Diatom analysis performed on sediment profiles from several localities provided information on past changes in the aquatic environment related to climatic and artificial shifts since the Last Glacial-Interglacial Transition. The practicality of diatom analysis from fish guts of three European fish species in palaeolimnological studies was tested.

Indiana University-Purdue University Indianapolis (IUPUI) / Paleoproductivity records during the late Pleistocene are sparse. The equatorial Pacific and the Southern Ocean are collectively responsible for the majority of the new production in the oceans. The nutrient and carbon mass balances of these regions must be constrained in order to fully understand net global biological productivity on glacial timescales. The geochemistry of two east-central equatorial Pacific Ocean cores (02° 33.48 N; 117° 55.06 W) and (00° 15.42 S; 113° 00.57 W) are used to examine changes in biological productivity due to nutrient upwelling on glacial timescales during the Pleistocene. The cores were recovered in March 2006 on the AMAT03 cruise, a site survey cruise for IODP Proposal 626. The total concentrations of Ca, Ti, Fe, Al, P, Ba, S, Mg, Sr, Zn and Mn were determined by a total sediment digestion followed by analysis by inductively coupled plasma-atomic emission spectrometry (ICP). Original solid forms of P for 34 evenly spaced samples throughout one core were determined using the P Sequential Extraction technique. This study is attempting to compare upwelling and productivity records by determining temporal records of nutrient proxies, using Latimer and Filippelli (2006) which focused on the Southern Ocean. Equatorial upwelling and Southern Ocean upwelling both appear to exhibit strong glacial timescale variability. The P geochemistry results indicate that the P signal is largely biological. The equatorial Pacific evidence, in accordance with Southern Ocean patterns, supports a nutrient budget-driven productivity signal over time. Gabriel M. Filippelli, Ph. D, Committee Chair

<p>Tephrochronology, or the dating and correlation of stratigraphic sediment sequences by the use of tephra, is a dating method that has been much refined in the last decade. This refinement has enabled the detection of cryptotephra, which has expanded the known distribution of different tephras. At the site Lake Mulakullegöl in the southwest of Sweden, three distinct tephra horizons have been detected, of which two have been geochemically identified. The identified tephras are the Vedde Ash (ca 12,000 cal. yrs BP) and the Hässeldalen Tephra (ca 11,500 cal. yrs BP), both of Icelandic origin. These tephras were deposited during the middle of the Younger Dryas Stadial and the Younger Dryas/Preboreal transition, respectively. The Vedde Ash is one of the most widespread tephras of Icelandic provenance, while the Hässeldalen Tephra so far only has been found at two sites in southeastern Sweden, prior to the current study. A third, unidentified, tephra was also detected. Based on the stratigraphic position, this tephra might be the Borrobol Tephra, which has been dated to ca 14,400 cal. yrs BP. This might indicate that warming had not yet occurred in this part of Sweden. The extended known distribution of especially the Hässeldalen Tephra, but also the Vedde Ash, has enabled a higher potential for correlations between different records deposited during the Last Glacial/Interglacial transition.</p>

Tephrochronology, or the dating and correlation of stratigraphic sediment sequences by the use of tephra, is a dating method that has been much refined in the last decade. This refinement has enabled the detection of cryptotephra, which has expanded the known distribution of different tephras. At the site Lake Mulakullegöl in the southwest of Sweden, three distinct tephra horizons have been detected, of which two have been geochemically identified. The identified tephras are the Vedde Ash (ca 12,000 cal. yrs BP) and the Hässeldalen Tephra (ca 11,500 cal. yrs BP), both of Icelandic origin. These tephras were deposited during the middle of the Younger Dryas Stadial and the Younger Dryas/Preboreal transition, respectively. The Vedde Ash is one of the most widespread tephras of Icelandic provenance, while the Hässeldalen Tephra so far only has been found at two sites in southeastern Sweden, prior to the current study. A third, unidentified, tephra was also detected. Based on the stratigraphic position, this tephra might be the Borrobol Tephra, which has been dated to ca 14,400 cal. yrs BP. This might indicate that warming had not yet occurred in this part of Sweden. The extended known distribution of especially the Hässeldalen Tephra, but also the Vedde Ash, has enabled a higher potential for correlations between different records deposited during the Last Glacial/Interglacial transition.