04 Feb 2021

04 Feb 2021

Review status: a revised version of this preprint is currently under review for the journal CP.

Evolution of mean ocean temperature in Marine Isotope Stages 5-4

Sarah Shackleton1,a, James A. Menking2, Edward Brook2, Christo Buizert2, Michael N. Dyonisius3,b, Vasilii V. Petrenko3, Daniel Baggenstos4, and Jeffrey P. Severinghaus1 Sarah Shackleton et al.
  • 1Scripps Institution of Oceanography, University of California, San Diego, La Jolla, 92093, United States
  • 2College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, 97331, United States
  • 3Earth and Environmental Sciences, University of Rochester, Rochester, 14642, United States
  • 4Climate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
  • apresent address: Department of Geosciences, Princeton University, Princeton, 08544 United States
  • bpresent address: Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark

Abstract. Deglaciations are characterized by relatively fast and near-synchronous changes in ice sheet volume, ocean temperature, and atmospheric greenhouse gas concentrations, but glacial inceptions occur more gradually. Understanding the evolution of ice sheet, ocean, and atmospheric conditions from interglacial to glacial maximum provides important insight into the interplay of these components of our climate system. Using noble gas measurements in ancient ice samples, we reconstruct mean ocean temperature (MOT) from 74 to 59.5 ka BP, covering the Marine Isotope Stage (MIS) 5-4 boundary, MIS 4, and part of the MIS 4-3 transition. Comparing this MOT reconstruction to previously published MOT reconstructions from the last glacial cycle, we find that the majority of interglacial-glacial ocean cooling occurred across MIS 5, and MOT reached full glacial levels by MIS 4 (−2.7 ± 0.3 °C relative to the Holocene). Comparing MOT to contemporaneous records of CO2 and benthic 𝛿18O, we find that ocean cooling and the solubility pump can explain most of the CO2 drawdown and increase in 𝛿18O across MIS 5. The timing of ocean warming and cooling in our record indicates that millennial scale climate variability plays a crucial role in setting mean ocean temperature during this interval, as seen during other periods, such as the last deglaciation.

Sarah Shackleton et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on cp-2021-8', Andreas Schmittner, 10 Feb 2021
    • AC1: 'Reply on CC1', Sarah Shackleton, 29 Jul 2021
  • RC1: 'Review of 'Evolution of mean ocean temperature in Marine Isotope Stages 5-4' by Shackleton et al. 2021', Anonymous Referee #1, 31 Mar 2021
    • AC2: 'Reply on RC1', Sarah Shackleton, 29 Jul 2021
  • RC2: 'Referee comment', Anonymous Referee #2, 18 May 2021
    • AC3: 'Reply on RC2', Sarah Shackleton, 29 Jul 2021

Sarah Shackleton et al.

Data sets

Mean Ocean Temperature in Marine Isotope Stage 4 Sarah Shackleton

Sarah Shackleton et al.


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Short summary
The ocean is the largest reservoir of heat and carbon in the climate system. Our study considers the role of ocean cooling and increased CO2 solubility in the last transition from interglacial to glacial conditions. We find that ocean cooling played a dominant role in lowering CO2 early in this transition but only a minimal role later in the glaciation. This provides unique insight into the evolving controls on atmospheric CO2 during glacial cycles.