The retreat of outlet glaciers along the Greenland coast continues to change the maps of the region, Steenstrup Glacier located at 75.2 N in Northwest Greenland is an example of this. The glacier terminates on a series of headlands and islands, the glacier immediately to the south is Kjer Glacier. The boundary between Steenstrup Glacier and Kjer Glacier is Red Head, Steenstrup Glacier’s northern margin is near Cape Seddon. Here we examine changes in the terminus position of Steenstrup and Kjer Glacier from 1999 to 2014. The retreat of the glacier during this interval has led to generation of new islands. Steenstrup Glacier has retreated 10 km over the past 60 years (Van As, 2010). A recent example of the retreat is the separation from the glacier of an island in 2014. In 2012 there was a narrow glacier connection, red arrow, with an island Tugtuligssup Sarqardlerssuua that is clearly not stable, based on narrowness and extensive crevassing, the connection remained in 2013 and was in 2014.
Google Earth 2012 image Cape Seddon/Tugtuligssup Sarqardlerssuua, how long will this connection last? Less than two years.
Landsat image comparison of 2013 and 2014 of Cape Seddon/Tugtuligssup Sarqardlerssuua separation from Steenstrup Glacier.
Image from Van As (2010).
McFadden et al (2011) noted several glaciers in Northwest Greenland; Sverdrups, Steenstrup, Upernavik, and Umiamako that had similar rapid thinning patterns of up to ~100 m a-1 since 2000. They further noted that thinning was not synchronous with Steenstrup and Sverdrups thinning fast from 2002 to 2005, Upernavik from 2005 to 2006, and Umiamako from 2007 to 2008. This is not exactly synchronous, but occurring within a few years is essentially synchronous in terms of glacier dynamics. Each glacier also had a coincident speed-up with a 20% acceleration for Steenstrup Glacier (McFadden et al, 2011). Kjer Glacier was noted as relatively stable until loss of connection with Red Head Peninsula in 2005 (Van As, 2010). This is a familiar pattern with thinning there is less friction at the calving front from the fjord walls and the fjord base, leading to greater velcoity. The enhanced flow leads to retreat and further thinning, resulting in the thinning and the acceleration spreading inland. The initial thinning comes from a combination of basal and surface melt. This has been the primary mechanism for increased velocity of outlet glacier of the Greenland Ice Sheet.
Here we examine Landsat images from 1999, 2013 and 2014 to identify changes of Steenstrup and Kjer Glacier. The yellow arrow indicates Red Head, which the glacier still reaches in 1999, though the connection is less than 2 km wide. The purple arrow indicates the ice front just north of Red Head that extends nearly due north to the next island at the icefront. The red arrow indicates the ice front of Steenstrup Glacier at Tugtuligssup Sarqardlerssuua. By 2013 the connection to Red Head has been lost, it is now an island, this occurred as noted by Van As (2010) in 2005. Retreat from Red Head is 6 km by 2013. There is a substantial embayment that develops, purple arrow southwest of an island still embedded in the icefront, indicating 4 km of retreat. North of this island that will soon lose it connection to the ice sheet, the embayment has expanded as well. The connection to the island at the north end of Kjer Glacier, has become much narrower since 1999 and will follow the route of Red Head and Tugtuligssup Sarqardlerssuua. In 2014 Steenstrup Glacier at the red arrow has separated from Tugtuligssup Sarqardlerssuua. The island west of the purple arrow still acts as a pinning point having stabilized the ice front here since 1975, but is now isolated in the same way as Red Head in 1999 and will soon be released from the glacier. From 2013 to 2014 the embayment is spreading inland and north.
The retreat here is coincident with the thinning and acceleration and follows the pattern of retreat and new island generation seen at Kong Oscar Glacier, Alison Glacier and Upernavik Glacier. The map of Greenland is continues to change at an accelerated rate, bottom image is a geologic Map from the Geological Survey of Denmark and Greenland. Red arrow again indicates Tugtuligssup Sarqardlerssuua.
The Grinnell Ice Cap Is located on the Terra Incognita Peninsula on Baffin Island. The name suggests the reality that this is a not often visited or studied region. Two recent studies have changed our level of knowledge. Way (2015) notes that the ice cap has lost 18% of its area from 1974 to 2013 and that the rate of loss has greatly accelarated and is due to summer warming, declining from 134 km2 in 1973-1975 imagery to 110 square kilometers in 2010-2013 images. Papasodoro et al (2015) report the area in 2014 at 107 km2 with a maximum of elevation of close to 800 m. The location on a peninsula on the southern part of the island leads to higher precipitation and cool summer temperatures allowing fairly low elevation ice caps to have formed and persisted. Way (2015) in the figure below indicates the cool summer temperatures have warmed more than 1 C after 1990. Recent satellite imagery of snowcover and ICESat elevation mapping suggest little snow is being retained on the Grinnell Ice Cap since 2004. Papasodoro et al (2015) identify a longer mass loss rate of -0.37 meters per year from 1952-2014, not exceptionally different from many alpine glaciers. They further observed that from 2004-2014 this rate has accelerated to over -1 meter per year, including a thinning rate above 1.5 meters along the crest of ice cap. This can only be generated by net melting not ice dynamics. Further such rapid losses will prevent retaining even superimposed ice. Here we examine Landsat imagery from 1994 to 2014 to illustrate glacier response.
Grinnell Ice Cap in Google Earth
From Way (2015)
The red arrows in each image indicate areas of small nunataks that have begun to expand in the last decade. The yellow and green arrows indicate specific locations on the western margin of the ice cap where lakes are developing. Point A-D note specific locations adjacent to ice cap outlet glaciers. In 1994 the late August image indicates snowcover across most of the ice cap. The green arrow is at the northern end of a narrow lake. The yellows arrows are at the northern and southern end of a narrow ice filled depression. The nunatak area exposed at the red arrows is limited. At Point C the terminus is tidewater. In 2000 snow pack covers 40% of the ice cap. A small lake is developing at the yellow arrows. The glacier reaches the ocean at Point C and D. The glacier extends south of Point A and the outlet glacier at Point B is over a 1.2 km wide. In 2012 a warm summer led to the loss of all but snowpack on the glacier. At the red arrows the nunataks have doubled in size. At the yellow arrows a 2.5 km long lake has developed. At the green arrow a lake that has developed, is now separated from the glacier margin by bedrock. The glacier now terminates north of Point A. In 2014 again snowcover is minimal with two weeks left in the melt season. The outlet glaciers at Point C and D are no longer significantly tidewater. At Point B the outlet glacier is less than 0.5 km wide. The lake at the yellow arrows is 3 km long and 400 m wide. Some nunataks are coalescing with each other or the ice cap margin. The majority of the western margin of the ice cap has retreated 300-500 m. This retreat is surpassed at outlet glaciers by Point A and C. What is of greatest concern is the loss in thickness of over 1.5 per year on the highest portions of the ice cap, indicating no consistent accumulation zone. This results from the persistent loss of nearly all snowcover in the summer. This pattern of limited end of summer retained snowcover seen in most years since 2004, is a snow deficit that this ice cap cannot survive in our current warmer climate (Pelto, 2010). Way (2015) projects that that if the observed ice decline continues to AD 2100, the total area covered by ice at present will be reduced by more than 57%. Given the recent increases and lack of retained snowcover, suggests an even faster rate is likely.
