The Antarctic Ice Sheets are the largest extant ice masses on Earth, and understanding their history is relevant not only to past environmental changes but also to ongoing changes in global climate and sea level. The glacial-geological record in Antarctica provides a means of reconstructing this history, but the unique features of the Antarctic environment present several challenges that do not arise in more temperate latitudes. In addition to the basic fact that the Antarctic continent is nearly completely covered in ice, leaving few exposed surfaces on which glacial deposits might be preserved, much of the ice in Antarctica is frozen to its bed. It transports little sediment to the terrestrial ice margins that do exist, and may advance and retreat repeatedly without appreciably disturbing the landscape. Antarctic moraines and glacial drift are usually very thin, often consisting only of scattered cobbles on an otherwise bare bedrock surface. The combination of cold-based ice and extraordinarily slow rates of subaerial erosion during icefree periods means that the deposits of both recent and long-past glacier advances and retreats may not only be found together, but be nearly indistinguishable. Finally, not only is it difficult to identify and correlate ice-marginal deposits, but there exist few ways to date them. Organic material that could be radiocarbon dated is rarely found outside of coastal areas, and waterlain sediment suitable for optical dating techniques is equally unusual.
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