Cool episodes in the Cretaceous — Exploring the effects of physical forcings on Antarctic snow accumulation

The question whether large scale glaciations on Antarctica were possible in a late Mesozoic greenhouse climate such as the Late Cretaceous is an intriguing one. The most recent years have provided an increasing number of studies investigating the growth and decay of paleo-continental ice sheets on Antarctica possibly large enough to affect sea level. Since the outcome of these studies doesnʹt provide a basis for a conclusive decision we have performed a number of model runs using an Atmospheric General Circulation Model (AGCM) to test whether large volumes of snow might have accumulated even under Late Cretaceous greenhouse conditions. By varying orbital parameters as well as topography, and atmospheric CO2 concentrations our models indicate the possibility of an Antarctic ice shield build-up large enough to drive sea level fluctuations on the order of tens of meters within ~ 20,000 years. This is supported under the assumption of pCO2 levels < 800 ppm, low insolation, and elevated topography. The growth of a major Antarctic ice sheet would be possible on reasonable time scales. To accumulate about half the present day snow/ice volume which is required to explain the documented shifts in oxygen isotopes our model results suggest a time span between 20,000 and 80,000 years for these ice volumes to accumulate.