Glacier distribution and recent fluctuations in the north Patagonian Andes

RUIZ, LUCAS.

Fairbanks

Simposio; International Symposium on Glaciers and Ice Sheets in a Warming Climate; 2012

International Glaciological Society

The spatial and altitudinal distributions and recent fluctuations of glaciers in a sector of the north Patagonian Andes of Argentina (42° S,70° W/42.5° S, 71° W) were determined using two glacier inventories developed from late-summer Landsat and ASTER scenes from 1987 and 2007, respectively. The identification of glaciers was based largely on a threshold band classification approach (TM3/TM5 and SVNIR2/SVNIR 4 for Landsat and ASTER, respectively) complemented with minor manual corrections. The basic inventory data obtained for each ice mass include: individual glacier identification, planimetric glacier boundaries, flow and firn lines, and polygonal glacier basins. Topographic parameters for each glacier were obtained from the ASTER GDEM v2 digital elevation model, whereas the GLIMS classification was used to discriminate between different glacier types. A total of 523 glaciers covering an area of 168.6 km2 were identified in 1987. Although the most common glacier type in this inventory was small glaciaretes (n = 287, 55% of total number of ice bodies), the larger glaciers, i.e. mountain glaciers (n = 219) and valley glaciers (n = 17), concentrated more than 50% of the glaciated area. The total glaciated area inventoried for 2007 was 148.5 km2, evidencing a 12% reduction in this 20 year period. A similar and widespread retreating pattern has also been observed in other ice masses throughout the Patagonian Andes. Our analyses indicate that the rate of frontal recession is highly dependent on the glacier type, with valley glaciers having the highest retreating rates (–65 m a–1 on average). Although a few small glaciers have disappeared between 1987 and 2007, the total number of glaciaretes has increased due to the disintegration of many of the larger ice bodies. We found a direct linear relationship between type, extent, mean and minimum elevation, orientation and firn-line altitude and the distance of the glaciers from the ocean (longitude). This relationship can be explained by the steep west–east precipitation gradients observed in the study area.