Walker Glacier Retreat and Lake Development, Alaska

On January 26, 2014March 13, 2014 By mspeltoIn Glacier Observations1 Comment

Walker Glacier terminates adjacent to the Alsek River, a popular rafting river route. Many rafting trips visit Walker Glacier since it is close to river, has a low slope and few crevasses.

Google Earth Image

In 1984 the glacier ended as a piedmont lobe separated from the river by meters. Today the terminus has retreated into a lake basin at the terminus. Here we examine Landsat imagery from 1984, 2011 and 2013 to identify retreat and lake development. In 1984 there is no lake at the terminus, red dots indicate glacier margin. The terminus particularly on the northwest side is debris covered. The yellow and red arrows indicate locations where the terminus is in 2013 and where new lakes have developed. The pink arrow indicates the end of a tributary that has fed the Walker Glacier. By 2004 the Google Earth imagery indicates a lake that is 400 m wide and 1500 m long. By 2011 the lake on the north side of the terminus is well developed, yellow arrow, but on the west side of the terminus no lake exists, red arrow. By 2013 the new lake is 750 m wide and 1800 m long. The glacier has retreated 800 m since 1984 on the north side, yellow arrow. A narrow lake has now developed on the west side. The combination of lakes indicates that the entire terminus lobe in the lake basin will soon be lost. The terminus remains quite debris covered, has a gentle slope and is relatively uncrevassed; hence, it is stagnant and will collapse-melt away. The last image is from Colorado River & Trail Expeditions , that shows low glacier slope looking north across new lake. This is similar to the collapse of glacier termini in proglacial lakes such as nearby East Novatak Glacier, Grand Plateau Glacier and Yakutat Glacier.
1984 Landsat image

2011 Landsat image

2013 Landsat image

Google Earth image from 2004

Colorado River & Trail Expeditions image-note low glacier slope looking north across new lake.

Koge Bugt Outlet Glacier, Southeast Greenland

On January 21, 2014 By mspeltoIn Glacier Observations4 Comments

Koge Bugt Glacier is an outlet of the Greenland Ice Sheet on the southeast Coast. The glacier empties into the bay of the same name, and has three main calving fronts. This glacier is the the sweet spot for high snowfall and hence, despite its smaller size is one of the larger outlet glaciers in terms of volume. Koge Bugt Glacier is not an oft mentioned glacier it is not as fast as Helheim or Jakobshavn, does not have as long a calving front as Humboldt Glacier. Does not calve icebergs nearly as large as Petermann Glacier. Does not penetrate into the midst of the ice sheet as far as Zachariae Ice Stream or 79 Glacier. However, according to observations of Enderlin et al (2014), Koge Bugt has the second largest volume flow for the entire ice sheet. They further note that the glacier has had the third greatest volume anomaly since 2000, that is increase in discharge. Murray et al (2010) indicate Koge Bugt had accelerated and thinned in concert with other glaciers in the region. The second image below is Figure 1 from their paper indicating the 27,000 square kilometer drainage area of Koge Bugt.

Howat and Eddy (2011) examing 210 outlet glacier in Greenland noted that 191 retreated from 2000-2010 including 89% in SE Greenland. Howat and Eddy (2011) data indicated limited retreat of Koge Bugt Glacier before 2000. From 2000 to 2010 they noted a retreat of 2300 m of outlet C, 1650 m for outlet B and 300 m for outlet A. Each of these outlets has a heavily crevassed active calving front having widths of 5000 m for A, 3500 m for B and 3500 m for C. Outlet B has calved a large iceberg, and there is a substantial rift near the calving front.

Greenland Velocity map with Koge Bugt indicated by red arrow.

Koge Bugt Drainage area from Murray et al (2010)

Danish Geologic Survey map of Koge Bugt area, outlets labelled A-C.

