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.
Your institute does not have access to this article
Subscribe to Nature+
Get immediate online access to the entire Nature family of 50+ journals
Subscribe to Journal
Get full journal access for 1 year
only $8.25 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
The data that support the findings of this study are archived on Zenodo at https://doi.org/10.5281/zenodo.347357.
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.
Wall, S. et al. Active shoreline of Ontario Lacus, Titan: a morphological study of the lake and its surroundings. Geophys. Res. Lett. 37, L05202 (2010).
Langhans, M. et al. Titan’s fluvial valleys: morphology, distribution, and spectral properties. Planet. Space Sci. 60, 34–51 (2012).
Burr, D. M. et al. Fluvial features on Titan: insights from morphology and modeling. Geol. Soc. Am. Bull. 125, 299–321 (2013).
Neish, C. D. & Lorenz, R. D. Elevation distribution of Titan’s craters suggests extensive wetlands. Icarus 228, 27–34 (2014).
Neish, C. D. et al. Fluvial erosion as a mechanism for crater modification on Titan. Icarus 270, 114–129 (2016).
Birch, S. et al. Geomorphologic mapping of Titan’s polar terrains: constraining surface processes and landscape evolution. Icarus 282, 214–236 (2017).
Stofan, E. R. et al. The lakes of Titan. Nature 445, 61–64 (2007).
Hayes, A. et al. Hydrocarbon lakes on Titan: distribution and interaction with a porous regolith. Geophys. Res. Lett. 35, L09204 (2008).
Hayes, A. G. The lakes and seas of Titan. Annu. Rev. Earth Planet. Sci. 44, 57–83 (2016).
Hayes, A. et al. Topographic constraints on the evolution and connectivity of Titan’s lacustrine basins. Geophys. Res. Lett. 44, 11745–11753 (2017).
Griffith, C. A. et al. The evolution of Titan’s mid-latitude clouds. Science 310, 474–477 (2005).
Ádámkovics, M. et al. Meridional variation in tropospheric methane on Titan observed with AO spectroscopy at Keck and VLT. Icarus 270, 376–388 (2016).
Lora, J. M. & Ádámkovics, M. The near-surface methane humidity on Titan. Icarus 286, 270–279 (2017).
Mitchell, J. L. & Lora, J. M. The climate of Titan. Annu. Rev. Earth Planet. Sci. 44, 353–380 (2016).
Lora, J. M. & Mitchell, J. L. Titan’s asymmetric lake distribution mediated by methane transport due to atmospheric eddies. Geophys. Res. Lett. 42, 6213–6220 (2015).
Perron, J. et al. Valley formation and methane precipitation rates on Titan. J. Geophys. Res. Planets 111, E11 (2006).
Jaumann, R. et al. Fluvial erosion and post-erosional processes on Titan. Icarus 197, 526–538 (2008).
Black, B., Perron, J., Burr, D. & Drummond, S. Estimating erosional exhumation on Titan from drainage network morphology. J. Geophys. Res. Planets 117, E8 (2012).
Birch, S., Hayes, A., Howard, A., Moore, J. & Radebaugh, J. Alluvial fan morphology, distribution and formation on Titan. Icarus 270, 238–247 (2016).
Faulk, S. P., Moon, S., Mitchell, J. L. & Lora, J. M. Regional patterns of extreme precipitation on Titan consistent with observed alluvial fan distribution. Nat. Geosci. 10, 827–831 (2017).
Hayes, A. G. et al. Transient surface liquid in Titan’s polar regions from Cassini. Icarus 211, 655–671 (2011).
Turtle, E. P., Perry, J. E., Hayes, A. G. & McEwen, A. S. Shoreline retreat at Titan’s Ontario Lacus and Arrakis Planitia from Cassini Imaging Science Subsystem observations. Icarus 212, 957–959 (2011).
MacKenzie, S. M. et al. The case for seasonal surface changes at Titan’s lake district. Nat. Astron. 3, 506–510 (2019).
Birch, S. et al. Morphological evidence that Titan’s southern hemisphere basins are paleoseas. Icarus 310, 140–148 (2017).