Annual mass balance is the difference between ice and snow added to the glacier via accumulation and snow and ice lost via ablation and in some cases calving. Alpine glacier mass balance is the most accurate indicator of glacier response to climate and along with the worldwide retreat of alpine glaciers is one of the clearest signals of ongoing climate change (WGMS,2010). For 25 consecutive years we (North Cascade Glacier Climate Project) have measured the mass balance of Sholes Glacier. On Sholes Glacier in 2014 we completed 162 measurements of snowpack depth using probing and crevasse stratigraphy, mainly probing on this relatively crevasse free glacier. We mapped the extent of snowcover on several occasions, and using the retreat of the snowline and stakes emplaced in the glacier observed the rate of ablation (melting). We also measured runoff from the glacier in a partnership with the Nooksack Indian Tribe, which provided an independent measure of ablation. The final mass balance in 2014 was -1.65 m of water equivalent, the same as a 1.8 meter thick slice of the glacier lost in one year. In 2014 we arrived at Sholes Glacier to find it already had 15% blue ice exposed, on August 7th. This had expanded to 25% by August 12th. This rapidly expanded to 50% by August 23rd, note Landsat comparison below. The snow free area expanded to 60% by the end of August and then close to 80% loss by the end of the summer. Glaciers in this area need 60% snowcover at the end of the melt season to balance their frozen checkbook. This percentage is the accumulation area ratio. This mass balance data is then reported to the World Glacier Monitoring Service, along with about 110 other glaciers around the world. Unfortunately the WGMS record indicates that Global alpine glacier mass balance was negative in 2014 for the 31st consecutive year. The video below explains how we measure mass balance each year with footage from the 2014 field season. Of course a key aspect is hiking to the glacier and camping in a tent each year.
The Sholes Glacier thickness has not been measured, but there is a good relationship between area and thickness, that suggests the glacier would average between 40 and 60 m in thickness. The 15 m of water equivalent lost from 1990-2014 is equal to nearly 17 m of ice thickness, which would be at least 35% of the glaciers volume lost during our period of measurement.
Sholes Glacier on August 7, 2014 and Sept. 15 2014, the glacier had lost 80% of its snowcover at this point an indicator of poor mass balance 2014.
Landsat 8 images of Sholes Glacier in 2014, with red line indicating snow line.
Measuring Accumulation on a glacier using Probing and crevasse stratigraphy.
Base Camp where we have spent more than 100 nights in a tent in the last three decades.
Dzhikiugankez Glacier (Frozen Lake) is a large glacier on the northeast side of Mount Elbrus, the highest mountain in the Caucasus Range. The primary portion of the glacier indicated in the map of the region does not extend to the upper mountain, the adjoining glacier extending to the submit is the Kynchyr Syrt Glacier. The glacier is 5 km long extending from 4000 m to 3200 m. Shahgedanova et al (2014) examined changes in Mount Elbrus glaciers from 1999-2012 and found a 5% area loss in this short period and accelerated retreat from the 1987-2000 period. As examination of Landsat images indicates Dzhikiugankez Glacier has the lowest percent of overall snowcover, as seen in the satellite image from August 2013 with the transient snow line shown in purple. The amount of blue ice is apparent on Dzhikiugankez Glacier (D). The main changes in this glacier are not at the terminus, but along the lateral margins, indicating substantial vertical and lateral thinning. Here we examine Landsat imagery from 1985 to 2013 to identify changes. In each image the red arrow indicates bedrock on the western margin, the yellow arrow bedrock on the eastern margin, Point A an area of glacier ice extending to the upper eastern margin, the purple arrow a medial moraine exposed by retreat and the green arrow the 1985 terminus of the glacier.
Map of northeastern side of Mount Elbrus, summit on left. Dzhikiugankez Glacier (Dzhikaugenkjoz) is outlined in black.
August 2013 Satellite image of Mount Elbrus
Google Earth image 2013
In 1985 the glacier connects beneath the subsidiary rock peak at the red arrow, a tongue of ice extends on the east side of the rock rib at the yellow arrow, Point A. The transient snow line is at 3550 m and less than 30% of the glacier is snowcovered. The medial moraine at the purple arrow is just beyond the glacier terminus. In 1999 the subsidiary peak is still surrounded by ice and the tongue of ice at Point A though smaller is still evident. The snowline is quite high extending to 3750 m, leaving only 10-15% of the glacier snowcovered. In 2001 the main terminus has retreated from the green arrow. A strip of rock extends up to the red arrow. The snowline is at 3500 m, with a month of melting left. In 2013 a wide zone of bare rock extends up to the subsidiary peak at the red arrow. The medial moraine, purple arrow is exposed all the way to its origin near the red arrow. In 2013 the tongue of ice at Point A, is gone. This glacier is retreating faster on its lateral margins as at the terminus, a 20% reduction between red and yellow arrows from 1985 to 2013. The snowline is at 3600 m, with several weeks of the melt season left. The key problem for the Dzhikiugankez Glacier is that there is an insufficient persistent accumulation zone. Pelto (2010) noted that a glacier cannot survive without a persistent and consistent accumulation zone, which Dzhikiugankez Glacier lacks despite being on the flanks of Mount Elbrus. Retreat of this glacier is similar to Azau Glacier, particularly the west slope of this glacier, and Irik Glacier. Unlike these glaciers it cannot survive current climate. The glacier is large and the glacier will not disappear quickly. Shahgedanova et al (2014) note the expansion of bare rock areas adjacent to glaciers on the south side of Mount Elbrus including Azau and Garabashi.
