PALEOCLIMATOLOGY

Author: Ferrio Diaz Juan Pedro.
Year: 2004.
University: LLEIDA [www.udl.es].
Place of defense: E.T.S. d'Enginyeria Agrària (ETSEA).
Place of preparation: E.T.S. d'Enginyeria Agrària (ETSEA).

Summary: Title: Reconstruction of climatic conditions and cultivation in the past from isotopic analysis of remains archaeobotanical The emergence and progressive development of agriculture over the past 10,000 years has dramatically changed the social structure and population groups, as well as its regarding the environment. In fact, the adoption of agriculture may be the first example in the time of interplay between the environment and mankind. Hence reconstruct environmental conditions (climate of origin or due to human activity) that characterized this process is of great interest to try to understand their possible causes as well as to understand the long-term effects it has had on the agricultural economy the medium. The overall objective of this thesis is to develop new tools to reconstruct the climatic conditions and cultivation during the origin and spread of agriculture in prehistory. The proposed methodology is based on the study of plant remains (charred wood and seeds) that are routinely recovered in the excavation, with particular emphasis on the use of stable isotopes as paleoenvironmental indicator. The work can be divided into two big blocs. The first aims to set the climatic environment in which evolved agriculture, while the second focuses on characterizing the specific conditions of growth of cultivated species. The first block is aimed at the development of a methodology to quantify changes in aridity in the past, based on the isotopic analysis of coals of forest species. This requires a prior calibration with current materials, as well as an assessment of the effect of carbonization in the isotopic signal of wood. In the first chapter, was characterized climatic signal present in the carbon isotopic composition (d13C) of wood in Mediterranean conditions, using Pinus halepensis Mill. And Quercus ilex L. As reference species, finding that in both species it could relate primarily to the precipitation. In the second chapter, we studied the relationship between climate and the oxygen isotopic composition (d18O) for P. Halepensis, as well as differences in the isotopic signal (d13C and d18O) in the two major components of wood cellulose and lignin. It was found that the signal climate of d13C is equally present in cellulose and lignin, while for the d18O extracting cellulose is necessary to get a climate information, which prevents its application in charred material. Finally, a third chapter demonstrated how the carbonization, while significantly affects the d13C of wood, it does not remove the original climate signal, which can be retrieved through a simple correction, including carbon as a variable reference. Using this methodology are reconstructed changes in aridity occurred in the valleys of Cinca and Segre (Depression Ebro) for the past 4,000 years, noting greater water availability in recent millennia in relation to this. The second section focuses on describing different aspects of the conditions of culti 8 th in the 763 agriculture prehistoric, combining the analysis of d13C with morphometric measures in seeds cultivated species, mainly cereals. The fourth chapter provides a critical review of existing information on isotope traces archaeobotanical, proposing new approaches to maximize the information extractable from these data. It shows how the combination of analysis in cultured species and forest, as well as the comparison between crops, can help detect changes in the availability of water crops due to human action. The fifth chapter is developing a new methodology for estimating the weight of grain in grain grown in the past, from its size, and considering the effect of carbonization. This allows for the first time a direct comparison between the data obtained from the literature remains archaeobotanical and agronomy. Finally, the sixth chapter combines data obtained by the methods described in the three previous chapters to resolve the possible causes of changes in the size of grain observed in the valleys of Cinca and Segre for the past 4,000 years.

Author: LOPEZ MARTINEZ CONSTANCIA.
Year: 2005.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: Sala d'Actes del.
Place of preparation: EDIFICI D1 Campus NORD.

