2020 Volume 38 Pages 13-24
Glacier lake outburst floods (GLOF) at Laguna de los Témpanos, a glacier-dammed side lake of Glaciar Steffen, Hielo Patagónico Norte, were documented for a period between December 1974 and February 2020. With manual interpretation of 150 remote sensing images of aerial surveys, vertical aerial photographs, Landsat MSS, TM, ETM and OLI, ALOS, and ASTER images, 19 GLOFs were captured/inferred by focusing on icebergs and water levels, except two periods in the 1980s and the 1990s for which no image was available. This translates to the occurrence of the GLOF on average once ca. every 14 months. Many GLOFs occurred in late summer to early fall, with a few in late spring: but one GLOF was inferred to have occurred in wintertime. The causes of GLOFs were supposed to be heavy rainfalls, probably accompanied with rapid snow/ice melting by warm air temperatures, judging from the general weather condition over the laguna area. The latest two GLOFs (2016 & 2017) were very large, enough to have completely exposed the lake floor in the middle section. The GLOF of 2017 (Mar. 31) was registered in a hydrograph set up at Lower Río Huemules. After this GLOF, the water level has become stable with a more or less continuous outlet stream along the glacier sidewall and there has been no GLOF to date. So probably the prospect of another GLOF has considerably diminished by now. As Glaciar Steffen receded about 6km during this study period, the glacier has thinned accordingly, to which the water level adjusted with three distinctive relatively stable states while fluctuating frequently.