Hysteresis of glaciations in the Permo-Carboniferous

Abstract

The hysteresis of glaciations in the Permo-Carboniferous is simulated in an iterative energy balance model with 84 scenarios of varied orbital elements, CO2 levels, and glacial modes. Gondwana attains its glacial maximum when CO2 is roughly the same or slightly higher than the preindustrial level. Once glaciated it maintains a large ice covered area under higher CO2 levels up to 4 to 6 times of the preindustrial value followed by an abrupt disappearance of ice beyond this threshold. The solutions arrived at by iteration indicate the existence of parameter thresholds of glaciations and deglaciations which lead to the alternating extremes of glacial coverage. Dominated by the large seasonal cycle over land, the concentrated geography of the Permo-Carboniferous is more sensitive to the CO2-forced climate than sparsely distributed land. Our conceptual modeling agrees well with the recent geological evidence of intercalations of three glaciations and two lacunae of deglaciations in this geologic time.