Grand Plateau Glacier, Retreat, Lake Expansion and Island Formation

On June 18, 2024June 26, 2024 By mspeltoIn Glacier ObservationsLeave a comment

Grand Plateau Glacier on June 15, 2024 Sentinel image, illustrating 5.5 km retreat from Island (I) where terminus was located in 1984. N illustrates nunatak the glacier terminated 11 km from 1948 terminus. Point A is new island emerging at terminus. The Lake that barely existed in 1948, has more than doubled in size since 1984 to 49 km².

Grand Plateau Glacier drains southwest from Mount Fairweather in southeast Alaska. The glacier advanced during the Little Ice age to the Alaskan coastline. Early maps from 1908 show no lake at the terminus of the glacier. The 1948 map (below) shows three small distinct lakes at the terminus of the main glacier and a just developing lake at the terminus of the southern distributary terminus (D). The distance from the Nunatak N to the terminus was 11 km in 1948. The lake at D is 400 m wide.

gp-terminus — **USGS 1948 topographic map of area Illustrating three small disconnected proglacial lakes at the terminus (I).**

**USGS 1948 topographic map of area Illustrating distribuatry tongue**

**Grand Plateau Glacier in 1984 Landsat image indicating 1984 terminus at orange arrows, 2013**

Landsat images from 1984 indicates the fromation of a single connected proglacial lake with an area of 24 km². Key reference points in each image are the Nunatak, N, and and Island, I. The retreat from 1984-2013 is evident with the orange arrows indicating the 1984 terminus and pink arrows showing the 2013 terminus location. The distance from the Nunatak to the terminus is 8.5 km in 1984 and 4 km in 2013. On the north shore of the lake the retreat between arrows is 2.7 km from 1984-2013. From the island the glacier retreated 3.3 km from 1984-2013, with the lake expanding to 43 km². The distributary tongue (D) retreated 2.2 km from 1984-2013. The retreat was driven by higher snowlines in recent years, the snowline had been reported at 1000 m in the 1950’s. Satellite imagery of the last decade indicates snowlines averaging 1500 m, red arrows. The glacier snowline is evident in Landsat imagery in 1984 and 2013 red arrows.

In 2024 the lake area has grown further to 49 km², as a result of a retreat of 8 km since 1948 and 5.5 km since 1984. Today a second island is emerging at the terminus, Point A. The distributary tongue to the southeast now terminates in a lake that is now 5.2 km long, a 4.8 km retreat since 1948 and 2.6 km since 1984. The combination of higher snowlines and increased calving into the terminus lake will continue to lead to retreat of this still mighty river of ice. This retreat parallels that of nearby Alsek Glacier and Yakutat Glacier. The rapid growth of the three lakes since 1984 when I visited them is amazing.

La Perouse Glacier, Alaska Lake Formation Retreat Acceleration

On May 27, 2024June 17, 2024 By mspeltoIn Glacier ObservationsLeave a comment

La Perouse Glacier in 2018 and 2023 Landsat images indicating the six developing proglacial lakes (1-6). The lakes in 2023 have a combined area of 1.3 km². Debris cover has expanded notably at Points D.

La Perouse Glacier flows from the Fairweather Range to the Pacific Coast. The glacier advanced to the coast in the mid-late 19th century and has remained tidewater on the coast since (Gaglioti et al 2019). I first saw this glacier in 1982 and its terminus stretched 3.5 km along the coast, a second terminus ended inland and was 3.2 km wide. Both of the terminus are piedmont fed by a significant accumulation area above 2300 m, that flows through a spectacular icefall from 1100 to 1800 m. This high accumulation zone helps make the glacier more resilent to warming temperature (Pelto, 1987). Berthier et al (2010) noted a ~0.5 m/loss average loss for glaciers in this region from 1962-2006, which has generated this retreat. The glacier because of its size and large piedmont lobe is slow to respond to climate change, 20 km² coastal lobe and 10 km² inland lobe.

