The Pine Island Glacier is a principal outlet glacier of the West Antarctic Ice Sheet draining into the Amundsen Sea. Recent retreat, thinning and acceleration have focussed attention on this glacier. This is a brief note in support of a RealClimate article. The grounding line is of principal concern here. This is where the glacier goes afloat. The grounding line is where the bottom of the glacier comes in contact with the ground, in this case the sea bottom. The grounding line is an anchoring point for the outlet glaciers. The length of the glacier that is grounded is being both slowed and stabilized by the basal friction. Beyond the grounding line toward the margin the floating ice shelf is susceptible to a rapid calving retreat and as the grounding line retreats, so would the calving front. Note in the image below that the current grounding line is on relatively high terrain, but is close to a deep basin. The annotated image below is from a British Antarctic Survey image, taken from their autosub program exploring beneath the ice shelf of the Pine Island Glacier combined with data from radar altimeter data flown by NASA. 
Grounding line retreat could lead to the glacier retreating into this basin, not a stable situation. The British Antarctic Survey, NASA and several universitiesin particular have been focusing on this glacier. The second image shows the grounding line in the surface. This is an annotated satellite image from NASA. Just above the grounding line you can not that the surface of the glacier has some large scale roughness which indicates the impact of the sub-glacier topography. 
This topography acts to slow and buttress the glacier. This area is above the topographic rise from the deep basin to the higher terrain of the current grounding line. The ongoing focus on the Pine Island Glacier will be fascinating to watch. In particular the emphasis on the oceanographic aspects beneath the ice shelf. This is an aspect that has received less attention and will certainly yield interesting results, considerable technologic frustrations and innovations.
Pine Island Glacier Grounding Line
Denali National Park, East Taklanika Glacier retreat
The glaciers of Denali National Park are shrinking. The National Park Service has been chronicling the retreat with repeat photographs of glaciers from locations where historic photographs exist. The program has been a cooperation between glaciologist Guy Adema and photographer Ron Karpillo. One example is East Taklanika Glacier. This glacier drains north from the east ridge of Mount Scott. The glacier is currently 5.1 km long, the lower 2.2 km of the glacier is nearly completely debris covered. That ice is beneath the debris is clear from the lack of a the glacier melt fed river in the valley bottom and the color of the sediments which is darker, largely because the debris is wet from the ice melt underneath. The glacier in the center of the Google Earth satellite view below is East Taklanika Glacier. 
The glacier has retreated 1100 m between 1916 and 2004 in the phtographs of Ron Karpillo and Stephen Capps. There is a lateral moraine in the foreground of the 2004 Ron Karpillo image. This marks the former surface elevation of the glacier during the Little Ice Age. Since that time the lower section of the glacier has lost over 100 m of ice thickness. 
The retreat is ongoing. Medial moraines are bands of debris on the surface of a glacier that separate tributaries of a glacier. The moraines represent material eroded from the edge of the tributaries before they join. This material does not appear at the surface until you reach the ablation zone where melting dominates. In the accumulation zone such debris bands would be buried. On East Taklanika Glacier the debris bands extend to within 1 kilometer of the head of the glacier. For a glacier to be in equilibrium a glacier needs to have at least 50 % of its area in the accumulation zone at the end of the summer. Based on the satellite image hear showing 10% of its area in the accumulation zone and the extent of the medial moraine indicating no more than 25% of the glacier area above the moraine. This glacier needs to lose the lower 2-3 kilometers to be in equilibrium. This may not be enough. A glance at the glaciers around East Taklanika, indicate the same story, very little retained snowpack. Some of these glaciers have an accumulation area ratio (% of glacier snow covered at the end of the summer), of zero. This is like having no income, and plenty of expenditures and the result for your bank account, net loss and without some change eventual bankruptcy. The story of retreat is the same though the snowpack extent greater on the Juneau Icefield. The retreat of East Taklanika is slowed considerably by the debris cover which protects the ice underneath from melting as fast. This glacier is a long way from completing its retreat to adjust to current climate. 