Langfjordjokulen is in the Finnmark region of northern Norway. This is a plateau glacier with a valley glacier extending east toward Langfjordhamm. The Norwegian Water Resources and Energy Directorate has monitored the length change and mass balance of this glacier from 1989-2014. The mean mass balance has been significantly negative averaging -0.7 m/year, with every year being a net loss since 1997. This is no way to sustain a glacier or a business. Retreat of the glacier has averaged 27 m/year from 2000-2014. Here we examine Landsat imagery of the glacier from 1989-2014 to identify key changes.
In 1989 the glacier terminated at the red arrow, two glacier tongues descended from the plateau and merged below the purple arrow indicating the northern arm. A ridge extends some distance into the main plateau separating the catchment areas of the two glacier tongues, marked by the letter A. The glacier is mainly snowcovered in August 1989 and had a negative mass balance of -0.55 m. In 1994 the two glacier tongues are still joined, and snowcover is extensive, retreat is limited since 1989. In 2000 snowpack is quite limited at the time of the image, the two glacier tongues have separated and the main terminus has retreated from the red arrow. In 2014, Norway’s warmest year, snowpack retained is minimal, the glacier mass balance reported by NVE to the World Glacier Monitoring Service was -0.78 m, an improvement over the record low year of 2013, -2.61 m. A new area of bedrock is emerging near Point A, due to glacier thinning in the plateau area which should be the accumulation zone. The two glacier tongues are further separated. The main terminus is at the yellow arrow a retreat of 600-700 m since 1989. This retreat rate is faster than other periods since 1900. The retreat is similar to that of the larger nearby Strupbreen and Koppangsbreen. The cumulative mass loss experienced by Langfjordjokulen is a significant portion of its total volume, 25-35% assuming typical glacier thickness for a glacier with this area. In 2014 NVE reported In Norway terminus fluctuation data from 38 glaciers with ongoing assessment indicate, 33 retreating, and 3 were stable. The average terminus change was -12.5 m
The Freshfield Glacier is a large glacier southeast of the Columbia Icefield in the Canadian Rockies where recent retreat has exposed a new glacier lake. Today the glacier is 9.8 km long beginning at 3070 meters and ending at 2000 m near the shore of the less than 5 year old lake. This glacier during the Little Ice Age stretched 14.3 km, one of the longest in the entire range extending beyond Freshfield Lake, which was a glacier filled basin. By 1964 the glacier had retreated 1900 meters exposing Freshfield Lake. From 1964-1986 the glacier retreated up this lake basin losing another 1200 meters of length. A comparison of a 1964 photograph from Austin Post and as close to the same view as I could get in Google Earth illustrates the 50 years of retreat. The red line halfway up the lake is the 1964 terminus and the red line at the edge of the lake the terminus location in the topographic map from the 1980’s. Here we examine Landsat images from 1986 to 2014 to further illustrate the changes. Clarke et al (2015) published this week indicates that it is likely that 70% of glacier volume in western Canada will be lost by 2100. In their Figure 4, three of the four scenarios show Freshfield Glacier as surviving to 2100. The adjacent Conway Glacier is also retreating leading to new lake formation.
Freshfield Glacier Google Earth view
1964 image of Freshfield Glacier from Austin Post
Google Earth view of Freshfield Glacier, indicating 1964, 1986 and 2014 terminus positions.
In each image the red arrow indicates the 1986 terminus position, the yellow arrow the 2014 terminus, pink arrow terminus of the eastern portion of the glacier in 2014, and blue dots the snow line on the date of the images. In 1986 the glacier still reaches the western end of Freshfield Lake, the snowline is at 2600 m and the eastern terminus reaches a bedrock step beyond the pink arrow. By 1994 the glacier had retreated to the southwest shore of the now fully formed Freshfield Lake, the snowline was between 2600 and 2700 meters. By 1998 has retreated several hundred meters from the shore of Freshfield Lake into a new basin terminating 600 m from the 1986 terminus location. The snowline is again near 2600 m. The eastern terminus has retreated from the bedrock step.
By 2009 the terminus has retreated from the basin where it terminated in 1998 exposing a new lake that is 300 m long the terminus no longer reaches. The lower 1000 meters of the glacier has a thin width suggesting the glacier terminus ice thickness is also thin. A Google Earth image from 2005 indicates two basins, circular depressions above the terminus that indicate the collapsing and stagnant nature of the lower portion of the glacier. The narrowness of the terminus reach is also evident. By 2013 the glacier has further retreated from the new lake and now ends near the base of the bedrock step. The eastern terminus has retreated to the pink arrow. The snowline in this Sept. 22, 2013 image is at 2700 m and is close to the end of the melt season position, the equilibrium line altitude. In 2014 the terminus has retreated 1700 m from the 1986 position and 2900 m from 1964. This is a rate of approximately 60 m year over a span of 50 years. The glacier remains nearly 50% snowcovered both in 2013 and 2014, indicating a persistent and consistent accumulation zone. The glacier terminus is nearing a bedrock step, with active crevassing on this step. This suggests that the retreat rate should slow in the short term. This glacier remains large and is not in danger of disappearing with present climate. Its behavior mirrors that of the Apex Glacier and Columbia Glacier but is less dramatic in terms of area loss than or the disappearing Helm Glacier. Glaciers in Alberta as a whole are losing a much greater percentage of their area than Freshfield Glacier as reported by Bolch et al (2010).
1986 Landsat image
For the last 31 years the first week of August has found me on the Columbia Glacier in the North Cascades of Washington. Annual pictures of the changing conditions from 1984 to 2014 are illustrated in the time lapse video below. This is the lowest elevation large glacier in the North Cascades. Columbia Glacier occupies a deep cirque above Blanca Lake and ranging in altitude from 1400 meters to 1700 meters. Kyes, Monte Cristo and Columbia Peak surround the glacier with summits 700 meters above the glacier. The glacier is the beneficiary of heavy orographic lifting over the surrounding peaks, and heavy avalanching off the same peaks. This winter has been the lowest year for snowpack in the North Cascades in the 32 years we have worked here. Below is a comparison from August 1, 2011 with Blanca Lake below the glacier still frozen and a beautiful scene on April 4, 2015 with the lake not frozen taken by Karen K. Wang. The winter in the region was unusually warm, but not as dry as in California; however, in the snowmelt and glacier fed river basins summer runoff will be low this year.
