The model is driven by sea-level change over the last 40,000 yr in association with assumed changes in the rate of melting beneath ice shelves. Ice growth and decay are characterized by thresholds which separate periods of steady state from periods
of rapid transition. Tests show that ice sheet behavior is most sensitive to sea-level change, basal marine melting and accumulation and is less sensitive to isostasy, spatial variation in accumulation, calving rates, and ice flow parameterization.