New Zealand Glacier Retreat will Impact Hydropower

On January 6, 2017May 1, 2024 By mspeltoIn New Zealand glacier3 Comments

Map of the Waitaki Hydropower system, from Meridian and images of the system taken by Jill Pelto January 2017.

Hooker Glacier, Mueller, Murchison and Tasman Glacier drain into Lake Pukaki, where water level has been raised 9 m for hydropower purposes. Classen Glacier, Grey Glacier and Godley Glacier drain into Lake Tekapo. Lake Tekapo and Lake Pukaki are both utilized for hydropower. Water from Lake Tekapo is sent through a canal to Lake Pukaki. Water from Lake Pukaki is sent through a canal into the Lake Ohau watershed and then through six hydropower plants of the Waitaki hydro scheme: Ohau A, B and C. Benmore, Aviemore and Waitaki with a combined output of 1340 MW. Meridian owns and operates all six hydro stations located from Lake Pūkaki to Waitaki. Below the Benore Dam is pictured,. Interestingly salmon have been introduced into the Waitaki River system for fishing near its mouth. Benmore Lake itself is an internationally renowned trout fishing spot, providing habitat for both brown trout and rainbow trout. The reduction of glacier area in the region due to retreat will reduce summer runoff into Lake Pukaki and this hydropower system, which will reduce summer flow in the Waitaki River.

Mueller Glacier has had a 1500 m retreat from 1990-2015, which will continue in the future as the lower 2 km section of the glacier is stagnant. Hooker Glacier retreated 1200 m from 1990 to 2015 and the lake expanded to 2300 m, with the retreat enhanced by calving. Tasman Glacier retreated 4.5 km from 1990 to 2015 primarily through calving into the expanding proglacial lake. Murchison Glacier has retreated 2700 m From 1990 to 2015. The rapid retreat will continue as 2010, 2013 and 2015 imagery indicate other proglacial lakes have now developed 3.5 km above the actual terminus. Classen Glacier has retreated 1000 m from 1990 to 2015 leading to expansion of the lake it ends in (Pelto, 2016). Godley Glacier has retreated 1300 m from 1990-2015 with an equal amount of lake expansion (Pelto, 2016). The expansion of debris cover is striking from 1990 to 2015 this indicates reduced flow from the accumulation zone. Grey Glacier has a heavily debris covered terminus that prevents accurate assessment of retreat. Overall these 7 glaciers make up the majority of the volume and area loss of New Zealand glaciers, which has been dominated by 12 large glaciers (Salinger and Willsman, 2008). The changes of 12 different glaciers have been examined in detail and are compile at the New Zealand Glacier Index. The loss of summer glacier runoff from each square kilometer of lower elevation glacier area that has disappeared is at least 50,000 cubic meters per day (Pelto, 2016). Given the 12 square kilometer loss in the terminus zone of just these seven glaciers, you have a 600,000 cubic meter per day loss in runoff that would be heading into the Pukaki-Takapo-Waitaki Hydro system. The retreat is driven by mass losses as indicated by the rising snowline observed by NIWA.

Map of the glaciers feeding Lake Pukaki and Lake Tekapo. M=Mueller, H=Hooker, T=Tasman, Mu=Murchison, Gr=Grey, Go=Godley and C=Classen. From Pelto (2016)

Canals connecting Lake Pukaki and Lake Tekapo

Volta Glacier New Zealand Losing Lower Volta section

On March 14, 2016May 2, 2024 By mspeltoIn New Zealand glacier

Comparison of Volta Glacier in 2001 and 2016. Yellow arrow is the 2016 terminus position and the red arrow the NZ topo map terminus location. Purple arrows indicate upglacier thinning and orange arrows regions of avalanching onto the lower Volta Glacier.

Volta Glacier drains northeast from Mount Aspiring entering the Waiatoto River. This region is 60 km south of the main region of glaciers around Mount Cook. The glacier is divided into two segments the upper Volta flowing west from Tantalus Rock at 2100 m to an icefall extending from 1600 m to 1400 m where the Lower Volta Glacier begins. The Lower Volta is also fed by steep glaciers that avalanche material onto the lower Volta Glacier from the south. In the New Zealand Topo Map the lower Volta flows down an additional icefall to 1050 m. The glacier has been noted as part of the pattern of the larger glaciers undergoing substantial retreat in New Zealand by NIWA (2007). The volume loss of New Zealand glaciers is reported as 36% from 1978 to 2015, from 54 cubic km to 34 cubic km. In 2015 the average snowline was approximately 40 m higher than average leading to mass losses overall (NIWA, 2015)

In 2001 the Lower Volta Glacier still descended through the icefall to the terminus lobe at 1050 m. By 2010 the glacier terminated at the top of this icefall near 1200 m. A 2012 Google Earth image indicates this position. It is also evident that icefall connecting the upper and lower Volta has narrowed and flow has been reduced. The heavily debris covered lower Volta in the 2012 image is clearly wasting away. The 2016 Landsat image indicates continued downwasting of lower Volta Glacier. The glacier has retreated 1600 m from the map position. Thinning of the upper Volta continues, purple arrows including the icefall is much narrower and bedrock areas are expanding in the region above the icefall. The upper Volta continues to retain significant snow covered areas throughout the years while the lower Volta does not. As the lower Volta Glacier continues downwasting rapidly the upper Volta downwasting is much slower. The glacier has experienced significant retreat just like other New Zealand glaciers: Murchison, Mueller and Tasman.