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2017-08-16T16:46:32Z No. of bitstreams: 1 Mega, A. M..pdf: 4299230 bytes, checksum: 4ff04b898e1e7eebe891e2a5a4dfcd98 (MD5) / Made available in DSpace on 2017-08-16T16:46:32Z (GMT). No. of bitstreams: 1 Mega, A. M..pdf: 4299230 bytes, checksum: 4ff04b898e1e7eebe891e2a5a4dfcd98 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / Os oceanos funcionam como um reservatório natural de carbono, no qual sua solubilidade na superfície dos oceanos varia de acordo com a temperatura. Antes do período industrial, as variações na concentração de CO2 atmosférico estavam fortemente associadas às transições glacial-interglacial (G-IG), onde os menores valores de CO2 na atmosfera foram registrados nos períodos glaciais, decorrente do aumento da solubilidade do CO2 nos oceanos. Nesses períodos, o aumento da solubilidade do CO2 na coluna d’água estimulou a produção de íons carbonato, beneficiando organismos que calcificam carbonato de cálcio (CaCO3) em suas conchas e esqueletos. O processo inverso, ou seja, menor solubilidade do CO2 e, consequentemente, menor disponibilidade de íons carbonatos nos oceanos marcou os períodos interglaciais. O presente estudo teve como objetivo avaliar os efeitos das variações no peso-normalizado pelo tamanho (do inglês, size-normalized weight, SNW) de foraminíferos planctônicos durante os últimos 70.000 anos no Sudoeste do Atlântico visando compreender os efeitos da calcificação e/ou dissolução do carbonato e da microestrutura das testas de foraminíferos planctônicos que viviam na porção superior da coluna d'água (G. ruber-white e G. sacculifer-sem saco). Para tanto, foi utilizado um testemunho coletado na Bacia de Santos a 2225 m de profundidade, que compreende os últimos 185 mil anos, dos quais os primeiros 70 mil anos foram estudados. Os resultados mostraram que ambas as espécies apresentaram um aumento do SNW na transição entre os períodos G-IG, associado com indícios de dissolução nas testas do período glacial, quando observada a microestrutura. Esses resultados demonstram a ação corrosiva das águas de fundo durante os glaciais e diferem dos obtidos em outros estudos realizados no Atlântico Norte que registram características menos corrosivas durante o último glacial em profundidades de até 3500 metros. A redução no peso das testas durante o período glacial foi atribuída à ação da dissolução dos carbonatos. A dissolução pode ocorrer abaixo da camada denominada lisoclina, porém apesar da grande mudança na profundidade da lisoclina durante os glaciais no Atlântico Sul, o testemunho, ainda assim, estaria 800 m acima da influência da lisoclina. Acima da lisoclina, a dissolução dos carbonatos pode ocorrer por diversos outros fatores, tais como pelo aumento da geração de CO2 pela atividade bentônica durante eventos de aumento de produtividade. Essa atividade bentônica tornaria a camada da interface água-sedimento corrosiva às estruturas carbonáticas. Nesse sentido, foram registrados no testemunho estudado um aumento nos teores de sílica e ferro, nutrientes que poderiam estimular um aumento da produtividade primaria, o que se refletiria nos altos níveis de carbono orgânico também registrados no testemunho durante o período glacial, estimulando, assim, a atividade bentônica. Outra possibilidade que explicaria a dissolução observada é decorrente de mudança na geometria das massas d’água durante os glaciais, o qual promoveria o contato do sedimento com massas d’água Antárticas (Águas de Fundo Antárticas-AFA), que são mais corrosivas. Entretanto, estudos anteriores realizados com o mesmo testemunho e baseados em isótopos de neodímio não corroboram a ocorrência de mudanças na geometria das massas d’água na região, pelo menos para os últimos 25 mil anos. / Oceans work as a natural reservoir of carbon, where the solubility in the surface varies with temperature. Before the industrial period, variations in the atmospheric CO2 concentration were strongly associated with the glacial-interglacial (G-IG) transitions, where the lowest atmosphere CO2 values were recorded in the glacial periods, due to the increase in the CO2 solubility. In these periods, the increase of the CO2 solubility in the water column stimulated the production of carbonate ions, benefiting organisms that calcify calcium carbonate (CaCO3) in their shells. The inverse process, that is, the lower CO2 solubility and, consequently, lower carbonate ions availability in the oceans marked the interglacial periods. The objective of this study was to evaluate the effects of size-normalized weight during the last 70.000 years in the Southwest