Turtle, E. P. et al. Titan’s meteorology over the Cassini mission: evidence for extensive subsurface methane reservoirs. Geophys. Res. Lett. 45, 5320–5328 (2018).
Lora, J. M., Lunine, J. I. & Russell, J. L. GCM simulations of Titan’s middle and lower atmosphere and comparison to observations. Icarus 250, 516–528 (2015).
Mitchell, J. L. The drying of Titan’s dunes: Titan’s methane hydrology and its impact on atmospheric circulation. J. Geophys. Res. 113, E08015 (2008).
Schneider, T., Graves, S. D. B., Schaller, E. L. & Brown, M. E. Polar methane accumulation and rainstorms on Titan from simulations of the methane cycle. Nature 481, 58–61 (2012).
Tokano, T. Orbitally and geographically caused seasonal asymmetry in Titan’s tropospheric climate and its implications for the lake distribution. Icarus 317, 337–353 (2019).
Horvath, D. G., Andrews-Hanna, J. C., Newman, C. E., Mitchell, K. L. & Stiles, B. W. The influence of subsurface flow on lake formation and north polar lake distribution on Titan. Icarus 277, 103–124 (2016).
Lopes, R. M. C. et al. Titan as revealed by the Cassini Radar. Space Sci. Rev. 215, 33 (2019).
Dhingra, R. D., Barnes, J. W., Yanites, B. J. & Kirk, R. L. Large catchment area recharges Titan’s Ontario Lacus. Icarus 299, 331–338 (2018).
Newman, C. E., Richardson, M. I., Lian, Y. & Lee, C. Simulating Titan’s methane cycle with the TitanWRF general circulation model. Icarus 267, 106–134 (2016).
Mitchell, J. L., Pierrehumbert, R. T., Frierson, D. M. W. & Caballero, R. The dynamics behind Titan’s methane clouds. Proc. Natl Acad. Sci. USA 103, 18421–18426 (2006).
Jennings, D. E. et al. Titan surface temperatures during the Cassini mission. Astrophys. J. Lett. 877, L8 (2019).
Jennings, D. et al. Surface temperatures on Titan during northern winter and spring. Astrophys. J. Lett. 816, L17 (2016).
Mitchell, J. L. Titan’s transport-driven methane cycle. Astrophys. J. 756, L26 (2012).
Lora, J. M., Lunine, J. I., Russell, J. L. & Hayes, A. G. Simulations of Titan’s paleoclimate. Icarus 243, 264–273 (2014).
Lorenz, R. D. et al. Titan’s inventory of organic surface materials. Geophys. Res. Lett. 35, L02206 (2008).
Birch, S. P. D. et al. Raised rims around Titan’s sharp-edged depressions. Geophys. Res. Lett. 46, 5846–5854 (2019).
Zarnecki, J. C. et al. A soft solid surface on Titan as revealed by the Huygens Surface Science Package. Nature 438, 792–795 (2005).
Barnes, J. et al. Global-scale surface spectral variations on Titan seen from Cassini/VIMS. Icarus 186, 242–258 (2007).
Soderblom, L. et al. Correlations between Cassini VIMS spectra and RADAR SAR images: implications for Titan’s surface composition and the character of the Huygens Probe Landing Site. Planet. Space Sci. 55, 2025–2036 (2007).
Janssen, M. A. et al. Titan’s surface at 2.18-cm wavelength imaged by the Cassini RADAR radiometer: results and interpretations through the first ten years of observation. Icarus 270, 443–459 (2016).
Griffith, C. A. et al. A corridor of exposed ice-rich bedrock across Titan’s tropical region. Nat. Astron. 3, 642–648 (2019).
Cornet, T. et al. Dissolution on Titan and on Earth: toward the age of Titan’s karstic landscapes. J. Geophys. Res. Planets 120, 1044–1074 (2015).
Lopes, R. M. et al. Nature, distribution, and origin of Titan’s undifferentiated plains. Icarus 270, 162–182 (2016).
Tobie, G., Lunine, J. I. & Sotin, C. Episodic outgassing as the origin of atmospheric methane on Titan. Nature 440, 61–64 (2006).
