Antarctic Ice Flow Revealed

The Antarctic continent's immense mantle of ice is diminishing as warming ocean waters drive melt and accelerated glacier flow at the coasts (1–4). The importance of this process is widely recognized: A mere 5% reduction in the total mass of ice, for example, would place much of Miami, Amsterdam, and Bangkok below sea level. Predicting such changes in the centuries ahead requires understanding not only climate and its direct impact on ice loss but also the glacial flow that carries ice from the continent's interior out to its edges. Crudely, the ice sheet's flow resembles, at enormous scale, the spreading puddle formed by pouring pancake batter onto a skillet. Ice sheet flow, however, includes interesting features such as narrow, fast-moving zones called ice streams (see the figure). Such irregularities largely govern how the ice sheet reacts to changes imposed at its edges (1). The spatial pattern of ice flow must therefore be known. On page 1427 of this issue, Rignot et al. (5) report the first nearly complete measurement and mapping of ice flow for the entire Antarctic continent, providing a new foundation for studies of ice sheet evolution.