Tungnafellsjökull, Iceland Recession and Thinning 1999-2020

Tungnafellsjökull Ice Cap in 1999 and 2020 Landsat images indicating  terminus changes at three northern outlets, red arrows, and at four locations of bedrock exposure.

Tungnafellsjökull Ice Cap is a ~32km2 ice cap located between Vatnajökull and Hofsjökull.  Gunnlaugsson (2016) reported on the mass balance changes of the Tungnafellsjökull Ice Cap and found it had lost 20 of its volume and 16% of its area from 1960-2013.  The ice cap was essentially in balance from 1960-1986 and had a slight mass balance loss from 1986-1995.  Almost all of the loss has been since 1995. Belart et al (2020) report on losses from 14 smaller glacier in Iceland including Tungnafellsjökull and found signficant increase in mass loss from a near equilibrium 0.07 m/year from 1960-1994 to -1.20 m/year from 1995-2010. Here we examine the impact of the 25 years of sustained mass loss on Tungnafellsjökull using Landsat images.

In 1999 the transient snow line in August is at ~1200 m.  Point A,B and D indicate bedrock knobs amidst the ice cap and Point C a bedrock ridge that the ice cap flows over near Point C.  The three northern outlets terminate at the red arrows. From east to west they are Nordur Tungnafellsjökull, Innri Hagajökull and Fremri Hagajökull. In 2000 the transient snowline in August is again at ~1200 m. In 2014 the snowline was above 1500 m laving the ice cap without any retained snowpack from the previous winter.  The area of exposed firn encompasses 40% of the ice cap indicating the size of the accumulation zone in the several years prior to 2014. By 2016 the ice cap no longer flows over the ridge near Point C.  The transient snowline is at ~1400 m. In 2020 the transient snowline is at ~1350 m.  The bedrock knob at Point B is no longer surrounded by the ice cap. The bedrock at Point A and D have expanded.  The retreat from 1999-2020 is most significant at the three northern outlet glaciers, where Gunnlaugsson (2016)  indicated thinning was greatest. The retreat has been 200 m at Nordur Tungnafellsjökull,  600 m at Innri Hagajökull and  500 m at Fremri Hagajökull.

With an accumulation area covering approximately 40% of the ice cap, mass balance losses will continue and the ice cap will continue to retreat.  Retreat has been the consistent response of more than 90% of  Iceland glaciers since 2000 (Iceland Glaciological Society), such as at Norðurjökull.

Tungnafellsjökull Ice Cap in 2000 and 2016 Landsat images indicating  terminus changes at three northern outlets, red arrows, and at four locations of bedrock exposure.

Landsat image in August 2014 indicating the lack of retained snowcover.  The glacier surface is bare ice blue-gray and exposed firn indicated by the zone inside of the yellow dots.

Hagafellsjokull, Iceland Reflects Langjokull Thinning & Retreat

Landsat comparison of the terminus of Hagafellsjökull from 2000 and 2016.  The red arrows are the 2000 terminus, the yellow arrows the 2016 terminus.  Purple arrows indicate upglacier thinning. 

Langjökull is the second largest iceap in Icalnd with an area of over 900 square kilometers. The mass balance of the icecap has been reported since 1997 and his lost over 1 m per year during this period (WGMS, 2016).  Pope et al (2010) noted that the icecap has lost an area of 3.4 ± 2.5 km2 yr-1 over the decade from 1997-2007.  Pope et al (2010) noted that the loss of ice volume confirms previously published predictions that Langjökull will likely disappear within the next 200 years if current trends continue. A key outlet of  Langjökull is  Hagafellsjökull which terminates in Hagvatn. Hagafellsjökull ended a sustained post Little Ice Age retreat in 1970.  The ensuing advance of approximately 1 km ended by 2000.  Here we examine Landsat imagery from 2000-2016 to identify recent changes in this outlet glacier.

