Model calculations of depth-age relations for deep ice cores in central Greenland are sensitive to stability of the ice-divide position. In addition, the folding of layers observed in the deep ice could be instigated by divide migration changing the velocity and particle paths of ice flow. We use simple steady-state calculations to show that lateral divide migration of between 10 km and 50 km and elevation change of approximately 100 m is likely on glacial-interglacial time scales, enough to affect model dating. The ice-divide location appears to be most sensitive to the position of the ice-sheet margins. By contrast, the ice-divide elevation is most sensitive to the accumulation rate, the temperature profile, and the ice-stiffness profile.