Google Earth image outlet A

Google Earth image outlet B

Google Earth image outlet C

Below is a sequence of Landsat images from 2001-2013 of the Koge Bugt Glacier three main termini. In each case the red dots indicate the calving front, the purple arrow is at the same spot on the north side of terminus A, the yellow arrow at the same spot on the west side of terminus B and the red arrow at the same spot on the west side of terminus C. From 2001 to 2011 terminus A has retreated little on the south side, but has retreated 1.5 km on the north side. Terminus B has retreated from halfway along the island on the southwest side of the terminus to the north of this island by 2011, a retreat of 2.2 km. Terminus C has retreated beyond the north end of the Peninsula noted by the red arrow, a distance of 600 m. Given the size and velocity of Koge Bugt this is a minor retreat, that can be erased by a year with more limited calving. The melt zone in these July and August images indicates how limited the ablation zone is compared to the west side of the ice sheet, this also limits the occurrence of supraglacial lakes.

Landsat Image 2001

landsat Image 2002

Landsat Image 2005

Landsat image 2010

Landsat image 2011

Lyell Glacier retreat and separation, New Zealand

On January 17, 2014January 17, 2014 By mspeltoIn Glacier Observations2 Comments

The Lyell and Ramsay Glaciers are the northernmost substantial valley glaciers in the Southern Alps of New Zealand. Their combined run-off is the chief source of the Rakaia River. The Lyell glacier was first observed by Dr.von Haast in 1862, from Mein’s Knob (M), at the time the glacier was 9 km long and ended close to Mein’s Knob. In 1949 Lyell glacier extended east from Rangiata Col some 7 km, and Lyell Lake (L) had not yet formed. (Gage, 1951). The Lyell Glacier has been the combined flow from the easterly tributary near Rangiata Col (E) and a northern tributary, Heim Plateau (H). Here we examine Google Earth Imagery and Landsat images from 2000-2013 to identify changes in the Lyell-Heim Glacier complex.

In 2000 the Heim Glacier (H) reached onto the Lyell Lake valley floor, yellow arrow. In 2001 this is evident along with the fact that Lyell Lake is a single lake. The terminus of the Lyell Glacier is obscured by thick glacier cover, and does end near Lyell Lake at the time, the end of the blue ice of the E tributary is not indicative of the terminus location. By 2013 Heim Glacier has retreated from the Lyell Valley and no longer is connected to the Lyell Glacier. A second small lake has formed as the terminus of Lyell Glacier has melted and retreated, red arrow. The terminus of Lyell Glacier does remain buried by debris, but it is stagnant and melting away. Both the Lyell Glacier and Heim Glacier have retreated 400 m from 2000-2013. The Lyell Glacier will likely experience a more rapid retreat in the near future as the debris covered tongue melts away. The 2013 austral winter featured record warmth, and the early melt season has also been warm in New Zealand, the impact on this glacier can be assessed in March or April as the melt season ends. The NIWA snowline surveys will document the impact on glaciers across New Zealand. The glaciers of New Zealand lost 15% of thier volume from 1976-2008 (Chinn et al, 2012). The retreat is like that of most all New Zealand glaciers today, Donne Glacier, Gunn Glacier, Tasman and Murchison Glacier

2000 Landsat image

2001 Landsat image

2013 Landsat image

Landsat image 2013

Google Earth image

Google earth image of terminus

East Novatak Glacier Retreat, Alaska

On January 12, 2014January 13, 2014 By mspeltoIn Glacier Observations3 Comments

Novatak Glacier and a large unnamed south-flowing glacier to the east, here designated as East Novatak Glacier, were connected when first mapped by the International Border Commission in the 1906-08 period. By the 1950’s maps indicated the Novatak and East Novatak Glacier have separated, with a lake (A) developing between them. Here we examined 1984-2013 Landsat images to determined changes over the last 30 years.

Map of East Novatak Glacier area.

Google Earth image

East Novatak Glacier ended in a lake (B) in 1984, this lake then drained a short distance south to the Alsek River. The glacier was separated from the main Novatak Glacier by 3.5 km. In each image the 1984 terminus is marked by red arrow and 2013 image by yellow arrow, N marks the location of a nunatak that develops after 1984. In 1987 glacier retreat has connected the northern and southern half of B Lake. Lake A is still getting glacier runoff leading to a lighter blue color. By 2010 A Lake is no longer getting much glacier runoff and the water color is much darker than B Lake. A nunatak has emerged as well due to thinning ice. East Novatak Glacier has retreated out of the lake basin on the low lying plain, and into the mountain valley. In 2013 the terminus has narrowed and has retreated 2.5 to 3 km since 1984. The glacier is now separated from the retreating Novatak Glacier by 6 km. The tributary that used to connect to the main glacier and is partly obscured by the red arrow, now ends well short of the East Novatak Glacier. Most of the East Novatak Glacier is below 1000 m in elevation, which has been the recent snowline elevation. The retreat of this glacier like that of nearby Yakutat Glacier, indicates how suscpetible the Alaskan glaciers in the region with lower elevation accumulation zones are to our warming climate (Truessel et al, 2013). The retreat is similar to Grand Plateau Glacier, but that glacier does have high elevation accumulation areas, that will allow that glacier to survive.