Summary: The last glacial abrupt climate episodes, known as Dansgaard/Oeschger (D/O) and Heinrich events (HE), were documented in ice, marine and continental deposits from different world regions, especially in the northern hemisphere. However, the triggering mechanisms and climatic impact of these rapid oscillations are still poorly understood. Most studies were centred in the northern and eastern North Atlantic and adjacent continents, whereas few works have involved western and central regions of subtropical North Atlantic. The aim of this Thesis is the study of the climate variability at millennial time-scale in the subtropical North Atlantic during the last glacial period (Marine Isotope Stage 3), in particular in the latitudinal band 30ºN-40ºN that has been much less studied. For this purpose, two marine cores located in western and central subtropical North Atlantic were analysed and compared with different paleoclimatic records obtained in nearby marine and ice cores. The study is using the organic molecules as source of information. Sea surface temperature records derived from the distribution of the C37 alkenones have been obtained in both studied cores. In addition, odd carbon numbered n-alkanes (C23-C33) and even carbon numbered n-alkan-1-ols (C20-C30) have been determined in the western North Atlantic sediments for the reconstruction of the inputs of continental organic material from North America. Comparison with other paleoclimatic records provided a general vision of the abrupt climatic and oceanographic changes that occurred in the subtropical North Atlantic. This approach has allowed the description of the hydrological changes in western and central regions between 60,000 years before present and the deglaciation. Additionally, changes in wind regime in the western region have been assessed for the period 30,000-60,000 years before present. The results from the subtropical North Atlantic show different behaviours of the various regions in response to the abrupt climate changes of the last glacial period. Western and eastern regions responded synchronously to the climatic variability of the high latitudes of the northern hemisphere but the central region responded to the climate changes of the southern hemisphere. This finding of signals from both hemispheres in the latitudinal band under study points to the subtropical North Atlantic as a key region for clarification of the mechanisms involved in the abrupt climate changes associated with the D/O and HE. In addition, the climate variability of the southern Iberian Peninsula has been examined in the context of the present Thesis. The pilot study integrated molecular biomarkers and fossil pollen from marine sediments. Palynological analyses were done in selected samples from a Mediterranean core during a three months stage in the Département de Géologie et Océanographie of the University of Bordeaux I. The results confirmed that the concentrations of both sporo-pollen and terrigenous biomarkers (n-alkanes and n-alkan-1-ols) responded to a common origin. On the other hand, sporo-pollen data showed that aeolian/fluvial transport efficiency was the main factor for the inputs of terrigenous material to the Alboran Sea in all of the climatic transitions studied, with the exception of MIS 3 interstadials, in which changes in the density vegetation cover were dominat.

Author: ALVAREZ GARCIA Ma. CARMEN.
Year: 2005.
University: SALAMANCA [www.usal.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The southeastern Pacific Ocean is a very interesting area under various viewpoints: atmospheric, oceanic, tectonic, economic, etc.. The dynamics of spin Subtropical both in the atmosphere and in the ocean, their interaction and impact on the status of ocean currents in the area, are already a matter of scientific interest, as well as the development and evolution of the two areas the most productive upwelling in the Pacific. At this point, science and economics intersect since the upwelling of Peru, is characterized by a high primary productivity that holds one of the largest fisheries in the world. Recently this interest has been heightened as a result of the attention aroused in society by climate change and the phenomenon of El Niño, and the extent that this phenomenon is having on the alteration of this source of wealth ocean. From the scientific point of view, the zone has been studied in other times low in the field of physics and climatology. Specifically, the ODP (Ocean Drilling Program) project to which belong the samples analyzed in this work, only available material 12 witnesses before this latest oceanographic campaign, which is relatively little information for studies of type paleoceanográfico. In an effort to remedy this situation is designing the campaign oceanographic 202 (Leg 202), of which two witnesses are studied in this work, the 1237 and 1238. The location of these witnesses under the upwelling of Peru (1237) and under the upwelling equatorial (1238) involves obtaining a privileged material for the study of the productivity of the southeast Pacific for the past 800 Ka. In this work, drawing on Paleoceanografía he meant to investigate fluctuations in the pattern of winds and ocean currents in the area. The Paleoceanografía is a Science of the Earth based on the analysis of marine sediments, reconstructs oceanographic conditions of the past (recent or remote), and in particular, the patterns of distribution of water bodies ocean currents and their associates. The evolution of these factors influencing changes or variations in climate and vice versa, and consequently it also regulates changes in biological systems. The analysis of marine sediments is carried out under the standpoint micropaleontológico and in particular by the group of cocolitofóridos, brown unicellular algae and planktonic reflecting changes in the first few meters of the water column where they live.

Author: FERRER CARRILLO MONTSERRAT.
Year: 2006.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: Sala d'actes del IIQAB-CSIC.
Place of preparation: EDIFICI D1 Campus NORD.

