Isotope calibrated Greenland temperature record over Marine Isotope Stage 3 and its relation to CH4

Earth and Planetary Science Letters, Vol. 243, p. 504-519, doi:10.1016/j.epsl.2006.01.002, 2006

C. Huber, M. Leuenberger, R. Spahni, J. Flükiger, J. Schwander and T. F. Stocker
Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland
S. Johnsen
Ice and Climate, The Niels Bohr Institute, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark
A. Landais and J. Jouzel
IPSL/Laboratoire des Sciences du Climat et de l'Environnement, UMR CEA-CNRS, CEA Saclay, 91191 Gif-sur-Yvette, France.

ABSTRACT.
Large temperature variations on millennial time scales in Greenland characterised the last ice age. Abrupt warmings, known as Dansgaard-Oeschger (DO) events, can be traced in the δ¹⁸Oice record of Greenland ice cores. However, it has been shown that δ¹⁸Oice is not a direct temperature proxy. Measurements of the isotopic composition of gases trapped in the ice can be used to calibrate the paleothermometer. Here we present a continuous temperature record based on high resolution δ¹⁵N measurements and firn model studies. It covers a sequence of 9 DO events (9-17) during the time period from 38 to 64 kyr BP for which temperature changes of 8 to 15 °C were estimated. The difference between the modern and the glacial δ¹⁸Oice-T relationship can be explained by a combination of source temperature changes and changes in the annual distribution of precipitation. A detailed comparison of the temperature evolution with reconstructions of the atmospheric methane (CH₄) concentration shows that CH₄ rises lag temperature increases at the onset of DO events by 25 to 70 yr within data resolution. The strong correlation between Greenland temperature and CH₄ on millennial and submillennial time scales suggests that variations on these time scales were probably of hemispheric extent.