RESPONSE-TIME OF GLACIERS AS A FUNCTION OF SIZE AND MASS-BALANCE - 2 - NUMERICAL EXPERIMENTS

Numerical experiments were made using a time-dependent nonlinear finit e element model of glacier flow to seek confirmation of theoretical pr edictions made in the companion to this paper [Bahr et al., this issue ]. The theoretical analysis indicates that under conditions of equal g radients in mass balance along the glacier surface (partial derivative (b) over dot/partial derivative x), other variables being held constan t, response time to mass balance perturbations will decrease as glacie r size increases. This behavior is confirmed by the numerical model ex periments, which are performed on a suite of 23 radially symmetric ice caps with sizes ranging over similar to 4 orders of magnitude. The sh ape and mass balance profiles of the ice caps are defined so that part ial derivative(b) over dot/partial derivative x is constant over all i ce caps, and for uniform perturbations in mass balance, the modeled re sponse times are faster for larger ice caps. The model results also co nfirm a volume/area scaling relationship established in the theoretica l discussion and confirm the equivalence between two measures of respo nse time, one arising from the present theory and the other a conventi onal expression of response time. The apparent discrepancy between the present results and preexisting theory is discussed, and it is shown that the results are compatible.