Mertz Glacier Changes, Antarctica

On January 8, 2014January 8, 2014 By mspeltoIn Glacier Observations2 Comments

The Mertz Glacier emerges from the mountains in East Antarctica in King George V land. The glacier is a true ice stream accelerating as it enters a pronounced trough. Berthier et al (2003) indicate an acceleration from to 100 m to 1000 meters/year as it enters the ice stream reach. The glacier then extends into the ocean with a floating tongue. This floating tongue advanced from 1956 to 2010 a distance of 43 km without calving indicating again a velocity of close to 1 km per day (Berthier et al, 2003). The floating ice tongue has only two means of losing ice calving and basal melting. Berthier et al (2003) indicate basal melting of 11 meters/year. Depoorter et al (2013) indicate that basal loss is small compared to calving flux for Mertz Glacier, this is due to lower melt rates than under other ice shelves and ice tongues. The tongue was impacted by the B9B iceberg causing the Mertz Glacier tongue to calve off an iceberg that was 78 km long and 35 km wide(Young et al, 2010).

Map of region (from NSIDC)

Google Earth Image

Impact image from Young et al (2010), Mertz Tongue left B9B right.

Tamura et al (2012) noted that the abrupt change to the regional icescape resulted in decreased polynya activity and sea ice production. Calving of the Mertz Glacier Tongue (MT) in February 2010 altered the regional distribution of ice and reduced the size and activity of the polynya. Shadwick et al (2013) noted that the calving of the Mertz Glacier Tongue altered the regional distribution of ice and reduced the size and activity of the Mertz Glacier polynya. In the years after the calving event there was a breakout and melt of thick multiyear sea ice released by the movement of iceberg B9B and the MT. The sea ice that was stable on the east side of the Mertz Glacier tongue, broke out from the coastline, and continues to not be as develped as before. Here we examine the floating tongue in Landsat and MODIS imagery from 2001-2013. In 2001 the floating had a rift crosscutting 30% of the eastern side of the ice tongue. By 2003 the rift had completely crossed the ice tongue. East of the tongue note the area of sea ice (SI). In 2007 and 2008 little has changed, again note the sea ice pinned to the east side of Mertz and the lack of sea ice to the west of the glacier. Than in 2010 and 2011 the tongue is broken off, and is not in view. The B9B iceberg is still in view (IB). The main change is the area of sea ice east of the former tongue is no longer as extensive and the open water west of Mertz Glacier is now has considerable sea ice. On January 3 2014 MODIS imagery indicates the extensive sea ice that exists west of the Mertz Glacier, and the region where both the Russian vessel, Akademik Shokalskiy, and Chinese vessel, Xue Long, became stuck in the ice. The vessels were stuck for ten days, broke free on January 8. Mertz Glacier is a large outlet ice stream of the Antarctic Ice Sheet. It differs from Pine Island Glacier in having lower basal melt rates, and that basal topography beneath the ice stream does not remain deep well inland of the coastline.

2001 Landsat image

2003 Landsat image

2007 Landsat image

2008 Landsat image

2010 Landsat image

2012 Landsat image

2014 MODIS image

Middle Lhonak Glacier Retreat, Sikkim, India

On January 6, 2014January 6, 2014 By mspeltoIn Glacier Observations1 Comment

“Middle” Lhonak Glacier is an unnamed glacier between North Lhonak and South Lhonak Glacier near the border of the state of Sikkim in India and Nepal, red arrow on first map. I have previously reported on the retreat of South Lhonak Glacier whose retreat has led to a significant proglacial lake expansion and nearby Changsang Glacier. Here we examine landsat and Google Earth imagery from 2000-2013. Like all glaciers in this region Middle Lhonak Glacier is a summer accumulation type glacier. This means that the glacier receives most ~80% of its snowfall during the summer monsoon. This is also the period when ablation low on the glacier is highest. Following the summer monsoon which ends in early September there is a transition period with some colder storm events where the snowline drops. Than from November-February is the dry winter monsoon with limited precipitation. Thus, strange compared to most glaciers as winter proceeds often the lower glacier remains snow free. The pre-monsoon season from March-May features increasing precipitation, temperature and rising snowlines. The glacier drains into the Teesta River, which has several existing and many proposed hydropower projects, mostly run-of-river with minor dams.
Map of Region

