Returned from the field yesterday. There was spectacular melting and forest fires in our field area of the North Cascades, Washington. Preliminary results will follow in 10 days. Alison Gletscher in western Greenland at 74.37 N and 56.08 W,had a spectacular retreat in the last decade. The 11 km retreat has been noted by Howat and Eddy (2011) and Joughin et al, (2010). The velocity of the glacier is typical of marine outlet glaciers increasing dramatically near the ice front to 3000 meters/year, image from Joughin et al, (2010). 
The recent increases in outlet glacier discharge have always been coincident with floating tongue losses. This causes reduced back pressure at the glacier front, letting up on the brakes; the resulting glacier thinning leads to less basal friction and further acceleration. If the glacier front retreats into deeper water the process will continue and increase. The acceleration is driven by changes at the calving front not by meltwater lubrication (Joughin et al, 2010) and (Bailey and Pelto, 2011). This post examines a 2000 and 2011 Landsat image of the glacier, the yellow arrows indicate the 2000 terminus and the red arrows the 2011 terminus location. 
. The glacier’s calving front is much longer than in 2000, however, there are a number of pinning points, purple arrows in image below that reduce the glacier velocity on the northern and southern margin. However, the high velocity, extensively crevassed middle section is still retreating. 
. MODIS imagery from 2012 indicates limited change to date this summer in the terminus position of Alison Gletscher, below is the August 9th image. This glacier is retreating similar to Kong Oscar, Upernavik and Epiq Sermia.
Author: mspelto
Professor of Environmental Science at Nichols College in Massachusetts since 1989. Glaciologist directing the North Cascade Glacier Climate Project since 1984. This project monitors the mass balance and behavior of more glaciers than any other in North America
Glacier Ground Truth-2012 Field Season
For the 29th summer in a row we will be measuring glacier mass balance in the field, in the North Cascades, Washington, over the next three weeks, no new posts during this period. Glacier mass balance is the most sensitive measure of glacier response to climate. In the past the only way to determine mass balance was detailed field measurements. Today there is sufficient satellite imagery to provide data that can be used in conjunction with ground truth to determine the mass balance of a glacier using a model. The ground truth we complete provides richer spatial detail than remote sensing can today.
Satellite imagery provides excellent big picture and time specific data, but still needs ground truth. For example the National Operational Hydrologic Remote Sensing Center (NOHRSC) now provides daily snowpack and snowmelt maps that are based on satellite imagery and climate models. A snapshot is provided of two of these from early July 2012 in the area of Mount Baker, WA, where we will be working shortly note blue arrows indicating specific glaciers. The first image is the snowpack in snow water equivalent (SWE). It is assessed at over 30 inches remaining. The second is of the snowmelt in SWE for the same area over a 72 hour period ranging from 1.5 to 4 inches. 
NOHRSC products are not really designed for glaciated elevations or mid-summer conditions, the system has been well verified for most areas of our nation for most times of the normal snowcover season. The Sholes Glacier in summer fits neither. We will be measuring the snowpack at over 500 locations around the blue arrows. We will also be continuing to measure the snowmelt on the same glaciers as the summer progresses. Other satellite images provide a detailed look at a glacier, but are acquired only on occassion. This is indicated by the excellent images in Google Earth from Sept. 2009 and Sept. 2011 of Sholes Glacier which show a much different story in terms of snowpack extent. The blue dots indicate the 2009 snowline, where snow from the winter survived the summer melt season up to that date. In 2009 the glacier was 30% snowcovered at the end of the melt season, in 2011 the glacier was 95% snowcovered. We will be taking over 100 measurements of snow depth on this glacier to provide the detail that allows the pattern of snowcover alone to be used to identify the snowpack distribution and hence mass balance of the glacier.
Lumding Glacier Retreat and Lumding Tsho expansion, Nepal
Lumding Glacier, Nepal terminates in Lumding Tsho, a proglacial lake, in Dudh Khosi Valley in the Mount Everest region of Nepal. This lake poses a hazard for a glacier lake outburst flood n the Dudh Khosi valley. The lake expansion results from retreat of the Lumding Glacier.Bajracharya et al (2008) in a International Centre for Integrated Mountain Development (ICIMOD) study examined the changes in Lumding Tsho from 1962-2000 and found the lake grew from 0.2 km2 in 1962 to 0.77 km2 in 2000. ICIMOD has an ongoing specific focus on assessing glacier lake outburst flood potential. This was the result of a retreat of 40 meters/year from 1976-2000 and 35 meters/year from 1962-2007, as noted in figure below from Bajracharya et al 2008). Here we update the changes to 2013 using Landsat imagery. 