**La Perouse Glacier coastal terminus area indicating the three developing proglacial lakes, yellow arrows. False color Sentinal images.**

Up to 2018 the coastal terminus was thinning, but had not experienced significant recession or proglacial lake development. There was significant marginal recession by 2018 exposing a forest overrun by the glacier in the 1860’s (Gaglioti et al 2019). In 2018 the inland terminus had developed 3 proglacial lakes wiyth a combined area of 0.4 km². By 2023 the inland terminus lakes spread across 90% of the width of the terminus, with a combined area of 0.7 km². In 2023 the main terminus had developed three proglacial lakes each, #1 at 0.12 km², #2 at 0.16km² and #3 at 0.36 km². Lake #3 has numerous bergs indicating the ability to rapidly expand by calving, due to having a greater water depth. In just five years the debris covered area has expanded notably. This combination of expanding glacial lakes and debris cover is an indication of ongoing rapid decline. The changes here are simialr to that at nearby Brady Glacier and progressing on the same trend as Fingers Glacier. Look for further lake development in 2024 particularly in the coastal lobe.

Baird Glacier, Alaska Terminus Tongue Breaks Off April 2024

On May 3, 2024May 4, 2024 By mspeltoIn Glacier ObservationsLeave a comment

**Baird Glacier terminus tongue gone in April 26, 2024 Landsat image. Red arrow indicates now joined 5 km² proglacial lake. Yellow dots terminus of Baird and North Baird Glacier**

Baird Glacier drains the west side of the Stikine Icefield in southeast Alaska. It is the only glacier of the Stikine Iceifield that did not retreat significantly from 1960-2010. Pelto et al (2013) predicted the onset of significant retreat of this glacier, which like Brady Glacier had been slow to begin retreat despite thinning that was evident when I visited the glacier in 1984. The proglacial lake that has emerged with retreat has an area of 3.25 km² and the glacier retreat is 2800 m from 1990-2024. The North Baird Glacier separated from Baird Glacier in 2019, with a proglacial lake extending downvalley to the tongue of Baird Glacier that separated this lake from the Baird Glacier proglacial lake until April 2024.

**Baird Glacier in Landsat images from 1990 and 2023 illustrating retreat and proglacial lake expansion.**

Baird Glacier in false color Sentinel images from September 10 2023 and May 2 2024. Proglacial lake (PGL) expanded from 3.2 to 5.1 km². Tongue extending upvalley toward North Baird Glacier (NB) broke up in late April, **yellow arrow**.

Baird Glacier in false color Sentinel images from July 2022 and July 2023. Proglacial lake (PGL) expanded from 3.00 to 3.25 km² width of tongue extending upvalley toward North Baird Glacier (NB) has declined from 700 m to 400 m.

In 1990 the Baird Glacier was sitting on an outwash plain, with no lake at the terminus. The North Baird Glacier was 1 km wide where it joined the Baird Glacier. By 2015 the glacier has retreated 750 m and the lake (PGL) has an area of ~1 km². In 2022 the glacier has retreated leading to a lake expansion to 3.00 km². In July 2023 the tongue of ice extending across the front of the North Baird Glacier valley has thinned 40% since July 2022. The tongue remained throughout 2023 into April of 2024 before breaking up. This leaves the main terminus of the glacier more vulnerable to further rapid calving retreat. Baird Glacier is catching up to the rest of the Stikine Icefield that has experienced significant retreat, Dawes Glacier, Patterson Glacier and Great Glacier. With Sawyer Glacier retreating from tidewater in 2023.

Bridge Glacier, Southeast Alaska Retreat & Lake Formation

On November 21, 2017April 28, 2024 By mspeltoIn alaska glacier retreat

Bridge Glacier in Landsat image from 1984 and Sentinel image from 2017. The red arrow indicates the 1984 terminus where no lake exists, yellow arrow is 2017 terminus, orange arrows are selected tributaries and purple dots the snowline.

