No description available.

Coupled atmosphere-ocean general circulation models are the simplest models which are capable of simulating both the variability which occurs within each component of the climate system, and the variability which arises from the interactions between them. Only recently has it become computationally feasible to use coupled general circulation models to study climate variability and change on timescales of O(104) years and longer. Flux adjustments are often employed to maintain a control climate that is both stable and realistic; however, the magnitude of the adjustments represents a source of concern. This study employs the CSIRO Mk3L climate system model, a low-resolution coupled atmosphere-sea ice-ocean general circulation model. The atmospheric and oceanic components are spun up independently; the resulting atmospheric simulation is realistic, while the deep ocean is too cold, too fresh and too buoyant. The spin-up runs provide the initial conditions for the coupled model, which is used to conduct a 1400-year control simulation for pre-industrial conditions. After some initial adjustment, the simulated climate experiences minimal drift. The dominant mode of internal variability is found to exhibit the same spatial structure and correlations as the observed El Ni˜no-Southern Oscillation phenomenon. The ability of Mk3L to simulate the climate of the mid-Holocene is evaluated. It correctly simulates increased summer temperatures at northern mid-latitudes, and cooling in the tropics. However, it is unable to capture some of the regional-scale features of the mid-Holocene climate, with the precipitation over northern Africa being deficient. The model simulates a 13% reduction in the strength of El Ni˜no, a much smaller decrease than that implied by the palaeoclimate record. A 1400-year transient simulation is then conducted, in which the atmospheric CO2 concentration is stabilised at three times the pre-industrial value. The transient simulation exhibits a reduction in the rate of North Atlantic Deep Water formation, followed by its gradual recovery, and a cessation of Antarctic Bottom Water formation. The global-mean surface air temperature warms 2.7◦C upon a trebling of CO2, and 5.3◦C by the end of the simulation. A number of modifications to the spin-up procedure for the ocean model are evaluated. A phase shift in the prescribed sea surface temperatures and salinities is found to reduce the phase lag between the model and observations, and to lead to a reduction in the magnitude of the diagnosed flux adjustments. When this spin-up run is used to initialise the coupled model, the reduced flux adjustments are found to have negligible impact upon the nature of the internal variability. While the flux adjustments are not found to have any direct influence upon the response of the model to external forcing, they are found to have an indirect influence via their effect upon the rate of drift within the control simulation. An iterative spin-up technique is also developed, whereby the response of the ocean model is used to derive a set of effective surface tracers. These result in a much more realistic vertical density profile within the ocean. The coupled model exhibits slightly increased internal variability, with reduced convection within the ocean. There is a slightly greater surface warming in response to an increase in the atmospheric CO2 concentration, with the reduced convection resulting in slower penetration of the surface warming to depth.

Rapidly rising levels of atmospheric greenhouse gases including carbon dioxide and methane since the industrial revolution have drawn scientific attention to the importance of the global carbon cycle to the climate (Cubasch et al., 2013). Tropical peatlands, the majority of which are located in the Indonesian region, are a major source of uncertainty in the carbon cycle as the relationships between carbon accumulation and hydrological changes remain poorly understood (Hergoualc’h & Verchot, 2011, Page et al., 2011). An important driver of carbon emissions in tropical peatlands is fire, which in the Indonesian region is strongly influenced on interannual timescales by the El Niño/Southern Oscillation (ENSO). However, it is not clear how ENSO and fire have varied at decadal to centennial scales over the past two millennia. This thesis explores long term tropical hydrological variability and ENSO-like climate change from palaeorecords and their interactions with fire. Using a wide range of instrumental, proxy and model datasets and a novel reconstruction method, two separate reconstructions of long-term ENSO-like climate change are produced based on precipitation and temperature data. These show no evidence of a difference between the ENSO-like behaviour of precipitation and temperature. There is limited evidence for a difference in long-term ENSO-like state between the Medieval Climate Anomaly and the Little Ice Age. Reconstructions of hydrological variability and biomass burning in the Indonesian region suggest that precipitation and fire have been positively correlated over the past 2,000 years, which is contrary to the modern-day relationship on ENSO timescales. This throws up questions of long-term versus short-term interactions and feedbacks between fire, climate and vegetation. It is likely that anthropogenic activity in the Indonesian region has significantly altered the stability of the fire regime. Further research combining proxy data, climate and fire models, and using more robust statistical analysis is necessary to untangle the natural and anthropogenic driving factors at different time resolutions.

No description available.