Blanca Lake Aug. 1, 2011 on left, and April 4, 2015 on right (Karen K. Wang, www.karenkwang.com)
Over the last 31 years the annual mass balance measurements indicate the glacier has lost 14 meters of thickness. Given the average thickness of the glacier of close to 75 meters in 1984 this represents a 20% loss in glacier volume. During the same period the glacier has retreated 135 meters, 8% of its length. Most of the loss of volume of this glacier has been through thinning not retreat. To survive a glacier must have a persistent and consistent accumulation zone (Pelto, 2010). On Columbia Glacier in 1998, 2001, 2003, 2004, 2005, 2009 and 2013 limited snowpack was retained, resulting in thinning even on upper part of the glacier. This thinning of the upper glacier indicates the lack of a persistent accumulation zone such as in 2005, note the exposed annual ice and firn layers green arrows, this indicates the lack of retained accumulation in recent years. This indicates the glacier is in disequilibrium and cannot survive. Mapping of the glacier from the terminus to the head indicates a similar thinning along the entire length of the glacier. The overall mass balance loss parallels that of the globe and other North Cascade glaciers in the last three decades.
2005 Accumulation zone of Columbia Glacier
On left cumulative mass balance of Columbia Glacier compared to the WGMS global record and other North Cascade glaciers. On right change in surface elevation along the glacier from terminus to head indicating a 14-15 m thinning on average.
A comparison of images from 1986, 2007 and 2013 photograph provide a view of glacier change at the terminus. The blue arrows indicate moraines that the glacier was in contact with in 1986, and now are 100 meters from the glacier. The green arrow indicates the glacier active ice margin in 1986 and again that same location in 2007 now well off the glacier. The red arrow indicates the same location in terms of GPS measurements, this had been in the midst of the glacier near the top of the first main slope in 1986. In 2007 this location is at the edge of the glacier in a swale. The changes are more pronounced in 2013 as the terminus slope continues to decrease. The low snowpack in 2015 on the glacier in March, 2-3 m versus 6-8 m, will lead to considerable changes in the terminus this summer, that we will assess.
1986 Terminus Columbia Glacier
2007 Terminus Columbia Glacier
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2013 Terminus Columbia Glacier
Jill Pelto painted the glacier as it was in 2009 (top) and then what the area would like without the glacier in the future, at least 50 years in the future (middle), and Jill at the sketching location (bottom), turned 180 degrees to view Blanca Lake. The lake is colored by the glacier flour from Columbia Glacier to the gorgeous shade of jade.
Clearly the area will still be beautiful and we will gain two new alpine lakes with the loss of the glacier. After making over 200 measurements in 2010 we completed a mass balance map of the glacier as we do each year. This summer we will be back again for the 32nd annual checkup. There will be likely be record low snowpack, comparable to 2005 the worst year from 1984-2014.
This is an index of posts on the response of specific Greenland glaciers to climate change. In the 1980’s when I first worked on Jakobshavn Isbrae, Greenland there was not much research occurring on the glaciers. Today in response to the dynamic changes discussed below and glacier by glacier in the index links, Greenland is the focus of numerous extensive, ongoing and important research projects. In 2015 scientists are gearing up for the main field season to better identify and understand the current and future response of this critical ice sheet. At the time of each post I reference the specific research relevant, the posts are from 2009-2014. In the intervening period new research has made some further advances, and I will endeavor to update each post to reflect this. The posts illustrate the significant response of Greenland Glaciers to climate change regardless of what type of glacier they are. The Polar Portal has developed an online viewer of change on selected glaciers. Each year the Arctic Report Card updates annual observations of Greenland Ice Sheet Change. The posts have benefitted from the insights and observations of Espen Olsen. Any questions about a glacier or suggestions on a glacier to look at let me know.
Base Map above right indicates the glacier types 1-4 distribution and key glacier locations with specific posts below. P=Petermann, R=Ryder, S=Steensby, H=Humboldt, Z=Zacharaiae, D=De Reste Bugt, T=Thyrm, N=Narssap Sermia, J=Jakobsan, E=Epiq Sermia, U=Umiamako, K=Kong Oscar.
Variations in Greenland Ice Sheet outlet glacier behavior
The Greenland Ice Sheet has an area of 2.17 million square kilometers (1.28 million square miles) and spans 18 degrees of latitude from north to south. It is not surprising that over this vast area that the geology and climate vary substantially and that this leads to variations in behavior of Greenland glaciers. Our tendency is to lump the Greenland Ice Sheet into one category impacted similarly by each of the dynamic forces that impact flow. This is akin to saying banks, credit unions and savings and loan institutions are impacted similarly by all the economic forces. In the case of a recession there is a shared signal, just as with global warming there is a shared signal among Greenland glaciers. This is a simplification that does not work. In this article we divide the glaciers into four main categories to illustrate the different properties and sensitiveness of each. This is an updated version of an article Dan Bailey and I wrote first for Skeptical Science, updated here with links above to the individual glaciers that emphasize the specific changes and with new references. In recent years the most striking aspect of Greenland Glaciers is that the signal of change is so strong and on so many of the different glaciers. The specific response is different, which if we try to lump the glaciers into one category, makes the data look noisy. Instead if we look at the response of glaciers with similar dynamics than the signal of response is strong indeed. Csatho et al (2014) note the variation in ice thickness across the ice sheet for the 1993-2012 period and that 48% of the thinning is driven by ice dynamics. The net loss is an equivalent contribution of 0.67 mm/year to sea level rise.
Greenland glaciers fall into at least 4 common types, each with its own unique sensitivity to sea surface temperature, surface melting, meltwater lubrication, calving changes, etc.
Type 1: Northern, with Large Floating Termini
Northern glaciers with large floating termini (Petermann, Ryder, Steensby, Zachariae, Academy, etc). Each of these is a marine terminating outlet glacier that has an extensive floating ice shelf. The large ice shelves can exist in part due to the lower surface melt rates and the lower flow rates of the glacier. Petermann Glacier is the fastest with a flow speed of 1000 m/year at the grounding line. This is much less than the average outlet glacier speed along the west coast. The large floating ice shelves are susceptible to bottom melting but, except for Petermann Glacier, we have no observations of the process or that more warm water is penetrating under these ice shelves. Rignot and Steffen (2008) found that at Petermann Glacier 80% of the ice loss into the ocean was from basal melting of the floating tongue. If the ice shelves are removed, the feeding glacier is less buttressed and will accelerate for a period and draw down its surface profile. The recent ice area lost by Petermann, Steensby, Academy and Zachariae Ice Stream indicate these glaciers are being impacted by the increased melting at the surface and likely the base of the ice shelf for Petermann Glacier at least.
