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Titan’s climate patterns and surface methane distribution due to the coupling of land hydrology and atmosphere

Abstract

Planetary surfaces beyond Earth’s are impacted by surface hydrology, and exhibit fluvial and lacustrine features. Titan in particular harbours a rich hydroclimate replete with valley networks, lakes, seas and putative wetlands, all of which are pronounced in the lower-elevation polar regions. However, understanding of Titan’s global climate has heretofore neglected the hydraulic influence of Titan’s large-scale topography. Here we add a surface hydrology model to an existing Titan atmospheric model, and find that infiltration, groundmethane evaporation, and surface and subsurface flow are fundamental to simultaneously reproducing Titan’s observed surface liquid distribution and other aspects of its climate system. We propose that Titan’s climate features infiltration into unsaturated low- and mid-latitude highlands and surface or subsurface flow into high-latitude basins, producing the observed polar moist climes and equatorial deserts. This result implies that a potentially massive unobserved methane reservoir participates in Titan’s methane cycle. It also illustrates the importance of surface hydrology in Titan climate models, and by extension suggests the influence of surface hydrology in idealized models of other planetary climates, including the climates and palaeoclimates of Earth, Mars and exoplanets.

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Fig. 1: Surface hydrology model and topography map.
Fig. 2: Surface distribution of liquid methane.
Fig. 3: Subsurface methane tables.
Fig. 4: Seasonal precipitation distributions.
Fig. 5: Seasonal temperature distributions.
Fig. 6: Groundmethane evaporation.

Data availability

The data that support the findings of this study are archived on Zenodo at https://doi.org/10.5281/zenodo.347357.

Code availability

The source code for TAM is currently not publicly available. Scripts used to analyse simulation output are available from the corresponding author on reasonable request.

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Acknowledgements

This research was supported by NASA Cassini Data Analysis and Participating Scientists (CDAPS) Program grant NNX16AI44G. We are grateful to A. Hayes for insightful discussions pertaining to groundmethane evaporation, and to S. Moon for thorough and thoughtful comments on earlier versions of the manuscript.

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Authors

Contributions

J.L.M. and J.M.L. devised the study. S.P.F. developed the land hydrology model with input from all authors. S.P.F. and J.M.L. carried out the analysis and prepared the manuscript, with contributions from all authors.

Corresponding author

Correspondence to Juan M. Lora.

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Peer review information Nature Astronomy thanks Mohit Melwani Daswani and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Faulk, S.P., Lora, J.M., Mitchell, J.L. et al. Titan’s climate patterns and surface methane distribution due to the coupling of land hydrology and atmosphere. Nat Astron 4, 390–398 (2020). https://doi.org/10.1038/s41550-019-0963-0

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