Kuhlbrodt, T.Griesel, A.Montoya Redondo, María LuisaLevermann, A.Hofmann, M.Rahmstorf, S.2023-06-202023-06-202007-04-248755-120910.1029/2004RG000166https://hdl.handle.net/20.500.14352/51894© 2007 by the American Geophysical Union. We are grateful to Miguel A. M. Maqueda for contributing many relevant ideas and for many discussions from which the paper has gained strongly. We are as well indebted to Andrey Ganopolski for many useful comments and suggestions that have improved this manuscript. The paper was considerably improved by the remarks of Wilbert Weijer and two anonymous reviewers. The authors appreciate the support of several funding agencies (T.K., German Federal Ministry for Education, Science and Research through the project ‘‘Integration’’; A.G. and M.H., McDonnell Foundation; M.M., Spanish Ministry for Science and Education through the Ramón y Cajal Program and project CGL2005-06097/CLI; and A.L., Gary Comer Foundation). [135] The Editor responsible for this paper was Henk Dijkstra. He thanks technical reviewer Wilbert Weijer and two anonymous reviewers.Because of its relevance for the global climate the Atlantic meridional overturning circulation (AMOC) has been a major research focus for many years. Yet the question of which physical mechanisms ultimately drive the AMOC, in the sense of providing its energy supply, remains a matter of controversy. Here we review both observational data and model results concerning the two main candidates: vertical mixing processes in the ocean's interior and wind-induced Ekman upwelling in the Southern Ocean. In distinction to the energy source we also discuss the role of surface heat and freshwater fluxes, which influence the volume transport of the meridional overturning circulation and shape its spatial circulation pattern without actually supplying energy to the overturning itself in steady state. We conclude that both wind-driven upwelling and vertical mixing are likely contributing to driving the observed circulation. To quantify their respective contributions, future research needs to address some open questions, which we outline.engjournal articlehttp://dx.doi.org/10.1029/2004RG000166http://onlinelibrary.wiley.com/open access52Ocean general-circulationCoupled climate modelDeep-water formationWind-energy inputGlobal thermohaline circulationResolution Antarctic modelTracer-release experimentNorth-AtlanticSouthern-oceanHeat-transportAstrofísicaAstronomía (Física)