Gilkey Glacier Retreat, Juneau Icefield
The Juneau Icefield Research Program has long monitored the mass balance of the Lemon Creek and Taku Glacier on the Juneau Icefield. This program begun by Maynard Miller in 1946 and continuing through today has also monitored the terminus behavior of the icefields outlet glaciers. Of the 17 significant outlet glaciers 5 have retreated more than 500 m since 1948, 11 more than 1000 m, and one glacier the Taku has advanced. I have a chance to visit the glaciers during a number of summers over the last 25 years as part of this ongoing annual program. The Gilkey Glacier is a 32 km long 245 km2 outlet glacier flowing west from the Juneau Icefield. In 1948 it terminate at the head of a braided outwash plain. At that time it was joined 5 km above the terminus by the Battle and Thiel Glaciers from the south. 
All three of these glaciers drain from the Juneau Iceifeld accumulation zone between 1500 and 2000 m, which maintain consistent snow cover. From 1948 to 1967 the Gilkey Glacier retreated 600 m and in 1961 a proglacial lake began to form. By 2005 Gilkey Glacier had retreated m , generating a proglacial lake that is now 3.9 kilometers long, which is approximately the amount of retreat in the last 60 years as well. 
The lake is partly filled with large icebergs from disintegration of the, note below in an image from Scott McGee of JIRP,Gilkey terminus. The lake is currently terminating in this still growing lake. Approximately half of this retreat occurred after a 1991 satellite image indicated the lake was close to half its current size. The retreat has been resulted from calving icebergs into the new lake as well as thinning from melting in the lower reach of the glacier. The extensive debris cover and lack of crevassing in the lower 1500 meters of the glacier indicates that this section is stagnant and will break up soon. 
Gilkey Glacier was in 1955 joined by the tributary glaciers Battle and Thiel Glacier. A visit to the Battle Glacier in 1982 indicated that it had separated from the Gilkey Glacier and the Thiel Glacier, but the Thiel Glacier was still connected. By 1991 the Thiel Glacier had separated. Today these glaciers terminate 3200 m and 1700 m up their respective valleys from Gilkey Glacier. Thiel has retreated 1700 m from the Gilkey Glacier. A retreat of 3200 m has created a glacier 70 % its former length. The vast bare valley beyond the terminus is in stark contrast to the map above. Thiel Glacier has extensive lateral moraines extending above the glacier terminus indicating the ongoing retreat. The lower 3 kilometers of this glacier are flat and are downwasting, indicating a substantial retreat is still underway. A view up the valley from the Gilkey toward the terminus of Battle Glacier indicates that most of the area deglaciated was a flat low elevation valley. Now that the glacier is retreating up a steeper slope, the retreat rate of Battle Glacier should slow.
Mass Balance of the Easton Glacier 2009
Immediately below is Easton Glacier on Mt. Baker in the North Cascades in late May 2009. The glacier is still completely snow covered. The bench where the small gray cloud shadows are at 6000 feet averages 20 feet of snow remaining.
Easton Glacier extends from the terminus at 5600 feet to the slopes near Sherman Crater at 9000 feet. Each summer since 1990 NCGCP has measured the mass balance of this glacier. View Youtube for a pictorial review of the full 2009 field season . The glacier has retreated 300 m since 1990. During this same period the glacier has lost a cumulative mean of 13 m of thickness. Given a thickness in 1990 between 60 and 75 m, this is about 20 % of the total glacier volume. Measuring mass balance requires assessing snowpack depth and areal extent at the end of the summer melt season and the amount of melting in areas where blue ice or firn (snow more than a year old) is exposed. Below is measuring crevasse stratigraphy and below that emplacing a stake to measure ablation with weather instruments on it. 
Mass Balance = residual snow accumulation – ice-firn melting.
The melt season began a bit late just when the May picture was taken Winter snowpack was between 75and 90% of normal in the area as of April 1. The melt season had been late to begin and snowpack by late May was near normal. Record heat was experienced at the end of May and the start of June, quickly causing snowpack to fall below normal.Each year we measure the snow depth via probing and crevasse stratigraphy at more than 200 locations. These depth measurements allow the completion of a map of snow distribution. This map is completed in early August and updated, based on a smaller number of observation in late September. The amount of melting is assessed from stakes emplaced in the glacier and the recession of the snowline in areas where snow pack depth has been assessed. below are images from early and then mid-August indicating the rise of the snowline. 
