Glacier variations of Hielo Patagónico Norte, Chile, over 70 years from 1945 to 2015

Hielo Patagónico Norte (HPN, or Northern Patagonia Icefield) is located in the southern part of Chile with an area of ca. 4200 km in 1975 and 3950 km in 2000. Variations of 21 major outlet glaciers in 70 years from 1945 to 2015 were documented in detail using aerial photographs and aerial survey photographs. The HPN lost an area of 126.73 km or ca. 3 % of the total area of 1975 due to glacier snout recessions. The largest loss was at Glaciar (Gl.) San Quintin (the largest glacier in the HPN) with 40.68 km. The four largest glaciers including Gl. San Rafael, Steffen and Reicher together account for 57.5 % of all the loss. The smallest area loss was 0.46 km at Gl. Arco. In terms of distance retreated, southwest snout of Gl. Reicher is the largest with 6350 m. The smallest retreat was ca. 350 m at Gl. León. While the trend was retreat in general, eight glaciers made advances although ephemeral, with some glaciers a few times. Snout disintegration was observed at eight glaciers, which was often preceded by advance. Gl. San Quintin and Steffen had seven snout disintegrations each since 1990. The east-west and north-south contrasts in glacier variations are very pronounced: glaciers on the west side and the north side lost substantially more than those on the east side and the south side, respectively. In this study period, glacial-lake outburst floods (GLOFs) were recognized at three glaciers and one moraine-dammed lake.