This would lead to a lake length increase of about 800 m. The lake was 625 meter long and had an area of 0.1 km2, by 2007 the lake was 2180 meters long with an area of 0.9 km2 (Bajracharya et al 2008)Here we look at a 1992, 2009 and 2013 Landsat image and 2008 Google Earth imagery. The lake begins at the end of the heavily debris covered Lumding Glacier. Yellow arrow on each Landsat image indicates 1992 terminus and red arrow 2009 terminus location. The lake was 1675 meters long in 1992, 2325 meters long in 2009 and 2500 meters in 2013. This represents a retreat of 40 meters/year. The lake at 2.5 km in length now has an area of over 1 square kilometer. The glacier is fed largely by avalanching off the flanks of, blue arrows. The larger problem for the glacier in the future is the retreat of the terminus of the tributary glaciers that avalanche onto the lower Lumding Glacier. The blue arrows around the letter A in the Landsat images indicate the retreat of these feeder glaciers. The retreat of the two noted in the Landsat images has been approximately 300 meters. The lower section of the Lumding Glacier is heavily debris covered, brown arrow in Google Earth image, which insulates the underlying ice, reducing melting and retreat. This also indicates the avalanche source of much of the accumulating snow and ice. The increased distance to the feeding snow and ice slopes will reduce this input.
1992 Landsat image
2009 Landsat image
2013 Landsat Image
2008 Google Earth
The Lumding Glacier retreat is similar to the retreat of nearby Menlung Glacier, Tibet, Imja Glacier, Nepal and North Lhonak Glacier, Sikkim each retreating continually leading to lake expansion. This also fits with the general area extent losses and retreat that dominate the high mountains of central Asia.
De Reste Bugt Glacier Retreat, East Greenland
I came across De Reste Bugt Glacier reviewing a recent paper by Walsh et al (2012). They identify a retreat of 1 km for the 2000-2010 period and a thinning of 40 m 15 km upglacier of the terminus and acceleration Walsh et al (2012). This is the typical model for glaciers along the Blosseville Coast of East Greenland, where 29 of 37 glaciers they examined retreated at least 500 meters from 2000-2010. This glacier does not reach the main ice cap, but drains the East Greenland Coastal mountain range.
In this post we review Landsat imagery from 1985, 2000 and 2011 to identify changes. The terminus retreated 2.7 km from 1985-2000 and 1100 meters from 2000-2011. The 1985 terminus is marked by purple dots, 2000 by blue dots and 2011 by green dots. The yellow arrow indicates a prominent spot at the1985 terminus, the purple arrow the island just beyond the 1985 terminus, the blue arrow and red arrow the eastern side of prominent tributaries for comparison, the green arrow the 2011 terminus location.
Beyond the terminus change of De Reste Bugt, there are substantial retreats of the tributaries 1-4. In 1984 all had much larger active fronts ending at lower elevations than today. 
This indicates that the changes are not due to just to terminus dynamics but that the mass balance that controls these smaller glaciers has been quite negative, as has been noted to the south on Mittivakkat Glacier by Mernild et al (2011). The summer of 2012 has every indication of being a record melt year for much of the Greenland Ice Sheet, and this will certainly have an impact going forward on De Rest Bugt and its neighboring glaciers. De Reste Bugt is just north of Sortebrae Glacier with the gorgeous twisting lateral moraines that is also retreating.