Atlantic to understand the effects of calcification and/or dissolution of carbonate and microstructure analysis of the Planktonic foraminifera that lived in the upper portion of the water column (G. ruber-white) and G. sacculifer). For that, a core collected in the Santos Basin at 2225 m depth was used, which includes the last 185 thousand years, of which the first 70 thousand years were studied. The results showed that both species showed an increase in SNW at the transition between the G-IG periods, associated with evidence of dissolution in the glacial period, when the microstructure was observed. These results demonstrate the corrosive action of the bottom waters during the glaciers and differ from those obtained in other studies conducted in the North Atlantic that record less corrosive characteristics during the last glacial in depths of up to 3500 meters. The reduction in the weight of the shells during the glacial period was attributed to the action of the carbonate dissolution. The dissolution may occur below the lysoclin layer, but despite the large change in lysoclin depth during the glaciers in the South Atlantic, the corer would still be 800 m above the influence of lysoclin. Above lysoclin, the carbonate dissolution can occur due to several other factors, such as the increase of CO2 generation by benthic activity during productivity increase events. This benthic activity would make the water-sediment interface layer corrosive to carbonate structures. In this sense, an increase in silica and iron contents was recorded in the studied corer, nutrients which could stimulate an increase in primary productivity, which would be reflected in the high levels of organic carbon also recorded in the corer during the glacial period, stimulating benthic activity. Another possibility that would explain the observed dissolution is due to a change in the geometry of the water masses during the glaciers, which would promote the contact of the sediment with Antarctic water masses (Antarctic Bottom Water-ABW), which are more corrosive. However, previous studies carried out with the same evidence and based on neodymium isotopes do not corroborate the occurrence of changes in the geometry of water masses in the region, at least 25 ka years

Afin d’étudier les variations climatiques enregistrées par les carottes de glace, il est nécessaire d’avoir des datations précises à la fois pour les phases gaz et glace. Le but de ce travail de thèse a été d’améliorer les chronologies des carottes de glace, couvrant les derniers 800 000 ans, au travers de nouvelles mesures de la composition isotopique de l’air (δ15N, δ18Oatm et δO2/N2) piégé dans la glace d’EPICA Dôme C (EDC) et de l’utilisation de l’outil de datation "Datice". Le premier résultat important de cette thèse a été la production de la chronologie cohérente pour les carottes de glace ("Antarctic Ice Core Chronology", AICC2012) pour EDC, Vostok, EPICA Droning Maud Land (EDML), TALos Dôme ICE core (TALDICE) et NorthGRIP. Sur cette nouvelle chronologie la théorie du see-saw bipolaire reste valable. AICC2012 donne un âge pour la Terminaison II en accord avec les autres archives climatiques. De plus, les durées des périodes interglaciaires restent inchangées par rapport à la chronologie EDC3. Lors de la construction d’AICC2012 nous avons mis en évidence plusieurs points nécessitant des améliorations. Nous avons donc procédé à l’amélioration de Datice dans le but d’intégrer correctement les contraintes issues du comptage des couches annuelles et leurs erreurs. Ces améliorations conduisent à des chronologies cohérentes tout en respectant les hypothèses sous-jacentes à Datice. Nous proposons aussi une nouvelle formulation de l’erreur associée à la fonction d’amincissement à partir de l’analyse des propriétés mécaniques de la glace dans le cas d’EDC. Pour finir, les nouvelles mesures du δO2/N2 et du δ18Oatm effectuées sur de la glace bien conservée d’EDC nous ont permis de définir de nouvelles contraintes d’âge. La comparaison de ces traceurs mesurés à Vostok, EDC et Dôme F sur le MIS 5 a permis de mettre en évidence une possible influence de paramètres climatiques locaux sur le δO2/N2. L’analyse du retard entre le δ18Oatm et la précession sur les derniers 800 ka montre des variations de ce dernier. Nous suggérons que ce retard est augmenté par l’occurence d’évènements de Heinrich à certaines périodes. Les résultats de cette thèse sont à prendre en compte pour le prochain exercice de datation cohérente pour les carottes de glace. / In order to study the climate variations recorded by ice cores, it is necessary to have precise chronologies for the ice and gas phases. The aim of this work has been to improve ice cores chronologies, covering