In 2000 the glacier terminated on an island in Hagavatn, red arrow.  The east margin of the glacier featured several locations where secondary termini overflowed a low ridge on the east side of the glacier.  By 2006 the glacier had retreated 500-600 m from the island.  By 2016 the terminus had retreated across its entire width by 800-850 m, 50 m/year, yellow arrows.  A closeup view from the Iceland online map application illustrates the 2014 terminus red dots. The end of the glacier has a low slope, low velocity and is debris covered.  The western side has terminated on land during this entire period and has approximately the same retreat rate as the eastern half that still ends in the expanding lake. There is little evidence of iceberg release into the lake, which helps explain the similar retreat rate. The low slope and upglacier thinning noted at the purple arrows indicate the retreat will continue.  In 2014 the transient snowline reached near the head of the glacier at over 1100 m.  In 2000, 2006 and 2016 the snowline with several weeks left in melt season ranged from 859-950 m. The retreat is similar to that of Norðurjökull another outlet of the Langjökull and Porisjokull.

Google Earth view of the terminus of Hagafellsjökull in 2014. Red arrow is the 2000 terminus position and yellow arrow the 2014 position.

 

Online Iceland Map Viewer indicating the terminus of Hagafellsjökull in 2014, red dots.

2006 and 2014 Landsat images of Hagafellsjökull indicating the transient snowline off the image in 2014 and at 850 m in 2006.

Blágnípujökull, Iceland Retreat 1986-2015

Blágnípujökull comparison in Landsat imagery from 1986 and 2014. 

Blágnípujökull is an outlet glacier on the western side of Hofsjökull. The Iceland Glaciological Society spearheads an annual terminus monitoring program led by Oddur Sigurðsson. This data set enabled an examination of glacier response to climate change in Iceland from 1930-1995 by Tómas Jóhannesson, Icelandic Meteorological Office and Sigurðsson (1998). This illustrated that Hofsjökull glaciers retreated little from 1950 to 1990, but all retreating significantly after 2000. Here we examine Landsat imagery of Blágnípujökull terminus change from 1986 to 2015.

Outlet map of the glacier from the Iceland Glaciological Society.

Iceland Glaciological Society data on terminus change, notice change from advance to retreat in the 1990’s

In 1986 the glacier terminated at the red arrow. North of the main terminus is a separate glacier terminus, purple arrow. By 1998 there is limited retreat less than 200 m. By 2014 the terminus area around the purple area has been largely lost. The glacier has retreated from the red dots to the yellow dots, a distance of 600 meters. The thinning is also evident in the region between the two main termini of Blágnípujökull, the margin is not as close to the edge of the lava flow capping the hill that the glacier terminus parts around. The snowline is also quite high on the ice cap in 2014. In 2015 the image is after a summer snowstorm and the is not clear enough to accurately assess further terminus change. The changes in this glacier parallel those of other Iceland Glaciers: Porisjokull and Langjokull.

1986 Landsat Image

1998 Landsat Image

2014 Landsat Image

Google Earth image

2015 Landsat Image

Eiriksjökull Reeat, Iceland

Eiriksjökull  is an ice cap just west of Langjökull In central Iceland.  Here we examine its main western outlet the Braekur using Landsat imagery from 1989 to 2014.  The Icelandic Glaciological Society website on terminus variations is the source of the map for the glacier. The IGS program monitors 50 glaciers, all of them are currently retreating.  Eiriksjökull ,  is not one that is in this monitoring program. 

In 1989 the Braekur outlet flowed over the edge of a lava cliff at the red arrow.  The glacier terminated on the bench between the upper and lower cliff.  In 1994 the glacier still extended  to the edge of the cliff.  By 2010 the Google Earth images indicates a retreat from the edge of the cliff.  In 2014 the glacier has receded 200 m from the edge of the cliff and 300 m from is 1989 position and terminates at the yellow arrow. The high snowlines in recent years will lead to continued retreat. The retreat and area loss of Eiriksjökull is less than on nearby Norðurjökull a primary outlet of Langjökull or on Porisjokull a small ice cap just south of Langjökull.

