Humboldt Glacier Retreat, Greenland

On September 4, 2010September 9, 2010 By mspeltoIn Glacier Observations4 Comments

Humboldt Glacier in northwest Greenland terminates in a 100 km wide calving front in the sea. This is the longest such calving front in Greenland, capturing our imagination for potential havoc. The lack of confining topography prevents the development of the strong ice stream flow we see on Jakobshavn Glacier or the weaker ice stream flow of Petermann Glacier and its subsequent long floating tongue. Humboldt Glacier’s unique calving front leads to a different set of feedbacks to climate change that are worth examining. Pelto and Warren (1991) (Do not laugh at my figures in that paper, that is back in the drafted with ink days) noted that water depth at the calving front even in the case of polar or floating tongues provides a good estimate of calving velocity. More than width we then need to look at the water depth at the front for answers. Below is Humboldt Glacier in 2008 from a NASA image. The active portion of the terminus begins above the tag on the image 2000 approximate terminus position.

From when observed by Koch in 1912-13 the glacier changed little over the next 60 years. The glacier is a principal source of icebergs to the Kane Basin. Generally the icebergs are tabular icebergs less than 1 km in their largest diameter. Most icebergs come from the northern portion of the calving front is fed by an active ice stream, a nice view of these is from Jason Box at OSU. The glacier has lost 200 square kiometers of area since 1982, mostly since 2000, including this summer’s losses. What is particularly noteworthy is the amount of eroded sediment raising the turbidity and color of the water to that of coffee at the calving front in 2009 in the images from Jason Box and of Nick Cobbing of Greenpeace. This is indicative of where major subglacial meltwater streams enter the ocean. . To understand the dynamics of Humboldt Glacier its pattern of velocity, ice thickness and ice bed depths need to be identified. Ian Joughin et al (2010) provide a detailed velocity map of Petermann and Humboldt Glacier shown below. The Petermann is the narrower tongue flowing towards the top, Humboldt to the left. The velocity does not exceed 80 m/year in the southern half of the calving front. The northern portion increases from 80 m/year at the equilibrium line to 200-300 m/year at the calving front. The low velocity of the southern half of the terminus indicates a terminus that is firmly grounded, not just at the glacier front, but also all along the flowline. The basal topography and surface topography of the ice sheet was captured by Thomas et al (2009). The graph below indicates that the bed is generally below sea level for 40 km inland of the calving front. The bed is not smooth. The bed is not deep, usually less than 200 m. The result is that ice less than 240 m thick cannot be afloat. The lack of smoothness and lack of a trough penetrating deep into the ice sheet indicates the lack of streaming flow dynamics that would erode and smooth such a channel. Behind the calving front the glacier slope is quite low the surface not reaching 1000 m until 60 km back of the calving front. In this span there is no specific bench of higher elevation either. The snowline, evident in the image below, on this glacier tends to be at 600 m. This is only 40-45 km inland from the calving front, compared to the 80 km long ablation zone on Petermann Glacier. There are three dotted lines I have added to this image. The first nearest the calving front indicates a clear zone of surface roughness that has to reflect the glacier is grounded and passing over a bedrock knob of sorts. The second is the transient snow line for that day. The third is the ela. Note the slightly wider distance to the ela on the north side indicating the lower slope and deeper bed that promotes the higher velocities in the area. One would anticipate an expansion of the calving embayment in the area where the embayment exists today, with retreat occuring mainly in this section. The size of the tabular bergs argues that at least locally the glacier is close to being afloat or is afloat at least sometimes during the tidal cycle.
We have a comparatively slow moving, not particularly thick, but wide glacier. The glacier does not have a deep bed penetrating to the core of the ice sheet. The volume produced by Humboldt compared to Jakobshavn and Petermann puts it in perspective. Jakobshavn annual flux 40 km3,(flux= annual depth average velocity x width x mean depth) Petermann Glacier has close to 12 km3 at the grounding line, but less than 1 km3 reaches the calving front, after all the melting along the ice tongue. With a shorter ice tongue the calving flux should rise.. Humboldt Glacier is closer to 4 km3. Helheim Glacier has been assessed at 26 km3. Thus, though the Humboldt Glacier has a magnificent and impressive front and taps into the core of the northwest corner of the ice sheet. It does not at present have the ability to discharge ice at volumes comparable to Jakobshavn or Helheim. The glacier does not have either a large floating section or a large ice stream section that lends itself to large rapid retreat or acceleration. The recent history of area and volume loss noted by Box indicates this glacier is more prone to a steadier progressive loss than many other outlet glaciers. The glacier continues to produce an impressive volume of icebergs as seen in the Nick Cobbing image below The depth at the calving front is a key variable and provides a good first estimate of average calving velocity. In the Pelto and Warren (1991) study four other polar glaciers have water depths that are in the vicinity of 100 m and have velocites at the calving front of 100-300 m/year. Humboldt fits this pattern. For Humboldt the relatively shallow water today across most of the front and in the future, noting depths behind the front, indicates the velocity of this glacier will remain comparatively low. Even the northern section has a limited section of higher velocity in width (25 km greater than 200 m) and distance inland from the ice front (50 km maximum). This region is centered on the main calving embayment. The northern margin is again well grounded.
Thanks to Neven and Pat Lockerby for all the inspiring arctic image work this year.