Coleman Glacier Retreat, Mount Robson, Alberta
Coleman Glacier flows north from the Reef icefield on the northeast flank of Mount Robson. This glacier is 6 km long and has a relatively low slope descending from 2500 m to a terminus just above 2100 meters. Coleman Glacier flows north from the British Columbia, in an inventory of western Canada glaciers Bolch et al (2010) found that from 1985-2005 Alberta glaciers lost 25% of their area and BC glaciers 11% of their area. Marshall et al (2011) examining the impact on streamflow of glacier volume loss, estimate an 80-90% volume loss for Alberta glaciers by 2100 with a commensurate decline in runoff. By the time a glacier has lost more than 20% of its area glacier runoff declines as the reduced area exposed for melting has a larger influence than the increased melt rate per unit area (Pelto, 2011). A comparison of Landsat images from 1991 (top image) and 2009 (middle Image) indicate a retreat of 250 m. Formation of a new lake at the terminus is evident at the burgundy arrow. The third image is from the Google Earth imagery of 2006, the purple line is the 1991 margin, the burgundy line the 2000 margin. The retreat from 1991-2006 is 250 m, with 50 m of further retreat by 2010. 
A more detailed look at the 2006 Google Earth Imagery illustrates a more detailed story. This glacier in 2006 has an accumulation zone that is too small to support the current glacier size, a glacier needs at least 60% of its area to be snowcovered at summers end, and only 30% is snowcovered. 
. This is simply not just a bad year either. The number of annual layers exposed at the surface is at least 50, such layers emerge at the surface below the snowline as a glacier thins below the snowline. The annual layers emerging at the surface are marked by dark horizons which indicate the former snow surface of a layer, which collects dust throughout the summer and is dirtier than the bulk of an annual layer. Above the snowline layers are progressively buried by more recent winter layers and below the snowline layers are exhumed as the layers above melt away (second image). The location and number of annual layers indicate that today the accumulation zone is typically fairly close to the 2006 snowline. 
. The terminus area and lower 1 kilometer of the Coleman Glacier is quite stagnant as indicated by the degree of incision of surface glacier streams, the lack of crevassing and the smooth nature of the debris cover on the western side of the glacier. This section of the glacier is melting away. Glacier streams in an active flowing glacier will exploit any current or fairly recent crevasse feature to drain toward the glacier bottom often through a moulin. The lack of such drainage indicates a lack of movement that generates crevassing. The bottom image is a closeup of the main supraglacial stream with the blue arrows identifying the channel. 
This glacier is further north than the Columbia Glacier or Apex Glacier but is following the same trend.
Mount Baker Glacier Mass Balance
Just published in Hydrologic Process is a paper from our 28 years of research on Mount Baker.
“Mass Balance Loss of Mount Baker, Washington glaciers 1990-2010” Mass balance is really the annual bank account for the glacier. Deposits are snow accumulation, withdraws are melting. A glacier that has greater income has a positive mass balance and increases in volume. Greater melting leads to losses in volume.
Mount Baker,North Cascades, WA has a current glacierized area of 38.6km2. From1984 to 2010, the North Cascade Glacier Climate Project has monitored the annual mass balance (Ba), accumulation area ratio (AAR), terminus behaviour and longitudinal profiles of Mount Baker glaciers. The Ba on Rainbow, Easton and Sholes Glaciers from 1990 to 2010 averaged 0.52mw.e. a1(m a1).
Terminus observations on nine principal Mount Baker glaciers, 1984–2009, indicate retreat ranging from 240 to 520 m,with amean of 370m or 14ma1. AAR observations on Rainbow, Sholes and Easton Glaciers for 1990–2010 indicate a mean AAR of 0.55 and a steady state AAR of 0.65. A comparison of Ba and AAR on these three glaciers yields a relationship that is used in combination with AAR observations made on all Mount Baker glaciers during 7 years to assess Mount Baker glacier mass balance. Utilizing the AAR–Ba relationship for the three glaciers yields a mean Ba of 0.55m/year for the 1990–2010 period, 0.03ma1 higher than the measured mean Ba. The mean Ba based on the AAR–Ba relationship for the entire mountain from 1990 to 2010 is 0.57m/year. The product of the mean observed mass balance gradient determined from 11 000 surface mass balance measurements and glacier area in each 100-m elevation band on Mount Baker yields a Ba of 0.50 m/year from 1990–2010 for the entire mountain. The median altitude of the three index glaciers is lower than that of all Mount Baker glaciers. Adjusting the balance gradient for this difference yields
a mean Ba of 0.77m/year from 1990 to 2010. All but one estimate converge on a loss of 0.5m/year for Mount Baker from 1990 to 2010. This equates to an 11-m loss in glacier thickness, 12–20% of the entire 1990 volume of glaciers on Mount Baker.
