Characterisation of rapid climate changes through isotope analyses of ice and entrapped air in the NEEM ice core

• Main Author: Guillevic, Myriam
• Other Authors: Centre for Ice and Climate Copenhagen, Niels Bohr Institute Copenhagen (NBI), Faculty of Science Copenhagen, University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH)-Faculty of Science Copenhagen, University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), University of Copenhagen, Faculty of Science, Denmark, Université de Versailles Saint Quentin en Yvelines (UVSQ), France, Dr. Amaëlle Landais, Dr. Valérie Masson-Delmotte, Prof. Thomas Blunier, Neem, North Greenland Eemian Ice Drilling, ANR-07-VULN-0009,NEEM,NEEM-FRANCE(2007)
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2013
• Subjects: Paleoclimate; ice core; firn; air isotopes; water stable isotopes; methane; methane isotopes; Dansgaard-Oeschger events; Heinrich events; Greenland; North Atlantic; rapid climate changes; temperature quantification; glacial period; Paleoclimat; carotte de glace; névé; isotopes de l'air; isotopes stables de l'eau; méthane; isotopes du méthane; Evénements de Dansgaard-Oeschger; Evénements de Heinrich; Groenland; Atlantique Nord; changements climatiques rapides; quantification de la température; période glaciaire; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; Greenland ice core; Greenland ice cores; GRIP; NGRIP; Sea ice
• Online Access: https://tel.archives-ouvertes.fr/tel-01277038; https://tel.archives-ouvertes.fr/tel-01277038/document; https://tel.archives-ouvertes.fr/tel-01277038/file/Guillevic_PhDthesis_2nd_edition_3feb2014.pdf

Greenland ice core have revealed the occurrence of rapid climatic instabilities during the last glacial period, known as Dansgaard-Oeschger (DO) events, while marine cores from the North Atlantic have evidenced layers of ice rafted debris deposited by icebergs melt, caused by the collapse of Northern hemisphere ice sheets, known as Heinrich events. The imprint of DO and Heinrich events is also recorded at mid to low latitudes in different archives of the northern hemisphere. A detailed multi-proxy study of the sequence of these rapid instabilities is essential for understanding the climate mechanisms at play.Recent analytical developments have made possible to measure new paleoclimate proxies in Greenland ice cores. In this thesis we first contribute to these analytical developments by measuring the new innovative parameter 17O-excess from ice at LSCE (Laboratoire des Sciences du Climatet de l'Environnement, France). At the Centre for Ice and Climate (CIC, Denmark) we contribute to the development of a protocol for absolute referencing of methane gas isotopes, and making full air standard with known concentration and isotopic composition of methane (d13C and d2H).Then, air (d15N-N2) and water stable isotope measurements from four Greenland deep ice cores (GRIP, GISP2, NGRIP and NEEM) are investigated over a series of Dansgaard– Oeschger events (DO 8, 9 and 10). Combined with firn modeling, d15N data allow us to quantify abrupt temperature increases for each drill site (1 sigma = 0.6°C for NEEM, GRIP and GISP2, 1.5°C for NGRIP). Our data show that the magnitude of stadial–interstadial temperature increase is up to 2°C larger in central (GRIP, GISP2) and central-North (NGRIP) Greenland than in northwest Greenland (NEEM). The same spatial pattern is seen for accumulation increases. This pattern is coherent with climate simulations in response to reduced sea-ice extent in the Nordic seas.Finally, we develop a multi-proxy approach to identify in polar ice cores the fingerprint of Heinrich Events and apply it to ...