Suchergebnisse

Archives and Proxies along the PEP III Transect -- Oceanic Climate Variability at Millennial Time-Scales: Models of Climate Connections -- Between Agulhas and Benguela: responses of Southern African climates of the Late Pleistocene to Current Fluxes, Orbital Precession and the Extent of the Circum-Antarctic Vortex -- Holocene climatic trends and rhythms in southern Africa -- Diatom productivity in Northern Lake Malawi during the past 25,000 years: implications for the Position of the Intertropical Convergence Zone at Millennial and Shorter Time Scales -- Late Quaternary climatic variability in intertropical Africa -- Decadal and century-scale climate variability in tropical Africa during the past 2000 years -- Late Quaternary climate changes in the Horn of Africa -- Palaeoenvironments, palaeoclimates and landscape development in Atlantic Equatorial Africa: a review of key sites covering the last 25 kyrs -- Aspects of Nigerian coastal vegetation in the Holocene: some recent insights -- Palaeoenvironmental changes in the arid and sub arid belt (Sahara-Sahel-Arabian Peninsula) from 150 kyr to present -- Historical chronology of ENSO and the Nile flood record -- Groundwater as an archive of climatic and environmental change: Europe to Africa -- Mediterranean Sea palaeohydrology and pluvial periods during the Late Quaternary -- Palaeoenvironmental changes in the Mediterranean region 250-10 kyr BP -- Holocene climate, environment and cultural change in the circum-Mediterranean region -- Speleothems as palaeoclimate indicators, a case study from Soreq Cave located in the Eastern Mediterranean Region, Israel -- Climatic and environmental variability in the Mid-Latitude Europe sector during the last interglacial-glacial cycle -- Atlantic to Urals – the Holocene climatic record of Mid-Latitude Europe -- Climate variability during the last interglacial-glacial cycle in NW Eurasia -- Holocene climate dynamics in Fennoscandia and the North Atlantic -- Recent developments in Holocene climate modelling -- Evaluation of PMIP coupled ocean-atmosphere simulations of the Mid-Holocene -- Famine, climate and crisis in Western Uganda -- Palaeo-research in Africa: relevance to sustainable environmental management and significance for the future -- Climate Variability in Europe and Africa: a PAGES-PEP III Time Stream I Synthesis -- Climate Variability in Europe and Africa: a PAGES-PEP III Time Stream II Synthesis.

Planktonic foraminifer oxygen isotopes through MIS 12 were analysed from Ocean Drilling Program Site 977 in the Alboran Sea. After the correction of the sea surface temperature (SST) effect on the δ18O composition of foraminiferal calcite, the resulting seawater δ18O (δ18Ow) was used to reconstruct variations in the δ18Ow of the Atlantic inflow into the Mediterranean. A synchronous record from the KC01B core, in the Ionian Sea, was used to evaluate changes in the oxygen isotope gradient within the Mediterranean due to hydrological variations during MIS 12. Instead of the glacial δ18Ow enrichment expected for the Mediterranean, lower values than today have been observed both in the Alboran and the Ionian seas, especially between 455 ka and the end of MIS 12 (424 ka). These negative oxygen isotope anomalies must have been caused by a flux of freshwater to the Mediterranean during MIS 12. Although the largest fraction of the freshwater anomalies entered the Mediterranean through the Atlantic inflow, especially during Heinrich stadials, the Mediterranean δ18Ow gradient allowed us to identify other sources of freshwater to the eastern basin. One of these sources was probably the meltwater generated at the southern margin of the Fennoscandian ice-sheet that entered via the Caspian and Black seas. However, the proximity of core KC01B to the Adriatic Sea points to meltwater delivered from the Alpine ice-sheet and transported through the Po river into the Mediterranean as the main cause of the Ionian Sea 18O depletions. ; This work was funded by the FPU contract of the Ministry of Education and Professional Formation FPU2015/03283 awarded to Lucia A. Azibeiro and project RTI 2018-099489-B-100 of the Ministry of Science, innovation and Universities of the Spain government granted to the Grupo de Geociencias Oceánicas (GGO) of the University of Salamanca. The Spanish Ministry of Science and Innovation, Severo Ochoa Project CEX2018-000794-S is likewise acknowledged. We are very grateful to IODP for providing the samples used in this study and appreciate the work of Jose Ignacio Martin Cruz in the picking of planktonic foraminifers for isotope analyses and Marta Casado, Yolanda Gonzalez-Quinteiro, Bibiano Hortelano, Walter Hale and Inma Fernandez for laboratory assistance. We thank the scientific data provided by Samuel Toucanne. The authors thank Philip Hughes and other anonymous reviewer for their constructive comments and suggestions. ; Peer reviewed

