Preprints
https://doi.org/10.5194/egusphere-2024-1842
https://doi.org/10.5194/egusphere-2024-1842
25 Jun 2024
 | 25 Jun 2024
Status: this preprint is open for discussion.

A simple physical model for glacial cycles

Sergio Pérez-Montero, Jorge Alvarez-Solas, Jan Swierczek-Jereczek, Daniel Moreno-Parada, Marisa Montoya, and Alexander Robinson

Abstract. Glacial cycles are the norm in Pleistocene climate variability. Models of varying degree of complexity have been used to answer the question of what causes the nonlinear response of the climate system to the periodic forcing from the Sun. At one end of the spectrum of complexity are comprehensive models which aim to represent all involved processes in a realistic manner. However, their high computational cost precludes their use in the ultra-long simulations needed. At the other end are conceptual models which are computationally less demanding but which generally lack a physical basis. Most of them yield good results in terms of capturing the shape and patterns of glacial cycles as indicated by the geological record, thus making it very difficult to identify the underlying mechanisms. Here we present a conceptual model that aims to physically represent the interaction between the climate and the Northern Hemisphere ice sheets while eliminating spatial dimensions in some of the fundamental ice-sheet thermodynamic and dynamic equations. To this end, we describe the Physical Adimensional Climate Cryosphere mOdel (PACCO) from its simplest to its most complex configuration. We discuss separately the implications of different fundamental mechanisms such as ice-sheet dynamics and thermodynamics, glacial isostatic adjustment and ice-sheet albedo aging for our model. We conclude that ice-sheet dynamics and a delayed isostatic response are sufficient to produce resonance around periodicities of 100 kyr, although the forcing has a spectrum concentrated around lower values. In addition, ice-sheet thermodynamics and ice aging separately enhance the model nonlinearities to provide 100 kyr periodicities in good agreement with reconstructions. However, we found that it is easier to reproduce the late Pleistocene glacial cycles using the simpler process of ice aging. Overall, PACCO is a valuable tool for analyzing the different hypotheses present in the literature.

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Sergio Pérez-Montero, Jorge Alvarez-Solas, Jan Swierczek-Jereczek, Daniel Moreno-Parada, Marisa Montoya, and Alexander Robinson

Status: open (until 06 Aug 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2024-1842', Mikhail Verbitsky, 02 Jul 2024 reply
    • CC2: 'Additional considerations regarding ice-sheet thermodynamics', Mikhail Verbitsky, 05 Jul 2024 reply
      • AC2: 'Reply on CC2', Sergio Pérez Montero, 19 Jul 2024 reply
    • AC1: 'Reply on CC1', Sergio Pérez Montero, 19 Jul 2024 reply
      • CC3: 'Reply on AC1', Mikhail Verbitsky, 20 Jul 2024 reply
Sergio Pérez-Montero, Jorge Alvarez-Solas, Jan Swierczek-Jereczek, Daniel Moreno-Parada, Marisa Montoya, and Alexander Robinson

Video supplement

Representation of the Late Pleistocene using the AGING experiment from PACCO. Sergio Pérez-Montero https://github.com/sperezmont/Perez-Montero-etal_YYYY_ESD/blob/a172bb2654cf525d4e5096365489514b0f62641f/figures/pacco_animation_s1_a1.gif

Sergio Pérez-Montero, Jorge Alvarez-Solas, Jan Swierczek-Jereczek, Daniel Moreno-Parada, Marisa Montoya, and Alexander Robinson

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Short summary
The climate of the last 3 Myr varies between cold and warm periods. Numerous independent mechanisms have been proposed to explain this, however no effort has been made to study their competing effects. Here we present a simple but physically motivated model that includes these mechanisms in a modular way. We find that the main trigger is the displacement of the lithosphere due to the ice thickness evolution, but reproducing the climate records additionally requires the natural darkening of ice.