Biogeosciences, 10, 7927–7942, 2013 Open Access www.biogeosciences.net/10/7927/2013/ doi:10.5194/bg-10-7927-2013 Biogeosciences © Author(s) 2013. CC Attribution 3.0 License. Evidence from “Köppen signatures” of fossil plant assemblages for effective heat transport of Gulf Stream to subarctic North Atlantic during Miocene cooling T. Denk1, G. W. Grimm1, F. Grímsson2, and R. Zetter2 1Swedish Museum of Natural History, Department of Palaeobiology, Box 50007, 10405 Stockholm, Sweden 2University of Vienna, Department of Palaeontology, Althanstrasse 14, 1090 Vienna, Austria Correspondence to: T. Denk (
[email protected]) Received: 8 July 2013 – Published in Biogeosciences Discuss.: 15 August 2013 Revised: 29 October 2013 – Accepted: 2 November 2013 – Published: 6 December 2013 Abstract. Shallowing of the Panama Sill and the closure 1 Introduction of the Central American Seaway initiated the modern Loop Current–Gulf Stream circulation pattern during the Miocene, The Mid-Miocene Climatic Optimum (MMCO) at 17–15 but no direct evidence has yet been provided for effec- million years (Myr) was the last phase of markedly warm cli- tive heat transport to the northern North Atlantic during mate in the Cenozoic (Zachos et al., 2001). The MMCO was that time. Climatic signals from 11 precisely dated plant- followed by the Mid-Miocene Climate Transition (MMCT) bearing sedimentary rock formations in Iceland, spanning at 14.2–13.8 Myr correlated with the growth of the East 15–0.8 million years (Myr), resolve the impacts of the devel- Antarctic Ice Sheet (Shevenell et al., 2004). In the Northern oping Miocene global thermohaline circulation on terrestrial Hemisphere this cooling is reflected by continuous sea ice in vegetation in the subarctic North Atlantic region.