The North Polar Ice Cap of Mars at Varying Obliquities, Simulated With a Coupled Atmosphere/Ice-Sheet Model

Details The North Polar Ice Cap of Mars at Varying Obliquities, Simulated With a Coupled Atmosphere/Ice-Sheet Model The North Polar Ice Cap of Mars at Varying Obliquities, Simulated With a Coupled Atmosphere/Ice-Sheet Model

Dec 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufm.c51a0094s&link_type=abstract

American Geophysical Union, Fall Meeting 2007, abstract #C51A-0094

Mathematics

Logic

0726 Ice Sheets, 0798 Modeling, 5405 Atmospheres (0343, 1060), 5416 Glaciation, 5462 Polar Regions

Scientific paper

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°.

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