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Tesi sul tema "Paleoclimatology"
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Griffin, Richard Daniel. "North American Monsoon Paleoclimatology From Tree Rings". Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/301558.
Testo completoAbstract (sommario):
The North American monsoon is central to Southwestern climate and is a research focus in climatology. Of the various monsoon paleoclimate proxies, precisely dated and seasonally resolved tree-ring records offer unique opportunity for contextualizing modern instrumental observations and climate model projections. Focused on latewood, the dark-colored sub-annual component of conifer tree rings that forms in the late growing season, this dissertation research represents a systematic effort to diagnose the tree-growth response to monsoon climate, to develop a replicated network of monsoon-sensitive chronologies, and to characterize monsoon paleoclimate variability in the southwestern United States. A pilot study using latewood measurements from five locations assessed seasonal climate response sensitivity to various chronology development techniques. Results informed a protocol for chronology development, which was used to produce a unique network of 53 monsoon-sensitive latewood chronologies for the southwestern United States. A chronology subset was used to develop the first monsoon precipitation reconstruction for a large and important region of the southwestern United States and northwestern Mexico. This reconstruction revealed monsoon paleodroughts more persistent and extreme than any during the instrumental era and indicated that the southwestern decadal droughts of the last 470 years were characterized not just by cool-season precipitation deficits, but also by persistently dry monsoon conditions. The previously noted tendency for winter and summer precipitation to be out of phase was found to be unstable through time and anomalously strong during the recent instrumental era. The paleoclimatic significance of the new sub-annual chronology network was characterized in terms of chronology signal strength, climate response seasonality, and dominant spatiotemporal structure. With only a few exceptions, the latewood chronologies were found to contain monsoon-specific climate signal that was not available from previously existing records of annual tree-ring width. Principal components analysis revealed that the chronology network captures both temporal variability and spatial structure inherent to monsoon precipitation. As such, proxy data developed in this dissertation are unique are uniquely suited for studying spatiotemporal variability in monsoon paleoclimate. Outcomes from this dissertation are broadly relevant in environmental research and could potentially inform long-term strategies for adaptive management of natural resources.
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Cisneros, Bermejo Mercè. "Reconstrucció climàtica dels darrers 2.700 anys a la Mediterrània occidental: sediments marins i estalagmites". Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668453.
Testo completoAbstract (sommario):
Donada l’alta sensibilitat de la regió central de la Mediterrània occidental a la variabilitat climàtica, s’han reconstruït les condicions de la mar superficials i profundes així com de les atmosfèriques pels darrers 2.700 anys. Les condicions marines han estat reconstruïdes a partir de multi-testimonis de sediment del nord de Menorca i les condicions atmosfèriques (hidroclimàtiques) en base a cinc registres d’espeleotemes de dues coves de Mallorca. La integració de la informació derivada d’aquests dos tipus d’arxius ha permès un millor enteniment de la interacció entre la mar superficial i profunda i l’atmosfera. Els principals períodes climàtics/històrics caracteritzats són: Període Talaiòtic (TP; fins el 123 BCE), Període Romà (RP; 123 BCE-470 CE(1)), Alta Edat Mitjana (EMA; 470 a 900 CE), Anomalia Climàtica Medieval (MCA; 900 a 1275 CE) i Petita Edat de Gel (LIA; 1275 a 1850 CE).
Les Temperatures de la Mar Superficial (SST) s’han obtingut a partir de la ràtio Mg/Ca analitzada al foraminífer planctònic Globigerina bulloides (Cisneros et al., 2016), re- ajustant el calibratge de les SST per a la Mediterrània Occidental. La intensitat dels corrents fondos s’ha reconstruït a partir d’anàlisis de la mida de gra (paràmetre UP10, fracció >10 µm; Cisneros et al., 2019). Aquest paràmetre UP10 ha estat revalidat amb dades oceanogràfiques mostrejades durant els anys 2012-2014 mitjançant dos ancoratges instrumentats d’aigües profundes. La variabilitat hidroclimàtica ha estat reconstruïda emprant una metodologia que integra varis indicadors (anàlisi geoquímics i texturals) a les estalagmites.
El període càlid més sostingut va tenir lloc durant el RP, el qual és seguit per una tendència de refredament interrompuda per vàries oscil·lacions a escala de centennis. Tot i que alguns períodes amb SST particularment càlides van tenir lloc durant la MCA, la LIA va estar marcadament inestable, amb alguns esdeveniments molt freds sobretot durant la segona meitat del període. Els esdeveniments més forts de formació d’aigua fonda van ocórrer durant intervals relativament càlids, com el RP, el final de la MCA i la primera part de la LIA. Per contra, les dades indiquen una reducció progressiva de la convecció durant l’EMA, resultant en esdeveniments durant la major part de la MCA.
Els registres obtinguts de les estalagmites ha permès elaborar la primera reconstrucció regional de la variabilitat hidroclimàtica pels darrers 2.700 anys. Els registres indiquen condicions generalment humides per l’inici del RP, la primera meitat de l’EMA i per tota la LIA, en contrast amb les condicions més seques enregistrades pel RP tardà (anys 200-470 CE), la segona part de l’EMA (anys 700-900 CE) i tota la MCA. Dins de la LIA, al voltant de l’any 1622 CE, la existència d’un nivell detrític, enriquit en Ti a l’estalagmita Seán ha estat interpretat com un marcador d’inundacions associat a un esdeveniment extrem de pluja.
La combinació integrada dels resultats derivats dels sediments marins i de les estalagmites suggereix condicions climàtiques no-estacionàries durant cadascun dels períodes estudiats dels últims 2.700 anys. Particularment durant el final del RP i la primera meitat de l’EMA, aquesta tesi suggereix una variabilitat climàtica més complexa i/o de més alta freqüència. L’EMA sembla haver estat caracteritzat com un període transició i, haver estat previ a una re-configuració atmosfèrica de diferents modes climàtics com el patró East Atlantic/West Russian i l’Oscil·lació de l’Atlàntic Nord.
(1) BCE: anys abans de l’era comú/CE: anys de l’era comúSurface-deep ocean and atmospheric reconstructions for the last 2.7 kyr have been performed taking the advantage of the high sensitivity of the central-western Mediterranean region. Ocean conditions have been reconstructed from sediment multicores recovered in the North Minorca and atmospheric conditions (hydroclimate) from five speleothem records of two Mallorca caves. The integration of this information has allowed a better understanding about the interaction between the surface-deep-sea and the atmosphere. The main climate/historical periods characterized are: Talaiotic Period (until 123BCE(1)), Roman Period (RP; 123BCE-470CE), Early Middle Ages (EMA; 470-900CE), Medieval Climate Anomaly (MCA; 900-1275CE) and Little Ice Age (LIA; 1275-1850CE). Sea-surface temperatures are derived from Mg/Ca-ratios analysed on planktonic foraminifera Globigerina bulloides (Cisneros et al., 2016) and deep-current intensity- changes from grain-size analysis (UP10-fraction; Cisneros et al., 2019). Hydroclimate variability has been reconstructed applying a multi-proxy approach (geochemical and textural analyses) on the stalagmites. The warmest sustained period occurred during the RP, followed by a general cooling trend interrupted by several centennial-scale oscillations. Although warm intervals took place during the MCA, the LIA was markedly unstable, with some very cold events mostly during its second half. The strongest deep-water formation events occurred during relatively warm intervals, such as the RP, the end of the MCA and the first part of the LIA. By contrast, our data indicate a progressive reduction in the overturning conditions during the EMA resulting in weaker deep-water formation events during most of the MCA. General wet conditions have been obtained for the early RP, the first half of the EMA and the entire LIA while drier conditions have characterized the late RP, the late EMA and the entire MCA. The combination of the results derived from marine sediments and stalagmites suggests non-stationary climate conditions during each period of the last 2.7 kyr. Particularly during the late RP and the first half of the EMA, more complex climate variability and/or with higher frequency seems to have occurred. The EMA seems to have been characterized like a transition period, previous to an atmospheric reconfiguration of different climate modes such as the East Atlantic/West Russian and NAO. (1) BCE: Before Common Era years/CE: Common Era years
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Maier, Éder Leandro Bayer. "Relações espaço-temporais entre dados paleoclimáticos do Nevado Illimani (Bolívia) e a precipitação na América do Sul". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/94677.