Bear Glacier, Kenai Alaska recedes, new lake formed

On August 28, 2010October 2, 2012 By mspeltoIn Glacier Observations

Bear Glacier in the Kenai Mountains of Alaska is a 25 km long outlet glacier of the Harding Icefield. When first mapped in 1909 it had a large piedmont lobe filling a basin and terminated 400 m from the edge of the forest, though it appeared the retreat had been quite recent within 25 years. By 1950 the glacier had retreated another 400 m. Austin Post observed in the 1960’s the drainage of a lake seven kilometers upglacier from the terminus indicating that slow thinning was occurring in the entire lower section of the glacier. The piedmont lobe slowly downwasted through the 20th century preconditioning the glacier for a rapid retreat. The repeat photographs of Bruce Molnia, USGS portray this spectacular change. By 1980 the terminus had retreated 1 km, thinned by 150 m, and was calving small icebergs into an ice-marginal lake that was beginning to develop in the still narrow basin. As thinning continued, much of the terminus became afloat by 2000. Bruce Molnia, USGS observed that passive calving, characterized by the release of large tabular icebergs from Bear’s low gradient, floating terminus became frequent. Between 2000 and 2007, the terminus retreated about 3.5 km, yielding large icebergs that floated in the lake. The first image is from Google Earth the second taken by Bruce Molnia in 2002 followed by GoogleEarth images from 2005 and 2011. The terminus position in 2005 is in green and 2011 in red, retreat was 400 m during this six year period. The last image is a Landsat image from 8/3/2012 and indicates continued retreat along the east margin and expansion of the length of the calving front. The amount of calving has declined from the period of more rapid retreat from 2002-2008. An examination of the expanding lake identified locations with depths exceeding 75 meters. Retreat indicates the response of the terminus region of a glacier to climate in this case long term downwasting, but does not reflect how healthy the higher regions of the glacier are. How does the large 150-200 m of thinning in the terminus region compare to further upglacier? The U of Alaska-Fairbanks established a program of laser altimetry examining thickness changes along the Bear Glacier that have been reported by A.Arendt, K.Echelmeyer and C.Larson. The graphs of the last decade of change indicate that little thinning has occurred above meters since 2007. In a satellite image of the region of the glacier from 2500-3500 feet, a small rock island (nunatak) generates a consistent and long term lateral moraine. in the lower center of the image belowThe size of the moraine and the size of this nunatak have not changed appreciably in the last decade, suggesting limited thinning in the region above 2700 feet. The accumulation zone of this glacier remains sizable, but insufficient to supply a large piedmont lobe-now gone, or a calving terminus. This is not unlike the retreat of the Gilkey Glacier, Norris Glacier or Field Glacier of the Juneau Icefield. In the St. Elias range Yakutat Glacier is another example.

