Analyzing Differences between Shallow-Shelf and L1L2 Approximations using BISICLES

Abstract:

Contributions to the MISMIP3d intercomparison showed a non-trivial difference in steady-state grounding-line positions produced from models using both a shallow-shelf approximation (SSA) and higher-fidelity models like the L1L2 approximation, even with identical spatial resolution and discretization. These differences in the initial state led to differences in response to the forced experiments. We analyze the impact of this difference more thoroughly by treating the results from a higher-order approximation as observational values, then performing an inversion to solve for the basal friction C(x,y) and stiffening coefficient φ(x,y) to initialize the SSA to match. The resulting dynamic response provides insight into the differences between these approximations in a context akin to how ice sheet models are employed when applied to realistic problems.