<p>The main aims of this project were to contribute to the knowledge about tropical climate variations, and to investigate the possibilities of obtaining cosmic ray influx data from stalagmites.</p><p>Stalagmites from Tanzania and northern South Africa were palaeoclimatologically analysed.</p><p>U-series dating, combined with previously published 14C-data (Goslar et al. 2000), shows that one of the Tanzanian stalagmites was precipitated during the latter half of the latest glacial, between approximately 39 and 27 ka. Results from stable isotope analysis (δ13C and δ18O) were interpreted as indicating millennial-scale fluctuations in atmospheric CO2-level during that time. These fluctuations show a pattern which is similar to that of the δ18O records from the GRIP and Byrd ice-cores – suggesting that the stalagmite record captures a global climate signal.</p><p>U-series dating shows that the largest of the South African stalagmites covers most of the last 25 ka. The δ13C- and δ18O-data indicate millennial-scale variation in the South African climate throughout the time of the formation of this stalagmite. Because of similarities to Antarctic records (Steig et al. 2000), the driving force for these variations was suggested to be atmospheric circulation changes associated with change in the Southern Hemisphere circumpolar westerly wind vortex. Like the Tanzanian results, these South African data lend further support to the theory about global persistent millennial-scale climate-fluctuations.</p><p>A beryllium isotope study was then performed on the two stalagmites described above. This study assesses, for the first time, the potential of the cosmogenic isotope 10Be as a tool in stalagmite studies. As a control, 9Be-analysis was also made on each 10Be-sample.</p><p>The aim of the study was to test the idea that stalagmites could be a new source of well-dated and directly climate-proxy synchronized information about past variations in cosmic ray influx intensity – i.e., a source that would serve as a new tool for general improvement of the knowledge about past variations in cosmic ray influx, and that could possibly also provide further clues to whether such variations can affect Earth’s climate.</p><p>The main excursions/fluctuations in the 10Be-and 9Be-data from these stalagmites do not coincide. Hence, the excursions in 10Be-content may be interpreted as indicating excursions in cosmic ray influx. The 10Be-data show three pronounced peaks at around 38, 35 and 21 ka respectively; plausibly corresponding to the peaks previously observed at approximately 39, 32 and 23 ka in cosmogenic isotope data from sediments and ice.</p><p>In glacial parts of the stalagmite material, the 9Be-concentration fluctuates on a millennial-scale; inversely synchronized with fluctuations in δ13C-data from the same material. This indicates that 9Be could, apart from being a necessary control for 10Be-results, also function as a palaeoclimatological proxy in stalagmite studies.</p><p>In order to improve dating facilities for stalagmites, a procedure for high-precision measurements of U and Th isotope ratios was also developed, using an IsoProbe® Multi Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS). The 230Th/232Th ratio for the thorium concentration-standard Alfa Th was determined to 7.96 (±0.012) × 10-7 (2σ), and the δ234U obtained for the uranium standard SRM950a was 18.4 ±0.6(2σ). The thorium results show, that even extremely biased isotope ratios, in low-concentration samples, can be measured with remarkably good precision. The quality of each sample measurement can also easily be evaluated. However, due to repeated technical problems with the instrument, it has not yet been possible to use the developed procedure for routine analysis and dating of samples.</p>

The main aims of this project were to contribute to the knowledge about tropical climate variations, and to investigate the possibilities of obtaining cosmic ray influx data from stalagmites. Stalagmites from Tanzania and northern South Africa were palaeoclimatologically analysed. U-series dating, combined with previously published 14C-data (Goslar et al. 2000), shows that one of the Tanzanian stalagmites was precipitated during the latter half of the latest glacial, between approximately 39 and 27 ka. Results from stable isotope analysis (δ13C and δ18O) were interpreted as indicating millennial-scale fluctuations in atmospheric CO2-level during that time. These fluctuations show a pattern which is similar to that of the δ18O records from the GRIP and Byrd ice-cores – suggesting that the stalagmite record captures a global climate signal. U-series dating shows that the largest of the South African stalagmites covers most of the last 25 ka. The δ13C- and δ18O-data indicate millennial-scale variation in the South African climate throughout the time of the formation of this stalagmite. Because of similarities to Antarctic records (Steig et al. 2000), the driving force for these variations was suggested to be atmospheric circulation changes associated with change in the Southern Hemisphere circumpolar westerly wind vortex. Like the Tanzanian results, these South African data lend further support to the theory about global persistent millennial-scale climate-fluctuations. A beryllium isotope study was then performed on the two stalagmites described above. This study assesses, for the first time, the potential of the cosmogenic isotope 10Be as a tool in stalagmite studies. As a control, 9Be-analysis was also made on each 10Be-sample. The aim of the study was to test the idea that stalagmites could be a new source of well-dated and directly climate-proxy synchronized information about past variations in cosmic ray influx intensity – i.e., a source that would serve as a new tool for general improvement of the