Antarctic ice sheet shape response to changes in outlet flow boundary conditions

Abstract

This paper investigates the response of the Antarctic ice sheet shape and volume to changes in outlet flow boundary conditions. We model the transmission of outlet flow boundary perturbations toward the inland ice sheet by taking into account the dynamical properties of the profile. We investigate the effect of outlet perturbations according to their time scales. We derive the analytical relation between the temporal wavelength of the perturbations and the induced wavelength of surface undulations. We show that the inland undulation wavelength and transmission increase with the temporal wavelength of the perturbation, so that the short time scale perturbations are strongly filtered. For a given outlet perturbation, the induced frequency depends on the distance to the coast and on the dynamical characteristics of the profile, so that two adjacent flow lines may have different signals. Because outlet perturbations are poorly quantified, it is difficult to predict their impact on sea level change. However, the impact seems to be smaller than that induced by other random processes, such as accumulation rate fluctuations. Finally, an analysis of the ice sheet topography anomalies suggests that in some places, the actual response to a past outlet perturbation can be suspected.