Testo completoAbstract (sommario):
Este trabalho investiga a possibilidade de reconstruir a variabilidade da precipitação pretérita na América do Sul a partir de uma série temporal de razão isotópica de oxigênio (δ18O) em um testemunho de gelo obtido na Bolívia, para isso é analisado as relações espaço-temporais entre a precipitação sobre a América do Sul e a série do δ18O. Utilizou-se dados do δ18O dos primeiros 50 metros do testemunho de gelo do Nevado Illimani (6.350 m, 16º37’S, 67º46’W) e totais mensais da precipitação coletada em 890 estações meteorológicas sobre o continente sul-americano no período 1979–2008. As amostras da precipitação foram dispostas em uma grade equiespaçada com resolução de ~2º de latitude e longitude. A variabilidade espacial e temporal da precipitação foram analisadas pela Análise das Componentes Principais no Modo T e S, respectivamente, com a identificação dos principais Padrões Espaciais Anômalos (PEA) e das zonas espaciais em que a variação temporal das anomalias da precipitação é correlacionada. No núcleo de cada zona foi selecionada uma série temporal anômala da precipitação para comparar com a série do δ18O. Constatou-se que há 12 PEA da precipitação e que são originários, predominantemente, da variação na temperatura superficial dos oceanos Pacífico Equatorial e Atlântico Tropical Norte e 8 zonas espaciais em que a variação da precipitação é parcialmente homogênea. Analisando características dos PEA da precipitação com a variação do δ18O constata-se que os registros de máximo (mínimo) fracionamento isotópico no verão estão relacionados à seca (chuvas acima da média) na Amazônia ou no nordeste brasileiro. Já no inverno, os registros de máximo (mínimo) fracionamento isotópico estão relacionados a secas (chuvas acima da média no litoral) na região tropical e chuvas acima da média (secas) na região extratropical. O índice de correlação entre todas séries de precipitação com a série do δ18O mostrou que a variação sincronizada das variáveis altera-se sazonalmente em função da migração espacial dos mecanismos de transporte e convergência da umidade. A comparação das séries de precipitação das 8 zonas com o δ18O possibilitou identificar possíveis áreas para a reconstrução paleoclimática. Nas regiões equatorial e subtropical foi testado a reconstrução. Nessas áreas, os fatores que controlam as duas variáveis são os mesmos, predominando os oceanos Pacífico Equatorial e Atlântico Norte nas alterações das séries temporais com frequência entre 24 e 60 meses. Para reconstrução da variabilidade da precipitação pretérita a partir da variação do δ18O foram testada duas técnicas, uma utilizando a análise de dependência por regressão e outra pela adoção de PEA para casos específicos da variação do δ18O. A primeira técnica não gerou resultados satisfatórios, por isso não foi usada. Com a segunda técnica foi possível identificar com 80% de chance de acerto as secas na Amazônia, no nordeste brasileiro e na região subtropical e com 68% de chance de acerto as chuvas acima da média na região subtropical, quando a avaliação não considera a magnitude das anomalias da precipitação. Por outro lado, a técnica é limitada, porque os PEAs adotados como referência não representam a grande variabilidade da precipitação nessas regiões.This thesis investigates the possibility of reconstructing the South American past precipitation variability based on an oxygen isotope ratio (δ18O) time series from a Bolivian ice core, for this we analysed the spatial-temporal relations between these two variables. We used δ18O data from the upper 50 meters of Nevado Illimani ice core (6,350 m, 16°37'S, 67°46'W) and monthly total precipitation collected at 890 weather stations in South America in the period 1979–2008. Precipitation samples were arranged in an equally spaced grid with a ~2° latitude and longitude. The precipitation temporal and spatial variability were analysed by Principal Component Analysis on Mode S and T, respectively, with the identification of the main Anomalous Spatial Patterns (ASP) and spatial zones in which temporal rainfall anomalies variations are correlated. At each zone core, we selected one anomalous precipitation time series to compare with the δ18O series. There are 12 precipitations ASP that originate predominantly from surface temperature variations in the equatorial Pacific and tropical North Atlantic oceans, and 8 spatial zones in which the precipitation variation is partially homogeneous. Analysing the precipitation ASP characteristics with the δ18O variation, it is observed that records of maximum (minimum) isotopic fractionation in summer are related to droughts (above average precipitations) in the Amazon and northeastern Brazil. In the winter, records of maximum (minimum) isotopic fractionation are related to droughts (above average rainfall in the coastal area) in the tropical region and above average rainfall (droughts) in the extratropical region. The correlation index among all series of precipitation with δ18O series showed that these variables synchronized variation alters seasonally depending on the transport mechanisms spatial migration and on the moisture convergence. The comparison of the 8 precipitation zones with the δ18O series enabled us to identify possible areas for paleoclimatic reconstruction, which are the equatorial and subtropical regions. In these areas, the factors controlling the two variables are the same, prevailing the equatorial Pacific and the North Atlantic changes in time series with frequency from 24 to 60 months. To reconstruct the precipitation variability from the past δ18O variation we tested two techniques, one using dependency analysis for regression and other adopting ASP for specific cases of δ18O variations. The first technique yielded no satisfactory results, so it was disregarded. Using the second technique, it was possible to identify droughts in Amazonia, the Brazilian northeast and in the subtropical region with 80% changes of success. Above the average rainfalls in the subtropical region are identify with 68% changes of success, if this assessment does not consider the magnitude of the precipitation anomalies. On the other hand, the technique has limitations because the ASPs adopted as reference do not represent the wide precipitation variability in these regions.
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Anchukaitis, Kevin John. "A Stable Isotope Approach to Neotropical Cloud Forest Paleoclimatology". Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/195637.
Testo completoAbstract (sommario):
Many tropical trees do not form reliable annual growth rings, making it a challenge to develop tree-ring width chronologies for application to paleoclimatology in these regions. Here, I seek to establish high-resolution proxy climate records from trees without rings from the Monteverde Cloud Forest in Costa Rica using stable isotope dendroclimatology. Neotropical cloud forest ecosystems are associated with a relatively narrow range of geographic and hydroclimatic conditions, and are potentially sensitive to climate variability and change at time scales from annual to centennial and longer. My approach takes advantage of seasonal changes in the d18O of water sources used by trees over a year, a signature that is imparted to the radial growth and provides the necessary chronological control. A rapid wood extraction technique is evaluated and found to produce cellulose with d18O values indistinguishable from conventional approaches, although its application to radiocarbon requires a statistical correction. Analyses of plantation-grown Ocotea tenera reveal coherent annual d18O cycles up to 9 permil. The width of these cycles corresponds to observed basal growth increments. Interannual variability in d18O at this site is correlated with wet season precipitation anomalies. At higher elevations within the orographic cloud bank, year-to-year changes in the amplitude of oxygen isotope cycles show a relationship with dry season climate. Longer d18O chronologies from mature Pouteria (Sapotacae) reveal that dry season hydroclimatology is controlled at interannual time scales by variability in the eastern equatorial Pacific (ENSO) and the Western Hemisphere Warm Pool (WHWP), which are correlated with trade wind strength and local air temperature. A change in the late 1960s toward enhanced annual d18O amplitude may reflect low frequency changes in the Atlantic and Pacific ocean-atmosphere system. This study establishes the basis for cloud forest isotope dendroclimatology and demonstrates that the local climate of neotropical cloud forests is sensitive to interannual, and perhaps, multidecadal changes in important large-scale modes of climate variability.
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Serefiddin, Feride Schwarcz H. P. "Paleoclimate models for western North America as inferred from speleothem isotope records /". *McMaster only, 2003.
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Wilhelms, Frank. "Messung dielektrischer Eigenschaften polarer Eiskerne = Measuring the dielectric properties of polar ice cores /". Bremerhaven : Alfred-Wegener-Institut für Polar- und Meeresforschung, 2000. http://www.gbv.de/dms/bs/toc/319750515.pdf.
Testo completo
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Dibenedetto, Joseph Nicholas. "Paleoclimatological implications of fossil tortoise bones". To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Sandau, Stephen D. "The Paleoclimate and Paleoecology of a Uintan (Late Middle Eocene) flora and fauna from the Uinta Basin, Utah /". Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd719.pdf.
Testo completo
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Minckley, Thomas A. "Holocene environmental history of the northwestern Great Basin and the analysis of modern pollen analogues in western North America /". view abstract or download file of text, 2003. http://wwwlib.umi.com/cr/uoregon/fullcit?p3113019.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Oregon, 2003.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 294-310). Also available for download via the World Wide Web; free to University of Oregon users.
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Rubio, de Inglés María Jesús. "Late Holocene Climate Variability in the North Atlantic based on biomarker reconstruction: The lake Azul (São Miguel, Azores archipielago) case". Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/402145.
Testo completoAbstract (sommario):
The principal objective of this PhD thesis is to obtain a high resolution reconstruction of the climate (temperature and precipitation) in the north Atlantic for the late Holocene. This new reconstruction is from a sedimentary lacustrine record located in Azores (Lake Azul) that has been compared and discussing with principal other climate reconstructions published on the North Atlantic region. Climate in the North Atlantic is modulated by the conjunction of atmospheric patterns and ocean dynamics. The main atmospheric pattern is the North Atlantic Oscillation (NAO) but, other climatic modes such as the Eastern Atlantic (EA) and the Atlantic Meridional Oscillation (AMO) are also present. The use of biomarkers has appeared as a cutting edge technique to reconstruct climate and their validity has been proved by previous works. The Azul lacustrine sedimentary sequence occupied the last 660 years, and on it has been applied a multiproxy study including: facies analysis, X-Ray Diffraction (XRD), X-Ray
Fluorescense (XRF), Total Organic Carbon (TOC), Total Nitrogen (TN), bulk isotopes of Carbon (δ13C) and Nitrogen (δ15N) and biomarkers (GDGTs and δD leaf waxes). Facies were grouped in two main facies types according to the velocity of sedimentation and the organic matter origin: (1) “Continuous facies” accumulated by a more or less continuously sedimentation processes and dominated by lake organic matter, and (2) “rapid facies” deposited from flood events and transporting mainly terrestrial organic matter. An accurate age-depth model based on 14C and 210Pb dates and XRF data was built to figure out those sudden changes (the Dynamic Age Model, DAM). The DAM calculates the age of the samples redistributing the time along the profile according to the amount of crystalline terrestrial particulated material. DAM can acquire short and long-term sedimentation rate (SR) changes and previous models only acquire long- term fluctuations. The biomarkers (GDGTs and δD leaf waxes) were extracted and studied on the continuous lacustrine facies to reconstruct temperature and precipitation. The relative percentage of GDGTs was transferred into temperature by the use of Pearson et al., (2011) calibration. The climatic factor affecting δD
fractionation was assessed by the weekly collection of rain water showing a clear depletion with the amount of precipitation. Results from realized reconstruction suggested a climatic model that converge oceanic currents with the principal atmospheric patterns, defining the NAO as the main factor triggering the others. The temperature in Azores depends on the position of the Gulf Stream (GS). A positive
(negative) NAO phase enhances (reduces) the Gulf Stream (GS) velocity that increases (reduce) the amount of Eddies around Bermuda driving towards north (east) the GS and heating up high (medium) latitudes. Therefore, a negative phase of NAO favors the GS heat to reach Azores. Since the temperature in Azores is modulated by the oceanic circulation, the AMO also plays an important role. The AMO is reflected in Ponta Delgada by the amplitude between maximum and minimum mean annual temperatures, which means an increase on seasonality. The AMO positive phase is reflected as an increase on temperatures in Lake Azul reconstruction. Otherwise, the AMO negative phase is masked by other climatic patterns. The precipitation in Azores is mainly triggered by the NAO phase, increasing (decreasing) precipitation during NAO negative (positive). The comparison with other reconstructions in the North Atlantic area suggested that an increase of precipitation in São Miguel produces an increase at other Azorean islands, the Iberian Peninsula and Morocco. This pattern has been observed for the last 700 years except for the period comprised between 1680 and 1920 AD where a possible southeastern shift of the NAO south dipole seemed to be produced. We suggest that this movement is produced by the occurrence, simultaneously, of an in phase and positive NAO and EA conjunction.
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Tarbet, Melissa Eileen Schlegel. "Evaluation of paleo-climate for the Boise area, Idaho, from the last glacial maximum to the present based on delta 2H and delta 18O groundwater composition /". Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd829.pdf.
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He, Yuxin, e 何毓新. "Biomarker based holocene climatic reconstruction in Northwestern China". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/197088.
Testo completoAbstract (sommario):
Holocene hydrological changes in regions influenced by the mid-latitude westerly and the tropical/subtropical Asian monsoon differ from each other. The arid/semi-arid northeastern Tibetan Plateau, lying in between, is very sensitive to climatic changes. It thus becomes a climatologically important region to disentangle the interactions between the two circulations. Yet, limited high-quality Holocene paleoclimatic reconstructions are available in this region. This thesis presents multi-biomarker proxy records from lakes in the Qaidam Basin on the northeastern Tibetan Plateau to investigate the nature of Holocene climate variability.
Firstly, late-Holocene paired alkenone-based temperature (U_37^K' ) and moisture (%C37:4) records from Lake Gahai and Lake Sugan were reconstructed. Paired temperature and moisture records confirm the warm-dry (e.g. Medieval Warm Period) and cold-wet (e.g. Little Ice Age) periods on the arid northeastern Tibetan Plateau over the late Holocene, opposite to the warm-wet and cold-dry association in Asian monsoonal regions. The records also suggest substantially warmer and drier conditions during the Medieval Warm Period than the current warm period. Further, a possible link between solar forcing and natural climate variability (both temperature and moisture) during the late Holocene is found on the northeastern Tibetan Plateau.
