January 12, 2020
Fiero Glacier in 1987 Landsat and 2020 Sentinel images. Red arrow indicates 1987 terminus location, yellow arrow 2020 terminus lcoation, and purple dots the snowline. Point A,B and C represent locations where bedrock has expanded.
Fiero Glacier is an outlet glacier draining the northeast quadrant of the Northern Patagonia Icefield (NPI) terminating in Lago Fiero. Loriaux and Casassa (2013) examined the expansion of lakes of the Northern Patagonia Ice Cap. From 1945 to 2011 lake area expanded 65%, 66 km2. Davies and Glasser (2012) noted the fastest retreat during the 1870-2011 period was from 1975-1986 for Fiero Glacier. They noted that Fiero Glacier proglacial lake had an area of 6.6 km2. Glasser et al (2016) note the recent 100 m rise in snowline elevations for the NPI, which along with landslide transport explains the large increase in debris cover since 1987 on NPI including Fiero Galcier. Here we examine the response of the glacier to climate change from 1987 to 2020.
In 1987 the glacier terminated at a narrow point in the 4.2 km long Lago Fiero that has an area of 5.6 km2. By 2001 the glacier had retreated 500 m and the transient snowline is at 1000 m. At point A there is a narrow rock rib. at Point B there are isolated rock rib and knobs and at Point C the rock rib is limited. In 2015 the lake has expanded to an area of 7.3 km2, and the debris cover has also expanded. The transient snowline is at 1200-1300 m. In 2020 the lake has expanded to an area of 9.5 km2 and a length of 6.5 km. The 2.3 km retreat has led to a near doubling in the area of the Lago Fiero, the retreat since 2011 is the fastest rate observed. At Point A the rock rib is now a prominent separation, at Point B and C the rock rib has become continuous much like at Point A. The snowline on January 1, 2020 is at 1200 m, midway through the melt season. The glacier slope increases 500-1000 m from the current terminus near a surface elevation of 600 m, which could mark the expansion limit of Lago Fiero (see map below).
The retreat of this glacier is larger than that of Colonia Glacier and Pared Nord Glacier further south and Verde Glacier to the north of the NPI. All the outlet glaciers of NPI have retreated significantly in the last 30 years most leading to expanding proglacial lakes (Loriaux and Casassa, 2913; Pelto, 2017).
Fiero Glacier in 2001 and 2015 Landsat images. Red arrow indicates 1987 terminus location, yellow arrow 2020 terminus lcoation, and purple dots the snowline. Point A,B and C represent locations where bedrock has expanded.
Terminus of Fiero Glacier from the Randolph Glacier Inventory in 2001 (Green) and 2011 (blue). the 500 m, 600 m and 700 m contour are indicated. Note the steeper slope near 600 m which likely is beyond the expansion limit of Lago Fiero. Base map from GLIMS