Summary
Accurate assessments of the past and future mass budgets of polar ice sheets are essential to resolving contributions to past sea-level rise and projecting responses to climate change respectively. Both tasks require that ice accumulation and ice flow are each accurately described, and that differing changes in interior and coastal margins are integrated. This is usually described as the mass budget method (e.g. Rignot and Thomas 2002). Current ice sheet mass imbalances and corresponding contributions to sea level change can also be estimated by directly observing changes in mass (e.g. GRACE mission) or elevation (e.g. satellite altimetry). Initial results from GRACE (Velicogna and Wahr 2006) suggest that East Antarctica is in balance, while satellite altimeter measurements of surface elevation changes over a slightly longer time-frame [Zwally et al (2005), Davis et al. (2005)] indicate that the interior of the East Antarctic ice sheet is thickening slightly, although there is not quantitative agreement about the magnitude. Direct estimates of ice sheet change appear capable of considerable accuracy and are useful in establishing the present state, but they only constrain the difference between the physical ingredients - current rates of net ice deposition and export by ice dynamics from the region surveyed. As a step towards testing how well current ice accumulation estimates correlate with the presently observed pattern of ice flow and how the East Antarctic interior might be presently contributing to sea-level change, historical field measurements of ice flow from Enderby Land to Wilkes Land (50°E to 140°E) are compared with estimates of ice accumulation to estimate the state of balance using computed “balance” ice fluxes (Budd and Warner 1996). This enables local estimates of the regional state of balance to be made, even for sparsely surveyed regions. The measured ice fluxes are drawn from ANARE field surveys of ice motion and ice sheet thickness, while the balance fluxes are computed using ice accumulation datasets and a satellite derived digital elevation model. The comparisons enable some inferences about differing regional states of imbalance of the ice sheet, about uncertainties involved in the component flux approach to the budget, and about the fidelity with which the available accumulation datasets reflect the long-term ice input.