This thesis also studied the late-Holocene grain size-based dust storm history from Lake Gahai to encode possible mechanism of dust storm interacting with hydrological parameters. Intensified dust storm events were identified in periods of 500 BC to 250 BC, 50 BC to AD 250 and AD 1100 to present. In multi-centennial to millennial scales, dust storm events might be caused by the intensified wind induced by strong westerlies or/and Asian winter monsoon. In multi-decadal to centennial scales, moisture and vegetation coverage might have impacted on the dust storm intensity and frequency.
Further, Holocene lake level history of Lake Gahai was reconstructed by multiple n-alkane and alkenone proxies. Combined biomarker results provide unambiguous evidence of relatively low lake level at 7-2 ka, probably lowest at ~6 ka. Considering the chronological uncertainty, Holocene lake level changes in this marginal region thus display a different pattern from either of the core regions dominated by the westerlies (anti-phase) and the Asian summer monsoon (out-of-phase). The temperature-induced evaporation in the arid marginal region could significantly affect regional hydrological balance, resulting in the discrepancy with the long-term decreasing trend in precipitation in Asian monsoon-dominated regions.
Lastly, n-fatty acid δD variation from Lake Hurleg over the past 10.5 ka was investigated. The C26 δD and C16 δD values can indicate water δD changes in terrestrial and aquatic sources, respectively. The heavier C26 δD values during cold and wet conditions suggest that terrestrial water δD changes might be caused by factors other than temperature and moisture, such as glacial melted water input and vegetation type change. The difference between C16 δD and C26 δD was used as an indicator of evaporation at the lake surface. At millennial timescale, less evaporation occurred during cold-wet periods in this region.published_or_final_version
Earth Sciences
Doctoral
Doctor of Philosophy
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Power, Mitchell J. "Recent and Holocene fire, climate, and vegetation linkages in the northern Rocky Mountains, USA /". view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?index=0&did=1232403871&SrchMode=1&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1180996482&clientId=11238.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Oregon, 2006.Typescript. Includes vita and abstract. Includes appendices with Foy Lake pollen and charcoal data and fire atlas metadata. Includes bibliographical references (leaves 233-244). Also available for download via the World Wide Web; free to University of Oregon users.
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Truebe, Sarah Anne. "Past climate, modern caves, and future resource management in speleothem paleoclimatology". Thesis, The University of Arizona, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10158145.
Testo completoAbstract (sommario):
My research focuses on reconstructing past climate in southern Arizona using cave deposits called speleothems. However, this necessitates a broader perspective than simply a geochemical time series, and therefore, I also investigate modern cave systems using a combination of modeling and observational datasets. Finally, cave deposits are fundamentally non-renewable resources, and sampling for past climate reconstruction can be destructive, unlike other cave uses. My last investigation is focused on developing possible best practice recommendations for paleoclimate scientists and other cave stakeholders moving forward.
We developed two new stalagmite records of past climate variability in southern Arizona over the past 7000 years. Past climate reconstruction from two caves (Cave of the Bells and Fort Huachuca Cave) highlights insolation control of southern Arizona hydroclimate from 7000-2000 years before present. Additionally, comparison between two stalagmites with different seasonal sensitivities uncovers a few eras of multi-decade long droughts in southern Arizona, which align with other regional reconstructions of past climates and elucidate forcings on Southwest paleoclimate as emergent from both external (insolation) and internal climate variability in the Pacific and Atlantic Ocean basins. Although the oxygen isotopic signal of cave calcite in speleothems is complex, agreement with these other records indicates that the speleothem records from these caves primarily record a climate signal.
Modeling and monitoring of modern caves both helps us interpret paleoclimate records and enhances our understanding of cave systems in their own right. Modeling of Cave of the Bells dripwaters demonstrates the effect of storage and mixing on the dripwater oxygen isotope signal; non-climate processes can imprint on dripwater variability on multidecadal timescales. Monitoring shows that on very small spatial scales, every cave is different, and even sites within the same cave respond uniquely to surface climate. Most notably, calcite oxygen isotopic composition, used to reconstruct past climate, shows seasonal variability unrelated to dripwater and surface rainfall oxygen isotope variability. Substantial oxygen isotope disequilibrium is identified at numerous caves sites in southern Arizona, and this understanding aligns with a growing number of cave studies that demonstrate the long-held assumption of isotopic equilibrium in cave systems may not always be valid or that the way in which we define isotopic equilibrium insufficiently captures the variety of processes controlling the oxygen isotopic composition of speleothems. Overall, however, monitoring can identify stalagmites that are more sensitive to surface climate and less sensitive to these in-cave processes by identifying sites with dripwater variability responses to surface rainfall variability and sites that precipitate close to oxygen isotopic equilibrium.
Finally, a major missing component in speleothem research is the fact that speleothems take thousands and sometimes hundreds of thousands of years to form. They are non-renewable resources on human timescales, and habitat for myriad microbes that have yet to be identified. Removal of speleothems for paleoclimate research is one of the only destructive uses of these deposits. With that in mind, I also analyze current methods of collecting speleothems and develop a framework based on two surveys of scientists and stakeholders to assist scientists and managers when evaluating potential methods of incorporating cave conservation into the speleothem sampling process.
Thus, I approach caves from a variety of angles and timescales, from the past through the present to the future, illuminating caves as complex scientific and social systems.
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Truebe, Sarah, e Sarah Truebe. "Past Climate, Modern Caves, and Future Resource Management in Speleothem Paleoclimatology". Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621105.
Testo completoAbstract (sommario):
My research focuses on reconstructing past climate in southern Arizona using cave deposits called speleothems. However, this necessitates a broader perspective than simply a geochemical time series, and therefore, I also investigate modern cave systems using a combination of modeling and observational datasets. Finally, cave deposits are fundamentally non-renewable resources, and sampling for past climate reconstruction can be destructive, unlike other cave uses. My last investigation is focused on developing possible best practice recommendations for paleoclimate scientists and other cave stakeholders moving forward. We developed two new stalagmite records of past climate variability in southern Arizona over the past 7000 years. Past climate reconstruction from two caves (Cave of the Bells and Fort Huachuca Cave) highlights insolation control of southern Arizona hydroclimate from 7000-2000 years before present. Additionally, comparison between two stalagmites with different seasonal sensitivities uncovers a few eras of multi-decade long droughts in southern Arizona, which align with other regional reconstructions of past climates and elucidate forcings on Southwest paleoclimate as emergent from both external (insolation) and internal climate variability in the Pacific and Atlantic Ocean basins. Although the oxygen isotopic signal of cave calcite in speleothems is complex, agreement with these other records indicates that the speleothem records from these caves primarily record a climate signal.Modeling and monitoring of modern caves both helps us interpret paleoclimate records and enhances our understanding of cave systems in their own right. Modeling of Cave of the Bells dripwaters demonstrates the effect of storage and mixing on the dripwater oxygen isotope signal; non-climate processes can imprint on dripwater variability on multidecadal timescales. Monitoring shows that on very small spatial scales, every cave is different, and even sites within the same cave respond uniquely to surface climate. Most notably, calcite oxygen isotopic composition, used to reconstruct past climate, shows seasonal variability unrelated to dripwater and surface rainfall oxygen isotope variability. Substantial oxygen isotope disequilibrium is identified at numerous caves sites in southern Arizona, and this understanding aligns with a growing number of cave studies that demonstrate the long-held assumption of isotopic equilibrium in cave systems may not always be valid or that the way in which we define isotopic equilibrium insufficiently captures the variety of processes controlling the oxygen isotopic composition of speleothems. Overall, however, monitoring can identify stalagmites that are more sensitive to surface climate and less sensitive to these in-cave processes by identifying sites with dripwater variability responses to surface rainfall variability and sites that precipitate close to oxygen isotopic equilibrium. Finally, a major missing component in speleothem research is the fact that speleothems take thousands and sometimes hundreds of thousands of years to form. They are non-renewable resources on human timescales, and habitat for myriad microbes that have yet to be identified. Removal of speleothems for paleoclimate research is one of the only destructive uses of these deposits. With that in mind, I also analyze current methods of collecting speleothems and develop a framework based on two surveys of scientists and stakeholders to assist scientists and managers when evaluating potential methods of incorporating cave conservation into the speleothem sampling process. Thus, I approach caves from a variety of angles and timescales, from the past through the present to the future, illuminating caves as complex scientific and social systems.
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Blake, Bascombe Mitchel. "Carboniferous paleobotany and paleoclimatology of the central Appalachian Basin, West Virginia, U.S.A". Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10655.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains xi, 240 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references.
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Hu, Feng Sheng. "An ecosystem approach to the study of late-Quaternary environmental change in southwestern Alaska /". Thesis, Connect to this title online; UW restricted, 1994. http://hdl.handle.net/1773/5577.
Testo completo
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Nelson, Nathan Alfred. "Holocene fire and climate in rangeland ecosystems of Southwestern Idaho". [Boise, Idaho] : Boise State University, 2009. http://scholarworks.boisestate.edu/td/24/.
Testo completo
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Brunelle-Daines, Andrea. "Holocene changes in fire, climate and vegetation in the northern Rocky Mountains of Idaho and western Montana /". view abstract or download file of text, 2002. http://wwwlib.umi.com/cr/uoregon/fullcit?p3061935.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Oregon, 2002.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 170-178). Also available for download via the World Wide Web; free to University of Oregon users.
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Winspear, Nigel Robert. "Environmental controls on late Quaternary aeolian sedimentation in the Salton Basin (California) and central Nebraska". Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384964.
Testo completo
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Clayton, James Dominic. "Modelling climate change in the sub-tropical Bolivian Andes through the last glacial-interglacial transition, using glaciers and palaeolakes". Thesis, University of Aberdeen, 1998. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=217036.