Daniels Glacier Recession Increases 2010

On August 19, 2010August 20, 2010 By mspeltoIn Glacier Observations

The 2010 North Cascade Glacier Climate Project Field Season found extensive retreat and areal extent loss on Daniels Glacier earlier this week. Daniels Glacier is on the east face of Mount Daniels on the Cascade Crest. A sequence of images indicates the loss of the glacier tongue in the lower left of the glacier, and the recession of the entire bottom margin of the glacier with emergence of rock islands where glacier ice previously existed. The first two images from 1985 and 1990 indicate a large blue glacier ice tongue extending to 6400 feet on the left side of the glacier.

By 2000 this area is just a gentle snow slope over a now stagnant section of glacier ice. The terminus extending to the right is also rising across the entire width of the glacier.Images from 2007, 2009 and 2010 indicate the continued emergence of new rock outcrops formerly covered by the glacier. The terminus continues to retreat up slope and by 2010 has retreated over 500 meters in 25 years. The loss of area is now 30% of the 1984 glacier area. Note the lines showing the 1985 margin and 2010 margin. In 2009 and 2010 we did not find an area on this glacier with accumulation depths over a large enough area to sustain a glacier. We have measured the glacier’s mass balance each year since 1984. The cumulative loss of -14 meters is nearly a third of the volume lost as well. In 2010 our measurements indicated another year of negative mass balance will occur this year. We measured the snow depth in crevasses and using probing at 90 locations on Daniels Glacier. The steep slope 34 degrees makes for cautious but good glissading down glacier in the last image.

North Cascade Glacier Climate Project 27th field season 2010 starts Aug. 1

On July 31, 2010August 1, 2010 By mspeltoIn Glacier Observations2 Comments

For the next three weeks I will be in the North Cascades of Washington visiting and measuring snowpack, snow melt and area change on North Cascade glaciers. There will be no new posts here during this period. Though you can take a look at the film documentary crews site travelling with us. Our main task is assessing glacier mass balance on 10 glaciers which are then reported to the World Glacier Monitoring Service (WGMS). We measure the snowpack by probing through it to the previous summer’s impenetrable surface, due to melting and refreezing or being blue glacier ice. The other means is examining snow depth in a crevasse using the evident stratigraphy. We monitor the snow melt and reset stakes in the glacier to monitor the snow melt as well. We also measure changes in surface elevation and margins of the glacier. We will report back shortly after our return on the status of these climate sensitive glaciers.

Lemon Creek Glacier Retreat Juneau Icefield Alaska

On July 26, 2010December 8, 2013 By mspeltoIn Glacier Observations2 Comments

Above is a paired Landsat image with 1984 left and 2013 right, indicating a 300 m retreat in this interval.

Annual balance measurements on the Lemon Creek Glacier, Alaska conducted by the Juneau Icefield Research Program from 1953 to 2013 provide a continuous 61 year record. This is one of the nine American glaciers selected in a global monitoring network during the IGY, 1957-58 and one of only two were measurements have continued. These show cumulative ice losses of –13.9 m (12.7 m we) from 1957-1989, of –19.0 m (-17.1 m we) from 1957-1995 and –24.4 m (–22.0 m we) from 1957-1998. The mean annual balance of the 61 year record is -0.43 m/a and a loss of at least 30 m of ice thickness for the full 61 year period from 1953-2013. In the second graph the similarity with other North American glaciers is evident (Pelto et al, 2013).

This negative mass balance has fueled a terminal retreat of 800 m during the 1953-1998 period, and an additional 200 meters of retreat by 2013. Below is a picture of the terminus enroute to Camp 17 in 1982, and below that from 2005. The annual balance trend indicates that despite a higher mean elevation and a higher elevation terminus, from thinning and retreat, mean annual balance has been strongly negative since 1977 (-0.60 meters per year). Dramatically negative mass balances have occurred since the 1990’s, with 1996, 1997 and 2003 being the only years with no retained accumulation since field observations began in 1948.