Bridge Glacier drains the same icefield as the Wright and Speel Glacier 45 km southeast of Juneau, Alaska. Here we examine the changes in this glacier from 1984-2017 using Landsat and Sentinel imagery.

In 1984 the glacier ended on an outwash plain at the head of a branch of Speel River. The red arrow indicates the 1984 terminus for each image, the yellow arrow the 2017 terminus and the orange arrows three tributaries feeding the glacier. The purple dots indicate the snowline at 1200 m. In 1984 all three tributary glaciers fed Bridge Glacier and the glacier has no proglacial lake at the terminus. In 1997 a lake basin is beginning to develop, though it is still largely filled by ice. The eastern tributary pink arrow, has lost all of its snowpack. The three tributaries at the orange arrows are connected to Bridge Glacier still and the snowline is at 1250 m. In 1999 the proglacial lake has formed and has length of 1 km, the lake has expanded south and north of the 1984 terminus position, and does not entirely represent glacier retreat. In 2013 the glacier has retreated 1200 m from the 1984 position and the lake is still expanding. The orange arrows indicate that none of the three tributaries are still connected to the main glacier. The glacier in a sense is losing its income flow from these subsidiaries. The eastern tributary has retained some snowcover with six weeks left in the melt season in 2013, but this is mostly gone a month later, the snowline is at 1100 m. nbsp; Total retreat from 1984 to 2017 is 1900 m. In 2017 the snowline is at 1300 m, and the separation of the tributaries is by more than 500 m in each case. The snowline has been high by the end of each summer from 2014-2017 indicating retreat will continue. The retreat of this glacier is the same story as seen at nearby Patterson, Gilkey and Norris Glacier.

Bridge Glacier in Landsat images from 1997 and 2013. The red arrow indicates the 1984 terminus , yellow arrow is 2017 terminus, orange arrows are selected tributaries and purple dots the snowline.

Bridge Glacier in USGS map when it ended on the outwash plain in 1948.

Pedersen Glacier, Alaska Rapid Retreat 1994-2015

On July 6, 2017April 28, 2024 By mspeltoIn alaska glacier retreat, Uncategorized7 Comments

Pedersen Glacier Kenia Peninsula, Alaska retreat from Landsat images in 1994 and 2016. The red arrow indicates 1994 terminus, yellow arrow is 2016 terminus, orange arrow indicates northern tributary and purple dots indicates snowline.

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 in a lake at 25 meters above sea level. The Harding Icefield glaciers that drain east are in the Kenai Fjords National Park, which has a monitoring program. Giffen et al (2014) observed that from 1950-2005 all 27 glaciers in the Kenai Icefield region examined retreated. Giffen et al (2014) observed that Pedersen Glacier retreated slow but steady from 1951-1986 at 706 m (20 m/a) and 434 m (23 m/year) from 1986-2005. Here we compare a 1994, 2013, 2015 and 2016 Landsat imagery illustrating a rapid increase in retreat rate from the previous periods.

In 1994 the terminus proglacial lake at the terminus is small and much of the terminus is on land. The snowline in 1994 is at 550 m. The tributary entering from the north, orange arrow, is 400 m wide as it reaches Pedersen Glacier. In 2005 the Google Earth image below indicates extensive terminus crevassing, indicating substantial terminus velocity, and that the retreat is driven by calving. In 2005 the lake is now 1.1 km long on its center axis. By 2015 the glacier has retreated 2600 m since 1994, a rate of 125 m/year, much faster than before. The snowline is average 800 m. The northern tributary is now barely reaching the main glacier and has a width of 150 m. Note there was a medial moraine separating the tributary from the main glacier in 1994 and now this is merely a lateral moraine. This tributary is not particularly impacted by calving losses and indicates a rising snowline is also a source of mass loss for the glacier. A comparison of the 2013, 2015 and 2016 terminus indicates the recession has remained rapid. The glacier is approaching the base of an icefall that would represent the inland limit of the lake and the end of rapid retreat. The snowline in 2013 averages 850 m and is at 800 m on Sept. 30 2016. The glacier follows the pattern of nearby Bear Glacier, Yakutat Glacier, Harris Glacier and the inital phase of retreat on Brady Glacier.

