17 Mar 2023
 | 17 Mar 2023

Hysteresis and orbital pacing of the early Cenozoic Antarctic ice sheet

Jonas Van Breedam, Philippe Huybrechts, and Michel Crucifix

Abstract. The hysteresis behaviour of ice sheets arises because of the different thresholds for growth and decline of a continental-scale ice sheet depending on the initial conditions. In this study, the hysteresis effect of the early Cenozoic Antarctic ice sheet is investigated with an improved ice sheet-climate coupling method that accurately captures the ice-albedo feedback. It is shown that the hysteresis effect of the early Cenozoic Antarctic ice sheet is about ~180 ppmv or between 3.5 °C and 5.5 °C, depending only weakly on the bedrock elevation dataset. Excluding the solid Earth feedback decreases the hysteresis effect significantly towards ~40 ppmv, because the transition to a glacial state can occur at a higher forcing. The rapid transition from a glacial to a deglacial state and oppositely from deglacial to glacial conditions is strongly enhanced by the ice-albedo feedback, in combination with the elevation – surface mass balance feedback. Variations in the orbital parameters show that extreme values of the orbital parameters are able to exceed the threshold in summer insolation to induce a (de)glaciation. It appears that the long-term eccentricity cycle has a large influence on the ice sheet growth and decline and is able to pace the ice sheet evolution for constant CO2 concentration close to the glaciation threshold.

Jonas Van Breedam et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-399', Anonymous Referee #1, 04 Apr 2023
  • RC2: 'Comment on egusphere-2023-399', Anonymous Referee #2, 19 Apr 2023

Jonas Van Breedam et al.

Jonas Van Breedam et al.


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Short summary
We investigated the different boundary conditions to allow for ice sheet growth and ice sheet decline of the Antarctic ice sheet when it appeared ~34 Ma ago. The thresholds for ice sheet growth and decline differ because of the different climatological conditions above an ice sheet (higher elevation and higher albedo) compared to a bare topography. We found that the ice-albedo feedback and the isostasy feedback respectively ease and delay the transition from a deglacial to glacial state.