Modelling sea-level reconstructions from southern Greenland: Implications for glacially-induced faulting and the response of the ice sheet to the Younger Dryas cold interval

Understanding the past evolution of the Greenland ice sheet (GrIS) is important for accurately simulating its future behavior and thus its contribution to global mean sea level rise. Data and models related to glacial isostatic adjustment (GIA) have provided critical constraints on past GrIS evolution. These models are necessary to interpret a variety of data, including past sea-level changes and geodetic observations of current land motion and gravity changes. In all studies to date, paleo sea level data from southern Greenland have presented the greatest challenge to GIA models. Poor data-model fits in this region have led to the hypothesis of glacially-induced faulting  during periods of rapid ice loss (with associated tsunami hazard).

In this study, we seek to determine if quality fits to the southern Greenland relative sea level (RSL) data can be obtained by improving the GIA model and exploring the parameter space more fully than past efforts. Specifically, we consider two recent advancements in model development: new 3-D models of earth viscosity structure based on the joint inversion of regional geophysical datasets, and GrIS reconstructions output from a leading glacial systems model. The improved 3-D earth models result in a larger RSL fall compared to past 1-D earth modelling and so that amplitude of the measured signal can be accurately simulated at most sites in southern Greenland. However, the rate and timing of RSL fall are generally too late and too slow to match many of the mid-Holocene sea-level index points. We seek to improve this aspect of the model fits by varying the ice history model. A two-step approach is used: (1) manually adjust the timing and rate of ice retreat in a chosen model to identify if plausible variations in these aspects can capture RSL data, and (2) assuming (1) is satisfied, seek to produce a glaciologically consistent ice history by varying parameters within the glacial systems model (e.g., climate forcing). In this presentation, we will provide an update on the status of our sensitivity analysis and the implications for glacially-induced faulting and the ice sheet response to the Younger Dryas cold interval.