Late Noachian Icy Highlands Equilibirum Line Altitude (ELA): Predicted Characteristics, Glacial and Periglacial Processes and Response to Climate Change
The Late Noachian Icy Highlands (LNIH) scenario describes the results of an early Mars General Circulation Model including a full water cycle: when atmospheric pressure exceeds a few tens to a hundred millibars, the atmosphere thermally couples to the surface, inducing adiabatic cooling and the preferential deposition of snow and ice at high altitudes, specifically in the southern uplands. In this environment, global mean annual temperatures (MAT) are ~225 K, almost 50 K below the melting temperature of water. An equilibrium line altitude (ELA) is an altitude at which net accumulation occurs above and net ablation occurs below. Models suggest that a plausible equilibrium line altitude (ELA) for this environmental setting is ~+1 km . Fig. 1 illustrates a LNIH scenario with all areas >+1 km altitude in white to illustrate snow and ice accumulation. In order to test the validity of the LNIH model and compare it to predictions of the alternative “warm and wet” climate scenario, we analyze the predicted characteristics of the ELA environment and assess the geologic processes operating there in 1) an ambient LNIH environment and 2) one in which punctuated global warming takes place.
J. W. Head and J. L. Fastook and A. M. Palumbo and C. A. Denton and D. R. Marchant, LATE NOACHIAN ICY HIGHLANDS EQUILIBIRUM LINE ALTITUDE (ELA): PREDICTED CHARACTERISTICS, GLACIAL AND PERIGLACIAL PROCESSES AND RESPONSE TO CLIMATE CHANGE, Lunar and Planetary Science Conference 48, #1540, 2017 https://www.hou.usra.edu/meetings/lpsc2017/