El cambio climático es un tema de gran interés en todo el mundo debido a sus graves consecuencias ambientales, agrícolas, hidrológicas y socioeconómicas. La región de Levante, como parte del Mediterráneo oriental, se considera una región particularmente vulnerable al cambio climático actual y futuro, también afectada por otros factores del desarrollo, como la escasez de agua, la fatiga de las infraestructuras, los conflictos políticos y étnicos, el crecimiento de la población y la creciente demanda de agua, alimentos y energía, que exacerban las implicaciones del cambio climático. Además, existe una falta de cooperación e intercambio de datos climáticos entre los países de la región, así como una falta de cooperación para hacer frente a los impactos del cambio climático en la región. Hasta el momento, no se cuenta con estudios previos en la literatura que evalúen los cambios y variabilidad en la temperatura máxima (Tmax) y mínima (Tmin), rango de temperatura diurna (DTR), precipitación, índices de temperatura y precipitación extrema, y sequía en toda la región de Levante (Siria, Líbano, Jordania, Palestina e Israel), utilizando datos climáticos obtenidos a partir de estaciones meteorológicas. La mayoría de los estudios climáticos en el Levante se limitan a áreas o países específicos, principalmente sobre Israel, y analizan la variabilidad climática y/o el cambio climático únicamente en términos de valores medios a partir de datos que presentan baja cobertura espacial y temporal. Por lo tanto, esta tesis tiene como objetivo el análisis de la variabilidad climática en la región de Levante a distintas escalas temporales, analizando y estableciendo las relaciones entre el clima de la región y los patrones de circulación a gran escala, con el objetivo de comprender mejor los mecanismos causales de dicha variabilidad climática. Así, esta tesis llena un vacío real en los estudios climáticos en esta región crítica del mundo, puesto que es el primer estudio de este tipo que se centra en el clima del Levante en su conjunto, utilizando la mayor cantidad de datos climáticos recopilados hasta ahora y analizando un conjunto completo de variables climáticas. Por tanto, los resultados de esta tesis podrían servir como base científica para cualquier futuro esfuerzo conjunto de los países levantinos para combatir el cambio climático a través de una estrategia científica unificada. La tesis se divide en diez capítulos. Los primeros tres capítulos presentan en detalle los objetivos, las características geográficas y climáticas del área de estudio, los datos brutos, los métodos de control de calidad de los datos, y la metodología aplicada en este trabajo. La temperatura, los índices de temperatura extrema, la precipitación y los índices de precipitación extrema, así como sus relaciones con los patrones de circulación a gran escala, se examinan en múltiples escalas de tiempo en los Capítulos 4-7. El capítulo 8 se ha dedicado al análisis de covariabilidad entre la temperatura y la precipitación estacionales en el Levante y los patrones generales de la SST y la SLP. En el capítulo 9 se realiza un análisis detallado de las sequías, estudiando sus características y su relación con los patrones de circulación a gran escala, la SST y la SLP. Cada capítulo del 4 al 9 consta de tres secciones: introducción, resultados, conclusiones y discusión. Finalmente, las principales conclusiones alcanzadas en esta tesis se resumen en el Capítulo 10. ; Climate change is a topic of great interest around the world because it has serious environmental, agricultural, hydrological, and socio-economic consequences. The Levant region, as a part of the East Mediterranean, is considered a region particularly vulnerable to current and future climate change, which also occurs in the context of other developmental stresses, such as water scarcity, fatigue infrastructure, and frequent drought events. Furthermore, political and ethnic conflicts, population growth, and increasing demand for water, food, and energy all exacerbate the implications of climate change. Additionally, there is a lack of cooperation and sharing of climate data among the region's countries, as well as a lack of cooperation in dealing with potential climate changes in the region. There have been no previous studies or comparisons in the literature assessing changes and variability in maximum (Tmax) and minimum (Tmin) temperatures, diurnal temperature range (DTR), precipitation, extreme temperature and precipitation indices, and drought in the entire Levant region (Syria, Lebanon, Jordan, Palestine, and Israel), using climatic data from ground stations. The majority of climate studies in the Levant are limited to specific areas or countries, primarily over Israel. Most of them measured climate change in terms of mean values, with low spatial and temporal coverage. Thus, it is essential to study and investigate the climate variability in the Levant region at multiple time and space scales. The thesis aims to uncover and establish the relationships between climate variability and the most important climate indicators such as large-scale circulation patterns, Sea Surface Temperature (SST), and Sea Level Pressure (SLP) indicators in the Mediterranean Sea and North Atlantic Ocean in order to, better understand the causal mechanisms of such climate variability. Besides, it also aims to identify the regions that are most vulnerable to drought, and assess the dry spells that affected this area and the current trends on multiple drought time scales. This thesis fills a real gap in climatic studies in this critical region of the world. It is the first study of its kind to focus on the climate of the Levant as a whole, using the largest amount of climate data ever collected. It does not focus on a single climate variable, but rather analyzes a number of them. For the first time, data have been compiled and long, homogeneous and quality-controlled climatic time series have been obtained for temperatures and precipitation, covering as many meteorological stations as possible in the Levant. Finally, this thesis serves as the scientific foundation for any future joint efforts by Levantine countries to combat climate change through a unified scientific strategy. The following thesis is divided into ten chapters. The first three chapters discuss and present in detail the objectives, geographic and climatic features of the study area, the raw data, data quality control methods, handling missing values, outliers, homogenization of data sets, and methodology applied in this work. Temperature, extreme temperature indices, precipitation, and extreme precipitation indices as well as their relationships with the large-scale circulation patterns are examined at multiple time scales in Chapters 4-7, respectively. Chapter 8 has been devoted to covariability analysis between the seasonal temperature and precipitation in the Levant and the general patterns of the SST and SLP. In Chapter 9, droughts have been analyzed, studying their characteristics, and its relationship with large-scale circulation patterns, SST and SLP. Each chapter from 4 to 9 consists of three sections, introduction, results, conclusions and discussion. Finally, the main conclusions reached in this thesis are summarized in Chapter 10. ; Tesis Univ. Granada.

