Paleoceanographic data have demonstrated that the ocean’s current mode of ventilation is not unique but can, and has, switched rapidly between dramatically different states with severe and far-reaching climate repercussions. Ocean circulation model experiments, and reconstructions from proxy data indicate that changes in meridional overturning circulation (MOC) are associated with ocean-wide reorganisation in heat transport and temperature distribution, notably in conjunction with rapid climate events of the last 60,000 years. Reduced deep-water formation in the North Atlantic results in cooling in the North Atlantic region, but warming in the tropical thermocline and much of the southern hemisphere. Tropical Atlantic thermocline waters may greatly impact on MOC variability by storing heat that becomes available for rapid release, thereby inducing climate shifts. The hypotheses concerning oceanic processes are however still poorly constrained by available observations and core material with sufficient temporal and spatial resolution, thus preventing reliable assessments of the ocean’s vulnerability to future changes.
Based on geostrophic theory, it will only be possible to interpret past changes in the dynamics of the Atlantic MOC, if ‘palaeo-property’ gradients can be estimated over depth transects perpendicular to the main ocean currents feeding the MOC. This forms the basis for contemporary observational programmes monitoring the behaviour of the MOC, and has guided the design of RETRO.
The project requires the retrieval of 10 Calypso-cores from two specified depth transects in the eastern- and western tropical Atlantic. Combining expertise and equipment from five (4IP and 1AP) leading European institutions in palaeoclimate research, we plan to: 1) reconstruct the vertical temperature and density gradients in the ocean interior and their evolution during climate shifts over the last 60,000 years; and 2) investigate the links between high- and low latitude climate change through innovative modeling experiments making use of high quality data that is generated.
Project Leader:
Dr. Trond Dokken
University of Bergen, Norway
Principal Investigators:
Dr. Stefan Mulitza
University of Bremen, Germany
Dr. Franck Peeters
Vrije Universiteit, Amsterdam, The Netherlands
Dr. Claire Waelbroeck
CNRS-CEA-UVSQ, Gif-sur-Yvette, France
Associated Partner:
Dr. Luke Skinner
University of Cambridge, United Kingdom