Testo completoAbstract (sommario):
The aim of this thesis is to model climate change in the Bolivian Andes through the last glacial-interglacial cycle, using glaciers and palaeolakes. This is important because the extent and timing of glacier and palaeolake fluctuations in this area are poorly understood. Furthermore, determining the synchrony of glaciers and palaeolakes has direct implications for understanding the nature of palaeoclimatic change in this high altitude sub-tropical region during the last glacial-interglacial transition. The results of this study are directly applicable to general circulation models (GCMs) attempting to simulate past and future global climate change. Glacier-fed delta depositional systems on massifs at the margin of the southern Altiplano, Bolivia, suggest a broadly coeval expansion of glaciers and palaeolake Tauca during the Late-glacial. This is shown by the succession of hummocky moraine, ice-contact fan sediment-landform associations that extend from within lateral moraines and connect with Hjulstrom and Gilbert-type deltas at Cerro Azanaques, Cerro Tunupa and Cerro Condor Iquina between altitudes of 3770 and 3720 m. Radiocarbon ages on peat underlying glacigenic debris flow and glacifluvial deposits reveal glaciers reached their maximum extent soon after 13,300-12,850 14C yr B.P. The delta-plain/delta-front contacts of the glacier-fed deltas confirm that this glacier advance broadly coincided with palaeolake Tauca radiometrically dated to the interval 13,500-11,500 14C yr B.P. Therefore these climatically sensitive systems in the Bolivian Andes attained their greatest extent during the Late-glacial and not during the Last Glacial Maximum (LGM). Independent modelling of the climatic controls required to produce the simultaneous lowering of Late-glacial glacier equilibrium line altitudes (ELAs) and volumetric changes in palaeolake water balance suggest the primary forcing mechanism was increased summer (wet season) precipitation, while overflow from the northern basin was also necessary to raise the level of palaeolake Tauca in the southern Altiplano. Palaeoclimatic simulations show that an increase in precipitation of 330-425 mm/yr above modern values, combined with greater cloud cover (10%) that depressed local temperatures (2-3 °C) and reduced evaporation rates (10%) could have generated the Stage 3 glaciers and a 3760 m palaeolake highstand in the southern Altiplano. The ELA of former glaciers rose towards the south and west, like the gradient of modem precipitation, which suggest that increased moisture during the Late-glacial was probably brought to the Altiplano by tropical circulation systems similar to those at present, but atmospheric conditions were cooler-and-cloudier than present.
22
Peña, Rabadán Juan Carlos. "La reconstrucción de la dinámica fluvial y su conexión con la variabilidad climática a partir de fuentes documentales y registros instrumentales". Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/397713.
Testo completoAbstract (sommario):
El estudio analiza los posibles vínculos entre la frecuencia de inundaciones en Suiza con la actividad solar (forzamiento exógeno), erupciones volcánicas, la variabilidad del clima y la dinámica del Atlántico Norte (forzamiento endógeno) durante los dos últimos siglos. La variabilidad de las inundaciones en Suiza para el periodo 1800-2010 se ha determinado a partir de un índice de verano de daños por inundaciones (INU). El índice considera inundaciones graves y catastróficas a partir de los inventarios existentes, que resume tanto la gravedad del evento y su extensión espacial. Se ha puesto especial atención en las diferencias entre la dinámica de inundación en las laderas norte y sur de los Alpes. La influencia del forzamiento solar en las frecuencias de inundación se investiga aplicando un análisis espectral cruzado entre el registro de las manchas solares e INU. Por último, el análisis de los vínculos entre las inundaciones y la dinámica del Atlántico Norte se centra en los patrones de variabilidad atmosférica de baja frecuencia. El clima de verano en el sector norte del Atlántico europeo muestra un patrón principal de la variabilidad de año en año, aunque este patrón es más débil que la Oscilación del Atlántico Norte en invierno y está confinado a latitudes septentrionales. Por analogía, la comunidad climatólogica se refiere a este patrón como la Oscilación de Verano del Atlántico Norte (SNAO), que se define como la principal función ortogonal empírica de las anomalías estandarizadas de la presión atmosférica a nivel del mar para el dominio europeo durante los meses julio y agosto.
El índice de daños por inundación muestra evidencias que los clústeres de inundación encontrados en los periodos 1830-1851, 1881-1927, 1977-1990 y de 2005 hasta la actualidad, ocurren en su mayoría en fase con proxies paleoclimáticos y en la dinámica del Atlántico Norte. Estos episodios coinciden con los reportados para Suiza y en algunas zonas del continente europeo, como la República Checa, Italia y la mitad oriental de la Península Ibérica. Este vínculo no es tan estrecho cuando se compara con la ocurrencia de las inundaciones en Alemania. El análisis espectral cruzado entre la variabilidad solar e INU documenta que los ciclos detectados en el espectro de coherencia y en el de fase de 11 y 110 años están relacionados con una alta frecuencia de inundaciones y una actividad solar baja. Las periodicidades de los llamados "eventos de 100 años" se podrían explicar por los ciclos solares a escala centenaria, los cuales han sido también identificados en otros registros de inundaciones, incluyendo aquellos en el este de Francia, Suiza, Países Bajos, el Reino Unido, España y California. El análisis del modo principal de baja
frecuencia de variabilidad atmosférica muestra que las cuencas fluviales suizas situadas en el centro y en el flanco sur de los Alpes, se ven afectadas por áreas de inestabilidad atmosférica definidas por la fase positiva del patrón SNAO, mientras que las cuencas ubicadas en la vertiente norte de los Alpes están asociadas principalmente con la fase negativa. Además, un cambio en el patrón de variabilidad relacionado con las grandes inundaciones que se produjeron en el periodo 1800- 2010: la SNAO en fase negativa prevalece durante el atmosférica de baja frecuencia de circulación está último pulso frío de la Pequeña Edad de Hielo (clústeres de inundación: 1817-1851 y 1881-1927), y la fase positiva de SNAO emerge durante el clima más cálido en las últimas cuatro décadas (clústeres de inundación de 1977-1990 y de 2005 hasta la actualidad).The study analyses the possible links between flood frequency in Switzerland and solar activity (exogenic forcing), volcanic eruptions, climate variability and the North Atlantic dynamics (endogenic forcings) over the last two centuries. The variability of floods in Switzerland for the period 1800-2010 has been determined from a high summer flood damage index (INU). The index considers severe and catastrophic floods from existing flood inventories, summarizing both the severity of these events and their spatial extent. Special attention will be focused also on the differences between flood dynamics at the northern and southern slopes of the Alps. The influence of solar forcing on flood frequencies is investigated applying a cross-spectral analysis to the sunspot record and INU. Finally, the analysis of the possible links between floods and North Atlantic dynamics is focused on the low-frequency atmospheric circulation patterns. Summer climate in the North Atlantic-European sector shows a principal pattern of year-to-year variability, although this pattern is weaker than the North Atlantic Oscillation in winter and is confined to northern latitudes. By analogy the climatology community refers to this pattern as the Summer North Atlantic Oscillation (SNAO), which is defined as the main empirical orthogonal function of the standardized anomalies of the European mean sea level pressure during July and August. The flood damage index provides evidences that the 1830-1851, 1881-1927, 1977-1990 and 2005 to present flood clusters occur mostly in phase with paleoclimate proxies and North Atlantic dynamics. These episodes coincide with those reported from Switzerland and from some areas of the European continent such as the Czech Republic, Italy and the eastern half of the Iberian Peninsula. This link is not so close when compared with the flood occurrences in Germany. The cross-spectral analysis between solar variability and INU documents that the cycles detected in the coherency and phase spectra of 11 and 110 years are related to a high frequency of flooding and solar activity minima. The periodicities of so-called "100-year events" could be explained by centennial-scale solar cycles, which have also been identified in other flood records, including those in eastern France, Switzerland, Netherlands, the UK, Spain and California. The analysis of the principal mode of low-frequency atmospheric variability shows that the Swiss river catchments situated on the centre and southern flank of the Alps are affected by atmospherically unstable areas defined by the positive phase of the SNAO pattern, while those basins located in the northern slope of the Alps are predominantly associated with the negative phase of the pattern. Furthermore, a change in the low-frequency atmospheric circulation pattern related to the major floods occurred for the period 1800-2010: the Summer North Atlantic Oscillation persists in negative phase during the last cool pulses of the Little Ice Age (1817-1851 and 1881-1927 flood clusters), whereas the positive phase of SNAO prevail during warmer climate of the last four decades (flood clusters from 1977-1990 and 2005 to present).
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Sánchez, López Giomar. "North Atlantic Oscillation imprints in the Central Iberian Peninsula for the last two millennia: from ordination analyses to the Bayesian approach". Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400758.
Testo completoAbstract (sommario):
The climate variability of the Iberian Peninsula (IP) can be explained in terms of relatively few large-scale atmospheric modes, such as the North Atlantic Oscillation (NAO), the East Atlantic (EA) and the Scandinavian (SCAND) patterns. The present-day IP climatology clearly show that the NAO is the most prominent mode, especially in winter. However, the recent investigations have highlighted that other climate modes play a key role in both modulating the NAO-climate relationship and controlling certain meteorological parameters, although little is known about the past evolution of these climate interactions. Furthermore, there is a reasonable understanding of the past NAO evolution in the northern and the southern IP, but almost no information is available in the Central IP. Within this framework, the main aim of this PhD thesis is to characterize the impacts of the NAO on the Central IP over the last 2,000 years.
The conceptual lake model formulated to understand the present-day influence of the NAO on the limnological evolution of Peñalara (2016 m asl) and Cimera (2140 m asl) alpine lakes (Iberian Central Range, ICR) was established using Pearson's correlation coefficients between seasonal data of the NAO index, climatic data (i.e., precipitation and air temperature data) and ice phenology records from both lakes. The results suggest that the effects of the NAO are only reflected in the thawing process via the air temperature and the insulating effect of snow accumulation on the ice cover. An altitude component is evident in our survey because the effects of the NAO on Peñalara Lake are restricted to winter, whereas for higher Iberian alpine lakes (i.e., Redon Lake, Pyrenees), the effects extend into spring. A latitudinal component is also clear: in northern Europe, the NAO signal is primarily reflected in lake ice phenology via the air temperature, whereas our results confirm that in southern Europe, the strong dependence of both precipitation and temperature on the NAO determines the importance of these climatic variables for lake ice cover.
The past NAO impacts on the Central IP were determined by the multi-proxy characterization of the sediments of Peñalara and Cimera lakes using ordination statistical analyses. This approach was used to reconstruct the intense runoff events, the lake productivity and the soil erosion in the Cimera Lake catchment and to interpret these factors in terms of temperature and precipitation variability in the ICR for the last two millennia. The spatio-temporal integration of this reconstruction with other Iberian reconstructions was employed to identify the main climate drivers over this region. During the Roman Period (RP; 200 BC – 500 AD), the generally warm conditions and the E–W humidity gradient in the IP indicate a dominant interaction between a negative NAO phase and a positive EA phase (NAO-–EA+), whereas the opposite conditions during the Early Middle Ages (EMA; 500 – 900 AD) indicate a NAO+–EA- interaction. The dominantly warm and arid conditions during the Medieval Climate Anomaly (MCA; 900 – 1300 AD) and the opposite conditions during the Little Ice Age (LIA; 1300 – 1850 AD) in the IP indicate the interaction of the NAO+–EA+ and NAO-–EA-, respectively. Furthermore, the higher solar irradiance and fewer tropical volcanic eruptions during the RP and MCA may support the predominance of the EA+ phase, whereas the opposite conditions during the EMA and LIA may support the predominance of the EA- phase. In addition, evidence of African dust inputs in these lakes could denote a coupled displacement between the Intertropical Convergence Zone and the NAO during the study period.