Weather records from Pyramid station at 5000 m in Nepal indicating the peak temperature and precipitation occurring in summer monsoon.
Proposed hydropower

In 2000 and 2001 Middle Lhonak Glacier ends in a proglacial lake at the yellow dot. The pink dot indicates a small peninsula in the lake. The green dot indicates a bare rock area that separates two arms of the glaciers. The green arrow indicates where the two arms of the glacier join. By 2005 the glacier had retreated from the yellow dot, but the two arms of the glacier still connected, green arrow. In 2006 a higher resolution image from Google Earth indicates the 300-400 m retreat since 2000 of the glacier. The two glacier arms still join, green arrow, though barely. There is a substantial icefall that begins at 5800-5900 m, as noted by red arrows. Above the icefall the glacier is almost always snowcovered, but the icefall the glacier often remains snow free for much of the year at around 5700 meters. This will be explored further in a sequence of 2013 images below the terminus change sequence. In 2013 the two arms of the glacier have separated, the green dot bare rock area has greatly expanded and the glacier terminus has retreated 500-600 m since 2000.
Landsat image 2000

Landsat image 2001

Landsat image 2005

Google Earth image 2006

Landsat Image 2013

A series of images below indicate the snowline in a period from October 12, 2013-December, 21 2013. On October 21 the snowline is at the last bend above the terminus at 5650 m. By November 21 the snowline has shifted little. By December 1 the snowline has begun to rise to 5700 m. The rise has continued to 5750 by December 21. The lake at the terminus remains unfrozen.

October 12 2013 Landsat

November 21, 2013 Landsat

December 1, 2013 Landsat

December 21, 2013 Landsat

Burroughs Glacier, Alaska Demise Continues

On January 2, 2014January 2, 2014 By mspeltoIn Glacier Observations1 Comment

Burroughs Glacier in Glacier Bay National Park, Alaska has been retreating without pause for the last century. The glacier is unusual in that it no longer has any areas that are in an accumulation zone, where snow persists through the year. Without an accumulation zone a glacier cannot survive (Pelto, 2010). Mickelson (1971) summarizes the retreat of the glacier from 1890-1970 and the amazing glacial geology it was leaving behind. Molnia (2007) provides a map of the regions glaciers from 1750 to 1985. Here we examine the glacier in Landsat imagery from 1986 to 2013 to illustrate both the retreat at the lack of snowcover. In the 1948 map of Burroughs Glacier, the glacier is 12.1 km long, and much of the glacier is already stagnant, the glacier has both a north and south terminus, purple arrows. To the west of Burroughs Glacier is Plateau Glacier. By 1986 Plateau Glacier has only three small remnants marked by P, surrounding these vegetation is still limited, with considerable expanse of bare glacial sediments. In 1986 Burroughs Glacier has now snowcover. The glacier terminates in proglacial lakes at both the north and south terminus red and yellow arrow respectively, and is 9 km long, purple arrows indicate 1948 terminus. By 2003 Plateau Glacier is gone and vegetation is filling in most of the area that was still bare sediment in 1986. In 2003 Burroughs Glacier again lacks any snowcover. The southern terminus has retreated 2.2 km from the lake, and the northern terminus has retreated into a second lake basin. The glacier is 6.3 km long, half of its length in 1948. In 2004 snowcover is again lacking anywhere on the glacier. In 2010 snowcover is lacking and retreat has continued shrinking the glacier to 5.4 km in length. In 2013 the glacier lacks snowcover in this September Landsat image even though snow has returned to the surrounding mountains. This indicates how far below the snowline the glacier lies. Portions of a glacier are supposed to be the first locations that receive snowcover. The terminus has continued to retreat and is now 4.6 km long. The northern terminus is retreating into a third basin of the proglacial lake. Vegetation has reclaimed almost all of the Plateau Glacier area and has reclaimed the region deglaciated by Burroughs Glacier before 2003.

