Retreat of Grewingk Glacier, Alaska 1986-2014

On May 13, 2015May 3, 2024 By mspeltoIn alaska glacier retreat, climate change glacier retreat, glacier climate change, Glacier Observations2 Comments

Grewingk Glacier drains west toward the Kachemak Bay, Alaska terminating in a proglacial lake in Kachemak Bay State Park. The glacier drains an icefield on the Kenai Peninsula, glaciers draining west are in the Kenai Fjords National Park. The glaciers that drain east toward are in the Kenai Fjords National Park, which has a monitoring program. Giffen et al (2008) 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 (2008)observed that Grewingk Glacier retreated 2.5 km from 1950-2005. Here we examine Landsat imagery from 1986-2014 to illustrate the retreat of the glacier. The icefront continues to calve into the expanding pro-glacial lake.

1951 based USGS Topographic map Seldovia C-3

The red arrow is the 1986 terminus location at the midpoint, the yellow arrow is the 2014 mid-point terminus location. In 1951 the glacier extended beyond the peninsula at the red arrow into the wider portion of the lake. By 1986 the glacier had retreated into the narrow section of the lake extending east into the mountains, the southern margin of the terminus is further advanced than the northern margin. The orange dots indicate discoloration of the glacier surface from volcanic ash deposited on the glacier surface from Augustine Volcano in 1986. In 1989 there is not a marked change. In a 1996 Google Earth image, there is considerable icebergs indicating a recent collapse of a section of the terminus. The pink arrow indicates concentric crevasses, indicating a depression, the red line is the terminus in 1996 and the brown line the 2003 terminus.

By 2001 the terminus has retreated m, and the glacier front is now oriented north-south across the lake. In 2003 the depression from 1996 now has a small supraglacial lake, the terminus has retreated 500 m on the southern margin and 200 m on the northern margin. In 2013 the glacier has retreated an additional 600 m and the southern margin has now receded further upvalley than the northern margin. Blue arrows indicate direction of glacier flow. By 2014 the glacier has retreated 1.4 km since 1986, 50 m per year. There is an increase in the glacier slope 2.5 km above the terminus where crevassing increases. This suggests the lake will end by or at this point, which would then lead to a reduction in retreat rate.

This retreat follows that of Pederson Glacier, Four-Peaked Glacier and Spotted Glacier. The continued reduction in glacier size leads to changes to the Kachemak Bay estuary. Kachemak Bay is the largest estuarine reserve in the National Estuarine Research Reserve System. It is one of the most productive, diverse estuaries in Alaska, with an abundance of Steller sea lions, seals, sea otters, five species of Pacific salmon, halibut,herring, dungeness crabs and king crabs (NERRS, 2009). The estuary salmon fishing industry is, one of Kachemak Bay’s most important resources and livelihoods.

1986 Landsat Image

1989 Landsat Image

1996 Google Earth Image

2001 Landsat Image

2003 Google Earth Image

2013 Landsat Image

2014 Landsat Image

Snow Deficit on Grinnell Ice Cap, Baffin Island, Canada

On May 1, 2015May 3, 2024 By mspeltoIn Canada glacier retreat, climate change glacier retreat, glacier climate change, Glacier Observations, Uncategorized

The Grinnell Ice Cap Is located on the Terra Incognita Peninsula on Baffin Island. The name suggests the reality that this is a not often visited or studied region. Two recent studies have changed our level of knowledge. Way (2015) notes that the ice cap has lost 18% of its area from 1974 to 2013 and that the rate of loss has greatly accelarated and is due to summer warming, declining from 134 km2 in 1973-1975 imagery to 110 square kilometers in 2010-2013 images. Papasodoro et al (2015) report the area in 2014 at 107 km2 with a maximum of elevation of close to 800 m. The location on a peninsula on the southern part of the island leads to higher precipitation and cool summer temperatures allowing fairly low elevation ice caps to have formed and persisted. Way (2015) in the figure below indicates the cool summer temperatures have warmed more than 1 C after 1990. Recent satellite imagery of snowcover and ICESat elevation mapping suggest little snow is being retained on the Grinnell Ice Cap since 2004. Papasodoro et al (2015) identify a longer mass loss rate of -0.37 meters per year from 1952-2014, not exceptionally different from many alpine glaciers. They further observed that from 2004-2014 this rate has accelerated to over -1 meter per year, including a thinning rate above 1.5 meters along the crest of ice cap. This can only be generated by net melting not ice dynamics. Further such rapid losses will prevent retaining even superimposed ice. Here we examine Landsat imagery from 1994 to 2014 to illustrate glacier response.