A warm June and July caused exceptional snow pack melt and by early August when we began assessing snow pack depth retained, the snowcover had receded to the 6400 foot level, 300-400 feet higher than normal. Snowpack remained below normal all the way to the 8600 foot level. the snowpack since early July had been rising nearly 100 feet per week. By mid-August at right the snow line on the glacier averaged 6800 feet. measuring crevasse stratigraphy below. By mid and Late September the snowline had risen to 7400 feet a rate of rise of 150 feet per week since mid-August. Below is an image from mid-September. 
The amount of melting on the glacier in July was the highest we have measured totaling, 2.1 m. This led to the exposure of a couple of new bedrock knobs evident in the picture at right near the 7000 foot level. Overall the mass balance of the glacier in 2009 was a negative 2.06 m. This glacier averages 55-70 m in thickness and this mass balance loss represents a 3% volume loss in a single year for the glacier. By this date the glacier is once again snowcovered, the melt season behind it and hopefully a good winter ahead.
Sperry Glacier Recession
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. 
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. 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. 
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.
Snowmaking for Alpine glaciers; where there are enough skiers there is a way.
Snowmaking on glacier’s, sounds like an oxymoron. However, several ski resorts in the Alps have begun doing just that to trying to offset the increased melting of glaciers that occupy a portion of their resorts. This is a more practical application than the insulating blanket that has been used at the Pitzal resort.
On the Pitzal Glacier, Austria they have begun using the IDE All Weather Snowmaker, which can produce snow in above-zero temperatures without chemical additives. This system, which produces snow directly on the slope at any temperature and without chemical additives, was installed in the Pitztal for the first time in Europe and at the same time as in Zermatt (Switzerland). The artificial snow cover forms a buffer layer on top of the glacier and prevents glacial melting. This also covers the glacier ice with a skiable surface. The high temperatures in recent years on the Pitztal Glacier were often not right in early autumn for producing normal snowfall so Dr. Hans Rubatscher, Manager of the Pitztal Glacier Railway, is employing a new way. In the future, the Snowmaker will be used alongside the existing snowmaking equipment, in particular at the start of the season in autumn and in late spring. This brings numerous benefits to the Pitztal Glacier optimizing ski run conditions, earlier opening of the slope section by the base station of the Pitz-Panorama Railway. The potential is emphasized by the interest of several ski teams who have expressed great interest in this special facility at the Pitztal Glacier. The 15m high production tower for the snow has been set up in its own building at an altitude of 2,840m right by the base station of the Pitz Panorama Railway. Below is the output of the snow with the glacier in the background
The snow produced here can be channeled directly onto the slopes below by the Gletschersee chair lift. The water for this innovative snow production system will be extracted using a vacuum system from the existing storage pools on the Pitztal Glacier. These pools are filled exclusively with melted glacier water, thus forming an ecological cycle on the glacier, returning its own meltwater as snow. After gaining experience, concrete attempts will be made to use the snow created by the Snowmaker to preserve the substance of the glacier in Austria’s highest glacier ski area. The glacier seen below has in most years been bare by late summer, not a skiable condition. The net volume loss of the glacier has also been notable.
In Zermatt’s case the snow is being used to make a path between the bottom of its high altitude glacier and the cable car station from where skiers and boarders can get back up the slopes to access the year round ski area. In years gone by the glacier did reach this lift station anyway, but over the past two decades it has melted away and in summer and autumn there may be no snow cover at all.
The IDE snowmaking system was developed by an Israeli company best known for its water desalination products. It created cooling systems for mines, which to their surprise produced snow as a by-product even under the scorching sun. The “Snowmaker system” can produce approximately 1900 cubic meters of snow in 24 hours whatever the outside temperature, humidity, and wind speed, and is highly energy-efficient. With traditional snowmaking systems, the temperature has to be at least minus 6 degrees Celsius and the humidity no more than 60 percent. With the IDE Snowmaker, these factors don’t come into the equation.
Currently 15% of the Tignes French ski area is covered by snow making canons and it is not just low lying areas. Tignes has equipped the bottom of the runs of the Glacier du Grande Motte with snow making to extend the summer ski season at 3000 meters and Val d’Isère is doing the same on the Glacier du Pisaillas to assure the summer skiing. The lift tower on Glacier Pissaillas is on the right of the image, the bare ice is not good ski conditions. Snow cannon shown at Tignes. 