Pedersen Glacier Kenia Peninsula, Alaska retreat from Landsat images in 2013 and 2015. The red arrow indicates 1994 terminus, yellow arrow is 2015 terminus, green arrow indicates 2016 terminus and purple dots indicates snowline.

Pedersen Glacier in 2005, note crevassing at the terminus, pink arrow. The northern tributary is indicated by orange arrow and green arrow indicates 2016 terminus position.

Yakutat Glacier Terminus Collapse, 10 km retreat 1987-2016

On April 21, 2017May 1, 2024 By mspeltoIn alaska glacier retreat

Landsat images from 1987 and 2016 with terminus indicated by yellow dots. Point A indicates the 1987 terminus location and Point E the 2016 terminus location.

The Yakutat Glacier during the 1894-1895 Alaskan Boundary Survey ended near a terminal moraine on a flat coastal outwash plain. By 1906 the glacier had retreated from the moraine and a new lake was forming. Harlequin Lake. Surveys of the terminus of the glacier indicated a retreat of 1 kilometer in that decade. From 1906-1948 the glacier retreated an additional 5 km. From 1948-1958 the glacier retreated 3.6 km. The retreat is evident in comparing the Yakutat B-3 quadrangle, from 1958 photography, and Landsat imagery from 1987, 2010, 2013 and 2016. Points A-E are the same in each image and the yellow dots are the terminus. In 1987 the terminus was just retreating from a peninsula marked A, the valley at D was filled with ice, there was no break in the surface at C and B was well inland of the terminus. By 2010 the glacier had retreated from A, the valley at D was deglaciated, a small strip of bedrock-sediment was exposed at C from what had been beneath the glacier, and B was still well inland of the terminus. By 2013 the northern arm of the glacier had retreated 6.4 km from the peninsula at A toward the peninsula at B. The central arm of the glacier toward C had retreated 7.5 km and the retreat on the southern edge of the glacier was 6.5 km. The glacier had retreated on average more than 6.6 km in 27 years, a rate of 240 m/year. From 2013 to 2016 the glacier had retreated from Point B to Point C on the northern side and to Point E on the southern side this is a distance of 10.2 km in thirty years 340 m/year.

Recently the glacier has been the focus of a study by the University of Alaska, Faribanks they have set up a time lapse camera to record frontal changes. The goal is to understand the controls on calving into Harlequin Lake of this glacier. More amazing than the retreat has been the observed thinning of the glacier. The glacier has thinned by more 200 m on average according to the preliminary thickness change maps from the UAF project (Truessel et al 2013) and updated by Truessel et al (2015). The Yakutat Glacier does not have a high accumulation zone and the recent increase in the snowline elevation and thinning of the glacier have led to a substantial shrinking of the accumulation zone and thinning of the glacier in the accumulation (Truessel et al 2013). This glacier does not have a persistent significant accumulation zone and cannot survive (Pelto, 2010), Truessel et al (2015). modelling suggests the glacier will disappear between 2070 and 2110 depending on the warming scenario. For a calving glacier to be in equilibrium it needs to have at least 60 % of its area snowcovered at the end of the summer. The glacier is in the midst of a large ongoing retreat. The retreat rate and calving mechanism is similar to that of Grand Plateau Glacier, Bear Lake Glacier and Gilkey Glacier. However, unlike these Yakutat Glacier lacks an accumulation zone, a better analog is East Novatak Glacier, which also has a lower elevation accumulation zone.

