Abstract

In recent years it has become apparent that circulation of warm ocean water under ice shelves in the Amundsen Sector of West Antarctica has lead to large amounts of mass loss from the shelves, and subsequently to acceleration and loss of grounded ice mass due to diminished ice shelf buttressing. The observational dataset for this region continues to grow, deepening our understanding of the system. Yet there are some questions—regarding, for instance, the timescales on which ocean circulation and ice shelf morphology co-evolve, and the sensitivity of grounded ice to spatial patterns in melt rates—that are best answered by a modelling approach.

To this end, experiments have been run with an idealized model of a coupled ice stream-ice shelf-ocean system, in which the shelf cavity is perturbed by far-field ocean conditions. A strong, nonlinear sensitivity of grounded ice to ocean temperature is seen, owing to the role of ice-ocean interactions in the ice shelf shear margin—even though this is not where melt rates are largest. This “structural weakness” is demonstrated through sensitivity experiments with an adjoint model, and is further shown to be a real feature of Pine Island Ice Shelf, raising questions about where under ice shelves melt rate variability is important, from a glaciological perspective.