Grinnell Ice Cap in Google Earth

From Way (2015)

The red arrows in each image indicate areas of small nunataks that have begun to expand in the last decade. The yellow and green arrows indicate specific locations on the western margin of the ice cap where lakes are developing. Point A-D note specific locations adjacent to ice cap outlet glaciers. In 1994 the late August image indicates snowcover across most of the ice cap. The green arrow is at the northern end of a narrow lake. The yellows arrows are at the northern and southern end of a narrow ice filled depression. The nunatak area exposed at the red arrows is limited. At Point C the terminus is tidewater. In 2000 snow pack covers 40% of the ice cap. A small lake is developing at the yellow arrows. The glacier reaches the ocean at Point C and D. The glacier extends south of Point A and the outlet glacier at Point B is over a 1.2 km wide. In 2012 a warm summer led to the loss of all but snowpack on the glacier. At the red arrows the nunataks have doubled in size. At the yellow arrows a 2.5 km long lake has developed. At the green arrow a lake that has developed, is now separated from the glacier margin by bedrock. The glacier now terminates north of Point A. In 2014 again snowcover is minimal with two weeks left in the melt season. The outlet glaciers at Point C and D are no longer significantly tidewater. At Point B the outlet glacier is less than 0.5 km wide. The lake at the yellow arrows is 3 km long and 400 m wide. Some nunataks are coalescing with each other or the ice cap margin. The majority of the western margin of the ice cap has retreated 300-500 m. This retreat is surpassed at outlet glaciers by Point A and C. What is of greatest concern is the loss in thickness of over 1.5 per year on the highest portions of the ice cap, indicating no consistent accumulation zone. This results from the persistent loss of nearly all snowcover in the summer. This pattern of limited end of summer retained snowcover seen in most years since 2004, is a snow deficit that this ice cap cannot survive in our current warmer climate (Pelto, 2010). Way (2015) projects that that if the observed ice decline continues to AD 2100, the total area covered by ice at present will be reduced by more than 57%. Given the recent increases and lack of retained snowcover, suggests an even faster rate is likely.

1994 Landsat image

2000 Landsat image

2012 Landsat image

2014 Landsat image

31 years of observations on Retreating Columbia Glacier, Washington

On April 7, 2015May 3, 2024 By mspeltoIn climate change glacier retreat, glacier climate change, Glacier Observations1 Comment

For the last 31 years the first week of August has found me on the Columbia Glacier in the North Cascades of Washington. Annual pictures of the changing conditions from 1984 to 2014 are illustrated in the time lapse video below. This is the lowest elevation large glacier in the North Cascades. Columbia Glacier occupies a deep cirque above Blanca Lake and ranging in altitude from 1400 meters to 1700 meters. Kyes, Monte Cristo and Columbia Peak surround the glacier with summits 700 meters above the glacier. The glacier is the beneficiary of heavy orographic lifting over the surrounding peaks, and heavy avalanching off the same peaks. This winter has been the lowest year for snowpack in the North Cascades in the 32 years we have worked here. Below is a comparison from August 1, 2011 with Blanca Lake below the glacier still frozen and a beautiful scene on April 4, 2015 with the lake not frozen taken by Karen K. Wang. The winter in the region was unusually warm, but not as dry as in California; however, in the snowmelt and glacier fed river basins summer runoff will be low this year.