the last 800 000 years, through new measurements of the isotopic composition of the air δ15N, δ18Oatm et δO2/N2) trapped in EPICA Dome C (EDC) ice core and the use of the Datice dating tool.The first important result of this PhD has been the production of the Antarctic Ice Core Chronology (AICC2012), common for EDC, Vostok, EPICA Droning Maud Land (EDML), TALos Dome ICE core (TALDICE) and NorthGRIP ice cores. The bipolar see-saw theory is still valid on the new chronology. The AICC2012 chronology gives an age for Termination II in good agreement with other climate archives. Moreover, the duration of interglacial periods is unchanged compared to EDC3. While building the AICC2012 chronology, we have pointed out several limitations. Since then, we have improved Datice in order to correctly integrate constraints deduced from layer counting and their associated uncertainties. These improvements permit to build coherent chronologies respecting the underlying hypotheses of Datice. Moreover, we propose a new parameterization of the uncertainty associated with the background thinning function based on ice mechanical properties of EDC ice core. Finally, we were able to deduce new age constraints thanks to the new measurements of δO2/N2 and δ18Oatm performed on well-conserved ice from EDC. A multi-proxy comparison of Vostok, EDC and Dome F ice cores over MIS 5 has highlighted a possible influence of local climatic parameters on δO2/N2. The analysis of the delay between δ18Oatm and precession shows some variability over the last 800 ka. We propose that the delay between δ18Oatm and precession is increased during periods associated with Heinrich events. The results obtained during this PhD should be used for the next ice core coherent chronology.

Cette thèse a pour but de reconstituer le climat des 100 000 dernières années en Europe de l’ouest. L’étude du climat du passé permet de mieux comprendre la variabilité naturelle du climat sur laquelle se surimpose aujourd’hui le réchauffement climatique d’origine anthropique. Ce sont des molécules fossiles bactériennes dont la structure varie en fonction des conditions environnementales qui ont permis dans cette étude de reconstituer le paléoclimat à partir des sédiments du lac St Front dans le Massif Central. Les indices dérivés de ces molécules révèlent la variabilité climatique à long terme mais également les évènements rapides de changement climatique ainsi qu’une forte action anthropique en surimposition des changements climatiques régionaux sur les 5000 dernières années. Ce travail montre l’importance de la compréhension de l’outil utilisé et du fonctionnement du système naturel dans lequel il est étudié, préalables indispensables à l’obtention d’une séquence climatique crédible / This thesis aims to reconstruct the climate of the last 100,000 years in western Europe. The study of past climate allows to better understand the natural variability of climate on which human-induced global warming is superimposed today. Bacterial fossil molecules whose structure varies according to the environmental conditions were used in this study to reconstruct the paleoclimate from the sediments of lake St Front in the Massif Central. The indices derived from these molecules reveal the long-term climatic variability but also the rapid events of climate change as well as a strong anthropogenic action in superimposition of the regional climatic changes over the last 5000 years. This work shows the importance of understanding the tool used and the functioning of the natural system in which it is studied, essential prerequisites for obtaining a credible climate reconstruction

Variability in the tropical ocean-atmospheric system causes global scale climate anomalies, most evident in the El Niño-Southern Oscillation’s coupled climate feedbacks. Despite being an area of high interest, many questions still remain regarding the west Pacific warm pool’s response to external forcing, particularly its response to increases in anthropogenic greenhouse gases. Paleoclimate reconstructions coupled with model simulations provide insight into the tropical Pacific’s role in past climate variability necessary to the development of robust climate projections. Most paleoclimate records, however, still lack the resolution, length, and chronological control to resolve rapid variability against a background of orbital-scale variations. Here we present stalagmite oxygen isotope (δ18O) reconstructions from Gunung Mulu National Park (4oN, 115oE ), in northern Borneo, that provide reproducible centennial-scale records of western Pacific hydrologic variability that are precisely U/Th-dated and continuous throughout most of the late Pleistocene (0-160 thousand years ago, kybp). The