knowledge about past variations in cosmic ray influx, and that could possibly also provide further clues to whether such variations can affect Earth’s climate. The main excursions/fluctuations in the 10Be-and 9Be-data from these stalagmites do not coincide. Hence, the excursions in 10Be-content may be interpreted as indicating excursions in cosmic ray influx. The 10Be-data show three pronounced peaks at around 38, 35 and 21 ka respectively; plausibly corresponding to the peaks previously observed at approximately 39, 32 and 23 ka in cosmogenic isotope data from sediments and ice. In glacial parts of the stalagmite material, the 9Be-concentration fluctuates on a millennial-scale; inversely synchronized with fluctuations in δ13C-data from the same material. This indicates that 9Be could, apart from being a necessary control for 10Be-results, also function as a palaeoclimatological proxy in stalagmite studies. In order to improve dating facilities for stalagmites, a procedure for high-precision measurements of U and Th isotope ratios was also developed, using an IsoProbe® Multi Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS). The 230Th/232Th ratio for the thorium concentration-standard Alfa Th was determined to 7.96 (±0.012) × 10-7 (2σ), and the δ234U obtained for the uranium standard SRM950a was 18.4 ±0.6(2σ). The thorium results show, that even extremely biased isotope ratios, in low-concentration samples, can be measured with remarkably good precision. The quality of each sample measurement can also easily be evaluated. However, due to repeated technical problems with the instrument, it has not yet been possible to use the developed procedure for routine analysis and dating of samples.

This thesis demonstrates some of the potential of Libocedrus bidwillii Hook. f. (Kaikawaka) for dendroclimatological research by developing tree-ring chronologies and then using these chronologies to reconstruct palaeoclimates. In order to assist with the modelling of tree-growth and climate relationships (response function analysis), the annual nature of Libocedrus bidwillii growth was investigated. Results showed that seedlings of Libocedrus bidwillii were sensitive to temperature and soil moisture. Greatest growth was at high soil moisture and under a variable temperature regime. It was also found that there was an obvious seasonal variation in the growth of the seedlings. Such information allowed some confidence in the use of the species as a proxy-climatic indicator. Twenty-three tree-ring chronologies were developed from different areas of New Zealand. These included 12 new sites, 5 sites collected by other people but then updated and 6 sites that were not updated. Standardisation of the tree-ring series from each site used double detrending methods - ERH+SP67% (linear-Exponential or linear Regression or a Horizontal detrending plus SPline detrending fitted to 2/3 the length of the tree-ring series). This meant some long-term trends in the data were retained (i. e. greater than 120 year cycles) although this led to some reduction of the strength of the common signal in the chronology as measured by EPS (Expressed Population Signal) and SNR (Signal of Noise Ratio). The retention of long-term trends in the chronologies was thought to be important because some low frequency signals, which are longer than 120 years, are present in the climate data. Autocorrelation in the chronologies was removed by the ARSTAN program using the Aikaike Information Criterion (AIC) to determine the filter model. No significant autocorrelations were left in the residual chronologies produced by this method. Inter-comparison of the chronologies showed a highly consistent and significant pattern between most of the sites. There was little reduction in inter-chronology correlation with separation distance. However, there was a difference, or an effect, due to altitude. In general the response functions for the relationship between climate variables and ring-width in any given growing season showed a negative relationship between temperature for the prior growth months February, March and current December, while there was a positive response to temperature in September and February. There were three significant negative coefficients (previous March, April and August) and one positive (current February) for precipitation. The results of using principal component analysis (PCA) showed that all the 27 significant response function analyses could be divided into four groups. The response pattern in the four groups was similar for temperature but the rainfall response was more variable. The climate reconstructions were based on two groups of chronologies: eleven chronologies from all over New Zealand and a subset of only the three longest chronologies. Comparison of the climate data of different seasons with the two groups of chronologies was carried out using the "bootstrap" transfer function. The average February-March temperature and total March-April precipitation were finally selected as the reconstructed variables. Both of the groups reconstructed the hot years better than the cold years. The reconstructed temperature series were similar to all the earlier New Zealand dendroclimatic reconstructions. The warming and cooling periods, extremely warm and extremely cold years were identified and compared with some other sources of evidence and found to be highly consistent. This led to the conclusion that Libocedrus bidwillii is very useful as a high resolution palaeotemperature indicator. In the precipitation reconstruction, all the periodicities (both high and low) in the observed data were reconstructed. The dry and wet periods, severe drought and very wet years were identified in both precipitation reconstructions and also compared with other more limited sources of evidence.