Examination of how far the high velocities extend inland in Figure 2 and 3 indicates that it is only Zachariae and Petermann that tap far into the ice sheet. This northern area has low accumulation rates, and a shorter less intense melt season. The early onset of melting and lack of accumulation in 2010 led to an early exposure of the ablation zone on these glaciers. This is their sensitivity Achilles Heel: relatively little increases in melt can expand the ablation zone appreciably given the low surface slopes and low accumulation rates. Based on the velocity map, it is the Zachariae that is likely the only of this group that would be comparable to a bank that is too big to fail as its increased velocity band extends well into the ice sheet (Joughin et al, 2010).
Figure 1. Velocity of Petermann and Humboldt Glacier, the latter does not have a deep bedrock trough extending to the heart of the GIS.
Fig 2. Ice flow speed for Zachariae Glacier (Joughin et al, 2010)
Type 2: Inland-terminating
Glaciers with inland termini lacking any calving (Sukkertoppen, Frederickshaab, Russell, etc). Between the fast flowing marine terminating outlet glaciers, the ice sheet particularly in the southwest quadrant has numerous glaciers that terminate on land or in small lakes. The velocity of these glaciers reaches a maximum of 1-2 meters/day. Each terminates on land because total ablation over the glacier equals total accumulation at the terminus. These glaciers are more like a typical alpine glacier and are susceptible to the forces that tend to cause alpine glaciers to experience peak flow during spring and early summer. Those forces are the delivery of meltwater to the base of the glacier, when a basal conduit system is poorly developed. This leads to high basal water pressure, which enhances sliding. As the conduit system develops the basal water pressure declines as does sliding, even with more water. In the long run it is not clear that more melt will lead to sustained higher velocities as a more efficient drainage system leads to lower basal water pressures. Sundal et al, (2011), best illustrated this.
Fig 3. An example of a two-dimensional ice-velocity map of the study area in southwest Greenland Inland terminating glaciers velocities (Sundal et al, 2011).
This is what has been recently reported to be the case by Sundal et al (2011). The meltwater lubrication mechanism is real, but as observed is limited both in time and area impacted. It is likely that, as on alpine glaciers, the seasonal speedup is offset by a greater slowdown late in the melt season. Most observed acceleration due to high meltwater input has been on the order of several weeks, leading to a 10-20% flow increase for that period. The role of supraglacial lakes in this has been a point of emphasis; Luthje et al, (2006) noted that the area covered by supraglacial lakes was independent of the summer melt rate, but controlled by topography. This led Luthje et al (2006) to conclude that the area covered by supraglacial lakes will remain constant even in a warmer climate. This suggests that the enhancement of flow by the drainage of such lakes would be limited.
The land terminating glaciers such as Sukkertoppen, Russell and Mittivakkat are retreating significantly in response to global warming. This is an indication of negative mass balance. The latter glacier in southeast Greenland has retreated 1200 meters since 1931 (Mernild et al, 2011). The Mernild study identified this slow rate compared to the outlet glaciers and, based on mass balance observations, that the current surface mass balance can only support a glacier at most one-third its current size. This indicates the slow but inexorable sensitivity of the non-calving glacier to surface mass balance change. Moon and Joughin (2008) observed that the retreat of the land terminating glaciers was relatively minor from 1992-2007, averaging 5 m/year or less. These glaciers are the equivalent in our banking system to the local banks: there are many and they are sensitive, but the changes in a single one is not important.
Type 3: Marine-terminating
Fast flowing marine terminating outlet glaciers of western and southeast Greenland (Rinks, Umiamako, Helheim, Jakobshavn, Epiq Sermia, etc). These are the glaciers that drain the greatest area of the ice sheet and deliver the greatest volume to the oceans via calving. The flux from many of the larger glaciers is over 10 km3/year (DMI). Each of these glaciers is fast-flowing at the terminus; the fast flow section extends inland into the ice sheet up a sub-glacial trough. The outlet glaciers act like a drain capturing ice from a larger area of the ice sheet than their narrow terminus would suggest.
Figure 4. Umiamako Glacier is typical with the highest velocity near the calving front and the high velocity ice stream extending back into the ice sheet.
Figure 5. Jakobshavn Glacier terminus retreat, the recent retreat has been associated with thinning and faster flow.
Pelto et al (1989), a paper on the equilibrium state of the Jakobshavn Glacier, showed that the terminus had not changed significantly in 30 years; its velocity had also been consistent. Furthermore, it was observed that the velocity was consistent throughout the seasons. This indicated that the glacier velocity was not being impacted by the meltwater pulse each summer.
Bob Thomas (NASA, 2004) and Terry Hughes (University of Maine, 1986) developed the basic mechanism of flow for the glacier that has proven to be true. The outlet glaciers have a balance of forces at the calving front. The fjord walls, the fjord base and the water column impede flow. The slope of the glacier, its upglacier velocity and the height of the calving face strive to increase flow. If the glacier thins than there is less friction at the calving front from the fjord walls and the fjord base, leading to greater flow. The enhanced flow leads to retreat and further thinning, resulting in the thinning and the acceleration spreading inland. In 1990 it was not envisioned that acceleration would occur as soon as it has, yet that was the motivation for the research.
Fig 6. Jakobshavn profile (Thomas et al, 2009)
In 2001 acceleration of Helheim, Jakobshavn and Kangerdlussaq Glacier caught the attention of the world. By 2007, acceleration had been noted at all 34 marine terminating outlet glaciers observed.
The acceleration was not significantly seasonal; Howat et al (2010) noted a 15% seasonal component to the acceleration, it had spread inland and had led to retreat and thinning. This demonstrated that the marine terminating glaciers were largely responding to a change in the balance of forces at the glacier front.
