Response in the tropical Atlantic thermocline waters due to changes in the Atlantic meridional overturning circulation - RETRO

• Applicant: Dr. Stefan Mulitza
• Subject Area: Palaeontology
• Term: from 2007 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 35840016

a) IP aims & objectives: Paleodata and simulations with ocean-climate general circulation models suggest that reductions in the strength of the meridional overturning circulation (MOC) are associated with a characteristic (seesaw) pattern of sea-surface temperature change in the Atlantic. Caused by the massive decrease in the Atlantic northward heat transport, the surface northern North Atlantic cooled by up to several degrees Celsius, while the South Atlantic surface slightly warmed by up to 1°C (e.g. Mix et af., 1986; Charles et al., 1996; Manabe and Stouffer, 1997; Arz et al., 1999; Rühlemann et al., 1999). Climate models furthermore predict a salient warming at intermediate depths for present climate conditions that can reach up to several degrees Celsius in the tropical latitudes (Fig. 1, Manabe and Stouffer, 1997). Using a vertical core profile over the depth range of the main thermocline down to intermediate waters, the Bremen group seeks to reconstruct the response of the vertical water mass structure during the past 60,000 years to changes in MOC in the eastern tropical Atlantic. Specifically we aim at exploring the following questions: What is the evolution of vertical gradients in temperature, oxygen and carbon isotopes in the main thermocline during the past 60,000 years? Are changes in the meridional overturnig circulation (e.g. during Heinrich Events), actually associated with a characteristic vertical temperature pattern, as suggested by climate models? What are the consequences of a THC slowdown for the vertical nutrient distribution in the western tropical Atlantic? What is the influence of the local wind field on the structure of the upper water column and are there relationships between precessiona! or half-precessional cycles and heat storage in western and eastern tropical Atlantic and the Caribbean?

• DFG Programme: Research Grants
• International Connection: France, Netherlands, Norway, United Kingdom
• Participating Persons: Dr. Trond M. Dokken; Dr. Frank Peeters; Dr. Luke Cameron Skinner; Dr. Claire Waelbroeck