 bytes, checksum: 896534b24761eed81c350463209426cc (MD5) Previous issue date: 2017-02-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The order Cingulata is one of the most representative members of the Pleistocene Brazilian Megafauna. It is composed by well-known animals (armadillos, pampatheres and glyptodonts) and characterized by a peculiar bony exoesqueleton. Several studies in paleoecology of cingulates involve this peculiar structure, whatever, few studies have directed their attention to pathological alterations in the exoskeleton, despite its great potential in terms of paleobiological information. The aim of this work was to describe and identify exoskeletal diseases in large cingulates from the Pleistocene of the Brazilian Intertropical Region, providing new paleoecological insights for such animals. We analyzed exoskeletal elements collected in six localities of the Brazilian Intertropical Region deposited in three relevant fossil collections in the states of Minas Gerais, Pernambuco and Rio Grande do Norte. Through macroscopic examination, we have detected pathological and pseudopathological alterations affecting the surface of components of the exoskeleton in specimens of Hoplophorus euphractus, Panochuthus sp., Glyptotherium sp. and Pachyarmatherium brasiliense. These lesions included traumatic and infectious alterations generated by parasites in different parts of exoskeleton and the first records of lesions caused by fleas in glypdonts and in a large non-glyptodontid cingulate (Pachyarmatherium). Finally, we verified the presence of pseudopathologies, which served as a base for we propose a protocol to differentiate pathological to taphonomical alterations / Na Megafauna Brasileira do Pleistoceno, a Ordem Cingulata, um dos principais integrantes da megafauna brasileira do Pleistoceno, é composta por animais bastante conhecidos (tatus, pampatérios e gliptodontes) e caracterizados por um peculiar exoesqueleto ósseo. Muitos estudos em paleoecologia de cingulados envolvem esta estrutura, no entanto, poucos trabalhos têm direcionado a atenção para alterações patológicas do exoesqueleto, embora se reconheça o seu enorme potencial em termos de informações paleobiológicas. O objetivo deste trabalho foi identificar e descrever alterações exoesqueletais em cingulados de grande porte do Pleistoceno da Região Intertropical Brasileira, fornecendo novos insights paleoecológicos sobre esses animais. Analisamos componentes do exoesqueleto coletados em seis localidades da Região Intertropical Brasileira depositados em três coleções relevantes nos estados de Minas Gerais, Pernambuco e Rio Grande do Norte. Por meio de exame macroscópico, detectamos alterações patológicas em superfícies ósseas acometendo o exoesqueleto em espécimes de Hoplophorus euphractus, Panochuthus sp., Glyptotherium sp. e Pachyarmatherium brasiliense. Estas lesões constituíram alterações traumáticas e infecciosas geradas por parasitas em diferentes partes do exoesqueleto e os primeiros registros de lesões causadas por pulgas em diferentes espécies de gliptodontes. Finalmente, constatamos a presença de pseudopatologias, as quais serviram de base para propormos um protocolo para diferenciar alterações patológicas de tafonômicas / 2017-09-12