A coupled climate-hydrology model for the long-term planetary evolution of surface water reservoirs on early Mars

Abstract

Understanding the hydrological evolution of early Mars is essential for interpreting geomorphological evidence of past liquid water, including valley networks, paleolakes, sedimentary deposits and possible northern oceans (for a review see Carr and Head, 2010). While Global Climate Models (GCM) can simulate atmospheric circulation and precipitation/evaporation patterns, they remain computationally limited to study climatic timescales. On the other hand, hydrological models generally rely on prescribed climatic conditions or are applied at regional scale. Because of this, the coupled long-term evolution of Martian climate and hydrology remains poorly understood.

Here we present a coupled climate-hydrology framework based on the Generic Planetary Climate Model (PCM; see the wiki in the references) and the Planetary Evolution Model (PEM, Clément et al., 2026). The PEM is designed to simulate the long-term evolution of surface reservoirs by asynchronous coupling with the PCM. The PEM evolves the long-term climate state from annual tendencies periodically provided by the PCM which computes the full climate physics. New PCM integrations are triggered when the evolving state deviates significantly from the climatic conditions under which the tendencies were derived. This strategy reduces computational cost and bridges the gap between detailed short-term climate simulations and planetary-scale long-term evolution.

The PEM includes a global high-resolution hydrology model (Gauvin et al., 2026) that evolves perennial liquid water reservoirs on the surface (e.g., lakes and oceans). This module computes the formation, disappearance, overflow and merging of lakes according to topography and PCM precipitation/evaporation tendencies. The resulting perennial water distribution is given back to the PCM to update the tendencies, allowing climate and hydrology to interact iteratively.

This work aims to explore how climatic forcing controls the spatial organization and hydrological connectivity of perennial surface water reservoirs on early Mars. As a first application, we consider idealized simulations using prescribed climate scenarios to analyze how precipitation/evaporation patterns influence the redistribution, persistence and connectivity of lakes and runoff systems. We investigate the role of topography in the stability of precipiation-fed reservoirs and runoff-fed reservoirs as well as the transition between isolated lacustrine systems and regionally connected drainage networks. Our results provide key insights into the climate scenarios required to reproduce the fluvial features observed on Mars (e.g., Barnhart et al., 2009; Carr and Head, 2010; Hoke et al., 2011).

This study represents a first demonstration of the PCM-PEM hydrology coupling strategy. Ultimately, this framework will provide a new tool to investigate the co-evolution of climate, hydrology and geomorphology on Mars over geological timescales.

 

References

Barnhart, C. J., Howard, A. D., and Moore, J. M. (2009). Long‐term precipitation and late‐stage valley network formation: Landform simulations of Parana Basin, Mars. Journal of Geophysical Research: Planets, 114(E1). https://doi.org/10.1029/2008JE003122.

Carr, M. H., and Head, J. W. (2010). Geologic history of Mars. Earth and Planetary Science Letters, 294(3–4), 185–203. https://doi.org/10.1016/j.epsl.2009.06.042.

Clément, J.-B., Forget, F., Vos, E., Lange, L., and Millour, E. (2025). Mars Through Time International Conference, 40.

Gauvain, A., Forget, F., Turbet, M., Clément, J.-B., Lange, L., and Vandemeulebrouck, R. (2025). A Global High-Resolution Hydrological Model to Simulate the Dynamics of Surface Liquid Reservoirs: Application on Mars, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-4992.

Hoke, M. R. T., Hynek, B. M., and Tucker, G. E. (2011). Formation timescales of large Martian valley networks. Earth and Planetary Science Letters, 312(1-2), 1-12. https://doi.org/10.1016/j.epsl.2011.09.053.

Wiki of the Generic Planetary Climate Model (PCM) online at https://lmdz-forge.lmd.jussieu.fr/mediawiki/Planets/index.php/Main_Page.