Finally, a Bayesian random walk-modularised model was formulated to quantitatively reconstruct the evolution of the NAO impacts in the ICR (NAOICR) for the last two millennia using the raw chemical element profiles obtained from the Cimera Lake sediments using an X-Ray-Fluorescence Avaatech® core scanner. The obtained quantitative values of the NAOICR were in accordance with previously reconstructed precipitation and temperature conditions. In addition, the comparison of the NAOICR with other NAO approaches show that the local impact of the NAO can also display global aspects of this climate mode and that this impact reconstruction couldLa variabilidad climática en la Península Ibérica (PI) puede ser explicada por un reducido número de modos atmosféricos como la Oscilación del Atlántico Norte (siglas en inglés NAO), el Atlántico Este (siglas en inglés EA) o el Escandinavo, aunque la NAO es el predominante, sobre todo en invierno. La construcción de un modelo conceptual basado en los coeficientes de correlación de Pearson entre el índice de la NAO, datos climáticos (temperatura, precipitación y nieve) y registros de la cubierta de hielo de lagos alpinos (Peñalara, 2016 m.; Cimera, 2140) situados en el Sistema Central Ibérico (SCI) ha permitido entender los efectos actuales de la NAO en estos lagos. Los resultados sugieren que dichos efectos sólo se reflejan en el proceso de deshielo de la cubierta a través de la temperatura del aire y del efecto aislante de la nieve acumulada en ella durante el invierno. A mayor altitud, este efecto se extiende hasta primavera y a mayor latitud este efecto depende principalmente sólo de la temperatura. El análisis multiproxy de los sedimentos lacustres de estos lagos ha permitido realizar una reconstrucción climática en el SCI para los últimos dos mil años. La integración espacio-temporal de dicha reconstrucción con otras reconstrucciones en la PI ha permitido determinar los principales factores climáticos que actuaron durante ese periodo. Las interacciones entre NAO y EA, la variabilidad solar y la actividad volcánica y quizás el movimiento acoplado entre la Zona de Convergencia Intertropical y al NAO fueron probablemente las principales causas de dicha variabilidad climática. Finalmente, el desarrollo de un modelo matemático basado en estadística bayesiana ha permitido reconstruir cuantitativamente el impacto de la NAO en el SCI (NAOSCI) para este periodo usando datos geoquímicos obtenidos mediante el análisis de fluorescencia de rayos X de los sedimentos de Cimera. A pesar de que el modelo no pudo ser validado por correlación cruzada, los valores de NAOSCI están en concordancia con la reconstrucción climática previamente obtenida. La comparación de NAOSCI con otras reconstrucciones de NAO sugiere que este impacto regional podría mostrar aspectos globales de este modo climático y por tanto, con algunas mejoras podría considerarse un índice regional para toda la PI.
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El, Ouahabi El Ghazi Anuar. "Estudi de molècules orgàniques fòssils per a la caracterització dels esdeveniments climàtics ocorreguts durant períodes glacials i interglacials". Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/462851.
Testo completoAbstract (sommario):
Arribar a comprendre les causes i efectes dels canvis globals i les interaccions sinèrgiques del sistema climàtic continua sent un repte científic complex. Els informes del Panell Intergovernamental sobre el Canvi Climàtic (IPCC) han proporcionat avenços substancials en la comprensió del canvi climàtic. No obstant, es basen en l'extrapolació de les condicions actuals i s'hauria de tenir en compte que en el passat l'evolució natural del clima ha manifestat reorganitzacions importants. La matèria orgànica (MO) sedimentària està formada per una gran varietat de components, de diferents estructures, característiques geoquímiques, fonts i estat de conservació. La matèria orgànica, tot i que originalment forma part de diferents organismes (Bacteria, Archaea o Eucarya), acaba acumulant-se en arxius sedimentaris de milers d’anys d’antiguitat, on es preserva, tot deixant registrades les condicions ambientals de l’hàbitat on vivien aquells organismes que les varen sintetitzar originalment. D’aquesta manera, les molècules orgàniques fòssils proporcionen una biblioteca molt valuosa d’esdeveniments climàtics, donat que, per exemple, proporcionen informació sobre temperatura, balanç hídric, productivitat primària fotosintètica, processos d’alteració diagenètica o l’activitat pre/post- deposicional (metanogènesi, oxidació aeròbica, etc.).
En aquest context, la memòria de Tesi Doctoral que s’ha elaborat se centra en l’anàlisi de molècules orgàniques fòssils dipositades en sediments marins situats a la plataforma continental de la Península Ibèrica, amb l’objectiu de determinar l'origen, distribució, evolució i processos d'alteració de la matèria orgànica sedimentaria, i contribuir a la reconstrucció de les condicions ambientals que van tenir lloc en el passat. Amb aquesta finalitat, es van agafar sediments marins del testimoni IODP U1385 situats en la confluència de l'oceà Atlàntic i Mar Mediterrani. Aquesta àrea d'estudi té un gran interès perquè correspon a una regió sensible als canvis climàtics ràpids, sotmesa a la influència de l’entrada de compostos continentals i de processos d’aflorament d’aigua profunda, que juntament amb taxes elevades de sedimentació, afavoreix l’acumulació ràpida i la preservació de la matèria orgànica sedimentària.
Paral·lelament, la recerca desenvolupada també va incloure la generació d'una base de dades de temperatura d'alta resolució temporal. L’element essencial d’aquesta base provenia dels arxius d’alquenones, juntament amb altres marcadors derivats de diferents registres ambientals, tals com els testimonis de gel i els espeleotemes. Aquesta base de dades nova té com a objectiu proporcionar informació sobre l'estructura espacial i temporal dels esdeveniments/transicions de la temperatura superficial del mar, les relacions de fase entre les variacions del clima regional, els canvis globals i el forçament extern del clima.To understand the causes and effects of global changes and synergistic interactions of the climate system still remains a complex scientific challenge. The reports of the Intergovernmental Panel on Climate Change (IPCC) have provided substantial advances in the understanding of climate change. However, it’s based on extrapolation of current conditions and should take into account that in the past the natural climate evolution has expressed major reorganizations. Sedimentary organic matter (OM) includes a variety of components, different structures, geochemical features, sources and conditions. Organic matter, although originally forming part of different organisms (Bacteria, Archaea or Eucarya), finally accumulates on sedimentary archives thousands of years old, where it remains perfectly preserved, while registering the environmental conditions from the habitat of its former synthesizers. Thus, fossil organic molecules represent an invaluable library of climatic events because they provide information, e.g. temperature, hydrological balance, primary photosynthetic production, diagenetic alteration processes or pre/post-depositional activity (methanogenesis, aerobic oxidation, etc). In this context, the thesis focuses on the analysis of fossil organic molecules deposited in marine sediments located on the continental shelf of the Iberian Peninsula. The aim of this research line focuses on determining the origin, distribution, evolution and alteration processes of sedimentary organic matter and contributes to the reconstruction of environmental conditions that occurred in the past. To this end, deep sea sediments samples were obtained from IODP U1385 located at the confluence of the Atlantic Ocean and the Mediterranean Sea. This study area is well known as a source of rapidly accumulating and preservation sedimentary OM and represents an important area for investigating past climate variability, subject to the influence of the entry of continental compounds by river discharge and upwelling phenomena. In parallel, the research line also included the creation of a high resolution database of alkenone-derived sea surface temperatures, together with other markers derived from different environmental records such as ice cores and speleothems. This new database aims to provide information about the spatial and temporal structure of sea surface temperature events/transitions, regional and global climate changes, and external forcings.
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Pérez, Zanón Nuria. "Climate analysis in the central Pyrenees from instrumental and paleoclimate proxy data". Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/461050.
Testo completoAbstract (sommario):
Es presenten les sèries termopluviomètriques que caracteritzen el clima del Pirineu central durant el període instrumental, que han permès la caracterització de la deriva climàtica durant el darrer segle. A més a més, aquestes series han estat utilitzades per realitzar anàlisis dels registres naturals capaços de capturar la senyal climàtica durant els últims 500 anys. Aquestes sèries termopluviomètriques han estat obtingudes a partir de dades observades in-situ (tant amb observatoris manuals com automàtics) durant el període instrumental 1910–2013 tractant-se de les sèries de temperatura i precipitació d'alta qualitat més llargues disponibles de la zona d'estudi. Després d'aplicar un control de qualitat i un procés d'homogenització a les dades climàtiques, les sèries d'anomalies regionals mostren la variabilitat i canvi climàtic a escales anuals i estacionals. Els sediments del llac Montcortès han estat analitzat i la influència del clima en l'alteració de la recurrència de la barreja de la columna d'aigua del llac, considerat meromíctic, ha estat estudiada. Per la seva banda, les cronologies dels gruixos dels anells del arbres han estat utilitzades per avaluar la seva capacitat de capturar la senyal climàtica regional, així com els règims de temps a escala sinòptica de l'Atlàntic Nord a l'estiu. Per això, el clima regional del Pirineu central ha estat caracteritzat mitjançant composicions sinòptiques (composites) de pressió a nivell del mar per als estius normals i extrems (mitjançant les sèries d'anomalies regionals).Se presentan las series termopluviométricas que caracterizan el clima del Pirineo central durante el período instrumental, que han permitido la caracterización de la deriva climática durante el pasado siglo. Además, estas series se han utilizado para realizar análisis de registros naturales capaces de capturar la señal climática durante los últimos 500 años. Estas series termopluviométricas han sido obtenidas a partir de datos observados in-situ, tanto en observatorios manuales como automáticos, durante el período instrumental 1910–2013, tratándose de las series de temperatura y precipitación de alta calidad más largas disponibles en la zona de estudio. Tras controlar los datos observados de calidad y aplicar el método de homogenización más adecuado, las series de anomalías regionales muestran la variabilidad y cambio del clima en escalas anuales y estacionales. Los sedimentos del lago Montcortès han sido analizados y la influencia del clima en la alteración de la recurrencia de la mezcla de la columna del agua del lago, considerada meromíctico, ha sido estudiada. Por otra parte, cronologías del grosor de anillos de los árboles del Pirineo han sido utilizadas para evaluar su capacidad de capturar la señal climática regional, así como los regímenes de tiempo de escala sinóptica del Atlántico Norte en verano. Para ello, el clima regional del Pirineo central ha sido caracterizado mediante composiciones sinópticas (composites) de presión a nivel del mar en los veranos normales y extremos (mediante las series de anomalías regionales).
This thesis deals with the thermopluviometric series that characterize the climate of the central Pyrenees during the instrumental period, which also allow to characterize the climatic drift during the last century. Furthermore, these series have been used to analyse natural records capable of capturing the climatic signal during the last 500 years. These thermopluviometric series have been obtained from data observed in-situ, both in manual and automatic observatories, during the instrumental period 1910-2013 for the longer series of maximum and minimum temperature and precipitation available in the study area. After quality controlling the observed data and applying the most appropriate homogenization method, the series of regional anomalies show the variability and climate change in annual and seasonal scales. The sediments of Lake Montcortès have been analyzed and the influence of the climate in the alteration of the recurrence of the mixture of the water column of the lake, that was considered meromictic, has been studied. On the other hand, tree ring thickness chronologies have been used to evaluate their ability to capture the regional climatic signal as well as the weather regimes of the North Atlantic in summer. To this end, the regional climate of the central Pyrenees has been characterized by synoptic compositions (composites) of sea level pressure in normal and extreme summers (through regional series of anomalies).