Burroughs Glacier has not been in equilibrium with climate since the end of the Little Ice Age. Its retreat has been hastened by the rising snowline of the last decade note by Pelto et al (2013) on Brady Glacier. This glacier is half of its length from 1986, the volume loss is likely less than 50%. Retreat usually increases as elevation declines and as the size of the remnant ice declines. There is no debris cover or persistent snowcover to slow the loss. Thus, it seems likely this glacier will be gone within 25 years. The 2011 Google Earth image at bottom indicates no snow, the reduced albedo from the dirty surface and a few crevasses near the margin that are collapse features. This is unlike nearby glaciers that are retreating significantly but not disappearing, like Brady Glacier, Grand Plateau Glacier, Yakutat Glacier and Riggs Glacier.
1986 Landsat image

2003 Landsat image

2004 Landsat Image

2010 Landsat image

2013 Landsat image

Google Earth image

Burphu Glacier Retreat, Uttar Pradesh, India

On December 28, 2013 By mspeltoIn Glacier Observations1 Comment

Burphu Glacier is in Uttar Pradesh, India draining into the Goriganga River. The Burphu Gad stream enters the Goriganga a short distance upstream of the proposed hydropower project at Bogudiyar. This project is slated at 370 MW, and will have only a minor dam to divert the water from the river for a short distance before running through turbines and returning to the river. The map of the area is a 1940’s era map with the terminus of the Burphu Glacier indicated by the yellow arrow.

Here we examine Google Earth imagery and Landsat imagery from 2000-2013 to identify more recent changes. The Burphu Glacier has a substantial accumulation zone above 5000 m, before the glacier narrows and flows through an icefall descending to 4300 m where the glacier reaches the main valley and turns southwest, yellow arrow indicates map terminus, red arrow 2012 terminus. In the 2000 Landsat image the blue ice tongue of the Burphu Glacier reaches the main valley at the westward turn where debris cover than dominates, red arrow. By 2013 the Landsat image indicates the blue ice tongue no longer reaches the main valley, red arrow. In 2012 the Google Earth image illustrates an area of bare rock at 4400 m at the red arrow indicating that the Burphu Glacier terminates above the main valley as suggested by the Landsat 2013 image, though some relict ice remains in the main valley below. An even closer view indicates that the other tributary to the main valley tongue of the Burphu Glacier no longer reaches it either, pink arrow. Thus, this area with some pockets of relict glacier ice buried under debris cover is now fully detached. The total glacier retreat from the 1940’s mapped terminus to 2012 is 2800 meters. The retreat from 2000-2012 is at least meters 250 m as this the distance from the relict main valley ice to the current terminus. The retreat of this glacier is very similar to that of the nearby Kalabaland Glacier and is following the pattern of Malana Glacier, Milam Glacier and Satopanth Glacier in this region.
Google Earth overview 2012

2000 Landsat Image

2013 Landsat Image

2012 Google Earth view

Kalabaland Glacier, Retreat, Uttar Pradesh, India

On December 23, 2013December 23, 2013 By mspeltoIn Glacier Observations1 Comment

Kalabland Gal (Glacier) in Uttar Pradesh, India drains into the Goriganga River, via Ralam Gad. The glaciers flows southeast from the Peak of Chhiring We, joins the Yankchar Glacier and turns sharply southwest. The combined terminus is referred to as Shunkalpa Gal, but here since Kalabaland is the largest contributing glacier, that name is applied to the terminus as well. Here we examine changes in the glacier from 2000 to 2013 using Google Earth and Landsat imagery.
Map of Region

Google Earth Image, blue arrows glacier flow, red arrow terminus.

The Goriganga River is fed by many glaciers and is a target for a number of run of river hydropower projects, some existing such as at Talla Dummar and others projected, such as at Bogudiyar. These projects have only minor dams to divert the water from the river for a short distance before running through turbines and returning to the river. In 2000 both Landsat and Google Earth imagery indicate the terminus location, red arrow. The terminus is heavily debris covered and is evident because of the glacial stream that emerges from beneath the debris covered ice. By 2012 the glacier had retreated 250 m to the yellow arrow. The lowest one kilometer of the glacier has thinned both in width and thickness, is stagnant and will melt away soon. The side by side view from 2000 and 2012 better indicates the change and the thinning of the terminus tongue. The two pink markers are at the 2000 and 2012 terminus respectively, dark pink 2000 and light pink 2012.