The two key measures of mass balance, which is direct measurements and measuring the snow covered fraction of the glacier at the end of the year, the accumulation area ratio. Below is the 2009 map of the snowcovered areas put together by Courtenay Brown, Simon Fraser University. This same year we were in the field and took measurements at the burgundy dots, in the second image. Each dot is worth three measurements.
In two weeks we will adding more measurements to this data set for 2012. We do this largely by using a probe that can be driven through the snowpack from last winter, or in crevasses where the annual layering is evident like tree rings. 
The contrast between the snowpack distribution in September 2009 and 2011 is evident. The burgundy arrows point out bare ice regions. In 2009 the bare ice extent darker blue, was much larger than in 2011, when snowcover was quite good. The net trend over the last 20 years of mass balance loss is leading to the ongoing retreat of all Mount Baker glaciers. 
Easton Glacier Assessment, Washington
In August we will be making a detailed study of the Easton Glacier for the 23rd consecutive summer. Our main focus is measurement of snow depth and snow melt on the glacier. We will be mapping the terminus position and two profiles of the surface elevation across the glaciers at 1800 m and 1950 m. We will also examine two new bedrock knobs that have melted out in the midst of the glacier at 2050 m. The Easton Glacier is important as a water resource for the Baker lake and Baker River Hydropower system. This hydropower system is capable of producing 170 MW of power. The runoff from Easton Glacier would normally flow into the Baker River below Upper Baker Dam, however it is extracted from the normal stream and routed through a pipeline to enter Baker Lake and then produce power via Upper Baker Dam (second image), note yellow dots showing runoff pathway.
The Easton Glacier retreated over 2 km from its Little Ice Age maximum to 1955. By 1965 the glacier was advancing, this advance ended in the early 1980’s and by 1987 retreat from the moraine was evident. Beginning in 1990 we have made an annual survey of the glacier terminus noting a retreat of 320 m from 1987-2010. The first image below is of Easton Glacier from 1912 the second from 2011 with the same locations highlighted. A prominent knob on the upper glacier has changed little, ocher arrow. The lower margin of the glacier on either side of the main Easton at the blue arrow and red arrow show substantial thinning and retreat. The purple arrow indicates the terminus change. The lower Easton Glacier has changed a great deal in the last 100 years, not the upper glacier. This is an indication of a glacier adjusting to climate change that is retaining an accumulation and can survive. The last image in the sequence indicates the Little Ice Age terminus yellow line, the 1993 terminus orange, 1998 terminus is purple, 2004 terminus is green and 2009 terminus is ochre. 
In the above image the red arrows indicate the location of the two survey profiles we complete across the glacier. The green arrows indicate two locations of investigation for the summer, to the left is the top of the Deming Glacier Icefall that will visit and the right green arrow a new bedrock knob that emerged from beneath the glacier in 2009. A month from now we will be surveying the glacier covering the glacier top to bottom and side to side. We will be joned by Peter Sinclair who is going to use is videography skills to examine how we measure glacier change. The first image below is from Steph Abegg a superb climber and photographer who was with us in 2010 as part of Team Juicebox working on the Uncertain Ice documentary.
The main goal of our research each year is assessing the glacier’s mass balance. This is the equivalent of its bank account, with snow accumulation being deposits and snow-ice melt being withdraws. We map the changes across the glacier and determine if the bank account grew or declined, 2011 map is below. Since 1990 the bank account has lost 10 meters of thickness of an average of 70 m total. Last year the glacier did gain over a meter. A key measure is the percent of the glacier in the accumulation zone (AAR), below 65% is a loss above a gain, bottom image. The 2012 winter was a La Nina which tends to lead to very good snowpack, the transition out of La Nina took place in late spring-early summer leading to greater melting than 2011, we will see in three weeks.
Alpine Glaciers BAMS State of the Climate in 2011
Below is the section I wrote on Alpine Glaciers for the BAMS State of the Climate in 2011 published on July, 10, 2012. The focus is on glacier changes in 2011.