Summary: During the last decade, the scientific community has recognized the importance of the tropical regions in the dynamic processes that control the global climate change. These regions are considered probable triggers of the changes observed at higher latitudes. On the other hand, since the marine sediments located in tropical oceans are not under the direct influence of continental ice sheets formed during glacial periods, they provide a continuous record of the climatic variations in the Earth. However, it is not well understood what is the specific role of tropical regions for the climate changes at submillennial scale because of the great lack of studies at high resolution in these areas. In addition, ice core records from Antarctica and sea surface temperature recorded in several marine sediment cores from the Southern Hemisphere, show different climatic patterns and time leads when compared with the well-known variations in the Northern Hemisphere (Heinrich and Dansgaard-Oeschger events). To clarify the role of southern tropical regions in global climate change at submillennial scale, we have studied the distribution of marine and terrestrial biomarkers at high resolution in two marine sediment cores from the Indian Ocean. First, the gravity core MD98-2165 (9º39âS, 118º20âE, 2100 m water depth, 42.3 m long) which was collected in the South-east Indonesian region. This area is characterized by having the highest sea surface temperatures in the West Pacific Warm Pool and a high convective activity, both influencing the distribution of moisture over a large region of the earthâs surface. Second, the gravity core MD00-2374 (46º2âS, 96º29âE, 3320 m water depth, 42.46 m long), that was selected as a reference for mid-latitudes in the southern hemisphere and is strategically situated to evaluate the connections with tropical regions and with Antarctica in warm and cold periods, respectively. The observed distributions of terrestrial biomarkers (C23-C33 n-alkanes and C20-C32 n-alkan-1-ols) are typical of higher plant lipids that arrive to the ocean by aeolian transport. In both cores, the most abundant homologues are the C31 alkane and the C28 or C32 alkan-1-ol. During glacial periods, the C32 alkan-1-ol is the most important homologue, suggesting an expansion of C4 tropical plants associated to arid conditions. The carbon isotope composition of these lipids allows distinguishing between the different photosynthetic pathways and corroborates the possible origin of these lipids. The variations in the amount of these terrestrial biomarkers show a clear glacial-interglacial pattern. The higher concentrations are found during glacial periods in both cores, suggesting the occurrence of stronger wind regimes under glacial conditions than in the interglacials. This contrast is more evident in the subantarctic core, where the terrestrial biomarker record follows exactly the circumpolar wind pattern measured in the dust profile of the ice cores from Antarctica. In relation to marine biomarkers (C37 alkenones), in core MD98-2165 the profiles of algal lipids show maxima during glacial periods corresponding to the characteristic upwellings found in this region. The sea surface temperature calculated through the UKâ37 index shows a glacial-interglacial pattern with increases of 2-4ºC during the deglaciations. In core MD00-2374, the observed alkenone distribution does not reflect the sea surface temperature changes. However, the presence of the C37:4 alkenone can be used to estimate the fresh water inputs from the sea-ice melting and can be used as an indirect proxy of the northward advance of the Antarctic polar front.

Author: ROMERO VIANA LIDIA.
Year: 2006.
University: VALENCIA [www.uv.es].
Place of defense: FACULTAD DE MATEMÁTICAS.
Place of preparation: UNIVERSITAT DE VALÈNCIA.

Summary: Study paleolimnológico two lakes karstic: signal climate in the sediment rolling and variability of organisms fototróficos. This study paleolimnologico focuses on the analysis of the temporal variability of the community of primary producers next two lakes, Lake La Cruz and Langunillo of Tejo (Cuenca, Spain). It was felt that the photosynthetic pigments preserved in the sediments were the most appropriate biomarkers to draw the variability of photosynthetic organisms due to the specific taxonomic presented and knowledge on the transfer of the water column to sediment obtained in a pilot study sedimentation process for three annual cycles in Laguna de La Cruz. The multidimensional analysis of the stratigraphic profile of the different pigments showed the specific response of each system to different environmental factors during the past centuries. The detailed analysis of the sedimentary signal indicated that the Lagunillo of Tejo fluctuations in water level associated with variability hidroclimática have significantly influenced the composition of the community of primary producers. But in La Laguna de La Cruz, characterized by stability in the composition of the community of photosynthetic organisms, inferred changes in primary production appear to have been influenced by solar variability. On the other hand this study has shown that the sediment rolling Laguna de La Cruz was an excellent climate quantitative indicator. The results of the analysis calibration of the thickness of the sheets of calcite show that these thicknesses are mainly related to cumulative rainfall during the winter months presenting a highly significant correlation. The winter precipitation, in turn, showed a highly significant correlation with the rate of atmospheric North Atlantic Oscillation (ANO). Given this significant climatic connection, we use the laminated sediment of Laguna de La Cruz to rebuild annual winter rainfall since 1589 AD to the present. Analysis of the signal climate showed a mastery of non-stationary processes in the high frequencies suggesting that the connection between him and regional rainfall pattern NAO has not been stable over the past centuries and probably other circulation patterns have exercised their influence in the region.