Mousis, O., Choukroun, M., Lunine, J. I. & Sotin, C. Equilibrium composition between liquid and clathrate reservoirs on Titan. Icarus 239, 39–45 (2014).
Frierson, D. The dynamics of idealized convection schemes and their effect on the zonally averaged tropical circulation. J. Atmos. Sci. 64, 1959–1976 (2007).
Philip, J. R. Evaporation, and moisture and heat fields in the soil. J. Meteorol. 14, 354–366 (1957).
Shah, N., Nachabe, M. & Ross, M. Extinction depth and evapotranspiration from ground water under selected land covers. Groundwater 45, 329–338 (2007).
Johnson, E., Yáñez, J., Ortiz, C. & Muñoz, J. Evaporation from shallow groundwater in closed basins in the Chilean Altiplano. Hydrol. Sci. J. 55, 624–635 (2010).
Corlies, P. et al. Titan’s topography and shape at the end of the Cassini mission. Geophys. Res. Lett. 44, 11754–11761 (2017).
Kurc, S. A. & Small, E. E. Dynamics of evapotranspiration in semiarid grassland and shrubland ecosystems during the summer monsoon season, central New Mexico. Water Resour. Res. 40, W09305 (2004).
Tokano, T. Meteorological assessment of the surface temperatures on Titan: constraints on the surface type. Icarus 173, 222–242 (2005).
MacKenzie, S. M., Lora, J. M. & Lorenz, R. D. A thermal inertia map of Titan. J. Geophys. Res. Planets 124, 1728–1742 (2019).
Cammeraat, E. L. Scale dependent thresholds in hydrological and erosion response of a semi-arid catchment in southeast Spain. Agric. Ecosyst. Environ. 104, 317–332 (2004).
O’Callaghan, J. F. & Mark, D. M. The extraction of drainage networks from digital elevation data. Comput. Vis. Graph. Image Process. 28, 323–344 (1984).
Tarboton, D. G. A new method for the determination of flow directions and upslope areas in grid digital elevation models. Water Resour. Res. 33, 309–319 (1997).
Freeman, T. G. Calculating catchment area with divergent flow based on a regular grid. Comput. Geosci. 17, 413–422 (1991).
Shelef, E. & Hilley, G. E. Impact of flow routing on catchment area calculations, slope estimates, and numerical simulations of landscape development. J. Geophys. Res. Earth Surf. 118, 2105–2123 (2013).
Overton, D. Route or convolute? Water Resour. Res. 6, 43–52 (1970).
Watt, W. E. & Chow, K. A. A general expression for basin lag time. Can. J. Civ. Eng. 12, 294–300 (1985).
Liston, G., Sud, Y. & Wood, E. Evaluating GCM land surface hydrology parameterizations by computing river discharges using a runoff routing model: application to the Mississippi basin. J. Appl. Meteorol. 33, 394–405 (1994).
Miller, J. R., Russell, G. L. & Caliri, G. Continental-scale river flow in climate models. J. Clim. 7, 914–928 (1994).
Coe, M. T. Modeling terrestrial hydrological systems at the continental scale: testing the accuracy of an atmospheric GCM. J. Clim. 13, 686–704 (2000).
Wang, J. et al. The Coupled Routing and Excess STorage (CREST) distributed hydrological model. Hydrol. Sci. J. 56, 84–98 (2011).
Askew, A. J. Derivation of formulae for variable lag time. J. Hydrol. 10, 225–242 (1970).
Singh, V. P. Hydrologic Systems. Volume I: Rainfall-Runoff Modeling (Prentice-Hall, 1988).
Vörösmarty, C. J. et al. Continental scale models of water balance and fluvial transport: an application to South America. Global Biogeochem. Cycles 3, 241–265 (1989).
Sellers, P. et al. A revised land surface parameterization (SiB2) for atmospheric GCMs. Part I: Model formulation. J. Clim. 9, 676–705 (1996).
Milly, P. et al. An enhanced model of land water and energy for global hydrologic and earth-system studies. J. Hydrometeorol. 15, 1739–1761 (2014).
Iess, L. et al. The tides of Titan. Science 337, 457–459 (2012).
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.
The authors declare no competing interests.
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.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
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
Nature Astronomy (2021)