Blanca Lake Aug. 1, 2011 on left and April 4, 2015 on right (Karen K. Wang, www.karenkwang.com) — **Blanca Lake Aug. 1, 2011 on left, and April 4, 2015 on right (Karen K. Wang, www.karenkwang.com)**

Over the last 31 years the annual mass balance measurements indicate the glacier has lost 14 meters of thickness. Given the average thickness of the glacier of close to 75 meters in 1984 this represents a 20% loss in glacier volume. During the same period the glacier has retreated 135 meters, 8% of its length. Most of the loss of volume of this glacier has been through thinning not retreat. To survive a glacier must have a persistent and consistent accumulation zone (Pelto, 2010). On Columbia Glacier in 1998, 2001, 2003, 2004, 2005, 2009 and 2013 limited snowpack was retained, resulting in thinning even on upper part of the glacier. This thinning of the upper glacier indicates the lack of a persistent accumulation zone such as in 2005, note the exposed annual ice and firn layers green arrows, this indicates the lack of retained accumulation in recent years. This indicates the glacier is in disequilibrium and cannot survive. Mapping of the glacier from the terminus to the head indicates a similar thinning along the entire length of the glacier. The overall mass balance loss parallels that of the globe and other North Cascade glaciers in the last three decades.

2005 Accumulation zone of Columbia Glacier

On left cumulative mass balance of Columbia Glacier compared to the WGMS global record and other North Cascade glaciers. On right change in surface elevation along the glacier from terminus to head indicating a 14-15 m thinning on average.

A comparison of images from 1986, 2007 and 2013 photograph provide a view of glacier change at the terminus. The blue arrows indicate moraines that the glacier was in contact with in 1986, and now are 100 meters from the glacier. The green arrow indicates the glacier active ice margin in 1986 and again that same location in 2007 now well off the glacier. The red arrow indicates the same location in terms of GPS measurements, this had been in the midst of the glacier near the top of the first main slope in 1986. In 2007 this location is at the edge of the glacier in a swale. The changes are more pronounced in 2013 as the terminus slope continues to decrease. The low snowpack in 2015 on the glacier in March, 2-3 m versus 6-8 m, will lead to considerable changes in the terminus this summer, that we will assess.

1986 Terminus Columbia Glacier

2007 Terminus Columbia Glacier

2013 Terminus Columbia Glacier

Jill Pelto painted the glacier as it was in 2009 (top) and then what the area would like without the glacier in the future, at least 50 years in the future (middle), and Jill at the sketching location (bottom), turned 180 degrees to view Blanca Lake. The lake is colored by the glacier flour from Columbia Glacier to the gorgeous shade of jade.

Clearly the area will still be beautiful and we will gain two new alpine lakes with the loss of the glacier. After making over 200 measurements in 2010 we completed a mass balance map of the glacier as we do each year. This summer we will be back again for the 32nd annual checkup. There will be likely be record low snowpack, comparable to 2005 the worst year from 1984-2014.

2010 Mass Balance map of Columbia Glacier

Widespread Retreat Gilkey Glacier System, Alaska

On March 23, 2015May 3, 2024 By mspeltoIn alaska glacier retreat, climate change glacier retreat, glacier climate change, Glacier Observations

Gilkey Glacier drains the west side of the Juneau Icefield and has experienced widespread significant changes since I first worked on the glacier in 1981. Here we examine the changes from the August 17, 1984 Landsat 5 image to the August 21, 2014 image from newly launched Landsat 8. Landsat 5 was launched in 1984, Landsat 8 launched in 2013. The Landsat images have become a key resource in the examination of the mass balance of these glaciers (Pelto, 2011). The August 17th 1984 image is the oldest Landsat image that I consider of top quality. I was on the Llewellyn Glacier with the Juneau Icefield Research Program (JIRP) on the east side of the icefield the day this image was taken. JIRP was directed by Maynard Miller at that time and by Jeff Kavanauagh now. The Gilkey Glacier is fed by the famous Vaughan Lewis Icefall at the top of which JIRP has its Camp 18 and has monitored this area for 60 years. Here I examine changes both in images and text below. The same analysis in a more depth is contained in the screen capture video of the same images. Choose the format you prefer and let me know which works for you.

