16°C Rapid Temperature Variation in Central Greenland 70,000 Years Ago

Abstract

Variations in the 29 N 2 / 28 N 2 ratio of air bubbles trapped in polar ice cores and their relation to variations of the 18 O/ 16 O of the ice allow past surface temperature variations and ice age–gas age differences to be determined. High-resolution measurements of 29 N 2 / 28 N 2 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 δ 18 O ice -temperature coefficient α 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 δ 18 O ice –surface temperature correlations.