Stable isotopes of water (18O, 2H) and their associated isotope fractionation during water-cycle ... more Stable isotopes of water (18O, 2H) and their associated isotope fractionation during water-cycle phase changes produce a natural labelling of the water cycle and can be efficiently use to study hydrological and climatic processes at the local, regional and global scales. Moreover, understanding the seasonal and inter-annualstable isotope behaviour in a lake system is a key for interpretingthe 18O data obtained from inorganic fractions of lake sediments in order to reconstruct past changes in local hydro-climatology. The natural mountain lake system, Aguelmam Azigza (32°58’N, 5°26’W, 1470 m asl), is located in the karstic Tabular Middle Atlas (Morocco), one of the most humid regions of Morocco, which can be seen as the “water tower” of the country. The regional climate receives alternative influences of Mediterranean, Atlantic and Saharan air masses. A lake monitoring has been implemented since October 2012 with a monthly water sampling (precipitation, lake, well and springs) for wa...
The relationship between surface sediment diatom assemblages and measured limnological variables ... more The relationship between surface sediment diatom assemblages and measured limnological variables in fifty eight lake samples from the south Bolivian Altiplano was examined by constructing a diatom-water chemistry dataset. Analysis of this dataset by canonical correspondence analysis revealed that salinity and ionic concentration accounted for a significant amount of the variation in the distribution of the diatom assemblages. Two methods
This paper provides a paleoenvironmental reconstruction of a Late Quaternary lagoon system in the... more This paper provides a paleoenvironmental reconstruction of a Late Quaternary lagoon system in the Jaguaruna region of Santa Catarina state, southern Brazil. Integrated results of bulk sedimentary organic matter characterization (d 13 C, d 15 N and C/N), microfossil (pollen and diatom) and grain-size analysis from three shallow cores ($2.5 m depth) allowed us to propose an evolving paleogeographic scenario in this coastal region for the last ca. 5500 cal a BP. The lagoonal system in this area was more extensive during the mid-Holocene than today, with a gradual and continuous lagoon-sea disconnection until the present. We add to the debate regarding relative sea-level (RSL) variations for the Brazilian coast during the Holocene and discuss the importance of sedimentary dynamics for interpreting changes in coastal ecosystems. The multi-proxy analysis suggests that changes in coastal ecosystems could be directly related to local sedimentary processes, which are not necessarily linked to RSL fluctuations and/or to climatic variations.
In 2009 the Alfred-Wegener-Institute organised an inter-laboratory comparison for analysing the o... more In 2009 the Alfred-Wegener-Institute organised an inter-laboratory comparison for analysing the oxygen isotope compositions of biogenic silica. The relationship of the oxygen isotope compositions of carbonate to climate-relevant parameters is widely utilized. However, challenges still exist in the use of biogenic silica. Problems arise during the sample preparation stage and during the isotopic analysis itself. The problems are commonly related to the removal of loosely bound exchangeable oxygen from the silica. Amorphous ...
A fossil hominin cranium was discovered in mid-Pliocene deltaic strata in the Godaya Valley of th... more A fossil hominin cranium was discovered in mid-Pliocene deltaic strata in the Godaya Valley of the northwestern Woranso-Mille study area in Ethiopia. Here we show that analyses of chemically correlated volcanic layers and the palaeomagnetic stratigraphy, combined with Bayesian modelling of dated tuffs, yield an age range of 3.804 ± 0.013 to 3.777 ± 0.014 million years old (1 s) for the deltaic strata and the fossils that they contain.
National audienceThe reduction in the surface area of Lake Chad from 25,000 to 4,000 km2 between ... more National audienceThe reduction in the surface area of Lake Chad from 25,000 to 4,000 km2 between 1972 and 1987, in connection with the great drought of the 1980s in the Sahel, had a major impact on the way of life of the riparian populations, although very low lake levels had already been observed several times during the 20th century. The assessment of the hydrological response of the Lake Chad watershed to climate variability is therefore a key issue in addressing the vulnerability of Sahelian populations. In this study, the levels of Lake Chad are reconstructed between 1851 and 2011 from climatic data (precipitation (P) and temperature (T)), by a lake model whose main forcing is the Chari-Logone flow (draining 85% of the inflows to the lake), itself simulated by a rain-flow model. The lake model and rain-flow model were previously adjusted over the period 1955-2011. The climatic series used (P, T) are obtained by the analogue method. This reconstitution method consists in particu...