2000 Google Earth

2012 Google Earth

Terminus closeup in Google Earth

Landsat images from 2000 to 2013 indicate that the terminus retreat is small compared to the full length of the glacier, red arrows. The width and length of blue ice extending southwest at the bend has been reduced from 2000 to 2013 indicating a continued reduction in net flow of ice to the terminus. This glaciers retreat is following the pattern of Malana Glacier, Milam Glacier and Satopanth Glacier in this region.

2000 Landsat image

2013 Landsat image

Glacier Ice Worm Investigations-A Long Slow Processs

On December 19, 2013 By mspeltoIn Glacier Observations4 Comments

Yes, worms really do live in glaciers and in fact, they can’t live off of them. Their scientific name is Mesenchytraeus solifugus. I first saw an ice worm in 1981 in Alaska, the number was small and they seemed insignificant overall. In 1984 I began working in the North Cascades of Washington, and Bill Prater (inventor of the snowshoe with crampon attached) told me I would see millions, and he was correct. In the evening and night hours ice worms feed primarily on the surface of snow on glaciers, and to a much less degree, on bare ice. During the day, ice worms hide out beneath the surface of the glacier, avoiding any sunlight. We have undertaken annual ice worm counts on Sholes Glacier for twenty years. They move slowly and are out only in low lights, which does not make for exciting video, as seen below, but that is reality. On Suiattle Glacier in 2002 we found a density of ~2600 ice worms per square meter. With an area of 2.7 square kilometers, this represents somewhat over 7 billion ice worms on this glacier.

In 2003, we sat at the edge of the Sholes Glacier looking at the glacier covered Mt. Baker volcano waiting for the sun to set. After sunset we counted the ice worms on the glacier. There were close to 1000 ice worms per square meter right up to the glacier margin. By the time we had traveled 10 meters from the edge of the glacier onto seasonal snowpack almost no ice worms existed on the snowpack, within 30 m we could not find a single ice worm. This is true even in cases where the snowpack adjacent to the glacier survived the summer. Thus, the ice worms need the permanent snowpack of glaciers to survive.

In a joint project with Oregon State in 1994 we collected Ice Worms for DNA analysis, they did not find differences between ice worms from various glaciers. In 2002 In a joint study with Clark University the Ice Worm genome was sequenced. In 2011 we joined Queens University in a study of ice worm anti-freeze proteins (AFP) which help keep them from freezing solid. These AFP’s inhibit the growth of ice by lowering the freezing point and coating ice molecules. This facet is seen in other organisms that inhabit cold environments, more details on ice worm AFP from Napolitano et al (2003). Queens University was examining the ability of the AFP’s to suppress the melt temperature of water for transplant surgical procedures. Ice worms are a critical part of the glacier ecosystem in the coastal ranges of the Pacific Northwest. Glacier ice worms only inhabit glaciers from southern Alaska’s coastal ranges through the Coast Ranges of British Columbia, the Cascades of Washington to the Three Sisters of Oregon and the Olympic Mountains. The Three Sisters and Mount Hood areas is south of the Cordilleran Ice Sheet limit, indicating that this ice sheet cannot be the only dispersal method for ice worms. It is also noteworthy that ice worms are not found in the interior ranges of British Columbia or in the Rocky Mountains, which is the interior side of the Cordilleran Ice Sheet. The ice worms are associated only with temperate climates. Ice worms are tough too, surviving the Mount Saint Helens eruption in the firnpack of the newly redeveloping glacier on the mountain. The most likely means of populations spread dispersion is birds, the Rosy Finch is the bird most commonly seen feeding along the surface of the glaciers. For further details note our Ice Worm Research Project page.

Clara Smith Glacier, Alaska-British Columbia Retreat

On December 16, 2013 By mspeltoIn Glacier Observations2 Comments

Clara Smith Glacier begins in the Coast Mountains of the British Columbia-Alaska boundary region and descends into Alaska. The USGS map shows the 1948 terminus of the glacier at 2100 feet, blue arrow, 4 km south of the border.

