L'enregistrement par les spéléothèmes des évènements climatiques d'échelle millénaire lors de la dernière période glaciaire ; implications pour la chronologie des carottes glaciaires

par Ellen Corrick

Projet de thèse en Sciences Terre, Univers et Environnement

Sous la direction de Russel Drysdale et de Fabien Arnaud.

Thèses en préparation à Grenoble Alpes en cotutelle avec The University of Melbourne , dans le cadre de École doctorale sciences et ingénierie des systèmes, de l'environnement et des organisations (Chambéry) , en partenariat avec Environnement, Dynamiques et Territoires de la Montagne (laboratoire) depuis le 01-04-2016 .


  • Résumé

    L'enregistrement par les spéléothèmes des évènements climatiques d'échelle millénaire lors de la dernière période glaciaire ; implications pour la chronologie des carottes glaciaires. This thesis aims to produce a high resolution, precisely dated time series of millennial-scale climate events from French speleothems. Millennial-scale climate events are rapid climate oscillations that occurred throughout the last glacial period (120,000 to 12,000 years ago) and are best recorded in isotope palaeotemperature proxies in Greenland ice. However, chronological uncertainties of Greenland ice-core records are large and thus the exact timing of the events is unknown. The absence of an absolute and precise chronology of the events restricts the testing of hypothesis surrounding their cause, forcing mechanisms and propagation across the Earth. As such, the cause of the events is uncertain, which ultimately hampers the understanding and ability to predict Earth's response to rapid climate changes, including anthropocentric climate changes. Speleothems are excellent climate archives as they preserve multiple palaeoclimate proxies and can be accurately and precisely dated using uranium-thorium methods. Speleothems have previously been shown to record millennial-scale climate events. However, existing records are hampered by short temporal coverage, discontinuities or are from sites far from the North Atlantic (the central site of millennial-scale climate changes). In this project, I aim to reconstruct a high resolution, continuous and precisely dated record of millennial-scale climate events from French speleothems. France, in particular the south-west, is an ideal location for this study due to the proximity to the North Atlantic and the absence of major glaciation events during the last glacial that may have caused hiatuses in speleothem growth. The precisely dated French speleothem record will be compared to existing Greenland ice-core records in order to assess the accuracy of the ice-core chronology. The potential of dating Greenland ice by establishing the timing of individual events from their timing in the speleothem record will be explored. We aim to use this approach to improve the accuracy and precision of the Greenland ice-core chronology. Such improvements to the chronology of millennial-scale climate events are essential to a better understanding of the abruptness, duration and ultimately cause of the events.

  • Titre traduit

    Speleothem records of millennial-scale climate events during the last glacial period: implications for ice-core chronologies


  • Résumé

    This thesis aims to produce a high resolution, precisely dated time series of millennial-scale climate events from French speleothems. Millennial-scale climate events are rapid climate oscillations that occurred throughout the last glacial period (120,000 to 12,000 years ago) and are best recorded in isotope palaeotemperature proxies in Greenland ice. However, chronological uncertainties of Greenland ice-core records are large and thus the exact timing of the events is unknown. The absence of an absolute and precise chronology of the events restricts the testing of hypothesis surrounding their cause, forcing mechanisms and propagation across the Earth. As such, the cause of the events is uncertain, which ultimately hampers the understanding and ability to predict Earth's response to rapid climate changes, including anthropocentric climate changes. Speleothems are excellent climate archives as they preserve multiple palaeoclimate proxies and can be accurately and precisely dated using uranium-thorium methods. Speleothems have previously been shown to record millennial-scale climate events. However, existing records are hampered by short temporal coverage, discontinuities or are from sites far from the North Atlantic (the central site of millennial-scale climate changes). In this project, I aim to reconstruct a high resolution, continuous and precisely dated record of millennial-scale climate events from French speleothems. France, in particular the south-west, is an ideal location for this study due to the proximity to the North Atlantic and the absence of major glaciation events during the last glacial that may have caused hiatuses in speleothem growth. The precisely dated French speleothem record will be compared to existing Greenland ice-core records in order to assess the accuracy of the ice-core chronology. The potential of dating Greenland ice by establishing the timing of individual events from their timing in the speleothem record will be explored. We aim to use this approach to improve the accuracy and precision of the Greenland ice-core chronology. Such improvements to the chronology of millennial-scale climate events are essential to a better understanding of the abruptness, duration and ultimately cause of the events.