A TUTORIAL ON THE USE OF CONTROL METHODS IN ICE-SHEET MODELING

Control methods are recommended as an efficient means to estimate undetermined physical parameters and boundary conditions and, in so doing, to improve the fidelity of a given ice-sheet flow model to specific ice-sheet velocity observations. To accomplish this task, the underlying dynamics of the model are inverted. This permits model-tuning adjustments to be represented explicitly in terms of model/observation misfit. Advantages of the control method over trial-and-error techniques in common use are: (1) it is readily automated with little additional programming effort, (2) the tuning parameters and boundary conditions it achieves are assured to give the best possible fit between model and observation, and (3) it quantifies the uncertainty of tuning parameters and boundary conditions in situations where they are not uniquely determined.