Millenial scale variations of the isotopic composition of atmospheric oxygen over Marine Isotopic Stage 4

Earth and Planetary Science Letters, Vol. 258, doi: 10.1016/j.epsl.2007.03.027, 2007

A. Landais
Institute of Earth Sciences, Hebrew University, Givat Ram, 91904 Jerusalem, Israel and 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.
V. Masson-Delmotte, N. Combourieu Nebout and J. Jouzel
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.
T. Blunier and M. Leuenberger
Climate and Environmental Physics, University of Bern, Sidlerstrasse, 5, 3012 Bern, Switzerland.
D. Dahl-Jensen and S. Johnsen
Ice and Climate, The Niels Bohr Institute, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark

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 (δ¹⁸Oatm) is influenced by global sea level changes, the global hydrologic cycle and the biosphere productivity. Since δ¹⁸Oatm 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 (δ¹⁸Oatm) 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 δ¹⁸Oatm associated with the DO events. With a few additional measurements of the third isotope of oxygen (¹⁷O) 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.