A. Rivera et al., RECENT FLUCTUATIONS OF GLACIAR-PIO-XI, PAGAGONIA - DISCUSSION OF A GLACIAL SURGE HYPOTHESIS, Mountain research and development, 17(4), 1997, pp. 309-322
The Southern Patagonia Icefield remains one of the least studied glaci
al areas in the world, although it is one of the largest mid-latitude
ice bodies. The largest glacier, Glaciar Pio XI, located on the wester
n maritime side, has been advancing during the last 50 years. In 1993
the tidewater front of the glacier was overriding trees at least 300 y
ears old. In a worldwide context of rapid deglaciation and retreat, wh
ich is particularly affecting Patagonia, there is no simple explanatio
n for the exceptional advance of Glaciar Pio XI. Careful examination o
f the fluctuations of the glacier front shows that there have been per
iods of enhanced movement, separated by retreat periods. Due to the ma
gnitude and characteristics of the advance periods, they are postulate
d to correspond to glacial surges. Four explanations are presented to
account for the surging behavior: increased sliding due to enhanced ba
sal water pressure, as is typical in surging glaciers; increased slidi
ng resulting from periods of increased geothermal activity associated
with Volcan Lautaro; increased precipitation during periods before the
surges; and reduction of the rate of calving as the depth of water de
creased due to proglacial sedimentation. Dendrochronological, geomorph
ological, and glaciological data, collected during 1992, 1993, and 199
5, have been interpreted in combination with satellite imagery, air ph
otographs, and historical maps. It is concluded that the data availabl
e are insufficient to permit selection of any one of the proposed mode
ls.