March 23, 2020

Yalik Glacier, Alaska Retreat and Lake Expansion 1986-2019

Posted by Mauri Pelto

Yalik Glacier (Y) in 1986 and 2019 Landsat images.  Red arrow is the 1986 terminus location and yellow arrow the 2019 terminus location. Petrof Glacier (P) is the western neighbor.

Yalik Glacier drains an icefield on the Kenai Peninsula, glaciers draining east are in the  Kenai Fjords National Park, which has a monitoring program.  From 1950-2005 all 27 glaciers in the Kenai Icefield region examined  retreated (Giffen et al 2014).  Yalik Glacier retreated 1057 m from 1950-1986, a rate of-29 m/year and 797 m from 1986-2000, a rate of 57 m/year (Giffen et al 2014).  Here we update the retreat using Landsat images from 1986, 2000, 2018 and 2019.

In the 1950 USGS map of the region Yalik Glacier terminates on a braided outwash plain, and does not have a proglacial lake.  By 1986 there is a 300-400 m wide fringing proglacial lake particularly on the eastern margin with an area of 0.6 km2. The glacier has retreated from the outwash plain into the developing proglacial lake basin.  By 2000 the proglacial lake has expanded to 1.3 km2 due to the ~800 m retreat.  In 2018 the proglacial lake has expanded to 2.1 km2 and a second proglacial lake has formed on the eastern margin.  This proglacial lake will merge with the main lake as the terminus retreats from a peninsula extending from the eastern margin. A bedrock knob has emerged east of Point 1 indicating substantial glacier thinning since 2000. In 2019 the total proglacial lake area is 2.4 km2.  The glacier has retreated 1500 m since 1986 and 700 m since 2000, the latter period has a retreat rate of 34 m/year.  The former braided river  that exited the glacier is now a single meandering stream channel as it leaves the proglacial lake. The retreat of Yalik Glacier is more than nearby Grewingk Glacier and less than nearby Excelsior Glacier.

What is driving the retreat is continued warming including warm summers.  The glacier generated few icebergs during this retreat, indicating melting not calving is the key factor. The 2019 Alaska Climate Review indicates 2019 was the state’s warmest year, see Anchorage example from this report below. Temperatures in nearby Homer averaged 4.2 F above normal with June-August averaging 4.4 F above normal.  These conditions also led to forest fires in the area reducing the 2019 image clarity due to forest fire smoke from the Swan Lake fire that burned ~167K acres.

Yalik Glacier in 2000 and 2018 Landsat images.  Red arrow is the 1986 terminus location and yellow arrow the 2019 terminus location. Point 1 is west of a bedrock knob that has emerged due to glacier thinning.

USGS map of Yalik Glacier in 1951

From the 2019 Alaska Climate Review .