The Fate of Ice Sheets on Near-Synchronously Rotating Land Planets
Abstract
Rocky exoplanets orbiting M dwarf stars are often assumed to be synchronously rotating, such that water-trapping in ice sheets on the permanent nightside may pose a threat to habitability. However, in compact M dwarf systems, gravitational interactions between planets may cause the substellar point to librate or circulate on millennial timescales and sporadically change direction or speed. Here, we use a 3D global climate model to quantify, for the first time, the water-trapping capabilities of these "near"-synchronously rotating exoplanets, with TRAPPIST-1e as our test case. Across a range of synodic day lengths, we find that there is a permanent polar ice reservoir and an increasingly large build-up of lower-latitude transient nightside ice for longer days. A persistent ice-free region develops on the dayside where surface conditions can sustain liquid water. However, this steady-state ice distribution may never be realized since the accumulation timescale may be slower than changes in the spin regime. Additionally, we revise the nightside ice build-up on a synchronously rotating exoplanet using a coupled atmosphere+ice numerical model that accounts for atmospheric lapse rate and isostatic adjustment feedbacks. We find that accounting for this ice-elevation feedback reduces the predicted ice accumulation by a factor of ~3. Taken together, our study suggests that water-trapping in ice sheets is less severe than previously thought for land planets orbiting M dwarf stars.
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BibTeX
@misc{silverman2026fate,
title = {{The Fate of Ice Sheets on Near-Synchronously Rotating Land Planets}},
author = {Sarah Silverman and Thomas Navarro and Martin Turbet and Nicolas B. Cowan and Natalya Gomez and Siddharth Bhatnagar and Emeline Bolmont},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.33884},
eprint = {2610.33884},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.33884},
}
RIS
TY - UNPB
TI - The Fate of Ice Sheets on Near-Synchronously Rotating Land Planets
AU - Sarah Silverman
AU - Thomas Navarro
AU - Martin Turbet
AU - Nicolas B. Cowan
AU - Natalya Gomez
AU - Siddharth Bhatnagar
AU - Emeline Bolmont
PY - 2026
DA - 2026/10/24
PB - arXiv
DO - 10.48550/arxiv.2610.33884
UR - https://arxiv.org/abs/2610.33884
AB - Rocky exoplanets orbiting M dwarf stars are often assumed to be synchronously rotating, such that water-trapping in ice sheets on the permanent nightside may pose a threat to habitability. However, in compact M dwarf systems, gravitational interactions between planets may cause the substellar point to librate or circulate on millennial timescales and sporadically change direction or speed. Here, we use a 3D global climate model to quantify, for the first time, the water-trapping capabilities of these "near"-synchronously rotating exoplanets, with TRAPPIST-1e as our test case. Across a range of synodic day lengths, we find that there is a permanent polar ice reservoir and an increasingly large build-up of lower-latitude transient nightside ice for longer days. A persistent ice-free region develops on the dayside where surface conditions can sustain liquid water. However, this steady-state ice distribution may never be realized since the accumulation timescale may be slower than changes in the spin regime. Additionally, we revise the nightside ice build-up on a synchronously rotating exoplanet using a coupled atmosphere+ice numerical model that accounts for atmospheric lapse rate and isostatic adjustment feedbacks. We find that accounting for this ice-elevation feedback reduces the predicted ice accumulation by a factor of ~3. Taken together, our study suggests that water-trapping in ice sheets is less severe than previously thought for land planets orbiting M dwarf stars.
ER -