Mechanisms returning water from nightside to dayside

Determine the physical mechanisms that return water transported to the nightside of a tidally locked exoplanet back to its dayside, including the role of ice melting at or near the terminator, particularly for land-dominated worlds.

Background

Tidally locked planets can transport water toward the permanent nightside, where it may become trapped as ice. This redistribution is especially consequential for land-dominated planets, for which a finite surface-water inventory may be depleted from the illuminated hemisphere.

The paper identifies the return pathway for this water as unresolved, mentioning processes such as melting at or near the terminator. Understanding these mechanisms is necessary for evaluating long-term water availability and habitability beyond idealized aquaplanet simulations.