Yakutat terminus map

2010 Landsat image with terminus indicated by yellow dots.

2013 Landsat image with terminus indicated by yellow dots.

Shoup Glacier, Alaska Retreat, Thinning, Velocity Decline

On February 24, 2017May 1, 2024 By mspeltoIn alaska glacier retreat, climate change glacier retreat

Shoup Glacier comparison in 1986 and 2016 Landsat images. The glacier retreated 1900 m in this interval. Red arrow is 1986 terminus, yellow arrow the 2016 terminus, green arrow rock rib emerging from beneath glacier, purple dots a landslide deposit, and purple arrow the snowline.

Shoup Glacier is between the Columbia Glacier and Valdez draining from the Chugach Mountains in southern Alaska. The glacier was a tidewater terminating glacier until 1953 (McNabb et al, 2014). From 1985 to 2011 McNabb et al (2014) noted a 1.7 km retreat. The retreat was enhanced by significant lacustrine calving in an expanding tidal lagoon. Here we examine Landsat and Sentinel images from 1986-2016 to identify recent and potential future changes.

In 1986 the glacier extends to the red arrow in the midst of a tidal lagoo. The glacier is 2.5 km wide at the sharp bend in the glacier 2.5 to 3 km from the terminus, green arrow. There is significant crevassing at this bend indicating an increase in slope. There is an landslide/avalanche deposit near the junction with a tributary, purple dots. By 2002 the glacier has retreated 1.5 km since 1986, the minor ice cliff at the terminus indicates the glacier ends in shallow water near the end of the tidal lagoon. The glacier is now 2 km wide at the sharp bend. The landslide deposit, purple dots, has shifted little since 1986. The snowline is at 1200 m in 2002. By 2016 the glacier has retreated an additional 400 m since 2002, 1900 m since 1986. The glacier no longer terminates in the lagoon. A bedrock rib at the sharp bend has been exposed and the glacier is only 500 m wide now and this bend is just 500 m from the terminus, green arrow. A closeup of this rib in a 2016 Sentinel image indicates why the crevassing had occurred, it is also clear this is an extension of the ridge that runs east from the glacier. This is a band of erosion resistant rock. This suggests that a basin exists above the this bedrock rib/ridge and a new lake will form. The glacier slope from the green arrow for the next 2 km upglacier is quite low 1/40, again indicative of a basin beneath the lower glacier. There is an increase in crevassing 2 km above the current terminus, suggesting another increase in surface slope and the probable limit of the basin. In 2016 the snowline is at 1250 m. The landslide deposit remains little changed since 2002, indicating a low velocity in this region. Burgess et al (2013) indicates the velocity of the Shoup Glacier near the terminus is in the range of 100 m annually. The tributary is clearly significantly less. The low velocity, thinning and retreat indicates the glacier is continuing to lose volume via surface melting, despite no longer calving as Larsen et al (2015) have indicated is the prime mechanism for ice loss. The retreat of this glacier is similar to that of nearby Valdez Glacier.

Shoup Glacier comparison in 2002 Landsat image. Red arrow is 1986 terminus, yellow arrow the 2016 terminus, green arrow rock rib emerging from beneath glacier, purple dots a landslide deposit, and purple arrow the snowline.

Shoup Glacier terminus in 2016 Sentinel 2 image. Green arrows indicate rock rib.

Herbert Glacier Retreat, Alaska 1984-2016

On September 14, 2016May 2, 2024 By mspeltoIn alaska glacier retreat, climate change glacier retreat1 Comment

Comparison of Herbert Glacier terminus position in Landsat images from 1984 and 2016. Red arrow 1984 terminus, yellow arrow 2016 terminus and pink arrow a tributary that has separated.

Herbert Glacier drains the west side of the 4000 square kilometer Juneau Icefield in Southeast Alaska. It is the glacier just north of the more well known Mendenhall Glacier and just south of Eagle Glacier. It is also the first glacier I ever visited, July 3, 1981 during my first field season with the Juneau Icefield Research Program. Here we examine the changes from the August 17, 1984 Landsat 5 image to a Sept. 1, 2016 Landsat 8 image.