International audienceNatural environmental changes may be reconstructed by studying lake sedimen... more International audienceNatural environmental changes may be reconstructed by studying lake sediments that record several climatic, hydrologic and environmental signatures. Such reconstructions must be based on a thorough knowledge of the current lake system conditions. According to this perspective, two karstic lakes in the Moroccan Middle Atlas, Aguelmam Azigza (32°58'N, 5°26'W, 1470 m absl) and Tiguelmamine (32°54'N, 5°21'W, 1650 m absl), have been the subject of hydrochemical and sedimentary investigations. Spatiotemporal monthly monitoring (since October 2012) of the physicochemical characteristics of waters (precipitation, lake, wells, springs and streams) shows that the waters of Azigza lake are alkaline (pH>8) with elevated contents of HCO3-, Ca 2+ and Mg 2+. The Aguelmam Azigza is a monomictic lake (with an overturn water during December to January) and indicates high sensitivity to seasonal climatic changes (temperature and precipitation) that control biog...
International audienceStable isotopes of water (18O, 2H) and their associated isotope fractionati... more International audienceStable isotopes of water (18O, 2H) and their associated isotope fractionation during water-cycle phase changes produce a natural labelling of the water cycle and can be efficiently use to study hydrological and climatic processes at the local, regional and global scales. Moreover, understanding the seasonal and inter-annualstable isotope behaviour in a lake system is a key for interpretingthe 18O data obtained from inorganic fractions of lake sediments in order to reconstruct past changes in local hydro-climatology. The natural mountain lake system, Aguelmam Azigza (32°58’N, 5°26’W, 1470 m asl), is located in the karstic Tabular Middle Atlas (Morocco), one of the most humid regions of Morocco, which can be seen as the “water tower” of the country. The regional climate receives alternative influences of Mediterranean, Atlantic and Saharan air masses. A lake monitoring has been implemented since October 2012 with a monthly water sampling (precipitation, lake, wel...
The copyright of individual parts of the supplement might differ from the CC-BY 3.0 licence. Supp... more The copyright of individual parts of the supplement might differ from the CC-BY 3.0 licence. Supplementary material References Data Localization Monitored period Number of data Lake state data processing strategy of use in our study Bader et al.
Hydrology and Earth System Sciences Discussions, 2010
We explore the reliability of large-scale climate variables, namely precipitation and temperature... more We explore the reliability of large-scale climate variables, namely precipitation and temperature, as inputs for a basin-lake hydrological model in central Argentina. We used data from two regions in NCEP/NCAR reanalyses and three regions from LMDZ model simulations forced with observed sea surface temperature (HadISST) for the last 50 years. Reanalyses data cover part of the geographical area of the Sali-Dulce Basin (region A) and a zone at lower latitudes (region B). The LMDZ selected regions represent the geographical area of the Sali-Dulce Basin (box A), and two areas outside of the basin at lower latitudes (boxes B and C). A statistical downscaling method is used to connect the large-scale climate variables inferred from LMDZ and the reanalyses, with the hydrological Soil Water Assessment Tool (SWAT) model in order to simulate the Rio Sali-Dulce discharge during 1950-2005. The SWAT simulations are then used to force the water balance of Laguna Mar Chiquita, which experienced an abrupt level rise in the 1970's attributed to the increase in Rio Sali-Dulce discharge. Despite that the lowstand in the 1970's is not well reproduced in either simulation, the key hydrological cycles in the lake level are accurately captured. Even though satisfying results are obtained with the SWAT simulations using downscaled reanalyses, the lake level are more realistically simulated with the SWAT simulations using downscaled LMDZ data in boxes B and C, showing a strong climate influence from the tropics on lake level fluctuations. Our results highlight the ability of downscaled climatic data to reproduce regional climate features. Laguna Mar Chiquita can therefore be considered as an integrator of large-scale climate changes since the forcing scenarios giving best results are those relying on global climate simulations forced with observed sea surface temperature. This climate-basin-lake model is a promising approach for understanding and simulating long-term lake level variations.
... The second group includes archives of the Patagonian climate, as well as the Salinas del Bebe... more ... The second group includes archives of the Patagonian climate, as well as the Salinas del Bebedero, and provides a record of past changes in the strength and latitudinal position of the Southern Westerlies. Keywords Pampean lakes · Late-Pleistocene/Holocene hydrological ...
