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Climate of the Past An interactive open-access journal of the European Geosciences Union
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© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 24 Nov 2017

Research article | 24 Nov 2017

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Climate of the Past (CP).

A Stalagmite Test of North Atlantic SST and Iberian Hydroclimate Linkages over the Last Two Glacial Cycles

Rhawn F. Denniston1, Amanda N. Houts1,a, Yemane Asmerom2, Alan D. Wanamaker3, Jonathon A. Haws4, Victor J. Polyak2, Diana L. Thatcher3, Sestsen Altan-Ochir1, Alyssa C. Borowske1,b, Sebastian F. M. Breitenbach5, Caroline C. Ummenhofer6, Frederico T. Regala7, Michael M. Benedetti8, and Nuno Bicho9 Rhawn F. Denniston et al.
  • 1Department of Geology, Cornell College, Mount Vernon, Iowa 52314, USA
  • 2Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA
  • 3Department of Geological and Atmospheric Sciences, Iowa State University, Ames, Iowa 50011, USA
  • 4Department of Anthropology, Louisville University, Louisville, Kentucky 40208, USA
  • 5Institute for Geology, Mineralogy, and Geophysics, Ruhr-University Bochum 44801, Germany
  • 6Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
  • 7Associação de Estudos Subterrâneos e Defesa do Ambiente, Torres Vedras, Portugal
  • 8Department of Geography and Geology, University of North Carolina Wilmington, Wilmington, North Carolina 28403, USA
  • 9Center for Archaeology and Evolution of Human Behaviour, Universidade do Algarve, Faro, Portugal
  • acurrent address: Department of Earth Sciences, University of New Hampshire, Durham, New Hampshire 03824, USA
  • bcurrent address: Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, Connecticut 06269, USA

Abstract. Close coupling of Iberian hydroclimate and North Atlantic sea surface temperature (SST) during recent glacial periods has been identified through the analysis of marine sediment and pollen grains co-deposited on the Portuguese continental margin. These reconstructions have lacked a directly-dated, site-specific record of continental Iberian climate spanning multiple glacial cycles as a point of comparison. Here we present a high-resolution, multi-proxy (δ13C, δ234U, and growth dynamics) stalagmite record of hydroclimate from two caves in western Portugal across the majority of the last two glacial cycles (~230ka). At orbital and millennial scales, stalagmite-based proxies of hydroclimate covaried with sea surface temperature (SST), with positive carbon isotope excursions and/or growth hiatuses indicating reduced effective moisture coincident with suppressed SST during major ice-rafted debris events and Greenland stadials, in agreement with changes in palynological reconstructions of continental climate. The Portuguese stalagmite record also reveal intervals during which the magnitudes of hydroclimate changes appear to have been somewhat decoupled from SST.

Rhawn F. Denniston et al.
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Rhawn F. Denniston et al.
Rhawn F. Denniston et al.
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Short summary
The sediment deposited off the coast of Portugal includes the remains of marine organisms and pollen washed to sea from Iberia. Analysis of both the pollen and the ocean sediments has revealed that the type and density of vegetation on land changed in concert with shifts in ocean temperature over centuries to tens of millennia. The research presented here tests these relationships across the last two glacial periods using a series of climate-sensitive stalagmites from western Portugal.
The sediment deposited off the coast of Portugal includes the remains of marine organisms and...