3) ALPINE GLACIERS—M. S. Pelto
The World Glacier Monitoring Service (WGMS) record of mass balance and terminus behavior (WGMS 2011) provides a global index for alpine glacier behavior. Mass balance was -766 mm in 2010, negative for the 20th consecutive year. Preliminary data for 2011 from Austria, Norway, New Zealand, and United States indicate it is highly likely that 2011 will be the 21st consecutive year of negative annual balances.
Alpine glaciers have been studied as sensitive indicators of climate for more than a century, most commonly focusing on changes in terminus position and mass balance (Oerlemans 1994). The worldwide retreat of mountain glaciers is one of the clearest signals of ongoing climate change (Haeberli at al. 2000). The retreat is a reflection of strongly negative mass balances over the last 30 years (WGMS 2011). Glacier mass balance is the difference between accumulation and ablation. The recent rapid retreat and prolonged negative balances has led to some glaciers disappearing and others fragmenting (Pelto 2010; Bhambri et al 2011; Shahgedanova et al. 2010).
The cumulative mass balance loss of the last 30 years is 13.6 m w.e. (Fig. 2.14), equivalent to cutting a 15 m thick slice off the top of the average glacier. The trend is remarkably consistent from region to region (WGMS 2011). WGMS mass balance results based on a global dataset of 30 reference glaciers with 30 years of record is not appreciably different, -13.1 m w.e. The decadal mean annual mass balance was -198 mm in the 1980s, -382 mm in the 1990s, and -740 mm for 2000–10. The declining mass balance trend during a period of retreat indicates that alpine glaciers are not approaching equilibrium and retreat will continue to be the dominant terminus response.
In 2011 there was below-average winter accumulation in the Alps and significantly above-average spring and summer temperatures. This resulted in consistently strong negative balances on Austrian glaciers in 2011: Sonnblickkees, -2460 mm; Jamtalferner, -1434 mm; Kesselwandferner, -640 mm; and Hintereisferner, and -1420 mm (Fischer 2012). The Austrian Glacier Inventory examined 90 glaciers. Of these, 87 were in retreat, 3 were stationary, and average terminus change was -17 m, reflecting the continued negative mass balances of the region. In Norway, terminus fluctuation data from 31 glaciers for 2011 indicated 27 retreating, 2 stable, and 2 advancing. The average terminus change was -17.2 m (Elverhoi 2012). The retreat rate closely matched the 2010 rates. Mass balance surveys found deficits on all Norwegian glaciers. In the North Cascades, Washington (Pelto 2011), La Niña conditions and record wet and cool conditions from March to June led to positive mass balances on all 10 glaciers examined. In southeast Alaska, 2011 snowlines were 50 m above average on Lemon Creek and Taku Glacier of the Juneau Icefield, indicative of moderate negative balances.
In New Zealand, observations on 50 glaciers found snowlines that were much higher than normal, indicating strong mass balance losses (NIWA 2011). Summer melt conditions were considerably above average.
In the high mountains of central Asia, detailed glacier mapping inventories, such as from GLIMS (Global Land Ice Measurements from Space) using ASTER, Corona, Landsat, and SPOT imagery, of thousands of glaciers indicated increased strong thinning and area loss since 2000 throughout the region except the Karakorum. In the Russian Altai, mapping of 126 glaciers indicated a 19.7% reduction in glacier area from 1952 to 2004, with a sharp increase in losses after 1997 (Shahgedanova et al. 2010). In Garhwal Himalaya, India, for 58 glaciers examined from 1990 to 2006, area loss was 6% (Bhambri et al 2011). In the Nepal Himalaya area, loss from 1963 to 2009 was nearly 20%, (Bajracharya et al. 2011), and thickness losses increased from an average of 320 mm yr-during 1962–2002 to 790 mm yr-1 during 2002–07 in the Khumbu region, including area losses at the highest elevation on the glaciers (Bolch et al. 2011). In the Tien Shan Range, over 1700 glaciers were examined: from 1970 to 2000, glacier area decreased by 13%, and from 2000 to 2007 glacier area shrank by 4% (Narama et al. 2010). An inventory of 308 glaciers in the Nam Co Basin, Tibet, noted an increased rate of area loss for the 2001–09 period; 6% area loss (Bolch et al. 2010). A new means of assessing global glacier volume is via GRACE (Rodell et al. 2011), which, due to its spatial resolution, is unable to resolve specific changes of individual glaciers or watersheds. In the high mountains of central Asia, GRACE imagery found mass losses of -264 mm yr-1 for the 2003–09 period (Matsuo and Heki 2010). This result is in relative agreement with the other satellite image assessments, but is at odds with another more recent global assessment from GRACE that estimated Himalayan glacier losses at 10% of that found in the aforementioned examples for volume loss for the 2003–10 period (Jacob et al.2012). At present, the detailed inventories are better validated.
