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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Discussion papers
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 12 Mar 2019

Submitted as: research article | 12 Mar 2019

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

Late Pliocene Cordilleran Ice Sheet development with warm Northeast Pacific sea surface temperatures

Maria Luisa Sánchez-Montes1, Erin L. McClymont1, Jeremy M. Lloyd1, Juliane Müller2, Ellen A. Cowan3, and Coralie Zorzi4 Maria Luisa Sánchez-Montes et al.
  • 1Geography Department, Durham University, Durham, DH1 3LE, UK
  • 2Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, 27568, Germany
  • 3Department of Geological and Environmental Sciences, Appalachian State University, North Carolina, 28608, USA
  • 4GEOTOP, Université du Québec à Montréal, Montreal, H3C 3P8, Canada

Abstract. The initiation and evolution of the Cordilleran Ice Sheet is relatively poorly constrained. International Ocean Discovery Program (IODP) Expedition 341 recovered marine sediments at Site U1417 in the Gulf of Alaska (GOA). Here we present alkenone-derived sea surface temperature (SST) analyses alongside ice rafted debris (IRD), pollen, terrigenous and marine organic matter (OM) inputs to the GOA through the late Pliocene and early Pleistocene. The first IRD contribution from tidewater glaciers in southwest Alaska is recorded at 2.9 Ma, indicating that the Cordilleran ice sheet extent increased in the late Pliocene. A higher occurrence of IRD and higher sedimentation rates in the GOA during the early Pleistocene, at 2.5 Ma, occur in synchrony with SSTs warming on the order of 1 °C relative to the Pliocene. All records show a high degree of variability in the early Pleistocene, indicating highly efficient ocean-climate-ice interactions through warm SST-ocean evaporation-orographic precipitation-ice growth mechanisms. A climatic shift towards ocean circulation in the subarctic Pacific similar to the pattern observed during negative Pacific Decadal Oscillation (PDO) conditions today appears to be a necessary pre-requisite to develop the Cordilleran glaciation and increase moisture supply to the subarctic Pacific. The drop in atmospheric CO2 concentrations since 2.8 Ma is suggested as one of the main forcing mechanisms driving the Cordilleran glaciation.

Maria Luisa Sánchez-Montes et al.
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Maria Luisa Sánchez-Montes et al.
Data sets

Alkenone sea surface temperatures, ice rafted debris, terrestrial/aquatic n-alkane ratio, pollen counts and a new age and depth models from IODP Expedition 341 Site U1417, Gulf of Alaska M. L. Sánchez-Montes, E. L. McClymont, J. M. Lloyd, J. Müller, E. A. Cowan, and C. Zorzi

Maria Luisa Sánchez-Montes et al.
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Publications Copernicus
Short summary
In this paper, we present new climate reconstructions in SW Alaska from recovered marine sediments in the Gulf of Alaska. We find that glaciers reached the Gulf of Alaska during a cooling climate at 2.9 million years ago and after that the Cordilleran Ice Sheet continue growing during a global drop in atmospheric CO2 levels. The Cordilleran Ice Sheet growth could have been supported by an increase in heat supply to the SW Alaska and warm ocean-evaporation-mountain precipitation mechanisms.
In this paper, we present new climate reconstructions in SW Alaska from recovered marine...