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Alves, Daniel Pavani Vicente. "Análise sismoestratigráfica das bacias de Barreirinhas e do Ceará como ferramenta para estudos paleoceanográficos no Cenozoico na Margem Equatorial Brasileira". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/21/21136/tde-28062018-162619/.
Testo completoAbstract (sommario):
A Margem Equatorial Brasileira (MEB) é uma área de extrema importância para os estudos paleoceanográficos e paleoclimáticos do Atlântico Equatorial, mas que ainda possui um vasto campo para pesquisa. Este trabalho visa aprimorar a compreensão desta importante região, fornecendo uma interpretação paleoceanográfica para a evolução sedimentar das Bacias do Ceará e de Barreirinhas no Cenozoico, a partir de uma análise sismoestratigráfica. Foram analisadas linhas de sísmica multicanal e informações de poços de exploração petrolífera para a construção de um modelo de evolução deposicional para as duas bacias. Este modelo foi criado a partir da análise dos registros sísmicos e de técnicas de sismoestratigrafia e mapeamento de horizontes. Como resultados, identificaram-se cinco marcadores cronoestratigráficos e definiram-se duas fases distintas: (1) o Paleógeno e (2) o Neógeno + Quaternário. Durante o Paleógeno, a sedimentação passa a ter maior influência oceânica, com a sedimentação de desenvolvendo em um clima quente e úmido, e ainda controlada por uma circulação de superfície e de fundo ainda muito restritas. Durante o Neógeno e Quaternário, a Corrente Norte do Brasil (CNB) e a Corrente de Contorno Oeste Profunda passaram a atuar efetivamente na MEB, remobilizando os sedimentos e erodindo os depósitos de águas profundas. Durante este período, foi também possível identificar o efeito das variações climáticas no aporte sedimentar nas bacias e na circulação, principalmente com enfraquecimento da CNB e da Célula de Revolvimento Meridional do Atlântico.The Brazilian Equatorial Margin (BEM) is an area of extreme importance for the paloceanography and paleoclimatology of the South Atlantic although still with a wide field for research. The scope of this work is improve the comprehension of this important region, with the paleoceanographic interpretation for the sedimentary evolution of the Ceará and Barreirinhas basins in the Cenozoic through a seismic stratigraphic approach. Multichannel seismic lines and bore hole geophysical data were analyzed to the construction of a depositional model for both basins. This model was created using seismic stratigraphy and horizon mapping techniques. As results, five chronostratigraphical markers were identified and two distinct phases defined: (1) Paleogene and (2) Neogene + Quaternary. During the Paleogene, the sedimentation became more controlled by marine influence, developing in a time of warm and humid climate and surface and bottom currents still incipient. During the Neogene and Quaternary, the North Brazil Current (NBC) and the Deep Western Boundary Current became more important in the sediment transport, erosion and rework in the BEM. During this period, it was also possible to identify the climatic changes effect on the sediment supply for both basins, and also the paleocirculation variations, especially with the weakening of the NBC and the Atlantic Meridional Overturning Circulation.
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McInnis, Heather E. "Middle Holocene culture and climate on the south coast of Peru : archaeological investigation of the Pampa Colorada /". view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1196396921&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Oregon, 2006.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 729-756). Also available for download via the World Wide Web; free to University of Oregon users.
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Osterberg, Erich Christian. "North Pacific Late Holocene Climate Variability and Atmospheric Composition". Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/OsterbergEC2007.pdf.
Testo completo
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Grigg, Laurie Davis. "Millennial-scale vegetation and climate variations in the Pacific Northwest during the last glacial period (60,000-16,000 cal yr B.P.) /". view abstract or download file of text, 2000. http://wwwlib.umi.com/cr/uoregon/fullcit?p9998032.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Oregon, 2000.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 237-250). Also available for download via the World Wide Web; free to University of Oregon users.
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Lisiecki, Lorraine E. "Paleoclimate time series : new alignment and compositing techniques, a 5.3-MYR benthic [exponents] d18O stack, and analysis of Pliocene-Pleistocene climate transitions /". View online version; access limited to Brown University users, 2005. http://wwwlib.umi.com/dissertations/fullcit/3174639.
Testo completo
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Wright, Aaron M. "A low-frequency paleoclimatic reconstruction from the La Plata Mountains, Colorado and its implications for agricultural productivity in the Mesa Verde region". Online access for everyone, 2006. http://www.dissertations.wsu.edu/Thesis/Fall2006/a_wright_120806.pdf.
Testo completo
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Weirauch, Daniel R. "A high-resolution record of climate instability spanning ~1.0 million years across the mid-Pleistocene transition". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 131 p, 2007. http://proquest.umi.com/pqdweb?did=1472642111&sid=21&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Testo completo
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Milne, Isla. "Climate and environmental change inferred from diatom communities in Lake Challa (Kenya-Tanzania)". Thesis, Kingston, Ont. : [s.n.], 2007. http://hdl.handle.net/1974/500.
Testo completo
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Seligman, Angela. "Oxygen and hydrogen investigation of volcanic rocks: Petrogenesis to paleoclimate". Thesis, University of Oregon, 2016. http://hdl.handle.net/1794/20547.
Testo completoAbstract (sommario):
Knowledge of the isotopic evolution of volcanic eruptions is essential to volcanologists, geochemists, and paleoclimatologists. I isotopically evaluate the evolution of magmas from their initial formation, to eruption, and then to their alteration during the diffusion of environmental waters into volcanic glass. I focus first on the formation and evolution of large, caldera-forming eruptions from both Gorely volcano in Kamchatka, Russia and 30–40 Ma caldera forming eruptions through Oregon in the United States of America. I utilize oxygen (δ18O), hafnium (εHf), strontium (87Sr/86Sr), and neodymium (143Nd/144Nd) isotopes to document the creation of caldera-forming eruptions at these eruptive centers through the melting of surrounding crust. I also use U-Pb and 40Ar/39Ar to document the timescales of the formation of these large-volume silicic eruptions.
Following eruption, the volcanic glass in tephra and ash can slowly take in environmental water. It is thought that the hydrogen isotopic ratio (δD) of these waters can be used to determine paleoenvironments from the time that the volcanic glass was deposited. The latter portion of my dissertation focuses on the use of hydrogen isotopes of environmentally hydrated volcanic glass to determine paleoenvironments, and the calibration of the TCEA to analyze oxygen isotopes of hydrated volcanic glass. I first focus on the rate of diffusion of water at ambient temperature to better understand the time frame necessary to hydrate volcanic glass for use as a paleoenvironmental indicator. I also document the hydrogen isotopic ratios that result from the diffusion of water into volcanic glass, which is documented as a decrease in δD with an increase in secondary hydration in all regions worldwide except equatorial. Finally, I focus on the earliest stages of diffusion of water into volcanic glass by analyzing tephra deposits that were collected within days of the 1980 eruptions of Mount St. Helens as well as tephra deposits recently collected in 2015 to identify changes in water concentration and hydrogen isotopic ratios over an ~35 year period.
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Torner, Perez Judit. "Paleoclimatic reconstruction of past interglacial periods and their transitions in the Iberian Peninsula and its surrounding seas = Reconstruccions paleoclimàtiques dels interglacials recents i les seves transicions a la Península Ibèrica i mars circumdants". Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/672465.
Testo completoAbstract (sommario):
This study combines cave speleothems and marine sediments to gain an insight into the climate variability of the Iberian Peninsula (IP) and its surrounding seas associated with previous warm interglacial periods. In particular, it centres in the interglacials comprised within the Marine Isotopic Stages (MIS) 13, 11, 9, 7, and 5, and their associated transitions. The speleothems are used as archives for changes in atmospheric moisture availability by means of stable isotopes and Mg/Ca analysis. The studied speleothems correspond mostly from the Balearic Islands (Minorca and Mallorca) but also from the Pyrenees. Marine conditions for the penultimate termination (T-II) and the MIS 5 have been reconstructed in the base to three sediment cores from three different marine locations around the IP: the Cantabrian Sea, the Alboran Sea, and the Balearic Sea. Surface conditions were explored by means of pair analyses of δ18O and Mg/Ca ratios measured in carbonate shells of the planktonic foraminifera Globigerina bulloides. These measurements let to the reconstruction of Sea Surface Temperatures (SST) and sea water δ18Osw values as a proxy of major changes in the regional precipitation/evaporation balance or as an indicator of the arrival of melting waters. In addition, changes in the intensity of western Mediterranean deep convection are explored through additional measurements of grain size distribution and XRF-geochemical ratios performed in the Balearic core (MD99- 2343).
The studied speleothem collection provides a nearly continuous 450 kyr record, unique for the Mediterranean region. Interglacial periods are characterized by light δ13C and low Mg/Ca ratios pointing to enhanced precipitation and climate amelioration that allowed the expansion of the vegetation cover. On the contrary, heavier/higher δ13C and Mg/Ca ratios during glacial stages highlight their dry conditions with reduced vegetation activity. The δ18Ospeleo records reveal also the overall dominance of lighter values during interglacial periods in contrast to the glacial periods but with a strong 23-kyr (precessional) imprint in the signal. The extraordinary resemblance between the cave and marine δ18O records support a strong influence of Mediterranean source rains over the studied caves whose δ18O signal was dominated by the precession control on the evaporation/precipitation ratio on the Mediterranean basin.
The MIS 11 appears in the studied speleothem as a long and stable interglacial with rather constant water availability over the Balearic Islands. The speleothem covering the MIS 9 and MIS 7 allows identifying sub-stage structures with wetter conditions associated with the warm periods. This record presents extraordinary resemblance to previously published pollen sequences from the Mediterranean region.
The MIS 5 is studied in detail through the integrated study of marine and speleothem records. During the Last Interglacial (LIG), the sea surface temperature evolution was heterogeneous around the IP with gradients among the three studied seas larger than those from today. The LIG end was coincident with an accelerated aridification phase that marked the glacial inception at 116.5 kyr BP. This was the first of a series of stadials that punctuated the early glaciation and where the sea thermal gradient almost disappeared around the IP. These intense coolings during stadials led the development of drier but intense westerlies over southern European latitudes that favoured deep convection in the western Mediterranean Sea. In contrast to this regional homogeneity among the studied records during stadial periods, the interstadials periods were rather heterogeneous pointing to much complex ocean-atmosphere interconnections during these warm intervals.