There are seven locations noted in the 1984 and 2014 image that are the focus of more discussion in a set of three more focused images

1984 Landsat Image

2014 Landsat image

Arrow #1 indicates the Gilkey Glacier terminus area. Gilkey Glacier had begun to retreat into a proglacial lake by 1984, the lake was still just 1 km long. A short distance above the terminus the Gilkey was joined by the sizable tributaries of the Thiel and Battle Glacier. By 2014 the main glacier terminus has retreated 3200 m, the lake is now 4 km long. A lake that did not exist in USGS maps from 1948. Thiel and Battle Glacier have separated from the Gilkey Glacier and from each other. Thiel Glacier retreated 2600 m from its junction with Gilkey Glacier from 1984-2014 and Battle Glacier 1400 m from its junction with Thiel Glacier and 3500 m from the Gilkey Glacier. Melkonian et al (2013) note the fastest thinning in the Gilkey Glacier system from to is near the terminus and in the lower several kilometers of Thiel Glacier.

Above: 1984-2014 Comparison of Gilkey Glacier terminus area with Landsat imagery

Arrow #3 and #4 indicates valleys which tongues of the Gilkey Glacier flow into. In 1984 at #3 the glacier extended 1.6 km upvalley ending where the valley split. The portion of the Gilkey flowing into the valley had a medial moraine in its center. At arrow #4 the glacier extended 1.5 km up Avalanche Canyon. In 2014 at #3 the glacier tongue ends 1.2 km from the valley split, and the medial moraine does not enter the valley. At #4 the glacier has retreated 1.3 km, leaving this valley nearly devoid of a glacier.

Above: Comparison of the Avalanche Canyon area 1984-2014.

Further upglacier arrow #5 indicates a side glacier that in 1984 featured an unending system of glacier flowing down the steep mountain sides into the valley bottom. By 2014 two rock ribs extend along most of the east and west valley walls separating the glaciers on mountain side from the main valley glacier, which has as a result been reduced in width and velocity. At arrow #6 a tributary glacier is seen merging with Gilkey Glacier in 1984. By 2014 this tributary no longer reaches the Gilkey Glacier, ending 300 m up the valley wall. At arrow #7 the Little Vaughan Lewis Icefall in 1984 is seen merging with the Gilkey Glacier across a 300 m wide front. This I can attest from seeing the glacier that summer to be an accurate observation. By 2014 at arrow #7 the Little Vaughan Lewis Icefall no longer feeds ice directly to the Gilkey Glacier. There is still avalanching but not a direct flow connection. JIRP has Camp 19 in this area, a spectacular area of ongoing research by JIRP. The main Vaughan Glacier Icefall is still impressive, just south of the rib beyond arrow #7. Measurements of snowpack are made annually by JIRP above the icefall, and indicate a mean snow depth exceeding 3 m in early August, note image below of measuring annual snow layers in a crevasse at head of the icefall. Pelto et al (2013) summarize the results of this ongoing research that Chris McNeil (USGS) is working to enhance with newer technology. The terminus change of all Juneau Icefield glaciers from 1984-2013 has been summarized in a previous post. The 2015 season will be of interest, since the area had a remarkably warm yet wet winter. This will lead to high ablation at lower elevations, likely a higher snowline than usual, but above the Vaughan Lewis Icefall will those warm wet events dumped snow? The 2014 winters season was warm and the snowline seen in the 2014 satellite imagery was at 1500 m, yet snowpack at 1760 m on the Vaughan Lewis Glacier was 3.3 m deep in late July. This has been the case in the past with warm wet winters featuring heavy snow above 1600 meters on the icefield. JIRP will be in the field answering this question in 2015.

Above: Comparison 1984-2014 of the Vaughan Lewis Glacier area

Crevasse stratigraphy Vaughan Lewis Glacier.

