Surface Ice Velocity near the Terminus of Grey Glacier in the Southern Patagonian Icefield, Based on Direct Field Measurements

Climatic variability, topography, and geological-structural controls play a fundamen-tal role in glacier mass balance and ice flow dynamics across multiple temporal scales. Surface ice velocity is a key parameter for understanding these processes. In situ measurements using GPS provide high-precision and high-resolution data, allowing for an objective characterization of glacier dynamics that may be overlooked by re-mote sensing techniques alone. However, due to the efforts required to collect such di-rect field data, these data remain scarce on many glaciers. This study presents direct measurements of surface ice velocity on Grey Glacier, a major outlet glacier of the Southern Patagonian Icefield (SPI) in Chile. Ice flow was monitored over a one-week period in late 2002 by tracking the displacement of six stakes installed on the glacier surface. The resulting velocity data reveal spatial patterns of surface flow that provide significant information for the comparison and validation of remote sensing observa-tions, which is particularly relevant considering that the ice mass from which the data were collected has since disappeared due to glacier retreat. The combined use of ground-based and remote sensing methods is essential for advancing our understand-ing of glacier motion and behavior, particularly in the context of climate forcing.