The dependence of the ice-albedo feedback on atmospheric properties

TL;DR

This study explores how atmospheric properties like pressure and composition influence the ice-albedo feedback on terrestrial planets, revealing that atmospheres can significantly weaken this climate destabilizing effect, especially around M stars.

Contribution

It provides a detailed analysis of how atmospheric factors modulate the ice-albedo feedback, extending previous work by including various atmospheric compositions and pressures.

Findings

Atmospheric pressure and composition significantly affect the ice-albedo feedback.

High CO2 atmospheres reduce the feedback strength, especially around M stars.

Trace gases like H2O, CH4, and O3 further weaken the feedback.

Abstract

The ice-albedo feedback is a potentially important de-stabilizing effect for the climate of terrestrial planets. It is based on the positive feedback between decreasing surface temperatures, an increase of snow and ice cover and an associated increase in planetary albedo, which then further decreases surface temperature. A recent study shows that for M stars, the strength of the ice-albedo feedback is reduced This study investigates the influence of the atmosphere (in terms of surface pressure and atmospheric composition) for this feedback. A plane-parallel radiative transfer model is used for the calculation of planetary albedos. We varied CO2 partial pressures as well as the H2O, CH4, and O3 content in the atmosphere for planets orbiting Sun-like and M-type stars. Results suggest that for planets around M stars, the ice-albedo effect is significantly reduced, compared to planets around Sun-like stars. Including the effects of an atmosphere further suppresses the sensitivity to the ice-albedo effect. Atmospheric key properties such as surface pressure, but also the abundance of radiative trace gases can considerably change the strength of the ice-albedo feedback. For dense CO2 atmospheres of the order of a few to tens of bar, atmospheric rather than surface properties begin to dominate the planetary radiation budget. At high CO2 pressures, the ice-albedo feedback is strongly reduced for planets around M stars. The presence of trace amounts of H2O and CH4 in the atmosphere also weakens the ice-albedo effect for both stellar types considered. For planets around Sun-like stars, O3 could also lead to a very strong decrease of the ice-albedo feedback at high CO2 pressures. (abridged)