Columbia Glacier year by year
The following pictures give a year by year view of Columbia Glacier within one day of August 1. The best year was 1999, the worst, 2005.The snowy peaks of the Monte Cristo region can be seen from the Everett area. With 30 glaciers many at low altitudes, this region may receive more snow than any other region in the North Cascades. The largest and lowest is Columbia Glacier occupying a deep cirque above Blanca Lake and ranging in altitude from 4600 to 5700 feet. Kyes, Monte Cristo and Columbia Peak surround the glacier with summits over 2000 feet above the glacier. The Monte Cristo range is the first major rise that weather systems coming off the ocean encounter on the way east to the Cascade Crest. As a result precipitation is heavy. During the summer if it is raining anywhere in the North Cascades it will be in the Monte Cristo region. The glacier is the beneficiary of heavy orographic lifting over the surrounding peaks, and heavy avalanching off the same peaks. We measure the mass balance of this glacier each year and report the data to the World Glacier Monitoring Service. Despite the advantages of snow accumulation the glaciers mass balance since 1984 has average -0.5 m a year for a cumulative loss of 13 m. For a glacier that averages 60 m in thickness this is over 20% of its volume. Details of the mass balance research and methods are at [url=http://www.youtube.com/watch?v=BMrlnISD-u0]
Columbia Glacier has retreated 134 m since 1984. Lateral reduction in glacier width of 95 m in the lower section of the glacier and the reduction in glacier thickness are even more substantial as a percentage. The major issue is that the glacier is thinning as appreciably in the accumulation zone in the upper cirque basin as at the terminus. This indicates a glaciers that is in disequilibrium with current climate and will melt away with a continuation of the current warm conditions. The glacier has lost 17 m in thickness since 1984, but still remains a thick glacier, over 75 meters in the upper basin and will not disappear quickly.
A lateral moraine deposited during the Little Ice Age, is visible at the western edge of the glacier, descending below the glacier to 4250 feet. This moraine has little vegetation on the inside, but is vegetated on the outside. Just in front of the terminus are two terminal moraines deposited during retreat in the last 20 years. Facing southeast Columbia Glacier is protected from any afternoon sun except during the summer. During the winters storm winds sweep from the west across Monte Cristo Pass dropping snow in the lee on Columbia Glacier. Avalanches spilling from the mountains above descend onto and spread across Columbia Glacier. The avalanche fans created by the settled avalanche snows are 20 feet deep even late in the summer. Nearly a third of the glacier is covered by avalanche fans, but no summer avalanches have been observed. Avalanches, shading from the sum provided by the high peaks, and wind drift snow deposition permits Columbia Glacier to exist at such a low altitude.
Devon Ice Cap
Two recent papers have examined the changes in flow, mass balance and volume of the Devon Ice Cap(Shepherd et al., 2007) (Dowdeswell, 2004). The Devon Ice Cap on Devon Island in the Canadian Arctic ice cap’s area has an area of 14,000 km2, with a volume of 3980 km3 . The ice cap area decreased by 332 km2 (2.4%) between 1960 and 2000.
The mass balance of the glacier has been assessed since 1960, the total mass loss due to surface melting and runoff between has been about 59 km3. Between 1960 and 1999 about 21 km3 of ice was lost from the ice cap by calving of icebergs, contributing 0.21 ± 0.02 mm to global sea level over this time. The long term mean net surface mass balance was 0.13 m from 1960-2000. From 1998-2007 the mean annual balance has been -0.23 m year, a substantial increase. 
The Belcher Glacier above is the principal outlet glacier calving up to 30% of the total iceberg volume from the ice cap.
Devon Ice Cap’s negative balance has been due to warming and greater ablation, as the upper part of the glacier has seen some increase in accumulation, which has been more than offset by increased melting. 