1989 Landsat image

1994 Landsat image

2010 Google Earth image

2014 Landsat image

Eiriksjökull Retreat, Iceland

Eiriksjökull  is an ice cap just west of Langjökull In central Iceland.  Here we examine its main western outlet the Braekur using Landsat imagery from 1989 to 2014.  The Icelandic Glaciological Society website on terminus variations is the source of the map for the glacier. The IGS program monitors 50 glaciers, all of them are currently retreating.  Eiriksjökull ,  is not one that is in this monitoring program. 

In 1989 the Braekur outlet flowed over the edge of a lava cliff at the red arrow.  The glacier terminated on the bench between the upper and lower cliff.  In 1994 the glacier still extended  to the edge of the cliff.  By 2010 the Google Earth images indicates a retreat from the edge of the cliff.  In 2014 the glacier has receded 200 m from the edge of the cliff and 300 m from is 1989 position and terminates at the yellow arrow. The high snowlines in recent years will lead to continued retreat. The retreat and area loss of Eiriksjökull is less than on nearby Norðurjökull a primary outlet of Langjökull or on Porisjokull a small ice cap just south of Langjökull.

1989 Landsat image

1994 Landsat image

2010 Google Earth image

2014 Landsat image

Eyjabakkajökull Retreat, Iceland

Eyjabakkajökull is a surging glacier that emanates from the north side of Vatnajokkull Ice Cap. The glacier surged in 1890, 1931, 1938 and 1972. During the latter advance the glacier advanced approxmately 2 km (Ívar Örn Benediktsson, 2009). A recent project focused on this glacial geology in front of this glacier led by Ólafur Ingólfsson and Ívar Örn Benediktsson (University of Iceland) and Dr. Frank Lisker (University of Bremen). The information was put together by Antje Herbrich. The first image is a map from this project indicating the glacier moraines emplaced by the four most recent surges. It is apparent that each surge has not extended as far as the previous surge. In the second image also from the Eyjabakkajökull project, the blue line is the 1973 terminus and the purple line the 1991 terminus position drawn on a 2000 Landsat image.

Here we examine Landsat Imagery from 1999, 2012 and 2013 and Google Earth imagery in 2000. The glacier tongue has a prominent medial moraine ridge that in 1999 ended just short of the outlet river in a stretch where it ran west to east, pink arrow. This is a ridge because it is an ice cored moraine, as the ice core melts the ridge disappears. By 2012 the glacier had retreated 2 km from the 1999 terminus, and ending at the yellow arrow. This distance is emphasized by the length of the green line to the terminus. The green line starts from a specific lake and terminates at the glacier. In 2013 the 2 km retreat since 1999, and the 1.1 km retreat from 1972-1999 places the terminus about a kilometer behind the terminus location prior to the 1972 advance. The 1972 terminus is marked with a red arrow. The current terminus has a very low slope and limited crevassing indicating that a rapid retreat will continue. Hence, when the next surge comes, it will begin from quite a recessed position and will fell well short of the 1972 advance moraines. The snowline in 2012 and 2013 is above 1100 m, purple dots, which is high enough to indicate significant negative mass balance.

1999 Landsat image

2000 Google Earth

2012 Landsat image

2013 Landsat image

This retreat is similar to that of draining the Tungnaarjökull west side of Vatnajokulland Skeiðarárjökull Glacier on the south side and Brúarjökull . The low slope is seen in the image below looking across the glacier from Ívar Örn Benediktsson