Glacial terminations (T-III, IV, and V) appear as periods of low rates in speleothem growth while T-II is only represented by growth interruptions. The marine δ18Osw for the T-II supports the occurrence of a major freshening event in correspondence to the Heinrich Event (HE) 11. Previous terminations are represented by an early light δ18Ospeleo anomaly, likely reflecting that this early deglacial major melting over the Atlantic Ocean was a rule for deglacial initiations.L’estudi combinat tant de sediments marins com d’espeleotemes ha permès determinar la variabilitat climàtica durant períodes interglacials recents (MIS 13, 11, 9, 7, i 5) a la Península Ibèrica i als seus mars circumdants. S’han utilitzat sediments marins de tres localitzacions diferents, del Mar Cantàbric, el Mar d’Alboran i el Mar Balear, en els quals s’han determinat les condicions superficials del mar, a partir del càlcul de les temperatures superficials (Mg/Ca-SST) i el δ18Osw mesurats en el foraminífer planctònic Globigerina bulloides. Addicionalment, s’han caracteritzat canvis en la intensitat de la corrent profunda a partir de la distribució granulomètrica i l’anàlisi elemental per fluorescència de raig X dels sediments del testimoni del Mar Balear. Per un altre banda l’anàlisi geoquímic tant d’isòtops estables com de la relació Mg/Ca mesurats en espeleotemes de les illes Balears i dels Pirineus han sigut utilitzats com indicadors de precipitacions. La nova col·lecció d’espeleotemes obtinguda en aquesta tesis doctoral ha proporcionat un registre continental pràcticament continu de 450 kyr únic a la zona de la Mediterrània. Els resultats d’aquesta tesis mostren que els períodes interglacials, caracteritzats per valors lleugers de δ13C i baixes relacions de Mg/Ca en espeleotemes, varen tindre cobertures vegetals més extenses que durant els períodes glacials i varen ser períodes humits degut al augment de les precipitacions. A més, els resultats indiquen peculiaritats entre els diferents períodes interglacials estudiats i permeten identificar sub-estructures climàtiques interestadials/interglacials. En concret el MIS 5, període estudiat amb detall, mostra alts gradients tèrmics de les aigües superficials marines entre les tres localitzacions estudiades al voltant de la Península Ibèrica, indicant una interconnexió oceà-atmosfera complexa durant aquests períodes més càlids. Contràriament, durant períodes estadials freds, els gradients tèrmics pràcticament varen desaparèixer, i juntament amb el desenvolupament de condicions atmosfèriques àrides varen afavorir la convecció profunda del mediterrani occidental.
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Steig, Eric J. "Beryllium-10 in the Taylor Dome ice core : applications to Antarctic glaciology and paleoclimatology /". Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/6745.
Testo completo
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Hunter, Rebecca L. Halanych Kenneth M. "Phylogeography and population structure of Antarctic ophiuroids effects of life history, oceanography and paleoclimatology /". Auburn, Ala, 2009. http://hdl.handle.net/10415/1754.
Testo completo
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Margalef, Marrasé Olga. "The last 70 kyr of Rano Aroi (Easter island, 27ºS) peat record: New insights for the Central Pacific paleoclimatology". Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/146186.
Testo completoAbstract (sommario):
The PhD entitled “Last 70kyr of Rano Aroi (Easter Island, 27ºS) peat record: New insights for Central Pacific paleoclimatology” presents an environmental and climate reconstruction of Easter Island during the last 70.000 years. To accomplish this purpose, two peat cores of 14 and 4 meters have been retrieved from the center and the margin of the Rano Aroi peatland. Facies description and age model allowed us to decipher that the peat started accumulating 70.000 years ago, what means that this is the oldest peat record recovered up to the moment over the Southern Pacific. To investigate changes in the type of accumulated peat we determined total carbon, nitrogen and sulfur (TC, TN, TS) of organic matter as well as stable isotope values of each element (delta13C, delta15N, delta34S). In order to decipher the composition of the mineral content, X-Ray Fluorescence measurements was performed over the cores, obtaining the quantity of Ca, Fe and Ti. Additionally, the concentration of the major, minor and trace elements was determined by spectrometry (ICP-AES). The geochemical approach was complemented by the study of macrofossil (plant or animal remains as seeds or insects) and pollen content, what permitted to reconstruct vegetation changes on the mire and the island. The combination of geochemical and biological proxies defined three main hydric conditions (flood, drought and baseline conditions) of the peatland that have been alternated along Late Pleistocene and Holocene.
During MIS 4 (70 to 60 kyr BP in Rano Aroi), the hydric and environmental conditions in the mire were stable and resembled mire baseline conditions. Open grasslands covered Rano Aroi catchment area and C4 Poaceae dominated the mire. Early MIS 3 (60 to 40 cal kyr BP in Rano Aroi) was marked by the onset of wet events. During the first half of MIS 3 and probably driven by the wetter and warmer conditions Asteraceae and other small trees became gradually more abundant, forming small and scattered forests around the Terevaka volcano, while C3 peat forming plants colonized the Aroi mire. Late MIS 3 was a very dry period, which led to peat oxidation and exposure shortly after 39 cal kyr BP. These conditions changed on early MIS 2 (27.8–19 cal kyr BP). The water table recovered and peat accumulation resumed under C3 plant dominance. The evidence of the onset of deglaciation is concordant with Raraku Lake environmental development and was dated at 17.5 cal kyr BP in both sites. The regional mid-Holocene dry period is well characterized at Rano Aroi from 5 to 2.5 cal kyr BP.
The correlation between Rano Aroi record and other circumpacific sites suggests important changes in the atmospheric or oceanic circulation on Central Pacific during Late Pleistocene. In particular, the Rano Aroi record indicates that the episodes of maximum precipitation over the island correlate with North Atlantic Heinrich stadials and other stadials. During these stadials, the Intertropical Convergence Zone (ITCZ) migrated to the south while the South Pacific Convergence Zone (SPCZ) shifted eastwards provoking the arrival of storm systems over the island. In accordance to this atmospheric and oceanic restructuration, Rano Aroi wet events also correlated with periods of a reduced Sea Surface Temperature (SST) gradient along the Equator. This fact indicates that more humid conditions over the Easter Island region occurred when the Walker circulation was reduced. The Central Pacific climate was also influenced by high latitude dynamics, like the changes in Intermediate Antarctic Water formation and the position of the Southern Westerlies.La tesi titulada: "Last 70kyr of Rano Aroi (Easter Island, 27ºS) peat record: New insights for Central Pacific paleoclimatology" presenta una reconstrucció climàtica i ambiental de l’illa de Pasqua (Rapa Nui) pels darrers 70.000 anys. Per aquest propòsit es van estudiat dos testimonis de 14 i 4 metres, extrets del centre i marge de la torbera de Rano Aroi. Per determinar els canvis en el tipus de torba acumulada es van obtenir els perfils de carboni, nitrogen i sofre total (TC, TN, TS) així com els corresponents isòtops estables (delta13C, delta 15N, delta 4S). La variabilitat en el contingut de Calci, Ferro i Titani (Ca, Fe, Ti) es va obtenir amb mesures de Fluorescència de Rajos X mitjançant core-scanner. Usant espectrometria (ICP-AES) es va determinat la concentració d’elements majoritaris, minoritaris i traça de la fracció inorgànica. El conjunt d’indicadors geoquímics es va complementar amb l’estudi de macrofòssils (restes animals i vegetals com insectes o llavors) i la determinació del contingut pol•línic del registre. La integració de les dades geoquímiques i biològiques ha permès establir tres condicions hídriques (inundació, sequera, condicions de base) de la torbera que s’han anat alternant durant els darrers 70.000 anys. Durant el MIS 4 la vegetació de la conca consistia en amplis prats de Poaceae i la formació de la torba es produïa per acumulació de restes de plantes de tipus C4. L’inici del MIS 3 va estar caracteritzat per l’ocurrència d’episodis de forta precipitació. Durant aquest període, les creixents temperatures i l’elevada precipitació varen afavorir l’establiment d‘Asteraceae formant possiblement petites clapes de bosc al voltant de Rano Aroi. La vegetació de tipus C3 va colonitzar la torbera, tot produint un canvi en la isotopia de carboni present fins a dia d’avui. El final del MIS 3 va ser caracteritzat per un llarg període sec situat en algun moment entre els 39 i els 31 kyr cal BP. A l’inici del MIS 2, la làmina d’aigua de la torbera es va recuperar tot reactivant l’acumulació de torba. L’Holocè es registra com a un període relativament sec, interromput puntualment per un episodi humit als 5.8 kyr cal BP. La correlació de la historia ambiental de Rano Aroi amb altres registres del circumpacific han permès deduir canvis en la circulació oceànica i atmosfèrica del Pacífic Central. En concret, el registre de Rano Aroi indica que els episodis de màxima precipitació de l’illa correlacionen amb períodes estadials freds definits a l’Atlàntic Nord al llarg del darrer cicle glacial. Durant els estadials, la zona de convergència intertropical (ITCZ) es va desplaçar cap el sud mentre que la zona de convergència del Pacífic Sud (SPCZ) va migrar en direcció est. Aquesta reestructuració atmosfèrica va comportar una major arribada de tempestes ciclòniques a l’illa. El clima del Pacífic central també es va veure influenciat per les dinàmiques de altres latituds, com els canvis en la formació d’aigües intermèdies antàrtiques o la posició dels vents meridionals de l’oest.
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Walsh, Megan Kathleen. "Natural and anthropogenic influences on the Holocene fire and vegetation history of the Willamette Valley, northwest Oregon and southwest Washington /". Connect to title online (Scholars' Bank) Connect to title online (ProQuest), 2008. http://hdl.handle.net/1794/9488.
Testo completo
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Chase, Geneva Erin. "Late-Glacial Climate as Inferred fom Chironomid Assemblages in Lake Sediments from Aroostook County, Northeastern Maine". Fogler Library, University of Maine, 2004. http://www.library.umaine.edu/theses/pdf/ChaseGE2004.pdf.
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Long, Colin James. "Holocene fire and vegetation history of the Oregon Coast Range, USA /". view abstract or download file of text, 2003. http://wwwlib.umi.com/cr/uoregon/fullcit?p3095260.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Oregon, 2003.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 255-270). Also available for download via the World Wide Web; free to University of Oregon users.
42
Van, Beynen Philip Edward. "Investigations into the fluorescence of calcitic speleothems /". *McMaster only, 1998.
Cerca il testo completo
43
Heine, Jan T. "Glacier advances at the Pleistocene/Holocene transition near Mount Rainier volcano, Cascade Range, USA /". Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/6748.
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Taylor, Meghan. "Continental-scale validation of the temperature signal in oxygen isotopes of Sphagnum cellulose and its application as a paleoclimate proxy". Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1597629811&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Viens, Robert J. "Late Holocene climate change and calving glacier fluctuations along the southwestern margin of the Stikine Icefield, Alaska /". Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/6737.