record comprises an entire glacial-interglacial cycle, which allows us to investigate orbital-scale climate forcings and compare two well-dated glacial terminations in the western tropical Pacific. The ice- volume-corrected δ18O records suggest that glacial boundary condtions, which include significantly lower atmospheric carbon dioxide levels, did not drive significant changes in Mulu rainfall δ18O. Similarly, Borneo stalagmite δ18O is poorly correlated to either global sea level shifts or Sunda Shelf areal exposure is not evident. The Borneo record does vary in phase with local mid-fall equatorial insolation, suggesting that precessional forcing may impart a strong influence on hydroclimate variability in the warm pool. This is best illustrated across Glacial Termination II, when the oscillation of equatorial fall insolation is large and out of phase with ice sheet decay. We also use a subset of well-dated, high-resolution stalagmite δ18O records from Mulu to investigate millennial-scale climate variability during Marine Isotope Stages 3-5 (30-100kybp). We find that regional convection likely decreased during the six massive iceberg discharges defined in the North Atlantic sediment records (“Heinrich events”). The inferred drying (increased stalagmite δ18O) during Heinrich events is consistent with a southward shift of the Intertropical Convergence Zone – the dominant paradigm to explain global climate anomalies originating in the north Atlantic (ref). However, any hydrologic variability related to Dansgaad-Oeschgar (D/O) events, millennial-scale sawtooth temperature anomalies of the last glacial period first evident in the Greenland ice records, is notably absent in the stalagmite records. . The Mulu stalagmite record’s absence of D/O signal, however, is in marked contrast to the regional west Pacific marine records and suggests D/O events and Heinrich events may be characterized by fundamentally different climate mechanisms and feedbacks.

La variabilité du système climatique influence la productivité et la distribution des espèces marines sur toutes les échelles de temps, de la variabilité saisonnière et inter-annuelle aux cycles glaciaires-interglaciaires. Mais ces liens entre climat et écosystèmes marins sont encore largement méconnus, de telle sorte que les prévisions des changements à venir sont difficiles. De plus, parce que les indicateurs paléoclimatiques issus des archives marines sont souvent liés au fonctionnement de l’écosystème, cette méconnaissance limite la fiabilité de la reconstruction de la variabilité climatique passée.Ce travail de thèse vise à améliorer notre connaissance de ces liens entre climat et écosystèmes marins : nous nous sommes intéressés aux changements de productivité marine au cours du dernier cycle glaciaire-interglaciaire, et nous nous sommes aussi penchés sur la réponse de l’écosystème, incluant l'ensemble des niveaux de la chaine trophique, à la variabilité inter-annuelle à décennale en climat pré-industriel. Ce travail est basé sur l’utilisation d’un modèle climatique (IPSL-CM), d’un modèle de biogéochimie marine (PISCES) et d’un modèle de niveaux trophiques supérieurs (APECOSM).Dans un premier temps, nous montrons que le lien entre l’intensité de la mousson indienne et la productivité primaire marine, en été boréal dans la mer d’Arabie, n’est pas direct. En effet, il apparait indispensable pour comprendre les changements de productivité de considérer, en plus de l'intensité de la mousson, la structure de la mousson. En particulier, la position du Jet de Findlater par rapport à la côte de la péninsule arabique est un paramètre important puisqu'elle conditionne la dynamique d'Ekman dans la région.Dans un second temps, nous avons étudié les variations de la productivité marine au large de l'embouchure du fleuve Congo et leurs liens avec le fleuve et les changements de dynamique atmosphérique africaine. Ce travail a mis en évidence que la relation entre l'intensité de la mousson et l'intensité des alizés, souvent utilisée dans les reconstructions climatiques, n'est pas toujours vérifiée. Selon le climat étudié, l'importance des effets thermiques ou dynamiques sur les changements de précipitations et de vents simulés est différente.Dans un troisième temps, nous avons étudié l'effet de la variabilité inter-annuelle sur les changements de productivité passés et sur le signal climatique potentiellement enregistré par des indicateurs climatiques biologiques.Enfin, la dernière partie de cette thèse se focalise sur la réponse des organismes marins des haut-niveaux trophiques à la variabilité climatique à différentes fréquences. Ce travail a révélé que les organismes marins répondent de façons différentes aux variations environnementales