THE PATAGONIAN ICEFIELDS - A GLACIOLOGICAL REVIEW

The Patagonian icefields are the largest mid-latitude ice masses and y et few glaciological data exist for them. The presence of the Andes ly ing athwart the westerlies makes for a dynamic glacial system with ste ep balance gradients and west-east equilibrium-line altitude gradients . The overall trend during the 20th century has been glacier retreat. However, whereas most eastern outlets retreated consistently from the beginning of the century, recession on the west began later, has been interrupted by readvances, and most recently has accelerated markedly, reaching higher mean rates of retreat than those on the east. This co ntrast may result from a predominantly precipitation-controlled mass-b alance regime in the west and a dominant temperature control in the ea st. Superimposed on these contrasts is the anomalous behavior of certa in calving glaciers, the oscillations of which contrast in magnitude, timing and sign with each other and with noncalving glaciers, and whic h in many cases do not relate directly to climate change. Two large ca lving outlets are at or near their Neoglacial maxima. The tantalizing fragments of information that exist suggest that there is a rich glaci ological source to be mined in Patagonia yielding insights into glacio climatic interactions, calving dynamics, Holocene climate change and t he role of topography in controlling glacier behavior.