Fig 7. Ice flow velocity as color over SAR amplitude imagery of Jakobshavn Isbræ in a) February 1992 b) October 2000. In addition to color, speed is contoured with thin black lines at 1000 m/yr intervals and with thin white lines at 200, 400, 600, and 800 m/yr. Note how the ice front has calved back several kilometers from 1992 to 2000. Further retreat in subsequent years caused the glaciers speed to increase to 12,600 m/yr near the front. (Ian Joughlin, Big Ice)
The recent increases in outlet glacier discharge have always been coincident with partially floating ice 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. This is why understanding the basal slope changes inland of the calving fronts is crucial. Moon and Joughin (2008) observed the terminus change of 203 glaciers from 1992-2007 and noted a synchronous ice sheet wide retreat of tidewater outlet glaciers. The thinning could be due to increased surface melt, basal melt or most likely a combination of the two. Certainly the supraglacial lake drainages are not the key as the widespread acceleration in the southeast and southwest Greenland, yet the southeast has less than 10% of the lakes of the southwest , as documented by Selmes et al (2013) in a paper submitted to the Cryosphere.
Moon and Joughin (2008) reported for the 2000-2006 period:In the southeast quadrant 35 glaciers retreated an average of 174 m/year. In the eastern quadrant 21 glacier retreated an average of 106 m/year. In the northwest 64 glaciers retreated an average of 118 m/year. Each quadrant’s retreat increased markedly after 2000. In east central Greenland Walsh et al (2012) noted the retreat of all 37 outlet glaciers examined. Bjork et al (2012) note the terminus change in 134 east Greenland glaciers, idenitifying the last decade as the most rapid for marine terminating glaciers but not land terminating glaciers. The largest of this group are comparable to the banks that are too big for our banking system to allow them to fail: they drain a substantial portion of the entire ice sheet and reach so far into the ice sheet that their behavior can impact that of other adjacent glaciers.
Type 4: Marine-terminating in Shallow Water
Marine terminating glaciers outlet glaciers in shallower water (Humboldt, Cornell, Steenstrup etc). These glaciers do have calving termini, but lack the large fast flowing feeder tongues extending into the glacier. This is because there is not a topographic low under the ice sheet that funnels the flow. Humboldt Glacier is the widest front of any Greenland Glacier, wider even than Petermann Glacier. However, the velocity on average is low at 100 m/year and the base of the glacier is quite high. This makes it difficult for a large calving retreat of the glacier to occur and extend inland. Humboldt Glacier is retreating but as the velocity profile indicates the glacier, despite its size, does not tap dynamically into the center of the ice sheet. These glaciers are substantial, but their failure (though significant for sea level) would not destabilize the ice sheet as a whole. Naarsap Sermia would be another example in southwest Greenland. Dodge and Storm Glacier an example in northwest Greenland.
The amazing aspect of Greenland glaciers is that (despite the specific variation in type, location specific fjord configuration, etc) their response has been as uniform and synchronous to global warming as has been observed. If this warming of the world persists long enough, the ice “banks” of Greenland will begin to fail. Those with the greatest reserves on their asset sheets and the fastest turnover, and thus having the greatest potential contributions to sea level rise over time, are: In the north, Zachariae (and to a lesser extent, Petermann). The fast flowing marine terminating outlet glaciers of western and southeast Greenland (Rinks, Umiamako, Helheim, Jakobshavn, Epiq Sermia and Kangerdlussaq).
The surface mass balance of the glacier is the difference of accumulating snow on the ice sheet (its income) and snow and ice losses from melting and calving (its expenditures). The volume of the ice sheet is its asset. On an ice sheet, the main factor driving flow is simply the mass balance input in the accumulation zone. The higher the accumulation rate the faster the movement; the accumulated snow is inexorably moved downslope towards the ocean and the margin of the ice sheet. Observation of a precipitation map (focused not on the outer margin, but on the accumulation zone of the ice sheet) indicates that highest accumulation rates, over 40 cm per year, extend along the western side of the ice sheet to the southeast quadrant of the ice sheet. The southeast quadrant also has many fewer surface lakes than the southwest quadrant.
Figure 9. Mass balance in Greenland from Van Den Broecke et al, (2009)D denotes change in ice discharge while SMB denotes the net surface mass balance (accumulation minus ablation).)
Fig 10. Distribution of precipitation in Greenland (in grams per square centimeter per year). Contours dashed where inferred. Ice-free areas are shown in dark gray. (USGS, Satellite Image Atlas of Greenland)
The overall topography of the ice sheet is controlled both by the basal and peripheral geology and the mass balance distribution of the ice sheet. The higher rates of mass accumulation inland and the greater melting nearer the margin yield a steeper profile for the ice sheet.
Figure 11 shows that the contours have the closest spacing along the west margin and in the southeast, just as the high accumulation rates in those areas would suggest. Thus the combination of the surface slope and the accumulation rate drive faster flow in these regions.
Climate change has led to an observed increase in surface melting, surface accumulation, increased discharge and overall mass balance losses. The very mechanism that establishes the basics of behavior of the GIS mass balance are changing (Zwally et al, 2011). This is leading to most Greenland glaciers retreating, most outlet glaciers accelerating, an increase in the number and elevation of Greenland lake, expanding melt extent on the ice sheet. The 2012 seasons extraordinary ice melt extent is illustrated by the video below of Marco Tedesco’s melt extent data set. .
Leroux Bay is on the west coast of the Antarctic Peninsula in Graham Land. Numerous glacier drain from the Antarctic Peninsula into the ocean along this coast, and as they retreat the coastline is changing. Air temperatures rose by 2.5°C in the northern Antarctic Peninsula from 1950 to 2000, which has led to recession of 87% glaciers and ice shelves on the Peninsula in the last two decades (Davies et al.,2012). Most spectacularly has been the collapse of Jones, Larsen A, Larsen B, Prince Gustav and Wordie Ice Shelves since 1995 (Cook and Vaughan, 2010). This has opened up our ability to examine sediments that had accumulated beneath the floating ice shelves. The LARISSSA Project has been pursuing this option and utilized the Korean icebreaker ARAON to explore and map the bathymetry of Leroux Bay. Last week Antarctica recorded its highest temperature at the Argentine Base Esperanza on March 24th, 2015 located near the northern tip of the Antarctic Peninsula reported a temperature of 17.5°C (63.5°F). Here we examine the changes from 1990 to 2015 of glacier on the north side of Leroux Bay.
Google Earth image indicating glacier flow directions, blue arrows, island yellow arrow and glacier terminus red arrow.
