Constraining global models of the glacial isostatic adjustment process: Where should we look next?

Models of the Glacial Isostatic Adjustment (GIA) process play a central role in our understanding of Earth-Ice-Ocean interactions. For instance, they provide fundamental insight on the viscosity structure of the Earth's interior, on the changes in sea level and ice cover that have characterized those cycles, and on regional characteristics of sea-level change over the next decades and centuries. The recent availability of high-quality constraints related to the GIA process has enabled us not only to revisit the ability of current state-of-the-art models to capture the nature of these complex interactions, but also to consider how to maximize the information content extracted from high-quality geological records. Here, we review some of the available data used to constrain GIA models, focusing on geological records of past sea level (Last Glacial Maximum to present) and on Global Positioning System (GPS) observations of present-day crustal motion. We specifically look at how each type of data may be important in the context of constraining various components and features of global GIA models. The spatial and temporal variability of available relative sea level records over this time period is emphasized, together with some key temporal and spatial gaps that may affect our ability to better constrain global GIA models. A series of sensitivity tests is performed, and we underscore how future data collection efforts could be directed to address some of the issues that have been identified.