Skilak Glacier, Alaska Retreat and Salmon Connection

On March 1, 2019April 25, 2024 By mspeltoIn alaska glacier retreat2 Comments

Skilak Glacier in 1986 and Sept. 2018 Landsat images. In 1986 icebergs and remnant glacier fill nearly the entire lake. The snowline in 1986 is at 1200 m and is at 1300 m in 2018. Red arrow is the 1982 terminus location and yellow arrow is the 2018 terminus location. Point A and C are bedrock outcrops at around 1200 m that have expanded.

Skilak Glacier is an outlet glacier on the northwest side of the Harding Icefield, Kenai Peninsula, Alaska. From 1952-1982 Skilak glacier terminated on a proglacial plain with a broad nearly flat terminal lobe, see map below. The glaciers that drain eastward 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). Giffen et al (2014) observed that retreated 1,800 m from from 1986-2000, with no retreat from 2000-2005. Here we examine Landsat imagery from 1986-2018 to illustrate the retreat of this glacier, recent snowline elevation and other upglacier changes. The glacier supplies meltwater to Skilak Lake which is a critical salmon habitat for the Kenai. Chinook Salmon spawn on a section of the Kenai River between Kenai Lake and Skilak Lake. With Skilak Lake being the resulting home for ninety percent of the salmon fry for the Kenai River, and with the most of any nursery in the Cook Inlet area. Escapements of chinook in the Kenai River exceed 50,000 annually in two runs (Heard et al 2007). Sockeye salmon is the largest run in the river with over 1,000,000 annual in the Kenai River run (Schoen et al, 2017).

In the 1958 USGS map from there is no lake evident at the terminus of the glacier. The lower 2 km of the glacier is nearly flat. By 1986 the flat terminus was breaking up with icebergs filling the lake. By 2002 the glacier had retreated 4 km generating a lake with an area of 6.2 square kilometers. The snowline in 2002 was at 1200 m. The glacier retreated 300 m from 2002 to 2018. From July 2018 to Sept. 2018 the snowline rose from 1050 m to 1300 m. Though retreat has been slow since 2002 upglacier thinning has been substantial At Point A and C from 1986 to 2018 and at Point A and B from 2002-2018. This will drive additional retreat. The retreat rate should be more in line with that of the neighboring Harris Glacier.

Skilak Glacier 1958 Map prior to lake formation.

Skilak Glacier in 2002 and July 2018 Landsat images. In 2002 is at 1100 m and is at 1150 m in July 2018. Red arrow is the 1982 terminus location and yellow arrow is the 2018 terminus location. The orange arrow indicates indicated banded snow formation. Point A and B are bedrock outcrops at around 1200 m that have expanded.

Harris Glacier Retreat, Kenai Fjords, Alaska

On June 14, 2016May 2, 2024 By mspeltoIn alaska glacier retreat, glacier climate change, Glacier Observations, glaciers salmon

Landsat images of Harris Glacier from 1986 and 2015. The red arrow indicates 1986 terminus location, yellow arrow the 2015 terminus position. The orange arrow indicates a key eastern tributary and the pink arrow a smaller eastern tributary.

Harris Glacier flows from the northwest corner of the Harding Icefield, Alaska and it drains into Skilak Lake. The glaciers that drain east toward are in the Kenai Fjords National Park, which has a monitoring program. Giffen et al (2014) observed the retreat of glaciers in the region. From 1950-2005 all 27 glaciers in the Kenai Icefield region examined are retreating. Giffen et al (2014) observed that Harris Glacier (A Glacier) retreated 469 m from from 1986-2005. Here we examine Landsat imagery from 1986-2015 to illustrate the retreat of this glacier and other upglacier changes. The glacier supplies meltwater to Skilak Lake which is a critical salmon habitat for the Kenai. Chinook Salmon spawn on a section of the Kenai River between Kenai Lake and Skilak Lake. With Skilak Lake being the resulting home for ninety percent of the salmon fry for the Kenai River, and with the most of any nursery in the Cook Inlet area. Escapements of chinook in the Kenai River exceed 50,000 annually in two runs (Heard et al 2007).

In 1986 the glacier extended to an elevation of 590 m, on the east side of the glacier there were two smaller tributaries reaching the glacier at the orange and pink arrow. By 2015 the terminus had retreated 600 m from 1986. The eastern tributary at the pink arrow had detached from the main glacier. The tributary at the orange arrow still reaches the main glacier, but the blue ice extent after joining the glacier has diminished significantly. Below is a closeup of the terminus from 1996 and 2015 illustrating a 225 m retreat and associated thinning. It is also interesting to note the prominent ash layer has shifted little. This suggests the terminus area is relatively stagnant. There is no active crevassing in the lower 1 km suggesting retreat will be ongoing. In 1989 the snowline is at 975 m whereas in 2014 the snowline is at 1125 m. This higher snowline is too high to maintain the glacier. The snowline in 2015 was again above 1100 m, though it is lower in the mid-August image at 1050 m. The retreat of this glacier is less than neighboring glaciers such as Grewingk, Pederson and Bear Glacier that have calving termini.

Landsat images from 1989 and 2014, with the snowline indicated by purple dots.

Terminus of Harris Glacier in Google Earth images from 1996 and 2015. Margin with purple dot, purple arrow indicates 1996 terminus lcoation, with a 225 m retreat by 2015. Note the prominent ash layer

Pedersen Glacier Retreat Lake Expansion, Alaska

On June 23, 2012June 23, 2012 By mspeltoIn Glacier Observations2 Comments

Pedersen Glacier is an outlet glacier of the Harding Icefield in Kenai Fjords National Park near Seward, Alaska. The glacier drops quickly from the plateau of the icefield through a pair of icefalls terminating 3.5 km in a lake at 25 meters. Bruce Molnia of the USGS as part of an effort in repeat photographs of Alaskan glaciers to show historic changes captures the changes of Pedersen Glacier. A photographic pair taken from about the same shoreline location of Pedersen Glacier. The photographs identify significant changes that have occurred during the 95 years between 1909 and 2004. The 2004 photograph a 1.5 km retreat of Pedersen Glacier from the field of view. In a recent study of the glaciers, by NASA and the NPS, (Hall et al, 2005) identify the retreat of the glacier as slow but steady from 1973-1986 at 510 m (35 m/a) and 110 m (8 m/year) from 1986-2000. Here we compare a 1994 Landsat, 2005 Google Earth, 2010 Landsat and 2011 Google Earth imagery illustrating a rapid increase in retreat rate from the previous periods. The red line in the Google Earth images is the 1994 terminus, the green line the 2005 terminus and the orange line the 2011 terminus. In 1994 the lake at the terminus is small and not continuous across the ice front (top image), the green dots are the terminus and the burgundy dots the snowline on the date of the image, near the top of the icefall. In the second image from 2005 the lake is now well developed but the number of icebergs in the lake limited. The third image from 2010 indicates a rapid lake expansion which is now largely filled by icebergs. In 2011 the lake remains filled with some very large icebergs indicating the recent nature of terminus collapse in the lake. The retreat from 1994-2005 was 450 meters (40 m/year) and 650 meters from 2005-2011,(110 m/year). The snowline is somewhat above the top of the icefalls on Pedersen Glacier. .. A closeup view of the terminus area from 2005 and 2011 indicate that the lake has more than doubled in size since 1994, and there is no distinct change in glacier width or surface elevation to suggest the glacier is near a point where the rapid terminus retreat will end. The glacier follows the pattern of nearby Bear Glacier, Yakutat Glacier, Gilkey Glacier and the predicted impending retreat of Brady Glacier.