The separation of natural and anthropogenically caused climatic changes is an important task of contemporary climate research. For this purpose, a detailed knowledge of the natural variability of the climate during warm stages is a necessary prerequisite. Beside model simulations and historical documents, this knowledge is mostly derived from analyses of so-called climatic proxy data like tree rings or sediment as well as ice cores. In order to be able to appropriately interpret such sources of palaeoclimatic information, suitable approaches of statistical modelling as well as methods of time series analysis are necessary, which are applicable to short, noisy, and non-stationary uni- and multivariate data sets. Correlations between different climatic proxy data within one or more climatological archives contain significant information about the climatic change on longer time scales. Based on an appropriate statistical decomposition of such multivariate time series, one may estimate dimensions in terms of the number of significant, linear independent components of the considered data set. In the presented work, a corresponding approach is introduced, critically discussed, and extended with respect to the analysis of palaeoclimatic time series. Temporal variations of the resulting measures allow to derive information about climatic changes. For an example of trace element abundances and grain-size distributions obtained near the Cape Roberts (Eastern Antarctica), it is shown that the variability of the dimensions of the investigated data sets clearly correlates with the Oligocene/Miocene transition about 24 million years before present as well as regional deglaciation events. Grain-size distributions in sediments give information about the predominance of different transportation as well as deposition mechanisms. Finite mixture models may be used to approximate the corresponding distribution functions appropriately. In order to give a complete description of the statistical uncertainty of the parameter estimates in such models, the concept of asymptotic uncertainty distributions is introduced. The relationship with the mutual component overlap as well as with the information missing due to grouping and truncation of the measured data is discussed for a particular geological example. An analysis of a sequence of grain-size distributions obtained in Lake Baikal reveals that there are certain problems accompanying the application of finite mixture models, which cause an extended climatological interpretation of the results to fail. As an appropriate alternative, a linear principal component analysis is used to decompose the data set into suitable fractions whose temporal variability correlates well with the variations of the average solar insolation on millenial to multi-millenial time scales. The abundance of coarse-grained material is obviously related to the annual snow cover, whereas a significant fraction of fine-grained sediments is likely transported from the Taklamakan desert via dust storms in the spring season. / Die Separation natürlicher und anthropogen verursachter Klimaänderungen ist eine bedeutende Aufgabe der heutigen Klimaforschung. Hierzu ist eine detaillierte Kenntnis der natürlichen Klimavariabilität während Warmzeiten unerlässlich. Neben Modellsimulationen und historischen Aufzeichnungen spielt hierfür die Analyse von sogenannten Klima-Stellvertreterdaten eine besondere Rolle, die anhand von Archiven wie Baumringen oder Sediment- und Eisbohrkernen erhoben werden. Um solche Quellen paläoklimatischer Informationen vernünftig interpretieren zu können, werden geeignete statistische Modellierungsansätze sowie Methoden der Zeitreihenanalyse benötigt, die insbesondere auf kurze, verrauschte und instationäre uni- und multivariate Datensätze anwendbar sind. Korrelationen zwischen verschiedenen Stellvertreterdaten eines oder mehrerer klimatologischer Archive enthalten wesentliche Informationen über den Klimawandel auf großen Zeitskalen. Auf der Basis einer geeigneten Zerlegung solcher multivariater Zeitreihen lassen sich Dimensionen schätzen als die Zahl der signifikanten, linear unabhängigen Komponenten des Datensatzes. Ein entsprechender Ansatz wird in der vorliegenden Arbeit vorgestellt, kritisch diskutiert und im Hinblick auf die Analyse von paläoklimatischen Zeitreihen weiterentwickelt. Zeitliche Variationen der entsprechenden Maße erlauben Rückschlüsse auf klimatische Veränderungen. Am Beispiel von Elementhäufigkeiten und Korngrößenverteilungen des Cape-Roberts-Gebietes in der Ostantarktis wird gezeigt, dass die Variabilität der Dimension der untersuchten Datensätze klar mit dem Übergang vom Oligozän zum Miozän vor etwa 24 Millionen Jahren sowie regionalen Abschmelzereignissen korreliert. Korngrößenverteilungen