Brúarjökull Retreat, Iceland

Brúarjökull is a major, 1600 square kilometers outlet glacier on the northeast side of the Vatnjokull Ice Cap in Iceland. Brúarjökull is a surging glacier that has surged n 1810, 1984 and 1964. During a surge a glaciers basal water pressure increases leading to reduced basal friction, a sharp velocity increase and terminus advance. Surges do not typically reflect climate change. In recent years Brúarjökull has been retreating at about 100 m/year. The glacier advanced 8-10 km during the 1964 surge. In this case an additional factor has been added, with the completion of a dam and the filling of the Hálslón Reservoir in 2007 that is now in contact with the terminus of Brúarjökull. Kárahnjúkar hydro power plant is Europe’s largest dam and a $2 billion project that produces 690 MW of power. Unfortunately with the dam now in operation it has not proved profitable for the Landsvirkjun, Iceland’s national energy company. In 2013 the surface level of the Hálslón Reservoir reached 625 meters above sea level at the end of August which is the spillway elevation.
The Brúarjökull Project has examined the glacier terminus and newly exposed landscape by retreat in recent years. The terminus they observe is quite stagnant. The elevation range of Brúarjökull is 600–1750 m a.s.l. with an equilibrium line altitude of 1200 m and accumulation area ratio AAR of 60%. The mass balance of Brúarjökull measured since 1994 and has been consistently negative, losing 10 m of ice thickness overall, with greater much greater thinning near the terminus. Here we examine Landsat images from 1999, 2008, 2012 and 2013 and Google Earth imagery from 2005 and 2009. The contorted medial moraines, red arrows are indicative of a surging glacier. The purple arrows indicate the snowline which leaves much too large an area of glacier in the ablation zone for equilibrium balances. In 2013 the ELA in late August is 1300 m, it will rise a bit more which will mean a negative mass balance of at least 1 m.
Landsat 2013 image
The terminus in each image is indicated by yellow dots with Points A-E being consistently located for comparison. The first image is a Landsat image from 1999, the Hálslón Reservoir does not exist. The distance from Point B to the ice front is 1 km, from Point C 1.75 km and Point D is 0.75 km upglacier of the ice front to the immediate west. By 2005 Google Earth image the Hálslón Reservoir is still not present. By 2008 the terminus has retreated with Point B now 1.5 km from the ice front, Point C 3.5 km and Point D at the ice front to the immediate west. The reservoir exists and frontage in the reservoir 1.75 km. This is better illustrated in the 2009 Google Earth image of the immediate ice front in Hálslón Reservoir. Numerous small icebergs are seen, read arrows. By 2013 the Landsat image indicates the glacier front is 2.5 km from Point B, 5.25 km from Point C and 0.75 km from Point D. The retreat from 1999-2013 is then 1.5 km at Point B, 3.5 km at Point C and 1.5 km at Point D. In 2013 the glacier frontage in the lake has decreased to 1.5 km, and will quickly diminish to where calving is not longer occurring. This retreat is similar to that of draining the Tungnaarjökull west side of Vatnajokulland Skeiðarárjökull Glacier on the south side
Landsat 1999 image

Google Earth 2005 image

Landsat 20008 image

Google Earth 2009 image

Landsat 2013 image

Porisjokull Retreat, Iceland

Porisjokull (Thorisjokull) is a small 25 square kilometer ice cap southwest of Langjokull. The top elevation of the icecap is just 1350 m. This ice caps outlet glaciers have been in retreat as have almost all Iceland glaciers in the last decade (Helgi Björnsson and Finnur Pálsson, 2008). Examination of Landsat images from 2000, 2002, 2011 and 2012, shown in that order below, are used to identify changes in Porisjokull. The primary changes in the periphery are retreat of two lobes on the east side of the icecap at the yellow and red arrow and loss of ice at glacier connections green arrow and purple arrow. The comparison of the 2000 and 2011 images in particular illustrate the complete loss of the lobes at the yellow and red arrow. Between outlets of the icecap areas of glacier area have diminished significantly at the green and purple arrow. The lobe at the yellow arrow has been lost, this represents a retreat of 500 m. At the red arrow the lobe has also been lost, a retreat of 400 m. In the Google Earth images below the lobes still exist. At the green arrow the glaciated area declined from 1.2 square kilometers to 0.5 square kilometers. At the Purple arrow the margin of this intermediate lob has retreated 300 m. The icecap changes has mirrored that of nearby Langjokull, Gudmundsson et al (2008) identified thinning across the accumulation zone of Langjokull from 2000-2007. This led to retreat of the largest outlets of Langjokull.
Bjornsson and Gislason (2010) have examined the climate change that is driving the response of the glaciers.