These data have been acquired primarily by employing consistent field methods, conducted on similar annual dates and calculated using a consistent methodology. The research is conducted from Camp 17 on a ridge above the glacier. This is a wet and windy place with three out of four summer days featuring mostly wet, windy and cool conditions in the summer. The camp was initially built for the IGY in 1957, and Maynard Miller and Robert Asher saw to its continued improvements through the 1980’s. The mass balance record have been were until 1998 precise, but of uncertain accuracy. Then two independent verifications indicated the accuracy (Miller and Pelto, 1999). Comparison of geodetic surface maps of the glacier from 1957 and 1989 allowed determination of glacier surface elevation changes. Airborne surface profiling in 1995, and comparative GPS leveling transects in 1996-1998 further update surface elevation changes resulting from cumulative mass balance changes. Glacier mean thickness changes from 1957-1989, 1957-1995 and 1957-1998 were -13.2 m, -16.4 m, and –21.7 m respectively. It is of interest that the geodetic interpretations agree fairly well with the trend of sequential balances from ground level stratigraphic measurements. The snowline of the glacier lies a short distance above a tributary glacier from the north that has separated from the main glacier since 1982. The snowline on the glacier was just below this juncture in the 1950’s and 1960’s but now has typically been above this former juncture. The two images below are looking down and upglacier from this former tributary in 2005.

At the head of the glacier is a supraglacial Lake Linda, which now drains under the ice. Robert Asher in the late 1970’s and 1980’s mapped this lake system when it drained under the head of the glacier not down under the terminus of the glacier.

Triftgletscher spectacular retreat and lake formation 2000-2008

On July 17, 2010October 12, 2013 By mspeltoIn Glacier Observations1 Comment

The Triftgletscher in the Bernese Alps of Switzerland has undergone a swift alteration in the last decade. The Swiss have been the most methodical chroniclers of glacier changes over the last century. The Swiss Glacier Commission faithfully recording the annual terminus change of approximately 100 glaciers. In 2009 81 glaciers retreated, 2 advanced and 5 were stationary. One of the retreating glaciers is the Trift, which after a period of limited retreat from 1955-1995 punctuated by a small advance, began a spectacular retreat in 1998, note the below graph from the Swiss Glacier Commission. The retreat began to expose a new glacier lake at 5700 feet (1750 meters) at its terminus in 2000 and then as observed in photographs by Jürg Alean (Glaciers Online) the lake quickly grew to its full size from 2002 into 2003 . The summer of 2003 featured remarkably high melt rates in the Swiss Alps mean losses of more than 2 meters of thickness, and no retained snowpack on two of the three glaciers examined for mass balance. and retreat of 99 of the 100 glacier examined, one was stationary. The lake is now 900 m long. By 2007 the glacier no longer was in contact with the lake, and had by 2008 retreated 180 meters from the lake margin. This is a retreat of 1100 meters since 2000. The lake will shrink as the river outlet from beneath the glacier fills part of the northern end of the lake with glacier sediment.The glacier has a large upper accumulation zone above 9000 feet that retains substantial snowcover (2750 Meters), an upper icefall immediately below this point. The lower icefall descends from 7700 feet (2350) m to 6600 feet (2000 meters). the lower icefall has thinned considerably in the last decade feeding little new ice to the terminus tongue below the icefall the terminus tongue has become stagnant as a result and retreat of this tongue will continue. The story is similar to that of Rotmoosferner Glacier and is driven by the same melt conditions that has led to use of blankets to protect Stubai Glacier.A new suspension bridge has been built to restore access to the glacier that was lost with the rapid retreat.