Southern Ocean, South Atlantic, Scotia Sea, diatom, Late Quaternary, Last Glacial, Holocene, sea surface temperature, sea ice, ash layer. - Climate variability of the late Quaternary, especially the Last Glacial (LG) to the Holocene, has become the most heated topic for the recent decades, which helps to better understand the shape of current and future climate on our planet. The millennial scale variations are mostly accepted to be modulated by the bipolar seesaw mechanism which redistributes heat between the northern and southern hemispheres through the Atlantic Meridional Overturning Circulation (AMOC). The validation of such hypothesis is hampered by the very limited high resolution records from the high latitudes Southern Ocean. This PhD project generated a series of new diatom based high resolution marine records covering wide area of the high latitudes South Atlantic, including from the Bouvet Island area and the Scotia Sea, aimed to provide new insights of the response and drive in Southern Ocean in the context of late Quaternary global climate change. A regional age model for the past 30 kyrs is established by AMS 14C dating and regional core correlation for the Southern Ocean Atlantic and western Indian sectors, and detailed climate variability has been reconstructed, mainly driven by the changes in AMOC and the status of the Western Antarctic Ice Sheet. The Scotia Stratigraphy of the past 300 kyrs has been established, the changes in stratigraphic parameters are closely related to the changes in surrounding environment; a possible correlation of the Scotia Sea ash layers and those of Antarctic ice core is established.

This book provides an updated overview of the processes determining the influence of solar forcing on climate. It discusses in particular the most recent developments regarding the role of aerosols in the climate system and the new insights that could be gained from the investigation of terrestrial climate analogues. The book's structure mirrors that of the ISSI workshop held in Bern in June 2005.