Datation et étude de la variabilité climatique à partir de la carotte de glace antarctique de TALDICE

par Ilaria Crotti

Projet de thèse en Météorologie, océanographie, physique de l'environnement

Sous la direction de Amaelle Landais et de Stenni Barbara.

Thèses en préparation à université Paris-Saclay en cotutelle avec l'Université Cà Foscari de Venise , dans le cadre de École doctorale des sciences de l'environnement d'Île-de-France , en partenariat avec Laboratoire des Sciences du Climat et de l'Environnement (laboratoire) , Glaces et Continents, Climats et Isotopes Stables (GLACCIOS) (equipe de recherche) et de Université de Versailles-Saint-Quentin-en-Yvelines (référent) depuis le 30-09-2018 .


  • Résumé

    Les carottes de glace polaires extraites à de grandes profondeurs fournissent des informations essentielles pour l'étude de différents processus climatiques et de leurs interactions en réponse aux forçages interne et externe. Ce projet de doctorat porte sur l'étude de la partie profonde de la carotte de glace TALDICE (1440 à 1620 m de profondeur) extraite à l'est du plateau antarctique. L'objectif principal est de proposer une première datation de cette section car la date officielle n'a pas été prolongée au-delà de 1500 m de profondeur, où l'âge de glace est estimé à environ 150 000 ans. De plus, des reconstructions à haute résolution des variations climatiques du passé et du cycle hydrologique seront effectuées dans cette partie la plus ancienne de la carotte. Enfin, une attention particulière sera accordée à la préservation des signaux climatiques et aux processus qui finissent par les altérer

  • Titre traduit

    Dating and investigating climate variability at high resolution in the deep portion of the TALDICE ice core.


  • Résumé

    The deep polar ice cores provide reference records commonly employed in the global correlation of past climate events. In particular, the EPICA-Dome C (EDC) deep ice core provided the longest and best-preserved record of climate and atmospheric composition changes in Antarctica, covering the last 800,000 years (Jouzel et al., 2007). On the other hand, the deep ice core retrieved at Talos Dome in the framework of the TALDICE project provided high-resolution climate reconstructions for the Holocene, the last deglaciation (Stenni et al., 2011) and the last glacial period in the Ross Sea sector of Antarctica. A common age scale, AICC2012, for Antarctic ice cores has been built for both EDC and TALDICE core (Bazin et al., 2013). However, an official chronology for TALDICE ice core was defined only until the depth of 1438 m, coinciding with an age of 154,000 BP. The bottom part of the core, down to 1620 m depth, still lacks an official dating. Our aim is to propose a new dating for the uninvestigated deeper part of TALDICE and to reconstruct climate variability for this portion. We will perform high-resolution (every 5 cm) discrete stable isotope analyses (18O/16O and D/H ratios) in the ice portion between the depth of 1440 and 1580 m. Furthermore, this new high-resolution record will be compared with the high-resolution isotopic profile already obtained for EDC, to define first age scale of TALDICE core deeper part. Additional high-resolution 18O measurements of atmospheric oxygen (d18Oatm) in the air bubbles of the bottom part of the core will be performed at LSCE. The record will allow performing dating through comparison with other d18Oatm records over the same period since d18Oatm is a global signal. Moreover, improvements of the TALDICE dating will be possible through new measurements of the 81Kr and 40Ar in air trapped in ice bubble that will be performed at the University of Science and Technology of China and at LSCE respectively. The investigation of the deeper part of TALDICE will provide a significant contribution to the understanding of past climate variability in the Ross Sea sector of East Antarctica. In particular, the high-resolution water stable isotopes record will contribute to the reconstruction of past Antarctic temperatures and the computation of deuterium excess (d = dD - 8‧d18O) will be essential to study past changes in the hydrological cycle. We will also investigate if the high-resolution isotopic records in the deep ice, which may be affected by diffusion processes as noted in the bottom part of the EDC ice core. Such results will contribute to the understanding of diffusion processes influencing the isotopic records in the deeper parts of the ice sheet, especially in light of the Beyond EPICA – Oldest Ice Core (BE-OIC) project, which aims at drilling and investigating the climate variability of the past 1,5 million years.