The glacier descended out of the mountains ending on the coastal plain in 1948. In 1984 we examined the terminus of this glacier, which was in the small proglacial lake at 150 m. Herbert Glacier has retreated 600 m since 1984. The width of the terminus has also declined. The pink arrow indicates a tributary that no longer feeds the main glacier. The retreat has not been enhanced by iceberg calving as is the case at Mendenhall Glacier. The overall retreat is also less than Eagle Glacier. In the Google Earth images below from 2005 and 2013 the retreat is 200 m, the terminus has fewer crevasses in 2013 suggesting a reduced velocity and faster retreat to come. The annual equilibrium line on the glacier has averaged 1150 m from 2003-2016. By contrast in August 1984 I skied to the top of the icefall and could see the snowline was at 1000 m. This leaves the glacier with an AAR of 0.45, too low to sustain equilibrium, retreat will continue. In 2015 and 2016 the snowline rose to over 1400 m by the end of the melt season, indicating two years of large mass loss, which will drive further retreat. The higher snow line elevation has been observed across the icefield Pelto et al (2013).

Transient snow line in Early Sept. of 2015 and 2016. The snow line is at the top of the icefalls, at 1400-1450 m.

2005 Google Earth Image, red line is 2005 margin, yellow line is 2013.

2005 Google Earth Image, red line is 1984 margin, yellow line is 2005.

Herbert Glacier Terminus in 2012

McBride Glacier Increased Retreat and Harbor Seals, Glacier Bay, Alaska

On July 4, 2016May 2, 2024 By mspeltoIn alaska glacier retreat1 Comment

McBride Glacier (M), its secondary terminus (Ms), MCbride Inelt (MI) and Riggs Glacier (R) in Landsat image comparison from 1985 and 2015. The red arrows indicate the 1985 terminus location and the yellow arrows the 2015 terminus location. Main terminus 4.4 km retreat, secondary terminus 2.7 km retreat.

McBride Glacier was part of the Muir Glacier complex in Glacier Bay, Alaska, until the 1960’s when it separated from Muir and adjacent Riggs Glacier. Riggs Glacier and Muir Glacier are no longer calving tidewater glaciers, while McBride has continues to terminate in a tidewater inlet. Riggs Glacier’s retreat from the sea was complete by 2009.The continued rapid retreat of McBride Glacier is enhanced by calving. Calving generates icebergs, the number of icebergs has had a direct relationship with number of harbor seals. The number of harbor seals observed has declined substantially in Glacier Bay since 1993 (Glacier Bay NPS). In particular the population has declined in front of Muir Glacier which no longer calves, while a smaller population has remained in front of McBride Glacier (Womble et al, 2010). Here we examine Landsat imagery from 1985 to 2015 to quantify the retreat and estimate how long until this glacier too will no longer calve.

Inn 1985 the main glacier terminated 1.3 km from Muir Inlet, with a narrow connecting stream to Muir Inlet. The secondary terminus extended west down a separate valley, 3.75 km from the main glacier nearly reached the Riggs Glacier. The snowline was at 900 m. By 1996 the main terminus had retreated 1.1 km, and the connection with Muir Inlet had expanded to 200 m. The secondary terminus had narrowed but still nearly reached Riggs Glacier. There are two tributaries from the east at purple arrows connected to main glacier. By 2013 the glacier has retreated an additional 2.0 km and reached a northward turn in the inlet, The secondary terminus had mostly disappeared extending only 1.25 km from the main glacier. The eastern tributaries, purple arrows, had both retreated and detached from main glacier. By 2015 the glacier had retreated 4.4 km since 1985 including 1.3 km since 2013. The glacier now terminates at the head of a 6 km long inlet. The glacier is still actively calving, which is good for the harbor seals. However, a small icefall 0.8-1.1 km from the current terminus indicates a possible location for the end of the tidewater portion of this valley, note orange arrow in Google Earth image below. The retreat of the secondary terminus has been 2.7 km during this same period, without any calving. In 2013 and 2015 the snow line was above 1000 m, which as on nearby Brady Glacier is well above the equilibrium average which will continue to drive retreat Pelto et al, 2013). In 2016 southeast Alaska has had its hottest spring, which will continue this chapter.