In 1990 and 1991 the Leroux Bay Glacier extended to the yellow arrow, which is an island connected by the glacier to the mainland and acts as a stabilizing point for the glacier. The ice front is marked with yellow dots in both cases. The terminus region of the glacier is floating, making this a small ice shelf, fed by three tributaries, one from the north, one from the east and one from the northeast. By 2001 the glacier front has retreated to the red arrow, losing most of the floating area, and the northern tributary now has an independent calving front. The red arrow also points to the tip of a peninsula, another stabilizing point, the ice front is marked by the red dots for 2001 and 2015. The yellow arrow indicates the new island that is detached from the mainland. The two images from January 2015 and Late February 2015 indicate limited retreat an the north and south sides of the terminus, but retreat in the glacier center has led to a concave shaped calving front. Retreat from 1990 to 2015 averages 2.1 kilometers. The USGS map (Blue Line) indicates the terminus in the 1960’s was 3 km beyond the 1990 terminus location. The calving front remains active with extensive crevassing. It is not clear simply from Landsat imagery if any of the glacier is afloat, if so it would likely be the southern half of the eastern tributary, There is limited melting in this region, so volume loss can occur via basal melt via ocean water or calving. Even in a warm summer there is little visible evidence of surface melting in 2015. The widespread loss of mass from ice shelves in Antarctica is mainly via basal melting (Paolo et al, 2015). An examination of the coast in the region illustrates numerous other examples where glacier retreat has led to separation of islands, such as with the loss of the Jones Ice Shelf.
Jill Pelto, my daughter returning from fieldwork with UMaine in the Falkland Island took a picture last week out the plane window of Leones Glacier of the northern Patagonia Icefield. The picture illustrated two changes worth further examination, and the fact that if you have a glacier picture that you would like more information on let me know. The picture indicates outlet glaciers of the Northern Patagonia icefield fed by the snowcovered expanse. Also evident is a large landslide that is both fresh and that I knew had not been there before, orange arrow,and it showed a new lake had formed due to retreat of the glacier north of Leones Glacier, red arrow, hereafter designated North Leones Glacier. The landslide extends 2 km across the glacier and is 3 km from the terminus. Here we use 1985 to 2014 Landsat imagery to identify changes in North Leones Glacier and the landslide appearance.
Jill Pelto took this picture on March 13th, 2015
In 1985 there are medial moraines on the glacier surface, but no large landslide deposit. The Northern Leones Glacier terminates on land, red arrow. A distributary terminus almost connects with another glacier to the north at the yellow arrow. In 1987 there is little evident change from 1985. By 2002 a small lake is beginning to form at the terminus of Northern Leones Glacier. By Feb. 2014 a substantial lake has formed at the end of the North Leones Glacier. There is considerable separation between the distributary terminus at the yellow arrow and the next glacier. There is no landslide deposit either. Google Earth imagery indicates the lack of a landslide deposit as well. A closeup of the terminus of North Leones Glacier in 2013, with Google Earth imagery, indicates ogives (blue arrows), which are annually formed due to seasonal velocity changes through an icefall. In January 2015 the landslide deposit is evident, extending about 2 km across Leones Glacier and 3 km from the terminus. The North Leones Glacier has retreated 700 meters from 1985-2015. The retreat of the distributary terminus indicates thinning upglacier of the icefall on North Leones Glacier. The landslide adds mass to Leones Glacier, which will lead to a velocity increase. The debris is thick enough to reduce melting in this portion of the ablation zone. The velocity of this glacier is indicated by (Mouginot and Rignot, 2015) as 200-400 meters per year, indicating that for the next decade at least this landslide will impact the lower Leones Glacier. (Willis et al, 2012) identify thinning of the Leones Glacier area around 1 m per year, which will be reduced on the landslide arm of the glacier.
(Davies and Glasser, 2012), indicate that this region experienced increased area loss from 1986-2011. Lago Leones feeds the Leones River which is also fed by the retreating General Lago Carerra Glacier.
Gilkey Glacier drains the west side of the Juneau Icefield and has experienced widespread significant changes since I first worked on the glacier in 1981. Here we examine the changes from the August 17, 1984 Landsat 5 image to the August 21, 2014 image from newly launched Landsat 8. Landsat 5 was launched in 1984, Landsat 8 launched in 2013. The Landsat images have become a key resource in the examination of the mass balance of these glaciers (Pelto, 2011). The August 17th 1984 image is the oldest Landsat image that I consider of top quality. I was on the Llewellyn Glacier with the Juneau Icefield Research Program (JIRP) on the east side of the icefield the day this image was taken. JIRP was directed by Maynard Miller at that time and by Jeff Kavanauagh now. The Gilkey Glacier is fed by the famous Vaughan Lewis Icefall at the top of which JIRP has its Camp 18 and has monitored this area for 60 years. Here I examine changes both in images and text below. The same analysis in a more depth is contained in the screen capture video of the same images. Choose the format you prefer and let me know which works for you.
There are seven locations noted in the 1984 and 2014 image that are the focus of more discussion in a set of three more focused images
.
1984 Landsat Image
2014 Landsat image
Arrow #1 indicates the Gilkey Glacier terminus area. Gilkey Glacier had begun to retreat into a proglacial lake by 1984, the lake was still just 1 km long. A short distance above the terminus the Gilkey was joined by the sizable tributaries of the Thiel and Battle Glacier. By 2014 the main glacier terminus has retreated 3200 m, the lake is now 4 km long. A lake that did not exist in USGS maps from 1948. Thiel and Battle Glacier have separated from the Gilkey Glacier and from each other. Thiel Glacier retreated 2600 m from its junction with Gilkey Glacier from 1984-2014 and Battle Glacier 1400 m from its junction with Thiel Glacier and 3500 m from the Gilkey Glacier. Melkonian et al (2013) note the fastest thinning in the Gilkey Glacier system from to is near the terminus and in the lower several kilometers of Thiel Glacier.
Above: 1984-2014 Comparison of Gilkey Glacier terminus area with Landsat imagery
Arrow #3 and #4 indicates valleys which tongues of the Gilkey Glacier flow into. In 1984 at #3 the glacier extended 1.6 km upvalley ending where the valley split. The portion of the Gilkey flowing into the valley had a medial moraine in its center. At arrow #4 the glacier extended 1.5 km up Avalanche Canyon. In 2014 at #3 the glacier tongue ends 1.2 km from the valley split, and the medial moraine does not enter the valley. At #4 the glacier has retreated 1.3 km, leaving this valley nearly devoid of a glacier.
