Palaeogeographic regulation of glacial events during the Cretaceous supergreenhouse.

The historical view of a uniformly warm Cretaceous is being increasingly challenged by the accumulation of new data hinting at the possibility of glacial events, even during the Cenomanian-Turonian (∼95 Myr ago), the warmest interval of the Cretaceous. Here we show that the palaeogeography typifying the Cenomanian-Turonian renders the Earth System resilient to glaciation with no perennial ice accumulation occurring under prescribed CO2 levels as low as 420 p.p.m. Conversely, late Aptian (∼115 Myr ago) and Maastrichtian (∼70 Myr ago) continental configurations set the stage for cooler climatic conditions, favouring possible inception of Antarctic ice sheets under CO2 concentrations, respectively, about 400 and 300 p.p.m. higher than for the Cenomanian-Turonian. Our simulations notably emphasize that palaeogeography can crucially impact global climate by modulating the CO2 threshold for ice sheet inception and make the possibility of glacial events during the Cenomanian-Turonian unlikely.