Idealized Wind-driven Ocean Circulations On Exoplanets

TL;DR

This study explores idealized wind-driven ocean circulation patterns on exoplanets using a simplified model, analyzing how planetary rotation, wind stress, viscosity, and land structure influence circulation regimes.

Contribution

It introduces a one-layer shallow water model to simulate exoplanet ocean circulations, highlighting the effects of planetary and land features on flow patterns.

Findings

Western intensification occurs due to planetary rotation.

Ocean circulation strength varies with wind stress and viscosity.

Reentrant channels produce zonal flow patterns similar to Earth's Southern Ocean.

Abstract

Motivated by the important role of the ocean in the Earth climate system, here we investigate possible scenarios of ocean circulations on exoplanets using a one-layer shallow water ocean model. Specifically, we investigate how planetary rotation rate, wind stress, fluid eddy viscosity and land structure (a closed basin vs. a reentrant channel) influence the pattern and strength of wind-driven ocean circulations. The meridional variation of the Coriolis force, arising from planetary rotation and the spheric shape of the planets, induces the western intensification of ocean circulations. Our simulations confirm that in a closed basin, changes of other factors contribute to only enhancing or weakening the ocean circulations (e.g., as wind stress decreases or fluid eddy viscosity increases, the ocean circulations weaken, and vice versa). In a reentrant channel, just as the Southern Ocean region on the Earth, the ocean pattern is characterized by zonal flows. In the quasi-linear case, the sensitivity of ocean circulations characteristics to these parameters is also interpreted using simple analytical models. This study is the preliminary step for exploring the possible ocean circulations on exoplanets, future work with multi-layer ocean models and fully coupled ocean-atmosphere models are required for studying exoplanetary climates.