Print button

Abstract EANA2025-161


Ocean circulation, tides and Habitability on a temperate paleo-Venus at 2.9 Ga

Diogo Quirino (1) (2) (3), J. A. Mattias Green (3), Pedro Machado (1), João C. Duarte (2), Michael J. Way (4) (5) (6), Soph F. Wilday (3), Cédric Gillmann (7), Diogo L. Lourenço (7)
(1) Instituto de Astrofísica e Ciências do Espaço (IA) and Physics Department, Faculty of Sciences, University of Lisbon, Campo Grande, PT1749-016 Lisbon, Portugal; (2) Instituto Dom Luiz (IDL) and Geology Department, Faculty of Sciences, University of Lisbon, Campo Grande, PT1749-016 Lisbon, Portugal; (3) School of Ocean Sciences, Bangor University Menai Bridge, LL59 5AB, United Kingdom; (4) NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA; (5) Theoretical Astrophysics, Department of Physics and Astronomy, Uppsala University, Uppsala, SE-75120, Sweden; (6) GSFC Sellers Exoplanet Environments Collaboration, NASA Goddard Space Flight Center, MD, USA; (7) Institute of Geophysics, Department of Earth and Planetary Sciences, ETH Zurich, Zurich, 8092, Switzerland.


We explore ocean circulation and heat redistribution on a temperate paleo-Venus, assuming surface water condensation from the steam atmosphere [1–4]. We simulate a hypothetical ocean on Venus at 2.9 Ga using a 3D General Circulation Model (GCM) - ROCKE-3D (Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics), developed at the NASA Goddard Institute for Space Studies [5]. We also explore ocean tidal dissipation using the Oregon State University Tidal Inversion Software (OTIS) [6].

We select a spatial resolution of 4ºx5º (latitude x longitude) in ROCKE-3D, a 40-layer atmosphere (top pressure, 0.1-hPa) and a 13-layer fully dynamic ocean [7], coupled to the atmosphere. We simulate three oceanic scenarios with different global equivalent layers (GEL): 310-m and 1000-m, using a modern Venus-like topography following the NASA/Magellan archive; and a 158-m aquaplanet. In the 310-m (1000-m) scenario, ocean surface coverage is ~60% (~88%) with 10% (35%) of Earth’s Ocean volume. Insolation is 2001 W/m2 (1.47x modern Earth) in all simulations. Atmospheric composition is Archean Earth-like (1.013-bar N2, 400-ppm CO2, 1-ppm CH4) [2]. We use modern Venus’s surface gravity, radius, obliquity, eccentricity and rotation rate (retrograde slow-rotator: -243 days) [1].

We discuss the main physical oceanographic parameters such as potential temperature, salinity, potential density, stratification and circulation. Our results indicate a monthly-long diurnal cycle, allowing for the development of a deep equatorial mixed layer during nighttime. Inversion of the equatorial surface currents is also observed from midday (westward) to the evening terminator (eastward). The 310-m southern ocean shows a positive salinity anomaly controlled by evaporation and limited exchange due to strait-like features. In all scenarios, a complex «meridional overturning circulation» develops, leading to a bathymetry-controlled heat redistribution. These results highlight the role of ocean circulation and landmass in energy redistribution in the paleo-Venus. For instance, the 310-m ocean’s sea surface temperature is ~15ºC colder than in the aquaplanet.

We will examine the ocean tidal dissipation in the paleo-Venus, assuming that modern volcanic topographic rises are a transient-geodynamic scenario (e.g., [8]). Ocean tides on Earth drive vertical fluxes of carbon and nutrients [9] and sustain high-latitude deep water formation through mixing-induced vertical volume fluxes [10]. Venusian tides are simulated using OTIS, which has been extensively used for deep-time, present-day and future tides on Earth [6, 11–13] and on Venus with a modern topography [14]. We will discuss the importance of ocean circulation, tides, landmass configuration to evaluate climate scenarios for a temperate paleo-Venus and implications for the Habitability of Earth-sized, slow-rotator exoplanets.

References: [1] Way, M.J., et al.,2016.GRL.43; [2] Way, M.J. & Del Genio, A.D.2020. JGR:Planets.125; [3] Yang, J., et al.,2014. ApJL.787,L2; [4] Way, M.J., et al.,2022. Sci.J.3:92; [5] Way, M.J., et al.,2017. ApJS.213:12; [6] Egbert, G.D., et al.,2004. JGRC.109.C03003; [7] Russell, G.L., et al.,1995. Atmos-Ocean.33:683; [8] Tian, J., et al.,2023. Icarus.399.115539; [9] Sharples, J., et al.,2007. LimOc.52.1735; [10] Munk, W., & Wunsch, C. 1998. Deep-Sea Research.45:1977; [11] Green, J., et al.,2017. E&PSL.461,46; [12] Green, J., et al.,2018. GeoRL.45.3568; [13] Wilmes, S.-B.,2017. JGRC.122,8354; [14] Green, J., et al.,2019. ApJL.876:L22.