en fonction de leur taille et de leur habitat. / Climate variability influences marine primary productivity and marine species distribution over all timescales, from seasonal to interannual variability and glacial-interglacial cycles. The links between climate and marine ecosystems are still sparsely known so that the predictions of futur changes are difficult. Moreover, because paleoclimate recorders extracted from marine archives are often linked to the functionning of the ecosystem, this lack of knowledge limits our ability to reconstruct past climate variability.This thesis work aims at improving our knowledge of these links between climate and marine ecosystems : we have looked into marine productivity changes during the last glacial-interglacial cycle, but we also examined the "end-to-end" ecosystem response to inter-annual to decadal variability in a pre-industrial climate. This work uses a climate model (IPSL-CM), a bio-geochemical model (PISCES) and a model of high trophic levels (APECOSM).First, we show that the link between Indian summer monsoon intensity and marine primary productivity in the Arabian Sea is indirect. Indeed, it appears necessary to consider the monsoon pattern, such as the Findlater Jet position, which drives the Ekman dynamics in the region, as well as its intensity to understand the productivity changes.Second, we study the marine productivity changes off the Congo river mouth and their links with the river runoff and the African atmospheric dynamics. This work shows that the relationship between monsoon intensity and trade winds intensity, often used to reconstruct past changes, is not always verified. Depending on the climate, thermal or dynamical effects are more or less prominent drivers of the simulated changes in precipitation and winds. Productivity off the Congo river mouth, which is mainly located in the subsurface, seems more affected by the ocean and atmosphere dynamics than by the river supply in nutrients.Third, we study the inter-annual variability effects over past productivity changes and over the climatic signal potentially recorded in the biological climate proxies.Finally, the last part of the thesis focuses on high trophic levels marine organisms response to climate variability at different frequencies. This study shows that marine organisms response to environmental changes varies with the organism' size and habitat.

Aquesta Tesi Doctoral està centrada en la reconstrucció de les condicions climàtiques del passat a la conca occidental del Mediterrani, i més concretament en l’estudi de l’efecte de la variabilitat climàtica d’escala orbital i mil•lenària sobre les condicions oceanogràfiques de la conca. El treball es basa en l’anàlisi i interpretació de dades de indicadors sedimentològics, com ara la mida de gra i la composició elemental dels sediments, d’on s’ha obtingut informació sobre els canvis en les aportacions terrígenes induïts per la variabilitat climàtica i oceanogràfica de la conca, reflectida en canvis del nivell del mar o de la circulació termohalina. Hom ha pogut investigar els canvis del nivell del mar associats als cicles glacials mitjançant l’estudi de les variacions en la mida de gra de les partícules sedimentàries i en la composició elemental d’un testimoni del marge progradant del Golf de Lleó. Les variacions eustàtiques del nivell del mar han determinat l’apilament d’unitats sedimentaries regressives en el talús superior amb una ciclicitat de 100 ka. Els canvis en el nivell del mar han modulat la sedimentació en el marge, la qual va oscil•lar entre aportacions principalment fluvials durant els períodes glacials coincidint amb nivells del mar baixos, i aportacions degudes a la reactivació de processos erosius a la plataforma continental com les Cascades d’Aigües Denses de Plataforma durant les èpoques amb nivell del mar alt corresponents als períodes interglacials. L’estudi de l’Estadi Isotòpic Marí 3, entre 65 i 20 ka, caracteritzat per condicions climàtiques fluctuants de escala mil•lenària, ens hauria d’ajudar a entendre com el clima es comporta sota condicions canviants ràpides i per lo tant pot ser clau per entendre millor el ràpid canvi climàtic induït per l’ésser humà. Les variacions de la mida de gra durant aquest període en el marge del Golf de Lleó han revelat per primera vegada l’existència d’oscil•lacions del nivell del mar d’escala mil•lenària associades a la variabilitat climàtica dels cicles de Dansgaard-Oeschger observats a l’Atlàntic Nord. Nivells del mar relativament alts s’associen a les fases càlides dels cicles de Dansgaard-Oeschger. Aquests resultats mostren una ràpida resposta dels casquets polars a la variabilitat climàtica ràpida del darrer període glacial. Resta