Above: Comparison of the Avalanche Canyon area 1984-2014.
Further upglacier arrow #5 indicates a side glacier that in 1984 featured an unending system of glacier flowing down the steep mountain sides into the valley bottom. By 2014 two rock ribs extend along most of the east and west valley walls separating the glaciers on mountain side from the main valley glacier, which has as a result been reduced in width and velocity. At arrow #6 a tributary glacier is seen merging with Gilkey Glacier in 1984. By 2014 this tributary no longer reaches the Gilkey Glacier, ending 300 m up the valley wall. At arrow #7 the Little Vaughan Lewis Icefall in 1984 is seen merging with the Gilkey Glacier across a 300 m wide front. This I can attest from seeing the glacier that summer to be an accurate observation. By 2014 at arrow #7 the Little Vaughan Lewis Icefall no longer feeds ice directly to the Gilkey Glacier. There is still avalanching but not a direct flow connection. JIRP has Camp 19 in this area, a spectacular area of ongoing research by JIRP. The main Vaughan Glacier Icefall is still impressive, just south of the rib beyond arrow #7. Measurements of snowpack are made annually by JIRP above the icefall, and indicate a mean snow depth exceeding 3 m in early August, note image below of measuring annual snow layers in a crevasse at head of the icefall. Pelto et al (2013) summarize the results of this ongoing research that Chris McNeil (USGS) is working to enhance with newer technology. The terminus change of all Juneau Icefield glaciers from 1984-2013 has been summarized in a previous post. The 2015 season will be of interest, since the area had a remarkably warm yet wet winter. This will lead to high ablation at lower elevations, likely a higher snowline than usual, but above the Vaughan Lewis Icefall will those warm wet events dumped snow? The 2014 winters season was warm and the snowline seen in the 2014 satellite imagery was at 1500 m, yet snowpack at 1760 m on the Vaughan Lewis Glacier was 3.3 m deep in late July. This has been the case in the past with warm wet winters featuring heavy snow above 1600 meters on the icefield. JIRP will be in the field answering this question in 2015.
Above: Comparison 1984-2014 of the Vaughan Lewis Glacier area
We often are more concerned with what is happening at the terminus of a glacier; however, often key changes are happening up glacier some distance. This is the case with the following example. The Northern Patagonia Icefield (Hielo Patagónico Norte, HPN) is one of the two main icefields in Patagonia. The remoteness of the region is evidenced by the number of significant lakes and glaciers that remain unnamed. This remoteness has led to several valuable detailed recent studies utilizing satellite imagery on glacier extent (Davies and Glasser, 2012), glacier thickness change (Willis et al, 2012) and glacier velocity (Mouginot and Rignot, 2015) Here we focus on a downwasting tributary to an unnamed glacier listed as HPN4 Glacier in the aforementioned studies. Davies and Glasser, (2012) identify this region of the icefield as retreating faster from 2001-2011 than during any measured period since 1870. Willis et al, (2012) in their Figure 2, seen below, identify this an area of pronounced thinning, approximately 5 m/year from 2000 to 2011. Why such rapid thinning in an area without calving? Mouginot and Rignot, (2015) indicate that this area is not an area of rapid flow, and given the thinning it should be an area of diminishing flow. Here we examine changes from 1987 to 2014 using Landsat imagery.
Digital Globe image of southern section of Northern Patagonia Icefield, with black arrow indicating downwasting tributary from the east flowing into HPN4 Glacier.
Figure 2 from Willis et al (2012) indicating thinning of NPI glaciers from 2000-2011, the blue arrow indicates the downwasting tributary of interest flowing into HPN4 Glacier from the east.
Ice Flow direction for HPN4 Glacier and the downwasting tributary (DT). The flow diagram above indicates the converging flow of the downwasting tributary and HPN4, that meet at the medial moraine.
In 1987 there are five contributing glacier tongues to the downwasting tributary, each indicated with a red arrow. It is like a bathtub being filled with five taps at once. The yellow arrow indicates a medial moraine at the mouth of the valley, signalling the lack of current contribution of the downwasting tributary to HPN4 Glacier. By 2004 only three of the contributing glacier tongues still merged with the downwasting tributary, and two of these are much more tentative. The medial moraine has shifted east indicating that the main HPN4 Glacier is now flowing into the valley instead of the downwasting tributary being a contributing tributary to HPN4. By 2014 there is only one contributing glacier tongue to the downwasting tributary, only one tap for this draining bathtub, the other four contributing tongues have retreated from contact with the downwasting tributary. The medial moraine has spread eastward and some fringing proglacial/subglacial lakes are evident. In 2015 the only change is that the rifting near the medial moraine is more pronounced. A closeup 2013 Digital Globe image indicates both fringing ponds-blue arrows, rifts caused by varying flotation-green arrows and expanding supraglacial ponds, red arrows. The rifts are a sign of instability and typically lead to break up of this portion of the terminus. The downwasting tributary continues to demise faster than HPN4 Glacier, which crosses the valley mouth, hence it is likely that a glacier dammed lake will form and that HPN4 Glacier will continue to flow further east up this valley, which could offset some of the downwasting and lake development. In either case this redirected flow of HPN4 into a high ablation valley, will help encourage a faster retreat of the main terminus. How large the lakes gets and how much of the time it is filled are difficult to speculate upon. Analogs for this type of lake are seen at. Allemania Glacier (Lago Martinic) and Baird Glacier (Witches Cauldron) . Schaefer et al (2013) discuss the HPN4 Glacier because the main terminus has changed little given its modelled mass balance, and the modelled mass balance to the east appears too negative, which they suggest indicates wind redistribution from the HPN4 to the Pared Sud Glacier just east. That is a challenge to sort out without some ground truth.
1987 Landsat image
2004 Landsat image
2014 Landsat image-not the fringing blue indicating trapped sub-glacial/proglacial lake.
Clearly the area will still be beautiful and we will gain two new alpine lakes with the loss of the glacier. After making over 200 measurements in 2010 we completed a mass balance map of the glacier as we do each year. This summer we will be back again for the 32nd annual checkup. There will be likely be record low snowpack, comparable to 2005 the worst year from 1984-2014.
From a Glaciers Perspective 