Longbashaba Lake Expansion Glacier Retreat, Tibet
A comparison of imagery from 1989 to 2009 indicates an expansion of Longbashaba Lake, a moraine dammed lake in Tibet (Yao et al, 2012). The Longbashaba Glacier has retreated 950 meters 1989-2009 and as the depth has increased the volume has quadrupled to 1.3 cubic kilometers (Yao et al, 2012). The concern is to the 23 villages downstream of the lake and the Rongkong Hydropower station. In this post we compare Landsat imagery from 1989, 2000 and 2011 and Google Earth imagery from 2006 and 2010 to identify changes in the terminus position of the glacier and the lake size. Longbashaba Lake is near the top trending northwest to the west is a north trending Pida Lake. The lake is quite small in 1989, and more than doubles in length by 2011 with a retreat of the glacier of 1050 m.
The terminus positions of the glacier are purple for 1989, orange for 2000, black for 2006 and red for 2011. The 2006 image also indicates the snowline on the glacier which is at 6300 meters. The glacier is following the pattern of Theri Kang Glacier, Reqiang Glacier and North Lhonak Glacier.
Longbasba Lake Expansion Glacier Retreat, Tibet
A comparison of imagery from 1989 to 2009 indicates an expansion of Longbasba Lake, a moraine dammed lake in Tibet (Yao et al, 2012). The Longbasba Glacier has retreated 950 meters 1989-2009 and as the depth has increased the volume has quadrupled to 1.3 cubic kilometers (Yao et al, 2012). The concern is to the 23 villages downstream of the lake and the Rongkong Hydropower station. In this post we compare Landsat imagery from 1989, 2000 and 2011 and Google Earth imagery from 2006 and 2010 to identify changes in the terminus position of the glacier and the lake size. Longbasba Lake is near the top trending northwest to the west is a north trending Pida Lake. The lake is quite small in 1989, and more than doubles in length by 2011 with a retreat of the glacier of 1050 m.
The terminus positions of the glacier are purple for 1989, orange for 2000, black for 2006 and red for 2011. The 2006 image also indicates the snowline on the glacier which is at 6300 meters. The glacier is following the pattern of Theri Kang Glacier, Reqiang Glacier and North Lhonak Glacier.
Olsokbreen Retreat, Svalbard
Svalbard is host to 163 tidewater glaciers with a collective calving front of 860 km (BŁASZCZYK et al, 2009). The southernmost of these glaciers on the west coast of Sørkappland is Olsokbreen, purple arrow.
Olsokbreen has a 5 km calving front and its retreat was observed to have retreated 3.5 km from 1900-2008 (Zjaja et al, 2008). here we examine Landsat imagery from 2002 and 2010 and Geoeye from 2012 to illustrate a significant change in the ice front of Olsokbreen in the last ten years. The glacier has pulled back from a peninsula extending into the sound from the north side of the fjord that the glacier ended upon in 2002, red arrow. In the 2002 image the 2010 ice front is noted with a violet arrow as is an area of proglacial lakes that become more evident in 2010. In 2010 there are two images, indicating that relatively straight north-south calving front has become quite irregular during the 300-1100 meters of retreat along the ice front. The first image indicates the 2002 calving front (green line) and the snowline. The second image indicates the location of the proglacial lakes and the peninsula. The 2012 image is a Geoeye image and the main changes from 2010 is the extension of open water at the north side of the glacier between the terminus and the peninsula. This extends the calving front width and should increased calving. The southern edge has experienced more retreat since 2010 with the angular shaped calving embayment, green arrow. 
