Preprints
https://doi.org/10.5194/cp-2020-58
https://doi.org/10.5194/cp-2020-58

  11 May 2020

11 May 2020

Review status: this discussion paper is a preprint. It has been under review for the journal Climate of the Past (CP). The manuscript was not accepted for further review after discussion.

Testing Hypotheses About Glacial Dynamics and the Stage 11 Paradox Using a Statistical Model of Paleo-Climate

Robert K. Kaufmann1 and Felix Pretis2,3 Robert K. Kaufmann and Felix Pretis
  • 1Department of Earth and Environment, Boston University, Boston, Massachusetts, USA, 02215, USA
  • 2Department of Economics, University of Victoria, Victoria, BC, Canada
  • 3Nuffield College, University of Oxford, Oxford, UK

Abstract. To test hypotheses about glacial dynamics, the Mid-Brunhes event, and the stage 11 paradox, we evaluate the ability of a statistical model to simulate climate during the previous ~800 000 years. Throughout this period, the model simulates the timing and magnitude of glacial cycles, including the saw-tooth pattern in which ice accumulates gradually and ablates rapidly, without nonlinearities or threshold effects. This suggests that nonlinearities and/or threshold effects do not play a critical role in glacial cycles. Furthermore, model accuracy throughout the previous ~800 000 years suggest that changes in glacial cycles associated with the Mid-Brunhes event, which occurs near the division between the out-of-sample period and the in-sample period, are not caused by changes in the dynamics of the climate system. Conversely, poor model performance during MIS stage 11 and Termination V is consistent with arguments that the stage 11 paradox represents a mismatch between orbital geometry and climate. Statistical orderings of simulation errors indicate that periods of reduced accuracy start with significant reductions in the model's ability to simulate carbon dioxide, non-sea-salt sodium, and non-sea-salt calcium. Their importance suggests that the stage 11 paradox is generated by changes in atmospheric and/or oceanic circulation that affect ocean ventilation of carbon dioxide.

Robert K. Kaufmann and Felix Pretis

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Robert K. Kaufmann and Felix Pretis

Robert K. Kaufmann and Felix Pretis

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Short summary
We show that a largely-linear empirical model of global climate can simulate glacial cycles during the previous 800 thousand years as a function of changes in Earth's orbit alone. This accuracy implies that nonlinearities and threshold effects probably do not play a critical role in glacial cycles. Results suggest that ice ages may end when changes in atmospheric circulation and/or the extent of sea ice accelerate the flow of CO2 from the ocean to the atmosphere, where it heats the planet.