TESTING THE HIGH OBLIQUITY HYPOTHESIS AS AN EXPLANATION FOR THE SNOWBALL EARTH MODEL

Many papers dealing with Neoproterozoic glaciation have recently been published, thanks to the renewed interest in the hypothesis of a snowball Earth . Only a few of these studies use climate models to test the consistency of the different hypotheses put forward to explain low latitudes glaciation . Here we use an AGCM coupled with a slab ocean to test the simplest solution proposed by G. Williams to explain the glaciation and the increased seasonal cycle at low latitudes : a higher obliquity of the Earth's rotation axis. In this paper, we show that a soft snowball Earth is easily simulated for the Sturtian episode (750 Ma), due to the location of continental masses in the tropical areas , but not for the Varangian episode when the continental mass is mainly located over the mid and high latitudes of the Southern Hemisphere . Such climate simulations, along with the difficulty of finding an appropriate mechanism to decrease the Earth's obliquity to present day values, makes the high obliquity hypothesis unable to explain both Neoproterozoic glaciations and therefore calls for a significant role for greenhouse gas variations in triggering the inception of a large ice sheet.