Counting harbor seals is a task completed by the Glacier Bay NPS, they follow two populations the larger in John Hopkins Inlet off of Glacier Bay and the other in Glacier Bay proper. Both have declined by over 80% since 1992. In 2009 there were 200 harbor seals in McBride inlet Glacier Bay NPS. Glaciers are part of the local ecosystem where they exist, glacier changes do result in broader ecosystem changes, in this case harbor seals is one monitored example. The NPS prepares annual reports on glacier change in the region and notes widespread thinning in the region since 1995 and a 15% decline in glacier area in the last half century Loso et al (2014). The team of N.Loso, A.Arendt, C Larsen, N.Murphy and J.Rich have produced annual reports in recent years with valuable detail on changes of glaciers across Alaskan National Parks.

1996 Landsat image indicating terminus positions from 1985, read arrow and 2015 yellow arrow. The purple arrow indicates tributaries attached to main glacier.

2013 Landsat image indicating terminus positions from 1985, read arrow and 2015 yellow arrow. The purple arrow indicates tributaries detached from main glacier.

2014 Google Earth image indicating the icefall in relation to 2014 terminus. The icefall has increased calving and a 100 m increase in elevation. This is certainly a location where the valley bottom rises, and may be the end of the tidewater reach of the inlet.

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

Eagle Glacier, Alaska Retreat Losing a Wing

On May 27, 2016May 2, 2024 By mspeltoIn alaska glacier retreat, glacier climate change, Glacier Observations

Above is a paired Landsat image from 1984 left and 2013 right indicating the 1100 m retreat during this period of Eagle Glacier.

My first visit to the Eagle Glacier was in 1982 with the, ongoing and important, Juneau Icefield Research Program, that summer I just skied on the glacier. In 1984 we put a test pit at 5000 feet near the crest of the Eagle Glacier to assess the snowpack depth. This was in late July and the snowpack depth both years was 4.3 meters, checking this depth in nearby crevasses yielded a range from 4-4.5 meters.In 1984 the snowline at the end of the summer melt season in early September was at 1050 meters.The equilibrium line altitude (ELA) which marks the boundary between the accumulation and the ablation zone each year. On Eagle Glacier to be in equilibrium the glacier needs to have an ELA of 1025 meters. In the image below the glacier is outlined in green, the snowpit location is indicated by a star and the snowline that is needed for the glacier to be in equilibrium at 1025 meters is indicated. The number of years where the ELA is well above 1050 meters dominate since 2002, all but two years see chart below, leading to mass loss, thinning and glacier retreat. This follows the pattern of Lemon Creek Glacier that is monitored directly for mass balance, which has lost 26 meters of thickness on average since 1953.The more rapid retreat follows the pattern of more negative balances experienced by the glaciers of the Juneau Icefield (Pelto et al. 2013). The high snowlines have left the western most tributary with no retained snowpack in 2013, 2014 and 2015, yellow arrow in the 2014 and 2015 Landsat image. This will lead to the rapid downwasting of this tributary.

Eagle Glacier has experienced a significant and sustained retreat since 1948 when it terminated near the northern end of a small lake. By 1982 when I first saw the glacier and when it was mapped again by the USGS the glacier had retreated to the north end of a second and new1 kilometer long lake. In the image below the red line is the 1948 terminus, magenta line the 1982 terminus, green line 2005 terminus and orange line the 2011 terminus. From 1984 to the 2005 image the glacier retreated 550 meters, 25 meters/year. From 2005-2015 retreat increased to 60 meters/year. Going back to the 1948 map the terminus in 2011 is located where the ice was 150-175 m thick in 1948. The high snowlines in 2014 and 2015 along with extended melt season continued the rapid retreat. Total retreat from 1984-2015 is now 1200 m. The retreat hear is less rapid than on nearby Gilkey Glacier or Antler Glacier, but the upglacier downwasting is more severe than at Gilkey Glacier.

