Patagonia icefield retreat – From a Glaciers Perspective

HPS-12 Glacier in 1985 and 2017 Landsat images. The red arrow indicates 1985 terminus, yellow arrows the 2017 terminus, purple dots the snowline and 1-4 are tributaries. By 2017 all tributaries have detached and the glacier has retreated 13 km.

HPS-12 is an unnamed glacier draining the west side of the Southern Patagonia Ice Cap (SPI). The glacier terminates in a fjord and is adjacent to Upsala Glacier to the east and Pio IX Glacier to the north. This developing fjord is also unnamed but feeds into Estero Falcon. Here we update the 2017 NASA Earth Observatory project I completed in 2017, that identified this as the fastest retreating glacier in Chile in the 1985-2017 period, using Landsat imagery from 1985-2025.

HPS-12 Glacier in 2015 and 2025 Landsat images. The red arrow indicates 1985 terminus, yellow arrows the 2025 terminus, black arrow the 2015 terminus. Former tributary 1 and 2 have declined in width .

In 1985 the HPS-12 terminates 1.5 km from the junction of two fjords that are occupied by HPS-12 and HPS-13. These are separated by a peninsula. The glacier is fed by four tributaries labelled 1-4. The snowline in 1985 is at 900 m. In 2001 the four tributaries still join the main glacier, but the terminus has retreated 3.5 km. In 2015 glacier retreat has led to separation of tributary 1, 2 and 4 from the main glacier, tributary 3 only feeds tributary 2 and not the main glacier. The glacier retreat has continued to 2017, the current terminus is 800 m wide vesus 2800 m wide in 1985 . Total retreat from 1985 to 2017 was 13 km. By 2025 the glacier has retreated 14.75 km and has lost more than 50% of its total length. Tributary 1 and 2 continue to narrow from 2015 to 2025 illustrating that flow from the icefield accumulation zone is being reduced. This suggests less discharge into the terminus reach of HPS-12.

This glacier follows the pattern of retreat we have reported from Bernardo Glacier, O’Higgins Glacier, Tyndall Glacier and Upsala Glacier. The retreat is driven by the SPI have been experienced significant mass loss a. Malz et al (2018) noted a ~1 m/year mass loss from 2000-2016 with HPS-12 and Jorg Montt Glacier losing the most. Minowa et al (2021) found that 35% of all ablation of the Patagonia Icefields stemmed from frontal ablation.

HPS-12 Glacier in 2001 and 2015 Landsat images. The red arrow indicates 1985 terminus, yellow arrows the 2017 terminus, purple dots the snowline and 1-4 are tributaries. By 2015 tributaries 1, 2 and 4 have detached.

Glaciar Olvidado (O) retreat illustrated in 1985 and 2017 Landsat images. Red arrow is 1985 terminus location, yellow arrow is 2017 terminus location and purple dots are the snowline. This illustrates an 1800 m retreat.

Glaciar Olvidado (G) is a glacier in the southeast portion of the Southern Patagonia Icefield (SPI), adjacent to Grey Glacier (G). The glacier terminates in a proglacial lake. Rivera and Casassa (2004) report the glacier terminating in a newly formed lake in 1986 and retreating slowly from 1986 to 2000. Here we examine changes in the glacier from 1985 to 2017 using Landsat imagery.

In 1985 the glacier terminates in small newly formed proglacial lake that is just 200 m long. The snowline in 1985 is at 1050 m. In 2000 the lake has expanded to a length of 900 m. The snowline in 2000 is at 950 m. By 2016 the proglacial lake has expanded to a length of 2 km. The snowline in 2016 is at 1100 m. In 2017 the glacier has retreated 1800 m since 1986. The snowline is at the base of the steep slopes at 1150 m. The high snowline leaves less than 30% of the glacier in the accumulation zone. The high snowlines indicate a limited accumulation zone, which generates a negative mass balance and drives retreat. The glacier continues to calve into this terminus lake adding to the negative mass balance and consequent retreat. This glacier adds to the growth of proglacial lakes seen in the Northern Patagonia Icefield (Glasser et al 2016) and SPI (Iribarren et al 2014). Olvidado Glacier retreat in terms of distance is similar to the adjacent Grey Glacier, but does represent 20% of its total length. The retreat is much less than the HPS-12 glacier on the west side of the SPI.

Glaciar Olvidado retreat illustrated in 2000 and 2016 Landsat images. Red arrow is 1985 terminus location, yellow arrow is 2017 terminus location and purple dots are the snowline.