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Isaza, Londoño Carolina. "Late Maastrichtian paleoclimatology and the paleobiology of Raceguembelina fructicosa, Contusotruncana contusa and Rugoglobigerina rugosa inferred from single specimen [delta]¹³C and [delta]¹⁸O data /". free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1421145.
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Wohl, Ellen Eva. "Northern Australian paleofloods as paleoclimatic indicators". Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184418.
Testo completoAbstract (sommario):
Paleoflood data are restrictive reflections of climatic conditions, representing one component of a region's climate; high rainfall intensity storms. In regions with a fairly simplistic, uniform hydroclimatological setting (floods above a given magnitude threshold are caused by predominantly one type of atmospheric circulation pattern), the temporal distribution of floods reflects that of the causal circulation pattern. Slackwater-deposit-based paleoflood reconstructions for three rivers in northern Australia cover an aggregate of 1200 years. Slackwater deposits (SWD) are fine-grained sediments which settle from suspension in low velocity areas during floods. These deposits approximate the flood's high water level, and allow reasonably accurate estimation of discharge. Radiocarbon dating of associated organics, and thermoluminescence (TL) dating of the 90-125 μm quartz fraction of the sediments, produce a paleoflood chronology. In this study, radiocarbon ages on SWD ranged from 1200 yr BP to modern, while TL ages on SWD and other fluvial sediments ranged from 2.6 to 60 ka. TL dating appears to have a large temporal range (1-100 ka) and a restricted spatial range (the lower reaches of a basin), while radiocarbon dating has a more restricted temporal range (0-35,000 yr BP) and a large spatial range (anywhere in the basin). The northern Australian paleoflood data formed clusters at 300-440 yr BP and 160 yr BP-present. This distribution is attributed to variations in the intensity of the El Nino/Southern Oscillation (ENSO) circulation (which prevents floods from occurring in northern Australia), and the anti-ENSO circulation (which is associated with large floods).
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Rech, André Rodrigo 1985. "Walking through the flower fields = the role of time and space on the evolution of pollination strategies". [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/315723.
Testo completoAbstract (sommario):
Orientadores: Marlies Sazima, Jeff OllertonTexto em português e inglês
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Os padrões encontrados em ecologia são resultado de processos contemporâneos interagindo com uma longa história de contingência. No entanto, poucos estudos têm buscado entender o papel relativo de fatores contemporâneos e pretéritos sobre padrões reprodutivos de plantas. No decorrer dessa tese foram consideradas essas duas dimensões (temporal e espacial) em estudos sobre polinização. A amplitude do estudo em relação ao tempo foi de horas até milênios, da mesma forma que para o espaço, para o qual se considerou desde metros até variações entre diferentes continentes na escala planetária. Os capítulos estão organizados em uma escala crescente de tempo e espaço. No primeiro capítulo foi considerada a variação fina de horas e metros no estudo sobre a polinização de algumas espécies de Davilla; nesse capítulo também são apresentados outros aspectos da história natural na família Dilleniaceae e uma abordagem filogenética para a evolução de algumas características florais. No capítulo 2, ao longo de vários anos, foi verificada a habilidade de visitantes florais depositar pólen, sua frequência e a importância de cada grupo de visitante nas flores de Knautia arvensis nesse período. O capítulo 3 demonstra variações no espaço tanto na morfologia floral e foliar como no crescimento do tubo polínico em diferentes testes de polinização, utilizando Curatella americana com populações distribuídas no Cerrado Brasileiro. No capítulo 4 é apresentada a variação espacial no sistema reprodutivo e a relação dos polinizadores com o nível de polinização cruzada e do passado climático com o nível de autopolinização espontânea, também tratando de C. americana. Para finalizar o capítulo 5 considera 50 inventários distribuidos ao redor do planeta categorizando as plantas em anemófilas ou zoófilas e demonstra o papel da precipitação (presente e passada) e da riqueza de espécies vegetais na prevalência de cada um dos modos de polinização. Como conclusão geral, fica clara a importância de se considerar as dimensões temporal e espacial nas interações entre plantas e polinizadores, a fim de entender como essas evoluem e como impactam na evolução da morfologia floral e nos sistemas de polinização
Abstract: Patterns in ecology are the products of current factors interacting with a longstanding history of contingency. Nevertheless, few studies have attempted to disentangle the contribution of past and current factors on plant reproduction patterns. Here we studied pollination considering both, spatial and temporal dimensions. Time variation goes from hours to millennia as well as space, whose importance was considered from meters to the whole planet. The chapter¿s sequence within the thesis is planned to go from the small to the large scale. We show the importance of fine grained variations such as hours and meters in the flower differentiation and pollination of two Davilla species in the chapter 1. In the chapter 2 we studied pollen deposition and visitation frequency in Knautia arvensis considering a year scale and showed the most important pollinator changing every year. In the Chapters 3 we used Curatella americana with populations studied across Brazilian Cerrado and show spatial variation in flower and leaf morphology and pollen tube growth. Chapter 4 also using C. americana shows the variation on the reproductive system across space, with cross-pollination related to pollinator availability and the level of autogamy underpinned by past climate. To finish, Chapter 5 deal with 50 community-based assessments of wind and animal pollination over the world and show the importance of precipitation (current and past) and plant species richness as major drivers of these proportion. As a general conclusion, it is clear that temporal and spatial factors cannot be ignored in spite to understand floral evolution and the interactions between plant and pollinators
Doutorado
Ecologia
Doutor em Ecologia
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Spera, Amanda Mattosinhos. "Avaliação das condições paleoclimáticas e paleoceanográficas dos últimos 1500 anos na Plataforma Continental de São Sebastião (Sudeste do Brasil) através do uso de proxies geoquímicos". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/21/21137/tde-21022017-080216/.
Testo completoAbstract (sommario):
Proxies geoquímicos (n-alcanos, alquenonas, GDGTs, δ13C, Fe/Ca e Ti/Ca), obtidos em amostras de um testemunho sedimentar, foram utilizados para avaliar as mudanças paleoclimáticas e paleoceanográficas na região da Plataforma Continental de São Sebastião ao longo do Holoceno Tardio. O modelo de idade, obtido através da análise conjunta dos métodos de 210Pb e 14C, demonstrou que testemunho aqui estudado cobre os últimos 1500 anos. A avaliação dos marcadores terrígenos permitiu a identificação das mudanças na drenagem e erosão continental, as quais estão relacionadas às alterações no regime de precipitação do continente adjacente. Variações ao longo do tempo na temperatura da superfície do mar foram relacionadas às mudanças no regime de ventos predominante, os quais são responsáveis por um aumento ou uma redução da frequência dos eventos de ressurgência. Já as mudanças nos valores de temperatura de subsuperfície foram relacionadas com a entrada e saída da Água Central do Atlântico Sul próxima às regiões costeiras, e com os processos de mistura na coluna d\'água. As variações na temperatura média do ar (TMA), por sua vez, provavelmente estiveram relacionadas com mudanças na irradiação total solar. Períodos representados pelos valores mais elevados de TMA correspondem aos períodos de máxima irradiação solar conhecidos como Máxima Medieval (1100 a 1250 DC) e Máxima Moderna (1950 - presente) e o período representado pelos menores valores de TMA coincide com o período de mínima solar conhecido como Spörer. Além disso, foi possível observar uma redução na entrada de material terrígeno para a plataforma continental durante a Anomalia Climática Medieval. Em contrapartida, o período que corresponde a Pequena Era do Gelo foi caracterizado por um aumento da contribuição terrígena. No geral, foi possível observar que o gradiente de temperatura da superfície do mar entre o Oceano Atlântico Norte e o Atlântico Sul parece desempenhar um papel importante desencadeando ou amplificando as mudanças climáticas observados nos trópicos. Este dipolo de temperatura pode ocasionar mudanças na posição da Zona de Convergência Intertropical e no regime de ventos predominantes, que por sua vez irão influenciar, direta e indiretamente, nas mudanças na circulação marinha de superfície e no regime de chuvas da região.Geochemical proxies (n-alkanes, alkenones, GDGTs, δ13C, Fe / Ca and Ti / Ca) were used to evaluate the paleoclimatic and paleoceanographic changes in the Continental Shelf of São Sebastião during the Late Holocene. The age model, obtained through the combined analyses of 210Pb and 14C methods, indicated that the core used in this study covers the last 1500 years. Variations in the sea surface temperature may be related to changes in the prevailing winds, which in turn are responsible for an increase or reduction in the frequency of the upwelling events. Changes in subsurface temperature values can be related to the presence of the South Atlantic Central Water near the coastal regions, and the mixing processes in the water column. Changes in mean air temperature (MAT), in turn, are probably related to fluctuations in total solar radiation, since periods represented by higher values of MAT correspond to the periods of maximum solar irradiation known as Medieval (1100-1250 AD) and Modern Maximum (1950 - present). While the period represented by the lower MAT values can be linked to the solar minimum period known as Spörer. The evaluation of terrigenous markers allowed the identification of variations in the drainage and continental erosion, which in turn are related to changes in the precipitation of the adjacent continent. Furthermore, the Medieval Climate Anomaly was characterized by a decrease in the terrigenous input, while the Little Ice Age could be characterized as a period of increased terrestrial contribution. Overall, it was observed that the sea surface temperature gradient between the North Atlantic and the South Atlantic Oceans appears to play an important role in triggering or amplifying climate change observed in the tropics. This temperature dipole can cause changes in the position of the Intertropical Convergence Zone and the direction of prevailing winds, which in turn will influence, directly and indirectly, the marine circulation and the rainfall.
50
Li, Xiaoyun, e 李瀟云. "Late quaternary climate and sedimentary history derived from N-alkanes, alkenones and bulk organic carbon analyses in Fujian coast, China". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/207998.
Testo completoAbstract (sommario):
Late Quaternary is an important period for paleoclimate study due to the boom of human civilization and thus its influence on climate conditions of the present interglacial period. In this study, a 52 m long borehole was drilled in a coastal embayment of Fujian, China, within which a thick marine layer from 16.05 to 32.60 m is found. Bulk organic geochemical analyses, containing total organic carbon content (TOC), carbon isotope ratio (δ13C), alkenones and n-alkanes, were analyzed for the whole core. Organic carbon isotope ratios (δ13C) of the sediment layers vary between -22.1‰ and -32.9‰, with higher values in the two marine sequences and lower in the two aquatic sequences. In the thick marine sequence, the δ13C is relatively stable, and it becomes gradually enriched from the base upwards and depleted rapidly at the top, indicating a full cycle of marine transgression and regression. The n-alkanes exhibit a similar trend, with several indexes, i.e., maximum concentration (Cmax), carbon preference index (CPI), average chain length (ACL), terrestrial-aquatic ratio (TAR), Paq and C31/(C29+C31). These results suggest the control of EAM and sea-level change in the sedimentary processes. Analysis on alkenones shows sea surface temperature (SST) variations as well as sea-level oscillations in the study site.published_or_final_version
Earth Sciences
Master
Master of Philosophy