Exoplanets & Exomoons

Thermocline Depth On Water-rich Exoplanets

By Keith Cowing
June 26, 2022
Filed under
Thermocline Depth On Water-rich Exoplanets
Equilibrated fields of the three 2D simulations with different ocean depths. Left: the ocean depth is 5 km; middle: 10 km; right: 40 km. (a) Potential temperature (◦C); (b) potential density (kg m−3 , a value of 1000 kg m−3 has been subtracted); (c) meridional current (m s−1 ); (d) zonal current (color shading) and the corresponding thermal-wind balance current (contour lines) (m s−1 ); (e) sea surface height (SSH, m). Note the y-axis in (a)-(d) is nonlinear.

Water-rich exoplanet is a type of terrestrial planet that is water-rich and its ocean depth can reach tens of to hundreds of kilo-meters with no exposed continents.

Due to the lack of exposed continents, neither western boundary current nor coastal upwelling exists, and ocean overturning circulation becomes the most important way to return the nutrients deposited in deep ocean back to the thermocline and to the surface ocean.Here we investigate the depth of the thermocline in both wind-dominated and mixing-dominated systems on water-rich exoplanets using the global ocean model MITgcm.

We find that the wind-driven circulation is dominated by overturning cells through Ekman pumping and subduction and by zonal (west–east) circum-longitudinal currents, similar to the Antarctic Circumpolar Current on Earth. The wind-influenced thermocline depth shows little dependence on the ocean depth, and under a large range of parameters, the thermocline is restricted within the upper layers of the ocean. The mixing-influenced thermocline is limited within the upper 10 km of the ocean and can not reach the bottom of the ocean even under extremely strong vertical mixing.

The scaling theories for the thermocline depth on Earth are applicable for the thermocline depth on water-rich exoplanets. However, due to the lack of exposed continents, the zonal and meridional flow speeds are not in the same magnitude as that in the oceans of Earth, which results in the scaling relationships for water-rich exoplanets are a little different from that used on Earth.

Yanhong Lai, Jun Yang

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph)
Cite as: arXiv:2206.12049 [astro-ph.EP] (or arXiv:2206.12049v1 [astro-ph.EP] for this version)
Submission history
From: Yanhong Lai
[v1] Fri, 24 Jun 2022 02:58:11 UTC (19,358 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