Melt rates at calving termini: a study at Glaciar León, Chilean Patagonia
Glaeiar León, a temperate, grounded outlet of the North Patagonian Icefield, terminates at an active but stable calving margin in Lago Leones. Glaciological and limno-logical data gathered during 2001 and 2002 are used to examine the relative contributions of calving and melting to mass loss at the terminus, and the interplay between glacier and lake processes. The calving rate of 880 m/a in a mean water depth of 65 m is high for lake-calving glaciers. Subaerial melt rates at the terminus are small compared with calving rates, but melting at the waterline facilitates calving by undercutting the subaerial calving cliff. Ice-proximal surface water temperatures of 6–7°C allow waterline melt notches to grow at rates of c. 0.8 m/day, suggesting that melt-driven calving accounts for c. 23% of ice loss at the terminus. The significance of melting at calving termini decreases with increasing calving speeds, but is greater than simple calculations of melt losses suggest because of the process-linkage with calving.
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The introduction of the term periglacial by Łoziński in 1909 to describe the cold-climate conditions in the zone adjacent to, but beyond, the Pleistocene glaciers encouraged the separate development of geocryological and glaciological research. Geological and geomorphological processes at the interface between glaciers and permafrost have, as a result, been given less attention than they warrant, and the influence of one on the other has in many respects been neglected. This book includes a collection of papers that emphasize glacier-permafrost interactions. Papers consider permafrost and its influence on glacitectonic processes, glacial meltwater systems and ground-ice development in proglacial and ice-marginal environments. In addition, recent research findings are reported on paraglacial processes, permafrost evolution, rock glaciers, the formation of ice-wedge casts and periglacial slope evolution. It is hoped that this book will stimulate interest in the interface between glacial and periglacial systems, and encourage further collaborative research involving glaciologists and glacial geologists on the one hand, and geocryologists and permafrost scientists on the other.