in Sedimenten erlauben Rückschlüsse auf die Dominanz verschiedenen Transport- und Ablagerungsmechanismen. Mit Hilfe von Finite-Mixture-Modellen lassen sich gemessene Verteilungsfunktionen geeignet approximieren. Um die statistische Unsicherheit der Parameterschätzung in solchen Modellen umfassend zu beschreiben, wird das Konzept der asymptotischen Unsicherheitsverteilungen eingeführt. Der Zusammenhang mit dem Überlapp der einzelnen Komponenten und aufgrund des Abschneidens und Binnens der gemessenen Daten verloren gehenden Informationen wird anhand eines geologischen Beispiels diskutiert. Die Analyse einer Sequenz von Korngrößenverteilungen aus dem Baikalsee zeigt, dass bei der Anwendung von Finite-Mixture-Modellen bestimmte Probleme auftreten, die eine umfassende klimatische Interpretation der Ergebnisse verhindern. Stattdessen wird eine lineare Hauptkomponentenanalyse verwendet, um den Datensatz in geeignete Fraktionen zu zerlegen, deren zeitliche Variabilität stark mit den Schwankungen der mittleren Sonneneinstrahlung auf der Zeitskala von Jahrtausenden bis Jahrzehntausenden korreliert. Die Häufigkeit von grobkörnigem Material hängt offenbar mit der jährlichen Schneebedeckung zusammen, während feinkörniges Material möglicherweise zu einem bestimmten Anteil durch Frühjahrsstürme aus der Taklamakan-Wüste herantransportiert wird.

This thesis focuses on reconstructing past temperatures using Scots pine (Pinus sylvestris L.) tree-ring chronologies developed from Scotland. The research aims to fill a spatial and temporal gap in understanding northwest European climate dynamics, thus providing the context for assessing future climate changes in this region. Development of both a spatially complete reconstruction from an extensive network of 44 'living' Scottish tree-ring chronologies for the last few centuries, but also a near-millennium length chronology from central Scotland using mainly lake-derived 'subfossil' wood material was undertaken. Before reconstruction development, a combination of treegrowth modelling and disturbance removal methodologies was utilised in order to understand the drivers of pine growth in the Scottish Highlands, and to assess and remove anthropogenic disturbance and other non-climatic influences on growth. The advantages and limitations of utilising the relatively new 'Blue Intensity' (BI) parameter was also explored and assessed, particularly in relation to its possible utilization as a more affordable surrogate for maximum latewood density in the development of temperature reconstructions and for crossdating validation of undated samples. Although BI showed much promise for dendroclimatology, elimination of low frequency biases resulting from sample discolouration still requires further attention. Chronologies from the Cairngorms in central Scotland were identified as most suitable for reconstruction development, while reconstructions based on chronologies from other areas in the west were found to be weaker due to a range of factors including disturbance. In order to maximise reconstruction strength, BI and ring width (RW) data were combined to produce composite high-frequency BI / low-frequency RW chronologies. Although it was possible to develop an ~800 year reconstruction of temperature from central Scotland, there is substantial potential to further extend this reconstruction back in time.

Les causes du refroidissement climatique global qui caractérisent le Crétacé supérieur (~100 – 65 Ma) ne sont pas encore bien établies. L’évolution de la courbe des températures des eaux de fond et de surface des océans montre une accélération de ce refroidissement au cours du Campanien (~84 Ma), aussi l’objectif de ce travail était-il d’explorer les causes possibles de ce refroidissement en se focalisant sur l’étude des sédiments d’âge Campanien de divers bassins sédimentaires téthysiens, boréaux et atlantiques.Le premier objectif fut de déterminer l’extension spatiale des changements de cortèges argileux dans la Téthys et le domaine boréal. La minéralogie des argiles de plusieurs sites (hémi)pélagiques, sélectionnés selon un transect N-S de 5 à 45° N, a révélé une intensification de l’altération continentale au Campanien, marquée notamment par des apports accrus de kaolinite. Au cours du temps, ces apports liés au soulèvement de nouveaux domaines continentaux semblent se propager du Sud au Nord. Cette propagation est très certainement gouvernée par le mouvement antihoraire de la plaque africaine et de son rapprochement progressif de la plaque européenne. L’intensification de l’altération continentale semble aussi s’accompagner de la mise en place d’une ceinture climatique plus humide à l’origine du développement des bauxites.Le Campanien est également marqué par d’importantes modifications