Deep sea records of past climatic variability

Abstract
Records of past climate enable us to test our understanding of the mechanisms at play in the current climate change situation, by providing data from different climatic regimes and from the transitions between these regimes. We present here a broad overview of the progress made in reconstructing past ocean circulation and climatic variability, from deep sea cores. To determine the mechanisms governing past climatic changes, it is important to establish good chronologies of the studied sequences. We first review the main dating methods that have been applied to deep-sea cores so far, highlighting the associated uncertainties. We then describe which aspects of surface hydrology and deep-water properties can be retrieved from the study of deep-sea sediments. In particular, we explain how climatic variables are derived from proxies and never directly measured. We give numerous illustrations of advances in the interpretation of important proxies and in the development of new ones.