Rapid climatic variability in the North Atlantic ocean during the last 128,000 years: relations between ice sheets and oceanic surface water

The slow variations of the terrestrial climate on time scales of several tens of thousands of years are essentially due to causes outside the terrestrial climatic system. Recently, some studies on ice and oceanic cores have shown that climatic changes can occur abruptly, on time scales of some centuries or some decades only. The aim of this work is the study of the rapid climatic variability in the North Atlantic during the last climatic cycle (128,000 years). The results are obtained both from continuous analyses of sediment cores (color changes and magnetic susceptibility) and isotopic geochemical methods. The continuous study of different parameters shows relationships between atmospheric (ice cores) and oceanic records (marine cores). The rapid climatic variations found in the ice are also recorded in the marine sediment. Bioturbation does not remove completely this high frequency signal. The detailed study of marine sediment shows that massive discharges of icebergs occurred several times during the last glacial period between 60 and 10 ka. As a result, the North Atlantic underwent huge hydrological changes during this time. Finally, the high resolution study of the last interglacial period between 128 and 113 ka shows a relative stability of the climate. (author)