On July 8, 2010February 5, 2013 By mspeltoIn Glacier Observations, Uncategorized4 Comments

The Lower Curtis Glacier on Mount Shuksan advanced from 1950-1975 and has retreated 150 meters from 1987-2009. A longitudinal profile up the middle of the glacier indicates that it thinned 30 meters from 1908-1984 and 10 m from 1984-2008. Compare the 1908 image taken by Asahel Curtis (glacier named for him) in 1908 and our annual glacier shot in 2003. The thinning has been as large in the accumulation zone as at the terminus, indicating no point to which this glacier can retreat and achieve equilibrium with the present climate. However, the glacier is quite thick, and will take 50-100 years to melt away. This glacier is oriented to the south and fed by avalanches from the Upper Curtis Glacier and the southwestern flank of Mt. Shuksan. This allows it to survive in a deep cirque at just 5600 feet. Because of its heavy accumulation via avalanching the glacier moves rapidly and is quite crevassed at the terminus. Image below is a 2009 sideview, note the annual dark layers in the ice. The number of crevasses in the nearly flat main basin of the glacier has diminished as the glacier has thinned and slowed over the last 20 years. The glacier lost nearly all of its snowcover in several recent years 2005, 2006 and 2009. In one month we will back on this glacier investigating its mass balance and terminus position. It is a key glacier this year, as the winter was quite warm yet wet, spring was not. Thus, snowpack was much below average below 5000 feet and likely above average above 7000 feet, where the transition will be is the key. In the google earth images below Lower Curtis Glacier is in the left center. The terminus is exposed bare glacier ice and is heavily crevassed. Typically the terminus loses its snowcover in mid-June. Below the terminus there are frequent ice and rock falls, so it is best not to go below the terminus. For our measurements we need to, but we always finish by 9 am. .

Okpilak Glacier Retreat, Brooks Range, Alaska

On June 25, 2010June 28, 2010 By mspeltoIn Glacier Observations3 Comments

The Brooks Range of Alaska contains many alpine glaciers. You hear little about them as there are no large ones and none that can be seen from a cruise ship as in southern Alaska. Though I have worked on many Alaskan glaciers for extended periods, it has always been in southeast Alaska on the larger Juneau Icefield. Hey one month until my 30th field season. The climate is much different as well, with the Arctic Ocean instead of the Pacific Ocean having a more dominant role. The Beaufort Sea Gyre is the nearest major ocean current feature. The Okpilak Glacier drains into the Arctic Ocean and is a large glacier by Brooks Range standards. Matt Nolan at the University of Alaska-Fairbanks has done a beautiful of duplicating a picture taken by Ernest Leffingwell in 1906 with pictures he has taken in 1994, 2004 and 2007. Below is the 1906 picture and the 1994 image, and the 2006 Google Earth view of the glacier. The large retreat is evident, the lateral moraine from the Little Ice Age today stands high above the glacier on the mountain side. The glacier was still near its Little Ice Age maximum when Leffingwell took his picture. By 2006 the glacier had retreated just over 2 kilometers, note the Little Ice age moraine in the Okpilak Glacier image from Google Earth. There is a bedrock knob apparent in both the 1994 and 2006 image, though the ice thickness around the knob is much reduced by 2006. Also the lake at the end of the glacier in 1994 is quickly filling in with glacier sediment and by 2006 is not as prominent. Bernhard Rabus and Keith Echelmeyer-Univ. Alaska-Fairbanks had reported in 1998 that this glacier had retreated 420 meters between 1973 and 1993, 5% of its length and a rate of 20 meters per year. This is larger than the rate of 6-7 meters per year from 1907 and 1958 reported by Ed Sable, who photographed and surveyed the glacier in 1958. The rate of retreat has remained rapid. The 2006 image illustrates the problem, the ELA-snowline is too high and leaves only a small percentage of the glacier snowcovered at the end of the summer. This has been the pattern in recent decades and has led to a loss in average thickness of 30-40 cm per year. This loss though it is in a different climate region is remarkably similar to the losses observed on Lemon Creek Glacier. A view of the terminus of the glacier in 2006 from Google Earth indicates a bedrock knob that is 800 meters upglacier of the terminus. Below this knob there is little crevassing, the ice is thin, both suggesting stagnation and that this section of the glacier will soon be lost. As the sea ice to the north diminishes this area will be interesting to observe, as the potential is there for increased snowfall, while the open water will clearly lead to more warming as well.

