Millenial scale variations of the isotopic composition of atmospheric oxygen over Marine Isotopic Stage 4 A. Landais a,b, ⁎ , V. Masson-Delmotte b , N. Combourieu Nebout b , J. Jouzel b , T. Blunier c , M. Leuenberger c , D. Dahl-Jensen d , S. Johnsen d a Institute of Earth Sciences, Hebrew University, Givat Ram, 91904 Jerusalem, Israel b Institut Pierre-Simon Laplace/Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ, l'Orme des Merisiers, 91191 Gif s/Yvette, France c Climate and Environmental Physics, University of Bern, Sidlerstrasse, 5, 3012 Bern, Switzerland d Department of Geophysics, Julianes Maries Vej 30, University of Copenhagen, 2100 Copenhagen, Denmark Received 20 September 2006; received in revised form 13 March 2007; accepted 14 March 2007 Editor: M.L. Delaney Available online 21 March 2007 Abstract During rapid events of the last glacial period (DO events), dramatic changes are recorded at high and low latitudes. Without a precise common timescale, links between changes in Greenland temperature and changes in biosphere productivity, hydrology regimes and sea level are difficult to establish. The composition of atmospheric oxygen (δ 18 O atm ) is influenced by global sea level changes, the global hydrologic cycle and the biosphere productivity. Since δ 18 O atm is measured in ice cores it gives the opportunity to investigate the underlying processes with no timescale uncertainty. Here, we present the first high resolution (50 yrs) record of the isotopic composition of atmospheric oxygen (δ 18 O atm ) measured in the air trapped in a Greenland ice core (NorthGRIP). Our record covers a sequence of DO events (18-19-20) corresponding to the Marine Isotopic Stage 4, ∼ 75 to 60 ka ago. Our measurements reveal rapid changes of δ 18 O atm associated with the DO events. With a few additional measurements of the third isotope of oxygen ( 17 O) during the DO event 19, we exclude the hypothesis that sea level changes are responsible for the isotopic variations. They originate more likely from large changes in relative humidity and latitudinal repartition of the continental vegetation over the DO events. © 2007 Elsevier B.V. All rights reserved. Keywords: Dansgaard–Oeschger events; oxygen isotopes; biosphere; hydrological cycle; ice core; glacial 1. Introduction Greenland ice cores have revealed the abrupt climate changes of the last glacial period [1]. Recent methods have been used to show that, during the so-called Dansgaard–Oeschger events (DO), the air temperature increases by up to 16±3 °C in less than 100 yrs in central Greenland [2,3] to reach a relatively warm period (interstadial) lasting several centuries. Then, the local temperature returns progressively to a cold period (stadial) lasting centuries to millennia. To address the latitudinal extent of the rapid events recorded with high resolution in these ice cores it is necessary to compare them to climate records representative of other latitudes. The signatures of DO events have been described in different areas using various indicators [e.g. [4] for a Earth and Planetary Science Letters 258 (2007) 101 – 113 www.elsevier.com/locate/epsl ⁎ Corresponding author. Institute of Earth Sciences, Hebrew University, Givat Ram, 91904 Jerusalem, Israel. E-mail address: amaelle.landais@cea.fr (A. Landais). 0012-821X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.epsl.2007.03.027