Snowline location and snowpit location in 1984

ELA of Eagle Glacier from Landsat images.

2014 and 2015 Landsat image indicating snowline on Eagle Glacier, purple dots. Yellow arrow indicates tributary that lacks any retained snowpack,

Terminus change map on 2005 Google Earth image. Red line is 1948, magenta line is 1982, green line is 2005 and orange line is 2011.

North Fork Grand Plateau Glacier, Alaska-Spectacular 3 km Retreat 2013-15

On May 1, 2016May 2, 2024 By mspeltoIn alaska glacier retreat, climate change glacier retreat, glacier climate change, Glacier Observations1 Comment

North Fork Grand Plateau Glacier comparison in 2013 and 2015 Landsat images. Illustrating the rapid retreat and lake expansion in just two years. Pink arrow is 1984 terminus, red arrow is the 2013 terminus and yellow arrow 2015 terminus. The orange dots are the 2013 terminus.

The Alsek Glacier is a large glacier draining into Alsek Lake and the Alsek River in southeast Alaska Its neighbor the Grand Plateau Glacier has one fork flows north and joins the Alsek Glacier terminating in Alsek Lake. The USGS topographic map compiled from a 1958 aerial image indicates a piedmont lobe spread out into a proglacial lake that is less than 3 km wide, with a combined ice front of the Alsek Glacier and North Fork Grand Plateau Glacier.. There is a 10.5 km wide calving front in the lake. By 1984 the glacier had separated into a northern and southern calving front on either side of an island and had a 13 km wide calving front. Here we focus on the southern lobe, which is comprised of a lobe of the Alsek Glacier and a the North Fork Grand Plateau Glacier that merges with Alsek Glacier. From 1984 and 1999 the two lobes separated as the North Fork retreated 2.2 km. From 1999 to 2013 the North Fork retreated 1.5 km up a newly forming southern arm of Alsek Lake. The retreat over the 30 period of 3.7 kilometers averaged ~120 meters/year. Landsat imagery in 2013 and 2014 indicate extensive calving from the North Fork Grand Plateau Glacier. From 2013 to 2015 the terminus has retreated 3.0 km, 1.5 km/year. This is likely the fastest retreat rate in recent years of any Alaskan glacier. The calving front in Alsek Lake has been reduced to 5.4 km in three separate sections.

The retreat has been similar in timing to nearby Alsek River watershed glaciers Walker Glacier, East Novatak Glacier and North Alsek Glacier.. The rapid retreat is enhanced by calving in proglacial lakes, a common issue increasing area loss of Alaskan glaciers. Yakutat Glacier is an example of rapid lake expansion. In the case of Yakutat Glacier unlike the Alsek or Grand Plateau Glacier the glacier lacks any high elevation accumulation zone and cannot survive without an accumulation zone (Trüssel et al 2015). Grand Plateau Glacier and Alsek Glacier both have large accumulation areas above 2000 m, that are well above the snowline at all times. The Alsek River is a destination for sockeye salmon fishing and river rafting, see Chilkat Guides or Colorado River and Trail Expeditions. Continued expansion of lake area as glaciers retreat in the watershed, is changing the nature of the Alsek River.

USGS Topographic map of region from 1958 aerial images indicating merging of Alsek Glacier and North Fork Grand Plateau Glacier.

1984 Landsat image indicating terminus locations. Pink arrow is 1984 terminus, red arrow is the 2013 terminus and yellow arrow 2015 terminus.

1999 Landsat image indicating terminus locations. Pink arrow is 1984 terminus, red arrow is the 2013 terminus and yellow arrow 2015 terminus.

2014 Landsat image. indicating terminus locations. Orange dots indicate the ice front. Pink arrow is 1984 terminus, red arrow is the 2013 terminus and yellow arrow 2015 terminus.