Norðurjökull outlet of Langjökull Retreat Iceland

Langjökull is the second largest icecap in Iceland with an area of 920 square kilometers (Jóhannesson (2009). One of the main outlet glaciers of Langjökull is the Norðurjökull which still reaches Hvítárvatn. Hvítárvatn is a large lake that recieves 70% of its inflow from Langjökull (Flowers et al, 2007). The lake has a maximum depth of 84 m and a surface area of 30 square kilometers. Glaciers in Iceland have begun a ubiquitous retreat since 1995, such as Tungnaarjökull and , Kötlujökull. Figure below is from Jóhannesson (2009). On Langjökull terminus fluctuations are not regularly observed and reported to the World Glacier Monitoring Service (WGMS). The mass balance of Langjökull has been reported to the since 1997, the glacier has lost 16 meters of water equivalent since 1997 (WGMS). This is 8-10% of the volume of the ice cap, and represent the loss of over 1 cubic kilometer of water equivalent per year from the glacier (Guðmundsson et al, 2008). In modelling studies this led Björnsson et al (2006) to project the loss of Langjökull in just over a century. Pope et al (2011) observed that Langjökull has lost an area of 3.4  2.5 km2 yr-1 over the decade.

Here we examine the changes in Norðurjökull from Landsat imagery in 1984, 1994, 2006 and 2009 and Google Earth imagery from 2005. The images are shown in chronologic order below. From 1984 (red line) to 1994 (yellow line) there was a minor advance of less than 100 meters and the glacier front in the lake remained 1.4 km wide. From 1994 to 2005/2006 (green line) the glacier retreated 350 meters, and by 2009 the retreat had reached 450 meters (orange line). This represents a retreat of 30 meters/year. In 2009 the glacier front has narrowed where it meets the lake to 600 meters.

Tungnaarjökull Retreat, Icleand

Tungnaarjökull drains the west side of the Vatnojökull Icecap. The glacier begins just west of the Grimsvotn Volcano at 1500 m. Just to the north of this large outlet glacier, 350 square kilometers, is the Loki Volcano. The first image below denotes these volcanoes and the epicenter of recent earthquakes. The volcanic activity is recorded in the dark ash layers that fall on the glacier in the accumulation area and are subsequently buried to emerge in the ablation zone. The snowline is visible in the imagery just above the highest ash horizon.The glacier terminates at 800 m, and has a snowline since 2000 averaging 1300 m. Like many of the glaciers draining the Vatnajökull the glacier experiences periodic surges. Surging is a short term, several months to several years, acceleration and the associated advance of a glacier that is not primarily dictated by changes in mass balance or climate. A surge is related to a change in the basal water pressure that in this region is related to volcanic activity. The glacier surged in 1920, 1945 and 1995, that latter surge led to an advance of 1175 m in 1995. From 1955-1970 the glacier retreated at a rate of 75 m/year. From 1973-1992 the glacier retreated 1400 m. The surge led to an advance of 1175 m in 1995 bringing the glacier back close to its 1973 position. Since then the glacier has continued to retreat. Tungnaarjökull terminus is surveyed each year and the data reported to the WGMS. From 1996-2000 the glacier retreated 80 m. From 2001-2005 the glacier retreated 240 m. Below is the margin of the glacier indicating the moraine from which the glacier receded after the 1945 surge, the 1995 surge did not emplace a moraine. The distance appears small, but averages 1.5 kilometers. This gives a sense of the scale of the glacier. The mass balance of this glacier has also been measured since 2000. During that period the glacier has had a negative balance every year, 8 of the nine years the mass balance exceeding 1 meter of water equivalent loss. The total loss for the period of 12 m, will lead to continued retreat. This is a substantial thinning of the glacier, but a small part of the total volume given a glacier that averages more than 500 m in thickness. The equilibrium line has been high since 2000, leading to only 40% of the glacier being snow covered at the end of the summer. on a glacier like this that lacks avalanche accumulation due to its low and consistent slope at least 60% of the glacier must be snow covered to have an equilibrium balance this would be 1150 m. This height is close to the elevation midpoint of the glacier. Beyond the terminus the retreat is exposing a large relatively flat plain that is rich with glacial geologic deposits, many linear examples are evident. These features are streamline features from glacier flow. The retreat here is similar to the Bruarjokull on the north side and Skeidararjokulli on the west side of the Vatnojokull.

