Fluctuations in the length of 72 glaciers in the Northern and Southern Patagonia Icefield (NPI and SPI, respectively) and the Cordillera Darwin Icefield (CDI) were estimated between 1945 and 2005. The information obtained from historical maps based on 1945 aerial photographs was compared to ASTER and Landsat satellite images and to information found in the literature. The majority of glaciers have retreated considerably, with maximum values of 12.2 km for Marinelli Glacier in the CDI, 11.6 km for O'Higgins Glacier in the SPI and 5.7 km for San Rafael Glacier in the NPI.Among the 20 glaciers that have retreated the most relative to their size, small (less than 50 km2) and medium (between 50 and 200 km2) glaciers are the most affected. However, no direct relation between glacier retreat and size was found for the 72 glaciers studied. The highest percentage retreat in the CDI was by the CDI-03 Glacier (37.9%) and Marinelli Glacier (37.6%). In the SPI, relative retreats were heterogeneous and fluctuated between 27.2% (Amelia Glacier) and 0.4% (Viedma Glacier). In the NPI, relative retreat was very high for Strindberg and Cachet glaciers (35.9% and 27.6%, respectively) but for the remaining glaciers in this icefield it ranged between 11.8% (Piscis Glacier) and 3.6% (San Quintin Glacier). In addition to surface area, the surface slope (calculated on the basis of the DEM SRTM) was also related to the relative retreat and no straightforward relation was found.From a global point of view, we suggest that glacier retreat in the region is controlled firstly by atmospheric warming, as it has been reported in this area. Besides the general increase in temperature observed, no signal of a geographical pattern for the fluctuations in glacier length was found. Consequently, glaciers appear to initially react to local conditions most probably induced by their exposition, geometry and hypsometry. The heterogeneity of rates of retreat suggests that differences in basin geometry, glacier dynamics and response time are key features to explain fluctuations of each glacier.

In the framework of this study, every glacier length was calculated according to five criteria in the following order: (1) glacier length is represented by a line which corresponds to the longest distance followed by the glacier; (2) the length was measured from the lowest to the highest point of the glacier; (3) the origin is the central position of the glacier's front; (4) the length/distance follows the central position of the glacier tongue and; and (5) the length follows surface flow trajectories if they are identifiable on the satellite image. Criteria 1, 2 and 3 were respected for every glacier, while the application of criteria 4 and 5 depended on the glacier's shape and surface characteristics. Data extracted in the frame of a joint ICSTI/PANGAEA IPY effort, see http://doi.pangaea.de/10.1594/PANGAEA.150150

Supplement to: Lopez, Paulina; Chevallier, Pierre; Favier, Vincent; Pouyaud, Bernard; Ordenes, Fernando; Oerlemans, Johannes (2010): A regional view of fluctuations in glacier length in southern South America. Global and Planetary Change, 71(1-2), 85-108