Conway Glacier Separation and Retreat, Alberta

On March 16, 2015May 3, 2024 By mspeltoIn alberta glacier retreat, Canada glacier retreat, climate change glacier retreat, Glacier Observations

Conway Glacier drains east from the border with British Columbia into the Howse River. The Howse River joins the Saskatchewan River upstream of the Bighorn Hydropower project, which impounds Lake Abraham and produces 120 MW of power. The map of this area was updated based on 1990 images which indicate Conway Glacier is comprised of two lobes that join near the terminus. An inventory of glaciers in the Canadian Rockies indicate area loss of 15% from 1985 to 2005 (Bolch et al, 2010). The more famous Columbia Icefield, 50 km north, has lost 23 % of its area from 1919-2009 with ice loss at a minimum during the 1970′s (Tennant and Menounos, 2013). Here we examine Landsat imagery from 1986 to 2014 to see the impact of recent climate change.

Map of Conway Glacier area from 1990 image.

In 1986 the two glaciers are still joined, with a surface lateral moraine at their junction, orange dots indicate this narrow surface rock band eroded from the ridge between the two lobes. The yellow arrow in each image indicates the 1986 terminus location of the northern lobe, the red arrow indicates a bedrock step near the southern lobe terminus, green arrow indicates an ice filled basin, and the purple arrow a small tributary joining the main glacier. In 1986 the southern lobe extends 300 meters beyond the bedrock step. By 1994 a small lake is developing at the basin indicated by the green arrow and the northern lobe is reduced in width. Overall less than 40% of the glacier is snowcovered. By 1998 the southern lobe has retreated to the bedrock step and the northern lobe has retreated from the end of the lateral moraine. The glacier again is less than 40% snowcovered. The 2013 image has better resolution thanks to the better Landsat 8 imagery, and has been sharpened using a higher resolution panchromatic image layer by Ben Pelto (Technique will be explained in a future post). The glaciers are no longer joined. The northern lobe has retreated 500-550 m since 1986 and a small lake has formed at the 1986 terminus location, another yellow arrow indicates 2013 terminus. The northern lobe has retreated above the bedrock step, a total retreat of 500-600 m since 1986. Two additional red arrows have been added to indicate 1986 and 2013 terminus location. The small lake at the green arrow has expanded. The tributary connection at the purple arrow is nearly severed. Retained snowpack on the glacier is also limited in area with most of the glacier in 2013 being bare glacier ice. This indicates that snow was not retained in recent previous years either. For a glacier to be in equilibrium it needs more than 50% of its area to be covered by snow at the end of the melt season, not 35% with a few weeks left in the melt season. as in 2013. This glaciers retreat and volume loss mirrors that of the region including Saskatchewan Glacier and Fraser Glacier. Peyto Glacier is the nearest glacier, just 20 km southeast, with a long term mass balance record, which indicates a cumulative loss or over 28 m w.e or 30 m of glacier thickness.

1986 Landsat image

1994 Landsat image

1998 Landsat Image

2013 Landsat image-Pan sharpened by Ben Pelto (Univ. Northern British Columbia)

Lys Glacier Rapid Retreat, Italy

On January 23, 2015January 23, 2015 By mspeltoIn climate change glacier retreat, Glacier Observations

Lys Glacier drains south from Lyskamm in the Monta Rosa Group of Italy. This glacier has a long history of observations that have indicated two short term advances in the 20th century 1912-21 and 1973-85 amidst a broader retreat. The net change for the 1915-2004 interval was a 600 meter retreat (Smiraglia et al, 2006). They also noted a 10% area extent loss from 1975-2003, and since the glacier was advancing up to 1985 this change occurred more rapidly. The Italian Glacier Commission report on terminus change of this glacier annually in the two latest reports Lys Glacier retreated 10 m in 2012 and 20 m in 2011. The total reported retreat from 2005-2012 was 186 m, more than 20 m per year. Here we examine Landsat images from 1990 to 2014.

