Waxing and waning of the perennial north polar H2O ice cap of Mars over obliquity cycles

The perennial north polar H2O ice cap of Mars is investigated with the dyna mic/thermodynamic ice-sheet model SICOPOLIS. Computational results for flow velocities, ice temperatures, and surface accumulation/ablation rates are presented for the steady state with present conditions as well as for trans ient scenarios over idealized obliquity cycles with periods of 1.3 Myr and 125 kyr. The transient simulations lead to a stop-and-go-type dynamics with a cold and almost stagnant modern ice cap and a warmer flowing ice cap for past large-obliquity periods. The most likely scenario for the present ice cap comprises an ice volume of 1.2 million km(3), a maximum thickness of 3 km, the absence of pronounced local isostasy, H2O-ice accumulation rates o f the order of tenth-mm water equivalent (w.e.) per Earth year (yr), flow v elocities of the order of mm/yr and an ice base far below pressure melting. (C) 2000 Academic Press.