Hysteresis and orbital pacing of the early Cenozoic Antarctic ice sheet

The early Cenozoic Antarctic ice sheet has grown non-linearly to a continental-scale ice sheet close to the Eocene-Oligocene boundary when environmental conditions were favourable. These favourable conditions included the movement of the continent towards the South Pole, the thermal isolation of the Antarctic continent and declining atmospheric CO₂ concentrations.  Once the threshold for ice sheet growth was reached, a series of positive feedbacks led to the formation of a continental-scale ice sheet.

The thresholds for growth and decline of a continental scale ice sheet are different. The ice sheet state is dependent on the initial conditions, an effect called hysteresis. Here we present the hysteresis behaviour of the early Cenozoic Antarctic ice sheet for different bedrock elevation reconstructions. The ice sheet-climate coupler CLISEMv1.0 is used and captures both the height-mass balance and the ice-albedo feedback accurately. Additionally, the influence of the different orbital parameters on the threshold to glaciation and deglaciation is investigated in detail. It appears that the long-term eccentricity cycle has a significant 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.