Google Earth Image

In 1990 two branches of the glacier merged in the valley bottom and extended to the red arrow marking the terminus of the glacier at that time. The yellow arrow indicates the 2014 terminus position, and the yellow A indicates a prominent bedrock knob that a branch of the glacier encircles, pink arrows. By 2013 the glacier in the main valley have separated, there are a few small lakes forming amidst the decaying stagnant ice tongue between the yellow and red arrow. The bedrock knob at Point A has greatly expanded. In 2014 none of the termini reach the floor of the main valley. As the stagnant ice melts, the lake area is expanding indicating that a new alpine lake will likely form. The retreat from 1990-2014 is 1300 meters. A closeup in 2009 from Google Earth indicates the two tongues with bedrock below separating them from the main valley floor, red arrows. There is still some relict ice below on the valley floor detached from the active glacier, blue arrows, that has small lake developing amid the stagnant ice. There is substantial crevassing above both actual termini, but not immediately. The retreat should slow now that the glacier has retreated onto steeper slopes, having lost the low elevation low slope valley tongue.
The retreat of this glacier is similar to that of nearby Verra Grande Glacier.
1990 landsat image

2013 Landsat image

2014 Landsat Image

Google Earth Image

Stephenson Glacier Retreat and Lagoon Development, Heard Island

On January 16, 2015January 18, 2015 By mspeltoIn afghanistan climate change, climate change glacier retreat, heard island glacier retreat, stephenson glacier retreat, stephenson lagoon glacier retreat5 Comments

The Australian Antarctic Division manages Heard Island Island and has undertaken a project documenting changes in the environment on the island. One aspect noted has been the change in glaciers. The Allison, Brown and Stephenson Glacier have all retreated substantially since 1947 when the first good maps of their terminus are available. Fourteen Men by Arthur Scholes (1952) documents a year spent by fourteen men of the Australian National Antarctic Research Expedition that documented the particularly stormy, inclement weather of the region. Their visit to the glacier noted that they could not skirt past the glacier along the coast. After crossing Stephenson Glacier they visited an old seal camp and counted 16,000 seals in the area. It is a rich area for wildlife, that should benefit from the lagoon formation overall. Thost and Truffer (2008) noted a 29% reduction in area of the Brown Glacier from 1947-2003. They also observed that the volcano Big Ben that the glaciers all drain from has shown no sign of changing geothermal output to cause the melting and that a 1 C warming has occurred over the same time period.

Hear Island Map from the Australian Antarctic Division

Stephenson Glacier extends 8-9 km down the eastern side of Big Ben. In 1947 it spread out into a piedmont lobe that was 3 km wide and extended to the ocean in two separate lobes around Elephant Spit. A picture from the Australian Antarctic Division taken in 1947 shows the glacier reaching the ocean and then in 2004 from the same location. Kiernan and McConnell (2002) identified an order of magnitude increase in the rate of ice loss from Stephenson Glacier after 1987. Retreat from the late 19th century to 1955 had been limited. As Kiernan and McConnell observed retreat began that by 1971 the glacier had retreated 1 km from the south coast and several hundred meters from the northern side of the spit. This retreat by 1980 caused the formation of Stephenson Lagoon and by 1987 Doppler Lagoon had formed as well. After 2000 the two lagoons have joined. The first image below shows the terminus locations over the last 60 years from the Australian Antarctic Division 1947-2008.

Here we examine a series of Landsat images from 2001 to 2013 to update the response of this glacier.
In 2001 the glacier has two separate termini, pink arrows,in two different lagoons, Doppler to the south and Stephenson to the east. There are numerous icebergs in Doppler lagoon but none in Stephenson Lagoon, indicating the retreat is underway. In 2008 the two lagoons are well joined, icebergs are even more numerous obscuring in this view the true location of the terminus, orange arrows. By 2010 the glacier has retreated from the main basin of the lagoon, and is at red arrow, and the lagoon is free of ice for the first time in several hundred if not several millenium. In 2013 the glacier has retreated into a narrower valley that feeds into Stephenson Lagoon. The northern arm of the glacier experienced a 1.7 km retreat from 2001 to 2013 and the southern arm as 3.4 km retreat. The period of rapid retreat due to calving of icebergs into the lagoon is over and the retreat rate will now be slower. There is still rapid glacier flow toward the terminus as indicated by extensive crevassing. The overall glacier slope is steep and accumulation rates high, which would also generate rapid glacier flow.