paléogéographiques, telles que l’élargissement de l’Atlantique Sud et Nord ainsi que la restriction du domaine téthysien. Le déplacement des masses continentales est probablement à l’origine d’une réorganisation majeure des courants océaniques. Dans le domaine téthysien, au Crétacé supérieur la courantologie est dominée par le « Tethyan Circumglobal Current » (TCC), courant latitudinal traversant l’océan téthysien et le passage des Caraïbes, d’est en ouest, qui semblerait s’intensifier au Campanien. Nous avons donc tenté de reconstituer l’évolution de la circulation profonde du TCC au cours du Crétacé supérieur, grâce une approche fondée sur les isotopes du néodyme (Nd). L’évolution de l’ɛNd des eaux de fond locales de trois sites (hémi)pélagiques situés sur le trajet potentiel de ce courant a été analysé à partir de la fraction carbonatée des sédiments : la coupe de Shahneshin à l’entrée du corridor téthysien (bassin du Zagros, Iran), la coupe de Gubbio – la Bottaccione dans la Téthys centrale (bassin des Marches – Ombrie, Italie) et le forage DSDP Site 146 dans le passage des Caraïbes (bassin du Venezuela, mer des Caraïbes). L’ɛNd de la fraction résiduelle des sédiments a également été déterminée, afin de discuter l’impact potentiel des échanges locaux eau-sédiments. L’évolution de l’ɛNd des eaux de fond locales, couplée à la minéralogie des argiles et à celle de l’ɛNd des résidus a révélé que les signatures minéralogiques et géochimiques des sites de Shahneshin et 146 semblent être affectées de façon significative par des processus locaux (tectonique, volcanisme). Une augmentation de l’écart entre l’ɛNd de l’eau de fond locale et des résidus est cependant compatible avec des apports accrus d’eaux du Pacifique dans l’est de la Téthys au cours du Campanien. Le site de Gubbio semble quant à lui recevoir des apports d’eaux atlantiques en profondeur, suggérant que si le TCC est présent dans cette région, il n’atteint pas la base de la colonne d’eau au niveau de ce site. / The origin of the Late Cretaceous (~100 – 65 Ma) global cooling is not yet well understood. The evolution of sea surface and bottom temperatures shows an acceleration of the cooling during the Campanian stage (~84 Ma). The main goal of this study was to explore the processes driving this cooling, focusing on Campanian sediments from the Tethyan, Boreal and Atlantic realms.The clay mineralogical assemblages of several (hemi)pelagic sites, selected along a S-N transect, from 5° to 45°N, reveal an increase in continental weathering during the Campanian, expressed by enhanced kaolinite inputs. The detrital input related to the uplift of new continental areas seems to evolve from south to north. This propagation is likely linked to the anticlockwise rotation of the African plate and the progressive closure to the Tethys Ocean. Enhanced continental weathering seems also linked to more hydrolysing conditions in the studied regions, resulting in bauxite development.The Campanian stage was characterised by major palaeogeographic changes, such as the widening of south and north Atlantic oceans and the closure of the Tethyan realm. The motion of continental plates is likely responsible for a major reorganization of the oceanic currents. During the Late Cretaceous, the so called “Tethyan Circumglobal Current” (TCC) current flows latitudinally through the Tethyan Ocean to the Caribbean gateway, from east to west, and seems to intensify during the Campanian stage. Thus, we tried to reconstruct the evolution of the deep oceanic circulation within the TCC pathway during the Late Cretaceous, based on a geochemical approach using the neodymium (Nd) isotopes. The evolution of ɛNd of local bottom water of three (hemi)pelagic sites located on the possible pathway of this current has been analysed on the carbonate fraction of the sediments : the Shahneshin section located at the main entrance of the Tethyan passage (Zagros basin, Iran), the Gubbio – la Bottaccione section located at the centre of the Tethys (Umbria – Marche basin, Italy) ocean and the DSDP site 146 located in the Caribbean gateway (Venezuela basin, Caribbean sea). The ɛNd of the insoluble fraction of the sediments was analysed, in order to discuss of the role of local exchanges between water and sediments. The evolution of the deep water ɛNd along with that of residue ɛNd and clay mineralogical assemblages shows that geochemical and mineralogical signatures of Shahneshin and 146 sites are largely controlled by local processes (tectonic and volcanism), although an increased input of radiogenic Pacific waters may be detected at Shahneshin during the Campanian. The Gubbio site seems to be influenced by atlantic waters entering western Tethys, suggesting that the TCC did not reach the base of the water column at this site.