Hoboe Glacier retreat, British Columbia

On June 17, 2010June 17, 2010 By mspeltoIn Glacier Observations

The Hoboe glacier is a distributary tongue of the Llewellyn Glacier draining the Juneau Icefied in Northwest Britsh Columbia. In 1984 I had the opportunity to hike the length of the glacier carrying supplies to the terminus for a master thesis research project of Richard Campbell at the Univ. of Idaho, during the JIRP summer field season. The glacier is 4 km long separating from the Llewellyn Glacier at 3800 feet and ending at approximately 3000 feet. This is our view from the glacier surface notice the evident trimline above the ice surface showing how thick the glacier used to be.This glacier has receded 2200 meters since early visitors to the area mapped its terminus around 1910, and 3900 m from its maximum advance of the Little Ice Age. The Google Earth views below are from 2001 images. The glacier has retreated 450-500 m in the fifty years that the Juneau Icefield Research Program has been examining it. The first view is looking up glacier and the next two looking down glacier. In all three a trimline is evident where vegetation has not had time to develop due to retreat of the last 75 years. The image above is an aerial photograph taken by Don McCully of JIRP. The trimline in the photograph is 75-85 meters above the glacier surface indicating the thinning that has occurred in the last century. Nearly one meter a year due to the recent climate change that has enhanced summer melting and reduced winter snowfall. The Hoboe Glacier is continuing its retreat like all but one of the nineteen outlet glaciers of the Juneau Icefield. Including the Gilkey Glacier and Tulsequah Glacier.

Grasshopper Glacier Wyoming disappearing

On June 13, 2010June 17, 2011 By mspeltoIn Glacier Observations

Grasshopper Glacier in the Wind River Range of Wyoming has a southern terminus calving into a lake , sometimes referred to as Klondike Glacier, and a northern terminus. The southern terminus is calving and retreating expanding the unnamed lake it terminates in. The southern glacier has retreated 350 m since 1966. This lakes drains north under the glacier and down the valley under the Grasshopper Glacier. This is quite unusual to have a stream draining under the glacier from a lake at a terminus of the glacier. The lake can drain to the east if it rises to the 12,000 foot threshold. This was the case in 1994. The terminus area is not being fed by the upper accumulation zone to the northwest any longer. The terminus is stagnant and will continue to melt away. The lake has existed since at least 1950. In 2003 it drained substantially and quickly below the glacier causing a downstream flood. An ice dam break released a glacier flood is a jokulhaup. The lake was reported by the USGS to have drained 90%. In the 2006 image it has largely refilled, but notenough to drain to the east again. It is likely given the stagnant nature of the glacier, that the drainage conduit will not be fully closed, and the lake can drain through the channel on more of an ongoing basis. The northern terminus has retreated 730 m the most extensive retreat in the Wind River Range. The main accumulation area on the west side of the glacier has become segmented by large bare rock areas as noted by comparing the 1966 map and 2006 image. The 1966 boundary indicated in orange noted area circled in burgundy in the second image below. The combined retreat of the two terminus is over one kilometer this is 40 % of its 1966 length of 2.4 km. The significant thinning and marginal retreat at the head of the glacier is symptomatic of a glacier that will disappear with current climate. The glacier seldom has significant snowcover at the end of the melt season is with the current climate will melt away. In 2009 the glacier did have significant snowcover at the end of the melt season for only the third time in the last 10 years.