Stable isotopes of water (18O, 2H) and their associated isotope fractionation during water-cycle ... more Stable isotopes of water (18O, 2H) and their associated isotope fractionation during water-cycle phase changes produce a natural labelling of the water cycle and can be efficiently use to study hydrological and climatic processes at the local, regional and global scales. Moreover, understanding the seasonal and inter-annualstable isotope behaviour in a lake system is a key for interpretingthe 18O data obtained from inorganic fractions of lake sediments in order to reconstruct past changes in local hydro-climatology. The natural mountain lake system, Aguelmam Azigza (32°58’N, 5°26’W, 1470 m asl), is located in the karstic Tabular Middle Atlas (Morocco), one of the most humid regions of Morocco, which can be seen as the “water tower” of the country. The regional climate receives alternative influences of Mediterranean, Atlantic and Saharan air masses. A lake monitoring has been implemented since October 2012 with a monthly water sampling (precipitation, lake, well and springs) for wa...
The relationship between surface sediment diatom assemblages and measured limnological variables ... more The relationship between surface sediment diatom assemblages and measured limnological variables in fifty eight lake samples from the south Bolivian Altiplano was examined by constructing a diatom-water chemistry dataset. Analysis of this dataset by canonical correspondence analysis revealed that salinity and ionic concentration accounted for a significant amount of the variation in the distribution of the diatom assemblages. Two methods
This paper provides a paleoenvironmental reconstruction of a Late Quaternary lagoon system in the... more This paper provides a paleoenvironmental reconstruction of a Late Quaternary lagoon system in the Jaguaruna region of Santa Catarina state, southern Brazil. Integrated results of bulk sedimentary organic matter characterization (d 13 C, d 15 N and C/N), microfossil (pollen and diatom) and grain-size analysis from three shallow cores ($2.5 m depth) allowed us to propose an evolving paleogeographic scenario in this coastal region for the last ca. 5500 cal a BP. The lagoonal system in this area was more extensive during the mid-Holocene than today, with a gradual and continuous lagoon-sea disconnection until the present. We add to the debate regarding relative sea-level (RSL) variations for the Brazilian coast during the Holocene and discuss the importance of sedimentary dynamics for interpreting changes in coastal ecosystems. The multi-proxy analysis suggests that changes in coastal ecosystems could be directly related to local sedimentary processes, which are not necessarily linked to RSL fluctuations and/or to climatic variations.
In 2009 the Alfred-Wegener-Institute organised an inter-laboratory comparison for analysing the o... more In 2009 the Alfred-Wegener-Institute organised an inter-laboratory comparison for analysing the oxygen isotope compositions of biogenic silica. The relationship of the oxygen isotope compositions of carbonate to climate-relevant parameters is widely utilized. However, challenges still exist in the use of biogenic silica. Problems arise during the sample preparation stage and during the isotopic analysis itself. The problems are commonly related to the removal of loosely bound exchangeable oxygen from the silica. Amorphous ...
A fossil hominin cranium was discovered in mid-Pliocene deltaic strata in the Godaya Valley of th... more A fossil hominin cranium was discovered in mid-Pliocene deltaic strata in the Godaya Valley of the northwestern Woranso-Mille study area in Ethiopia. Here we show that analyses of chemically correlated volcanic layers and the palaeomagnetic stratigraphy, combined with Bayesian modelling of dated tuffs, yield an age range of 3.804 ± 0.013 to 3.777 ± 0.014 million years old (1 s) for the deltaic strata and the fossils that they contain.
National audienceThe reduction in the surface area of Lake Chad from 25,000 to 4,000 km2 between ... more National audienceThe reduction in the surface area of Lake Chad from 25,000 to 4,000 km2 between 1972 and 1987, in connection with the great drought of the 1980s in the Sahel, had a major impact on the way of life of the riparian populations, although very low lake levels had already been observed several times during the 20th century. The assessment of the hydrological response of the Lake Chad watershed to climate variability is therefore a key issue in addressing the vulnerability of Sahelian populations. In this study, the levels of Lake Chad are reconstructed between 1851 and 2011 from climatic data (precipitation (P) and temperature (T)), by a lake model whose main forcing is the Chari-Logone flow (draining 85% of the inflows to the lake), itself simulated by a rain-flow model. The lake model and rain-flow model were previously adjusted over the period 1955-2011. The climatic series used (P, T) are obtained by the analogue method. This reconstitution method consists in particu...