In this case the mass balance record indicates a dramatic worsening after 1995. It will be interesting to see the ablation results from the summer of 2008, when record melting was noted both in northern Greenland and northern Ellesmere Island. The glacier is not alone in its behavior, the Prince of Wales Icefield has had a negative mass balance over the last forty years of -80 km3, equivalent to a mean-specific mass balance across the ice field of -0.1 m w.e. a-1, contributes 0.20 mm to global eustatic sea level rise (Mair et at., 2008). http://www.agu.org/pubs/crossref/2009/2008JF001082.shtml
Photographs of the fieldwork coordinated by the University of Alberta
Stubai Glacier’s Protective Blanket
The north facing side of the Stubai Glacier that comprises the biggest ski area in the area is open all summer down to the Eisgrat lift station. There are two main lifts that traverse up the glacier, some of the towers for the ski lifts are set right on the glacier. The linear features extending down glacier in this satellite view of the glacier are the ski lifts and the ski runs. 
The Stubai Glacier has been retreating and thinning significantly as have most all glaciers in the Alps. Austria has a long term program monitoring the terminus position of over 100 glaciers. From 2000-2005 of the 115 glaciers observed and reported to the World Glacier Monitoring Service, all 115 experienced net retreat. The mass balance of Austrian glaciers, which represents volume loss, reported to the WGMS has been averaging a loss of more than 0.5 m per year since 1998. The loss of 5 m of ice in a decade on glaciers like the Stubai represents about 10% of their volume lost this decade. This ongoing ice loss prompted the ski area in 2003 to begin to explore means to preserve the glacier and maintain there ski season. They turned to the University of Innsbruck’s Andrea Fischer and Marc Olefs, who explored three means to reduce the summer melting. Olefs and Fisher (2007) Innsbruck University.The first was injecting water during the winter into the cold snowpack to make it denser. This did add mass, but did not reduce the melt rate. The second methods was to pack down the snow periodically in the winter, again making it denser. Likewise this did not reduce ablation. This is not surprising given that ablation rates on dense ice and less dense snow are very similar on glaciers. The third method was to cover the glacier with a blanket, they used both felt and plastic. The plastic was more reflective, thinner and easier to deploy and as seen in the next two photographs blends in well with the glacier surface. The top image is from Ineedsnow.com.
This technique reduced ablation by 60%. Is snow making now being employed a better answer? The problem is that even one small glacier ski slope is still a large area to cover. Because of this success in 2005, the ski resort continues to employ these white polyethylene sheets to reduce melting in strategic areas on the glacier. They are typically spread out in May. The sheets can be seen emplaced around the lift towers in particular. The bare ice of the main section of the glacier is an area of 400,000 square meters (4,300,000 square feet) tough to cover with material, even if it is a low cost per square meter. This type of geoengineering applied to just part of one small glacier maybe practical, but it is not practical at a significant scale. The severity of the climate change we are experiencing is emphasized by the extent to which the ski area is being forced to adapt to try and maintain its summer ski area. In the pictures below, the problem is illustrated by the extent of bare glacier ice late in summer. The ski lifts are apparent as are the square snow patches around the lift towers in the upper image. In the lower image the view from the gondola shows a glacier with very little snow remaining, this is a sign of a glacier that is quickly losing mass. 
26th Annual North Cascade Glacier Climate Project 2009 Field Season
This video examines the 2009 North Cascade Glacier Climate Project Field Season. It is a look more at where we work, than what we find. At this point the mass balance results are preliminary. The winter season was wetter than average, with close to average snowpack in the North Cascades. Summer melt conditions were exceptionally warm, leading to enhanced melting and considerable losses in glacier volume. It is evident that mass balance losses will average more than 1.2 m, which will represent about 2% of total glacier volume. Final observations of melting will be made at the end of September. In July ablation averaged 8.5 cm per day. For glaciers that average 50-60 m in thickness that is the loss of 2.5 m in one month. Most of the melt was snowpack from the previous winter. However, by mid-August blue ice was exposed on the majority of the glacier surfaces across the North Cascades and any ablation was a loss in long term glacier volume. Glacier retreat was slowed on Rainbow and Ice Worm glaciers hwere the terminus was buried under avalanche snow. Retreat of Easton Glacier was 20 m, Lower Curtis Glacier 11m, Daniels Glacier 12 m, Lynch Glacier 8 m. More details on this project North Cascade Glacier Climate Project
[url=http://www.youtube.com/watch?v=DJGQXlvWXy8]
