HR: 0800h
AN: C51A-0094    [Abstracts]
TI: The North Polar Ice Cap of Mars at Varying Obliquities, Simulated With a Coupled Atmosphere/Ice-Sheet Model
AU: Stenzel, O J
EM: stenzel@mps.mpg.de
AF: Max-Planck-Institute for Solar System Research, Max-Planck-Str. 2, Katlenburg-Lindau, 37191, Germany
AU: * Greve, R
EM: greve@lowtem.hokudai.ac.jp
AF: Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo, 060-0819, Japan
AU: Grieger, B
EM: Bjoern.Grieger@sciops.esa.int
AF: European Space Astronomy Centre (ESAC), P.O. Box 50727, Madrid, 28080, Spain
AU: Fraedrich, K
EM: klaus.fraedrich@zmaw.de
AF: Meteorological Institute, University of Hamburg, Bundesstr. 55, Hamburg, 20146, Germany
AU: Kirk, E
EM: e.kirk@gmx.de
AF: Meteorological Institute, University of Hamburg, Bundesstr. 55, Hamburg, 20146, Germany
AU: Lunkeit, F
EM: Frank.Lunkeit@zmaw.de
AF: Meteorological Institute, University of Hamburg, Bundesstr. 55, Hamburg, 20146, Germany
AU: Keller, H U
EM: keller@mps.mpg.de
AF: Max-Planck-Institute for Solar System Research, Max-Planck-Str. 2, Katlenburg-Lindau, 37191, Germany
AB: Two numerical models, a general circulation model of the atmosphere (Planet Simulator Mars) and a dynamic/thermodynamic ice sheet model (SICOPOLIS) for the perennial north polar H₂O ice cap and the underlying layered deposits (considered as a morphological unit), have been coupled in order to simulate the climate system of Mars. The experimental set-up includes three runs of the atmospheric part for two Martian years each for obliquities of 15°, 25.2° and 35°, respectively, which covers the variability of the last 5~Ma. The climatic fields of the second model year are then used to force the ice component over a period of 125~Ma, with the present-day ice cap used as initial condition. At 15° obliquity, glaciation southwards to 70°N takes place within the first 10~Ma. Given an unlimited amount of available water, the ice cap grows even further through extensive glacial flow until equilibrium is reached. In case of the high obliquity of 35°, the difference between precipitation and evaporation is negative southward of about 85°N, and the ice cap shrinks until glacial flow compensates for evaporation in the vicinity of the ice sheet. The ice cap subsequently grows again and reaches 82°N at the end of the simulation after 125~Ma. At an obliquity of 25.2° the ice cap reaches equilibrium with its margin at 78°N. In all cases, it takes tens of millions of years to reach the equilibrium state, and we conclude that the present-day north polar ice cap is most likely not in or close to equilibrium with the present-day climate. Re-running the simulations with ice-free initial conditions shows that an ice cap forms only for obliquities less than a critical value of approximately 22°.
DE: 0726 Ice sheets
DE: 0798 Modeling
DE: 5405 Atmospheres (0343, 1060)
DE: 5416 Glaciation
DE: 5462 Polar regions
SC: Cryosphere [C]
MN: 2007 Fall Meeting