The impact of sea-level rise on baselines: a question of interpretation of the UNCLOS or evolution of customary law?

In the framework of the broader question of the adverse impact of sea-level rise on low-lying coastal and archipelagic States, the specific question of the effects on baselines has been receiving increasing attention in the international debate. The question is whether, once a State has determined its baselines by a legislative or administrative act, these lines are fixed and will not be altered by any subsequent physical change due to the SLR. In other words, could baselines be opposable to other States regardless of a substantial change in the configuration of the coasts? Or, on the contrary, are baselines ambulatory so that in case of inundation of coastal areas, the baselines will move in a landward direction? To put it differently, might third States challenge the discrepancy between the charted and actual baselines?