Global change over the last climatic cycle from the vostok ice core record (Antarctica)

The study of ice cores provides the opportunity of access to numerous parameters which are related to climate or environmental changes. Many of these variables are of regional or even global geographical significance. There are now several ice cores which penetrate into ice which has formed at the surface of polar ice sheets during the last ice age and the recently obtained Vostok (Antarctica) record provides detailed information over the last climatic cycle (160 ka). In comparison with current Holocene conditions, the Last Glacial Maximum (20 ka BP) is characterized by much colder conditions (up to 10°C) and reduced precipitation (× 1 2). A large increase of continental and marine aerosols is explained by a more vigorous large scale atmospheric circulation associated with changing continental deserts and shelves as well as changes in sea ice extent. The drastic climatic change occurring at the last glacial termination is correlated with a large increase of atmospheric CO₂ (from about 200 to 270 ppmv). The isotopic temperature record from the Vostok ice core depicts two drastic glacial-interglacial terminations (around 15 and 140 ka BP) and a long glacial period (110-15 ka BP) which includes two interstadials. Full glacial stages are characterized by larger aerosol loadings. The CO₂ record of global significance is well correlated with the isotope temperature profile with high (270 ppmv) during interglacials and low (200 ppmv) during full glacial conditions. Spectral analysis of the Yostok temperature record supports the existence of a relationship between the Pleistocene climate and orbital forcing. On the other hand, the existence of a CO₂-climate correlation suggests that CO₂ changes have had an important climatic role in amplifying the relatively weak orbital forcing.