The AAD has a number of images in their gallery of Heard Island glaciers including Stephenson Glacier. The climate station at Atlas Cove indicates a 1 C temperature rise in the last 60 years. The AAD will also certainly be looking at how this new lagoon impacts the local seal and penguin communities. The map above indicates the importance of Stephenson Lagoon for wildlife, king penguins and cormorants are noted by AAD. The retreat of this glacier follows the pattern of glacier retreat at other glaciers on islands in the circum-Antarctic region Cook Ice Cap, Kerguelen Island , Purvis Glacier, South Georgia and Neumayer Galcier, South Georgia.

Map of retreat from superimposed on Google Earth image.

2001 Landsat image

2008 Landsat image

2010 Landsat image

2013 Landsat image

Sperry Glacier Recession

On October 17, 2009March 31, 2011 By mspeltoIn climate change glacier retreat, Glacier Observations

In 1900 Sperry Glacier had an area of 3.39 km2. By 1938 it had diminished to 1.58 km2 and by 1946 it was only 1.34 km2 in area. The estimated loss in volume between 1938 and 1946 was a 23 meter reduction in the level of the surface of the lower half of the glacier during that period. Recession proceeded at an annual rate of 15.3 m. be¬tween 1938 and 1945; 11.9 m. from 1945 to 1947; 10.5 m. from 1947 to 1948; and 12.9 m. from 1948 to 1949 (Dyson, 1950).
Recession of Sperry Glacier continued from about 1950-1970 and has been accompanied by loss of volume of the lower part of the glacier. Sperry Glacier has been examined in reconnaissance (Johnson, 1958, 1960, 1964). Comparison of longitudinal and transverse profiles shows that since 1947 the upper part of the glacier has increased in vol¬ume during some years and remained constant during others, whereas the lower part has decreased in volume. Throughout this time span slow terminal recession has been continuous. Surface ice velocities on Sperry Glacier average about 3 m./year.
Sperry Glacier retreated at a slower rate of 5 m/a, from 1950-1979 (Cararra and McGrimsey, 1981). The retreat has ranged from 3-5 m/a from the 1979-1993 period (Key, Fagre and Menicke, 2002).
In 1993 0.87 square kilometers remained. This glacier still has crevasses and is not merely stagnant and melting away. A comparison of imagery from 1991 top (orange line for terminus), 2003 middle (green line) and 2005 bottom (blue line) indicate the marginal changes during this 14 year interval. These images are all from Google Earth using the historic imagery function. Sperry 1991 sperry 2003 Marginal recession averages 95 meters in this period ranging from 20-200 meters. The glacier was 1200 meters long in 1990 so this is close to a 10% loss in length. The current rate of retreat is slightly higher than the 3-5 m/a average fro the 1979-1993 period. The image in 1991 is from Aug. 25th, the glacier still has 70% of its area covered with snow from the previous winter. This is called the accumulation area ratio and in general must be above 60 at the end of the summer for the glacier to not lose mass. In 2003 the accumulation area ratio is about 30 and this is on Sept. 25th at the end of the melt season. In 2005 the accumulation area ratio is 30 at the most. Both years this limited a snowcover would lead to a significant negative mass balance, volume loss. The thinning in the upper portion of the glacier appears limited. There is not an evident change in the upper margin of the glacier. The crevassing which is indicative of movement has also not decreased much suggesting limited changes in the dynamics of the upper glacier. The comparatively slow changes in the accumulation zone, suggests a glacier that still has a consistent accumulation zone and is not likely to melt away rapidly, within the next 30 years, given the current climate. The glacier is showing no signs that it is approaching equilibrium, and that it can survive the current climate. This is in contrast to nearby Harrison Glacier which is receding quite slowly. There are new outcrops appearing at points A and B in the 2005 image indicating thinning and retreat is continuing. Annual layers are evident at point c in the 2005 image. Crevassing in the same area at point D is evident in each image. Sperry Glacier 2005

The USGS and the NPS have made Sperry Glacier a focus of field study beginning in 2005. The long term record of glacier area and glacier retreat makes it a good candidate. To date no mass balance data has been completed or reported. This data is essential to understand future terminus and volume responses. This project has been particular good at acquiring historic images to compare to current images 1913 and 2008. Bob Sihler captured the lack of snow remaining on Sperry Glacier in 2009., with a month still left in the melt season.