per identificar, però, amb precisió el inici d’aquestes pujades del nivell del mar i la seva amplitud. La circulació termohalina del Mediterrani occidental també s’ha vist afectada per les oscil•lacions climàtiques dels cicles de Dansgaard-Oeschger durant l’Estadi Isotòpic Marí 3. Els resultats confirmen que la circulació profunda del Mediterrani occidental funcionà de manera asincrònica respecte a la Circulació de Retorn de l’Atlàntic Nord durant els cicles de Dansgaard-Oeschger. Aquest fet posa de manifest la rapidesa en la transmissió de la variabilitat climàtica entre latituds altes i intermèdies, probablement induïda per un mecanisme de teleconnexió atmosfèrica similar a l’actual Oscil•lació de l’Atlàntic Nord. Tot i així, la circulació profunda del Mediterrani occidental també fou modulada per canvis en la hidrologia de la conca. A l’Holocè hom ha identificat igualment una sèrie d’esdeveniments de curta durada de intensificació de la circulació termohalina, els quals mostren una ciclicitat d’uns 1000 anys. Hom ha pogut correlacionar aquest esdeveniments amb altres observats a l’Atlàntic Nord i en altres regions del planeta, fet que confirma que les reorganitzacions ràpides del sistema climàtic són també comuns en els períodes interglacials. / This PhD Thesis focuses on the reconstruction of past climatic conditions in the Western Mediterranean Basin, and more precisely on the study of the impact of climate variability at orbital and millennial time scales over oceanographic conditions. The work relies on the study of sedimentological proxies like grain-size and elemental geochemical composition of the sediments for unravelling the changes in terrigenous supplies led by oscillations in climate and oceanographic conditions, namely sea level fluctuations and changes in the termohaline circulation of the Western Mediterranean Sea. Sea level changes associated with glacial cycles have been investigated by analysing the oscillations in grain-size and geochemical composition of the sediment records from the progradational Gulf of Lion margin. Eustatic sea level oscillations have determined stacking of regressive progradational units in the upper slope following a 100 kyr cyclicity. Sea level fluctuations have modulated sediment accumulation over this margin, with a succession of periods dominated by high fluvial supplies, and periods characterized by the reactivation of erosive processes in the continental shelf such as Dense Shelf Water Cascading during glacial lowstands and interglacial highstands, respectively. The study of climate variability during Marine Isotope Stage 3, between 65 and 20 ka, characterized by rapid climate fluctuations of millennial time scales, may help us to understand how the climate behaves when undergoing rapid changes and therefore might also further increase our understanding of rapid, anthropogenic climate change. The high-resolution study of grain-size oscillations during Marine Isotopic Stage 3 in the Gulf of Lion margin has shown by the first time the occurrence of millennial scale sea level fluctuations associated with climate variability during the Dansgaard-Oeschger cycles identified in the North Atlantic region. Relative high sea level has been observed to occur during warm interstadials of the Dansgaard-Oeschger cycles. These results point to a rapid response of the ice sheets to climate variability during the last glacial period. However, the precise timing and the amplitude of these millennial-scale sea level rises are still to be determined. The termohaline circulation of the Western Mediterranean Sea has been affected by Dansgaard-Oeschger climate oscillations during Marine Isotopic Stage 3 too, as determined by the study carried out in the IMAGES core MD99-2343 offshore Minorca island. Our results show that during Dansgaard-Oeschger cycles the circulation of deep-water masses in the Western Mediterranean was not synchronized with the Atlantic Meridional Overturning Circulation. This confirms the rapid transmission of climate variability between high and mid-latitudes, likely induced by an atmospheric mechanism similar to the present-day North Atlantic Oscillation. Hydrological oscillations within the basin further modulated the termohaline circulation in the Western Mediterranean Sea. During the Holocene a series of short-lived events of enhanced deep-water circulation have been identified to occur with a cyclicity close to 1000 yr, which have been correlated to relatively cold periods recently recognized from the North Atlantic region and in other regions of the world. These results confirm that rapid reorganizations of the climate system usually ascribed to glacial stages are also a common feature during interglacial periods.