Tungnaarjökull Retreat, Iceland

Tungnaarjökull drains the west side of the Vatnojökull Icecap. The glacier begins just west of the Grimsvotn Volcano at 1500 m. Just to the north of this large outlet glacier, 350 square kilometers, is the Loki Volcano. The first image below denotes these volcanoes and the epicenter of recent earthquakes. The volcanic activity is recorded in the dark ash layers that fall on the glacier in the accumulation area and are subsequently buried to emerge in the ablation zone. The snowline is visible in the imagery just above the highest ash horizon. The glacier drains into the Skaftá River which experiences jökulhlaups such as in June 2015.A June 6, 2015 Landsat image indicates little ablation being generated in the area.

June 6, 2015 Landsat Image

 
Google Earth Images

Iceland Met Service map of Skaftá River and jökulhlaup source.

The glacier terminates at 800 m, and has a snowline since 2000 averaging 1300 m. Like many of the glaciers draining the Vatnajökull the glacier experiences periodic surges. Surging is a short term, several months to several years, acceleration and the associated advance of a glacier that is not primarily dictated by changes in mass balance or climate. A surge is related to a change in the basal water pressure that in this region is related to volcanic activity. The glacier surged in 1920, 1945 and 1995, that latter surge led to an advance of 1175 m in 1995. From 1955-1970 the glacier retreated at a rate of 75 m/year. From 1973-1992 the glacier retreated 1400 m. The surge led to an advance of 1175 m in 1995 bringing the glacier back close to its 1973 position. Since then the glacier has continued to retreat. Tungnaarjökull terminus is surveyed each year and the data reported to the WGMS. From 1996-2000 the glacier retreated 80 m. From 2001-2010 the glacier retreated 640 m. Below is the margin of the glacier indicating the moraine from which the glacier receded after the 1945 surge, the 1995 surge did not emplace a moraine. A comparison of Landsat images from 1999 and 2014 illustrates the retreat. Note the expansion of the lakes and the formation of a new one at the red and yellow arrow.  The exposure of new moraine ridges at the purple arrow also indicates retreat.

1999 Landsat image

2015 Landsat image

The mass balance of this glacier has also been measured since 2000. During that period the glacier has had a negative balance every year, 12 of the 13 years the mass balance loss has been larger than 0.8 meter of water equivalent. The total loss for the period of 15 m, will lead to continued retreat. This is a substantial thinning of the glacier, but a small part of the total volume given a glacier that averages more than 500 m in thickness. The equilibrium line has been high since 2000, leading to only 40% of the glacier being snow covered at the end of the summer. on a glacier like this that lacks avalanche accumulation due to its low and consistent slope at least 60% of the glacier must be snow covered to have an equilibrium balance this would be 1150 m. This height is close to the elevation midpoint of the glacier.

Beyond the terminus the retreat is exposing a large relatively flat plain that is rich with glacial geologic deposits, many linear examples are evident. These features are streamline features from glacier flow. The retreat here is similar to the Bruarjokull on the north side and Skeidararjokulli on the west side of the Vatnojokull.

