16^oC Rapid Temperature Variation in Central Greenland 70,000 Years Ago

Science, Vol. 286, No. 5441, p. 934-937, 1999 

C. Lang, M. Leuenberger, J. Schwander
Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, Bern CH-3012, Switzerland.
S. Johnsen
Departement of Geophysics, The Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen.

ABSTRACT.
Variations in the ²⁹N₂ / ²⁸N₂ ratio of air bubbles trapped in polar ice cores and their relation to variations of the ¹⁸O/¹⁶O of the ice allow past surface temperature variations and ice age-gas age differences to be determined. High-resolution measurements of ²⁹N₂ / ²⁸N₂ in Dansgaard-Oeschger event 19 (around 70,000 years before the present) in ice from Central Greenland show that at the beginning of the event, the ice age-gas age difference was 1090 ± 100 years. With the use of a combined firn densification, temperature, and gas diffusion model, the δ¹⁸O_ice-temperature coefficient a was determined to be 0.42 ± 0.05 per mil per kelvin. This coefficient implies a mean surface temperature change of 16.0 kelvin (between 14.3 and 18.1 kelvin), which differs substantially from values derived from borehole temperatures and modern spatial δ¹⁸O_ice-surface temperature correlations.