1948 aerial photograph based USGS map.

Google Earth images with flow directions.
Here we focus on changes from 1987 to 2013 in Landsat images. The glacier is just east of Gracey Creek Glacier, which in the landsat images below also is marked with arrows, By 1987 the glacier had retreated 1.9 km to the magenta arrow. The glacier was fed by two significant tributaries from the west at the light and dark pink dots. The glacier also has a north flowing terminus marked by a red arrow, the divide between the two is marked by a magenta D. By 1997 the main southern terminus has retreated 400 m since 1987 and the dark pink dot tributary is just separating from the main trunk glacier. In 2010 the dark pink dot tributary is well separated from the main glacier and the terminus is at the yellow arrow. In 2013 the tributary at the light pink dot is only half its width from 1987 and is following the course of the other tributary and will separate. The main terminus is at the yellow having retreated 1000 m since 1987. The terminus is about 1 km south of the border today. The northern terminus has retreated 500 m since 1987 and a small lake has appeared at the terminus, though this could be a temporary feature. In the 1987 and 2013 images the divide between the north and south flowing terminus is marked by a magenta D, the width of the glacier at this point has declined 35-40%, a sign that both termini will continue to retreat with less ice being delivered down valley from the divide region. Notice that in 1997, 2010 and 2013 the snowline is well above the divide even though the images are not at the end of the ablation season. The divide is at 1270 m, a snowline higher than this will not maintain any portion of the main trunk of Clara Smith Glacier. This glacier is experiencing not just substantial retreat of the terminus, but tributary separation, lateral retreat on upper sections of the glacier and thinning in the accumulation zone. This trait is shared by Bromley Glacier, and Gracey Creek Glacier.

1987 Landsat image

1997 Landsat image

2010 Landsat image

2013 Landsat image

Gracey Creek Glacier Retreat and Tributary Loss, Alaska

On December 10, 2013December 12, 2013 By mspeltoIn Glacier Observations1 Comment

Gracey Creek Glacier is a small glacier in southeast Alaska that terminates near the Canadian border. The glacier’s main terminus is the northern terminus (red arrow), though it has southern terminus as well (purple dot), both drain into Behm Canal via different rivers. Here we examine Landsat images from 1987 to 2013 to identify retreat and tributary separation in the last quarter century.

USGS map of Gracey Creek Glacier

Google Earth image indicating direction of flow.

In 1987 Gracey Creek Glacier is fed by several main tributaries yellow, pink and light green arrows. The glacier’s northern terminus is at the red arrow and the southern terminus at the purple dot. By 1997 the pink tributary no longer connects to the main glacier, and the other tributary connections are much narrower. The glacier has retreated 200 m at the northern terminus and 50 m at the southern terminus. Snowcover is quite limited on the glacier. In 2010 the yellow tributary is no longer connected to the main glacier. The area of bedrock at the orange arrow near the southern terminus is greatly expanded. The northern terminus has retreated 400 m and the southern terminus 100 m. Of more importance in 2010 is the limited snowpack that is left, even though this is in mid-August with five weeks left in the melt season. By 2013 the only tributary connection is at the green arrows though this is only 40% of its 1987 width. The northern terminus has retreated 600 m since 1987 and the southern terminus 200 m.

There is limited snowpack in this late August image as was the case in the 1997 and 2009 image, this has become typical not unusual. The bad news is that in 2013 the melt season extended into mid-August and it is likely little snow remained on the glacier. The limited snowcover, loss of connection with higher elevation tributaries and thinning of the glacier even at its higher elevations indicates this glacier cannot survive current climate (Pelto, 2010). This thinning in the accumulation zone is evident from the reduction in width of the glacier at the divide between the southern and northern terminus, this is indicative of retreat of the lateral margins of the upper portion of the glacier, another sign of a glacier that cannot survive. The glacier is still 6.8 km long and it will not disappear quickly. The retreat here is less than on nearby Chickamin Glacier, Bromley Glacier and Nass Peak Glacier, however the changes on the upper glacier are the story. This glacier is similar in size and retreat to Lemon Creek Glacier of the Juneau Icefield.

1987 Landsat image

1997 Landsat image