Preprints
https://doi.org/10.5194/cp-2021-94
https://doi.org/10.5194/cp-2021-94

  20 Jul 2021

20 Jul 2021

Review status: this preprint is currently under review for the journal CP.

A theory of glacial cycles: resolving Pleistocene puzzles

Hsien-Wang Ou1, Hsien-Wang Ou
  • 1Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY10964, USA
  • retired

Abstract. Since the summer surface air temperature that regulates the ice margin is anchored on the sea surface temperature, we posit that the climate system constitutes the intermediary of the orbital forcing of the glacial cycles. As such, the relevant forcing is the annual solar flux absorbed by the ocean, which naturally filters out the precession effect in early Pleistocene but mimics the Milankovitch insolation in late Pleistocene. For a coupled climate system that is inherent turbulent, we show that the ocean may be bistable with a cold state defined by the freezing point subpolar water, which would translate to ice bistates between a polar ice cap and an ice sheet extending to mid-latitudes, enabling large ice-volume signal regardless the forcing amplitude so long as the bistable thresholds are crossed. Such thresholds are set by the global convective flux, which would be lowered during the Pleistocene cooling, whose interplay with the ice-albedo feedback leads to transitions of the ice signal from that dominated by obliquity to the emerging precession cycles to the ice-age cycles paced by eccentricity. Through a single dynamical framework, the theory thus may resolve many long-standing puzzles of the glacial cycles.

Hsien-Wang Ou

Status: open (until 14 Sep 2021)

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Hsien-Wang Ou

Hsien-Wang Ou

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Short summary
We present a theory of the glacial cycles for which the ocean constitutes the intermediary of the orbital forcing of the ice volume. We show that the ocean is bistable, so is the ice sheet, which thus allows large ice-volume signal when modulated forcing exceeds certain thresholds. Such thresholds are set by the global-mean convective flux, which is lowered during the Pleistocene cooling, so the model can explain the mid-Pleistocene transition and resolve many longstanding glacial puzzles.