Stability and accessibility of saltwater pocket steady states

Establish whether saltwater pocket steady states that arise in non-uniform subglacial aquifer geometries are stable under the transient evolution governed by the complementarity formulation for groundwater flow and seawater intrusion beneath a marine ice sheet, and determine whether physically realistic initial conditions and time-dependent grounding-line forcings can lead to the formation of such pocket steady states.

Background

The paper shows that, for certain basement geometries and ice overpressures, the governing complementarity model for groundwater/seawater intrusion admits steady states with isolated saltwater “pockets” disconnected from the nose near the grounding line. These pocket steady states are non-unique, depending on geometric criteria, and can significantly alter freshwater exfiltration patterns.

While explicit constructions illustrate their possibility, the authors note uncertainty about how such pockets influence the transient dynamics described by the complementarity problem for saltwater thickness h(x,t). In particular, they raise questions about whether pocket steady states are stable and whether realistic combinations of initial conditions and grounding-line forcing lead to pocket formation.