International audienceNatural environmental changes may be reconstructed by studying lake sedimen... more International audienceNatural environmental changes may be reconstructed by studying lake sediments that record several climatic, hydrologic and environmental signatures. Such reconstructions must be based on a thorough knowledge of the current lake system conditions. According to this perspective, two karstic lakes in the Moroccan Middle Atlas, Aguelmam Azigza (32°58'N, 5°26'W, 1470 m absl) and Tiguelmamine (32°54'N, 5°21'W, 1650 m absl), have been the subject of hydrochemical and sedimentary investigations. Spatiotemporal monthly monitoring (since October 2012) of the physicochemical characteristics of waters (precipitation, lake, wells, springs and streams) shows that the waters of Azigza lake are alkaline (pH>8) with elevated contents of HCO3-, Ca 2+ and Mg 2+. The Aguelmam Azigza is a monomictic lake (with an overturn water during December to January) and indicates high sensitivity to seasonal climatic changes (temperature and precipitation) that control biog...
International audienceStable isotopes of water (18O, 2H) and their associated isotope fractionati... more International audienceStable isotopes of water (18O, 2H) and their associated isotope fractionation during water-cycle phase changes produce a natural labelling of the water cycle and can be efficiently use to study hydrological and climatic processes at the local, regional and global scales. Moreover, understanding the seasonal and inter-annualstable isotope behaviour in a lake system is a key for interpretingthe 18O data obtained from inorganic fractions of lake sediments in order to reconstruct past changes in local hydro-climatology. The natural mountain lake system, Aguelmam Azigza (32°58’N, 5°26’W, 1470 m asl), is located in the karstic Tabular Middle Atlas (Morocco), one of the most humid regions of Morocco, which can be seen as the “water tower” of the country. The regional climate receives alternative influences of Mediterranean, Atlantic and Saharan air masses. A lake monitoring has been implemented since October 2012 with a monthly water sampling (precipitation, lake, wel...
The copyright of individual parts of the supplement might differ from the CC-BY 3.0 licence. Supp... more The copyright of individual parts of the supplement might differ from the CC-BY 3.0 licence. Supplementary material References Data Localization Monitored period Number of data Lake state data processing strategy of use in our study Bader et al.
Hydrology and Earth System Sciences Discussions, 2010
We explore the reliability of large-scale climate variables, namely precipitation and temperature... more We explore the reliability of large-scale climate variables, namely precipitation and temperature, as inputs for a basin-lake hydrological model in central Argentina. We used data from two regions in NCEP/NCAR reanalyses and three regions from LMDZ model simulations forced with observed sea surface temperature (HadISST) for the last 50 years. Reanalyses data cover part of the geographical area of the Sali-Dulce Basin (region A) and a zone at lower latitudes (region B). The LMDZ selected regions represent the geographical area of the Sali-Dulce Basin (box A), and two areas outside of the basin at lower latitudes (boxes B and C). A statistical downscaling method is used to connect the large-scale climate variables inferred from LMDZ and the reanalyses, with the hydrological Soil Water Assessment Tool (SWAT) model in order to simulate the Rio Sali-Dulce discharge during 1950-2005. The SWAT simulations are then used to force the water balance of Laguna Mar Chiquita, which experienced an abrupt level rise in the 1970's attributed to the increase in Rio Sali-Dulce discharge. Despite that the lowstand in the 1970's is not well reproduced in either simulation, the key hydrological cycles in the lake level are accurately captured. Even though satisfying results are obtained with the SWAT simulations using downscaled reanalyses, the lake level are more realistically simulated with the SWAT simulations using downscaled LMDZ data in boxes B and C, showing a strong climate influence from the tropics on lake level fluctuations. Our results highlight the ability of downscaled climatic data to reproduce regional climate features. Laguna Mar Chiquita can therefore be considered as an integrator of large-scale climate changes since the forcing scenarios giving best results are those relying on global climate simulations forced with observed sea surface temperature. This climate-basin-lake model is a promising approach for understanding and simulating long-term lake level variations.
... The second group includes archives of the Patagonian climate, as well as the Salinas del Bebe... more ... The second group includes archives of the Patagonian climate, as well as the Salinas del Bebedero, and provides a record of past changes in the strength and latitudinal position of the Southern Westerlies. Keywords Pampean lakes · Late-Pleistocene/Holocene hydrological ...
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