The Olsokbreen like the nearby Hambergbreen and Hornbreen is retreating and thinning.This glacier would seem to be particularly prone to impacts from warming water in the Barents Sea. In 2011 the ocean heat flux (Walczowski, 2011) passing Olsokbreen illustrates this. The sea ice off of Olsokbreen has also been exiting earlier as is evidenced in a recent image sequence from the Arctic Sea Ice Blog 
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Sarqardliup Sermia Supraglacial Lakes
The progression of supraglacial lakes on the surface on particularly the western side of the Greenland Ice Sheet during the course of the melt season illustrates key processes. In this post we are looking at lakes on the surface of the ice sheet just south of Jakobshavn inland of the Sarqardluip Sermia terminus. Box and Ski (2007) surveyed over 300 lakes in this region and found that the maximum volume occurred close to June 24 during the 2000-2005 period. The image below is from their study, lake F and C from this post are also evident in their figure. 
They further used the water color to determine depth, corroborated by field work, indicating a maximum depth of 12 m and a mean depth of 4 or 5 m. Sundal et al (2009) examined several regions including this same area for lake evolution and found that below 1000 m peak lake area was June 6, between 1000-1200 m June 17, bweteen 1200-1400 m, June 24th and above 1400 m July 18th. Further they found that 90% of the lakes had drained by August 18th, with drainage peaking below 1000 m in late june, from 1000-1200 m in early July and from 1200-1400 m in late July. The evolution and drainage is well illustrated by a figure from the Sundal et al (2009) paper.
. Liang et al (2012) provide an excellent view of how often the lakes occupy the same location, it is evident in their figure that most of the large lakes reform the majority of the years, red and white lakes form more than 60 % of the years. This tendency is what Box and Ski (2007) noted that many lakes refill the same topographic depression each year. This topographic depression is the result of flow dynamics of the ice sheet in some cases resulting from bed topogpaphic changes. 
Below is a sequence illustrating the development of lakes from June 2012 using MODIS and Landsat imagery. The Landsat images are from June 2 and June 19 the arrows and letters indicating specific locations. Note the shift in the main lake formation area from the light green to the dark green arrows. The light green arrows are below 1000 m and the dark green from 1200 to 1300 m, except for lake A which has persisted. Most of the lakes below 1000 m from June 2 are gone by June 19. The same area is also seen in 2005 with some of the same lakes filled The MODIS images are from June 2 and June 30 and again indicate the shift in location of the supraglacial lakes. The lakes evident below 1000 m are almost all gone by the June, and few lakes exist except above 1200 meters, indicating an earlier melt cycle this year. The location of Tiningnilik Lake is also shown, and it has filled somewhat during the month, being the recipient of some of the water from lake drainage events. 
This is indicative of the progression of the melt season and the development of the hydrologic drainage system. As the melt season begins snowmelt first percolates into the snowpack and can refreeze. After the snowpack has warmed meltwater percolates quickly through the snowpack and gathers into streams and lakes on the glacier surface. The higher the elevation the deeper the snowpack to be warmed and the colder the temperatures further delaying the melt process. Hence, the melt progression with elevation. I have found the lakes to be useful for navigation purposes days to day on the ice sheet, but the lakes do not tend to persist long, most draining within a few week of formation. The drainage of lakes indicates the maturation of the drainage system beneath the ice sheet that takes the water to the margin. The volume of water released is immense, and initially the meltwater would exceed the capacity of the drainage system leading to high basal water pressure which can enhance sliding for a short period (Zwally et al 2002). However, after the drainage system is developed water pressure falls and velocity does dramatically as well, the net impact of the brief acceleration is not large on the mean annual velocity as noted by Sundal et al (2011), but the increased meltings has led to an overall decline in flow speed as the hydrologic system matures over a shorter period. Luthje et al (2006) found that the number of supraglacial lakes is largely controlled by topography and enhanced melting should not increase their number. What will be important is to continue to examine changes in timing of formation and drainage, distribution of the lakes and volume of the lakes. For 2012 the drainage of almost all lakes below 1200 meters by June 30 is an early loss of lake area.
From a Glaciers Perspective 