Gígjökull Retreat and Eruption Impact on this Glacier-Updated 2/2011

Gígjökull drains north from the Eyjafjallajökull Ice cap. Eyjafjallajokull began to erupt on March 20. In the initial eruption the fountains of lava were vented from a fissure in a relatively ice free area, east of the ice cap, and did not generate much flooding from ice melt. The vent indicated by NASA from early April has shifted closer to the main ice cap, but is still peripheral to it. The ash plume is also travelling east away from the still white ice cap on April 1. In the renewed eruption on April 13-16, 2010 the eruption has shifted closer to the summit of the ice cap melting several holes in the glacier visible in radar imagery from the Icelandic Coast Guard. These are located at the crest and just south of the crest of Gígjökull. The glacier has not been vaporized, but has experienced considerable melt. . The current eruption is close to the head of Gígjökull . Gígjökull is a 7.5 kilometer long glacier that empties out of the summit crater area at 1600 meters flowing across the ice cap plateau to 1500 meters then descending steeply in an icefall from the ice cap plateau to the terminus at 200 meters. There are pictures of lahars, Icelandic Met Service, from 4/16/2010 from just east of Gigjokull indicating this glacier is experiencing some substantial melt. The impact of the volcano will result in this glacier not being a good indicator of climate change impact on a glacier going forward, and will exacerbate the rapid recent retreat due to global warming. The Icelandic Met Office conducted a comparison of the runoff from glaciers draining the area around the volcano and from an ice cap in northeast and one in west Iceland indicate that the thick ash layer actually insulated the snow and ice underneath retarding glacier melt. Runoff in Jun-August 2010 a warm, dry period was just below normal in a gaged river draining the icecap near the volcano, and far above normal on ice caps farther from the volcano during summer 2010. Typically it takes a thickness of debris of 2 cm to switch from enhancing to retarding melting. The lahars visible in radar imagery on the 16th are mainly flowing to the south side of the ice cap. Contrast the series of images below from 4/17/2010 and 3/9/2010 from the Icelandic Met Office with the 2005 and 1992 images below. Below are the hydropgraphs from the Icelandic Met Office comparing the 2010 hydrograph of 2010 to those of 2006-2009, 2010 is the black year. The climate induced retreat continued up to 2010 as the glacier lost its entire stagnant section adjacent to the lake. And now the lake has been filled in by mud in a matter of days. As of May 2nd the glacier still exists, many would think it had melted away completely, but glacier are tough to melt. The last image is from the Icelandic Institute of Earth Science (Sigrún Hreinsdóttir) The image above is from Tómas Jóhannesson, Icelandic Meteorologic Office, and shows that in 1992 there is no indication of stagnation and breakup in the proglacial lake at the teriminus. In addition compare the width of the glacier in that base of the icefall region. In 2005 the large exposed bedrock region is evident, in 1992 it is an active crevassed glacier across this entire region. Given the thickness of the glacier 100-200 meters in this region, this is a very rapid change in thickness. The glacier retreated in the first half of the 20th century but then began an advance that lasted until 1997. From 1997-2005 the glacier has retreated 700 meters according to data reported to the World Glacier Monitoring Service. This is leading to the expansion of the proglacial lake. The current rate of retreat is nearly 100 meters per year. The lower 1.1 kilometers is stagnant and poised for further fairly rapid retreat. The glacier is several hundred meters thick in this region and would melt slowly in place, but can breakup quickly via calving in the proglacial lake at its terminus. How far will this sub glacial trough extend upglacier from the current terminus will be key to understanding how fast this will occur. The view across the lake and a section of the terminus area that was breaking up in 2004 resulting in a retreat of 370 meters from 2003-2005 is seen in the image below from Ó. IngólfssonNote that in the image above and below. The lower 1.1 kilometers of the glacier lack crevassing and further has as its upglacier end a large bedrock area that is exposed across half the width of the glacier. this indicates the lack of flow from the icefall region of the glacier into the stagnant terminus zone.