RAPID CLIMATIC VARIABILITY IN NORTHERN ATLANTIC : ISOTOPIC MEASUREMENTS OF AIR TRAPPED IN GREENLAND ICE CORES

• Main Author: Landais, Amaelle
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Université Pierre et Marie Curie - Paris VI, Jouzel Jean([e-mail])
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2004
• Subjects: Greenland; North Atlantic; rapid climate changes; ice core; firn; air isotopes; temperature quantification; glacial period; glacial inception; Groenland; Atlantique Nord; changements climatiques rapides; Dansgaard-Oeschger; carotte de glace; névé; isotopes de l'air; quantification de la température; période glaciaire; entrée en glaciation; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Antarc*; Antarctica; Dansgaard-Oeschger events; Greenland ice cores; GRIP; Ice Sheet
• Online Access: https://theses.hal.science/tel-00007403; https://theses.hal.science/tel-00007403/document; https://theses.hal.science/tel-00007403/file/tel-00007403.pdf

Mme Dorthe Dahl-Jensen, examinatrice, M. Jean Jouzel, directeur de these, M. Hervé Letreut, examinateur, Mme Valérie Masson-Delmotte, Co-directrice de thèse M. Dominique Raynaud, rapporteur M. Alain Saliot, president du jury M. Jakob Schwander, rapporteur The water isotopes records from Greenland ice cores depict a succession of rapid warmings (Dansgaard-Oeschger) during the last glacial period. The records corresponding to the last interglacial and the glacial inception suggest as well a highly variable climate. We use here a recently developed method to perform isotopic measurements of the air trapped in the ice (N2, O2 and Ar) combined to firn modelling to (i) separate the true climatic variability from ice stratigraphic disturbance, (ii) quantify the temperature changes in Greenland during Dansgaard-Oeschger events and the glacial inception, and (iii) give a phasing between Greenland temperature evolution and other climatic parameters (Greenhouse gases concentration, ice sheet volume, vegetation, other latitude temperature). We first define the limits and precautions associated to the method. On the one hand, the isotopic composition of trapped oxygen can only be performed on ice conserved below -25°C to have a high precision. On the other hand, firn studies have enabled us to improve its description and modelling. However, even if we better understand the firn dynamic, uncertainties remain on the surface parameters (temperature, accumulation rate). The climatic interpretation of nitrogen and argon isotopes in Antarctica ice cores must consequently remains cautious as we show it on a deglaciation. We then essentially concentrate on Greenland (GRIP and NorthGRIP ice cores). The combination of air isotopes (nitrogen, argon, oxygen), water isotopes (oxygen, hydrogen) and a powerful firn model enables us to reconstruct the surface temperature evolution and to get rid of any bias due to the hydrological cycle in North Atlantic (the water isotopes can not be used as a quantitative paleothermometer). The ...