Spearhead Glacier and Decker Glacier retreat, Whistler, British Columbia

On June 6, 2010October 9, 2016 By mspeltoIn Glacier Observations1 Comment

Spearhead Glacier is just east of the Whistler-Blackcomb Ski area in sw British Columbia and can be reached easily from the top Blackcomb lift. Adjacent to Spearhead is Decker Glacier. Both glaciers flow northwest and have retreated extensively. Recently both have developed new alpine lakes at their termini that illustrate the recent increase in retreat that could continue thanks to these new lakes. Spearhead Glacier has retreated between 500 and 600 meters since 1928. The glacier lost 62 m in mean thickness since 1928 Koch and others (2009) found. A map of the region indicates the extent of the glaciers in the range from the Little Ie Age and today Osborn and others (2007). The first image is from 2003, the low sloped glacier has few crevasses and end in a gently sloping terminus at the edge of the bedrock basin. Notice in the fall 2008, second image, that a new lake has formed at the terminus Spearhead Glacier. This lake is expanded further in 2009 as seen in this view below across the lake back at the glacier. This looks much like the expanding lake view and stagnant terminus area of Colonial Glacier in the North Cascades. The glacier is largely confined to a single basin, that suggests the potential for considerable lake expansion as the glacier retreats. There is a step in the glacier in the image above, that indicates the likely maximum extent, notice the bedrock step on the right side of the glacier. Decker Glacier retreat is even more substantial as a percentage of glacier area. illustrated in a comparative image from Osborn and others (2007) The glacier has also developed a new lake, leading to the breakup of a portion of the end of the glacier, notice the rifted ice pieces in the image below from October 2008. That was not present in the lower image from 2003. This area of broken ice at the end of the glacier and near the image bottom, represents nearly a third of the total glacier area. It is not as apparent as it is in summer conditions when the lake is not frozen over.

Impact of Artesonraju Glacier, Peru Retreat

On May 29, 2010April 16, 2024 By mspeltoIn Glacier Observations, Uncategorized1 Comment

Artesonraju Glacier is a 3.3 km long glacier in the Cordillera Blanca of Peru drains west from Nevado Artesonraju.Updated July 2015 at

The glacier feeds both Lake Artesonraju, a new lake that formed after 1930 and Lago Paron. The two lakes are dammed by glacier moraines and together have posed a hazard of a glacier dammed lake outburst. In 1951 an outburst of water and alluvium traveled from the upper Artesonraju Lake into Lago Paron, raising the water level in Paron causing downstream flooding and concern about the strength of its moraine dam.

There are numerous moraine dammed lakes in Peru, the dams are just comprised of gravel, sand and clay dumped by the glacier. High water levels caused by upstream floods, avalanches or landslides can cause failure of these moraine dams and down stream flood damage prompted the Peruvian government to develop a strategy to address the problem. They began in the by building tunnels , concrete pipes, through the moraine to allow drainage to a safe level, they then rebuilt the moraine over the drainage system and strengthened it. Since development these systems have worked preventing serious flood issues from the lakes. At Lago Paron a hydropower project has been built that is fed by the tunnel drainage system and Lago Paron has been partially drained to service the hydropower facilities needs. The hydropower faility is owned by Egenor, owned largely by Duke Energy. The lake level has declined substantially by 2003 as the trimline indicates in the image above. This had led to a battle over water resources with local farmers. This Artesonraju Glacier that is the principal feeder to the two lakes retreated 1140 meters from 1932-1987 and by 2004 had retreated another 200 meters. From 2003 to 2013 the glacier continued to retreat and the terminus to narrow. An expanding lake at the terminus is evident in the Google Earth images of 2003 and 2012, pink arrow. A melt pond has also drained at the yellow arrow as the glacier thinned. In the 2013 Landsat image the terminus has further narrowed.

2003 Google Earth image

2012 Google Earth image

2013 Landsat Image

This is 30% of its length gone in the last 75 years.The lower section of the glacier is flat, uncrevassed and is continuing to thin and melt. The upper reaches of the glacier are heavily crevassed indicating continued vigorous flow fed by healthy accumulation on the flanks of Nevado Artesonraju and Nevado Piramide. The equilibrium line of this glacier is at 5150 m, investigations by the Tropical Glaciology Group, Innsbruck, Austria and Hydrology Resources and Glaciology group in Huarez, Peru. In 2005, the surface on many parts of the flat tongue showed that sublimation is important to the mass balance when short wave radiation is limited, and short wave radiation dominates melting during the day.
A new book by Mark Carey, In the Shadow of Melting Glaciers, examines the history of the impact of these glaciers on Andes towns in the Cordillera Blanca.