The calving glaciers of southern South America

Calving glaciers constitute a great majority of all glaciers in Patagonia a nd Tierra del Fuego, and are dynamically important elements of the southern South American icefields. Large numbers of tidewater glaciers calve into t he Chilean fjords, and many outlet glaciers terminate in proglacial lakes. Most probably, all are temperate and grounded, with steep mass balance grad ients. A majority of these glaciers remained largely unknown to science unt il very recently. This paper reviews recent research in the region in the c ontext of glaciological and Quaternary debates, and discusses current under standing and uncertainties. During the 20th century most glaciers have retr eated, but the particular dynamics of calving glaciers have produced some s triking exceptions to this regional trend, producing sustained advances (e. g., Glacier Pio XI, Glaciar Perito Moreno), accelerated retreats (e.g., Gla ciar O'Higgins, Glaciar Marinelli), and long-maintained stillstands of glac iers with very high accumulation area ratios (e.g., Glaciar Calvo). The rel ative importance of climatic, topographic, and glaciodynamic controls on re gional patterns of glacier fluctuation remain an enigma, especially in the Cordillera Darwin, but space-borne radar imagery is now yielding much infor mation. Key research themes in recent years include: (1) glacier inventory work using remotely-sensed data; (2) calving rates and calving dynamics, pa rticularly the contrast between calving rates in tidewater and freshwater; (3) glacier/climate relationships, both in historic and longer timeframes; and (4) geographic contrasts in glacier behaviour, especially the relative significance of precipitation and temperature for glacier mass balance in t his region of steep climatic gradients. Many intriguing and important quest ions cannot presently be resolved due to the paucity of mass balance and cl imatic data, but current research is yielding data that have regional, inte rhemispheric and theoretical significance. (C) 1999 Elsevier Science B.V. A ll rights reserved.