Clim. Past Discuss., 7, 1339-1361, 2011
© Author(s) 2011. This work is distributed
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This discussion paper has been under review for the journal Climate of the Past (CP). Please refer to the corresponding final paper in CP.
Middle Jurassic-Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean
H. C. Jenkyns1, L. Schouten-Huibers2, S. Schouten2, and J. S. Sinninghe Damsté2
1Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
2Royal Netherlands Institute for Sea Research (NIOZ), Department of Marine Biogeochemistry and Toxicology, P.O. Box 59, 1790 Den Burg, Texel, The Netherlands

Abstract. Although a division of the Phanerozoic climatic modes of the Earth into "greenhouse" and "icehouse" phases is widely accepted, whether or not polar ice developed during the relatively warm Jurassic and Cretaceous Periods is still under debate. In particular, there is a range of isotopic and biotic evidence that favours the concept of discrete "cold snaps", marked particularly by migration of certain biota towards lower latitudes. Extension of the use of the palaeotemperature proxy TEX86 back to the middle Jurassic indicates that relatively warm sea-surface conditions (26–30 °C) existed from this interval (~160 Ma) to the Early Cretaceous (~115 Ma) in the Southern Ocean. The Jurassic and Cretaceous "cold snaps" represent falls of only a few degrees. Belemnite δ18O data give palaeotemperatures that are consistently lower by ~14 °C than does TEX86 and these molluscs likely record conditions below the thermocline. Such long-term warm climatic conditions would only be compatible with the existence of continental ice if appreciable areas of high altitude existed on Antarctica, and/or in other polar regions, during the Mesozoic Era.

Citation: Jenkyns, H. C., Schouten-Huibers, L., Schouten, S., and Sinninghe Damsté, J. S.: Middle Jurassic-Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean, Clim. Past Discuss., 7, 1339-1361, doi:10.5194/cpd-7-1339-2011, 2011.
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