New Zealand Topographic Map indicating flow of upper and lower Volta Glacier, blue arrows. Red arrow is the terminus location for the map and yellow arrow the 2016 terminus location.

Google Earth image in 2012 of the lower Volta Glacier and the icefall connection. The terminus diverges to the yellow arrows left and right.

View across lower Volta Glacier to the southwest, from Mountain Recreation News

Murchison Glacier, New Zealand Rapid Retreat Lake Expands 1990-2015

On January 14, 2016May 2, 2024 By mspeltoIn glacier climate change, Glacier Observations, glaciers salmon, New Zealand glacier1 Comment

Murchison Glacier change revealed in Landsat images from 1990 and 2015. The red arrow indicates 1990 terminus location, the yellow arrow indicates 2015 terminus location and the purple arrow indicates upglacier thinning.

Murchison Glacier is the second largest in New Zealand. The glacier drains south in the next valley east of Tasman Glacier and terminates in a lake that is rapidly developing as the glacier retreats. The lower 6 km section is debris covered, stagnant, relatively flat and will not survive long. There was not a lake in the 1972 map of the region. In 1990 the newly formed lake was limited to the southeast margin of the terminus . From 1990 to 2015 the terminus has retreated 2700 m. A rapid retreat will continue as 2010, 2013 and 2015 imagery indicate other proglacial lakes have now developed 3.5 km above the actual terminus. These lakes are glacier dammed and may not endure but do help increase ablation, and in the image below show a glacier that is too narrow to provide flow to the lower 3.5 km. The demise of the lower section of this glacier will parallel that of Tasman Glacier. The expanding lake will continue to enhance the retreat in part by sub-aqueous calving noted by Robertson et al (2012) on nearby glaciers. The increased retreat has been forecast by the NIWA and Dykes et al (2011). The glacier still has a significant accumulation area above 1650 m to survive at a smaller size. The ongoing retreat is triggered by warming and a rise in the snowline in the New Zealand Alps observed by the NIWA. Notice the changes upglacier indicated at the purple arrows above, where tributary flow has declined, bedrock areas in accumulation zone have expanded and the snowline is higher. Gjermundsen et al (2011) examined the change in glacier area in the central Southern Alps and found a 17% reduction in area mainly from reductions of large valley glaciers such as Murchison Glacier.

Terminus reach of Murchison Glacier in Google Earth images from 2007 and 2013. Note expansion at pink arrow on the terminus lake and the development of proglacial lakes 3.5 km upglacier at blue arrows.

The Feb. 2011 earthquake near Christchurch led to a major calving event of a portion of the rotten stagnant terminus reach of the Tasman Glacier. There was no evident calving event from Murchison Glacier.This has led to increased exposure of bedrock high on the glacier and reduction of tributary inflow noted at purple arrows.

Murchison Glacier drains into Lake Pukaki,a along with Hooker, Mueller and Tasman Glacier, where water level has been raised 9 m for hydropower purposes. Water from Lake Pukaki is sent through a canal into the Lake Ohau watershed and then through six hydropower plants of the Waitaki hydro scheme: Ohau A, B and C. Benmore, Aviemore and Waitaki with a combined output of 1340 MW. Meridian owns and operates all six hydro stations located from Lake Pūkaki to Waitaki. Reductions in glacier area in the watershed will lead to reduced summer runoff into the Lake Pukaki system. Below the Benore Dam is pictured,. Interestingly salmon have been introduced into the Waitaki River system for fishing near its mouth. Benmore Lake itself is an internationally renowned trout fishing spot, providing habitat for both brown trout and rainbow trout.

Google Earth Image with Benmore Dam in foreground and Benmore Lake. This hydropower system is fed by a canal from Lake Pukaki which in turn is fed by Murchison Glacier.

Hooker Glacier Retreat, 1990-2015

On January 11, 2016May 2, 2024 By mspeltoIn glacier climate change, Glacier Observations, New Zealand glacier3 Comments

Glacier change revealed in Landsat images from 1990 and 2015. Mueller Glacier (M) and Hooker Glacier (H). The red arrow indicates 1990 terminus location, the yellow arrow indicates 2015 terminus location and the purple arrow indicates upglacier thinning.

Hooker Glacier parallels the Tasman Glacier one valley to the west draining south from Mount Hicks and Mount Cook. Hooker Glacier is a low gradient which helps reduce its overall velocity and a debris covered ablation zone reducing ablation, both factors increasing response time to climate change (Quincey and Glasser 2009). Hooker Lake which the glacier ends in began to from around 1982 (Kirkbride, 1993). In 1990 the lake was 1100 m long (Figure 11.2). From 1990 to 2015 the lake expanded to 2300 m, with the retreat enhanced by calving. The 1200 m retreat was faster during the earlier part of this period (Robertson et al.,2013).

Map of the region in 1972 indicating the lack of proglacial lakes at the end of Mueller, Hooker and Tasman Glacier.

The lower 3.4 km of the glacier has limited motion. Robertson et al, (2012) suggest the retreat will end after a further retreat of 700-1000 m as calving will decline as the lake depth declines. The peak lake depth is over 130 m, with the terminus moving into shallow water after 2006 leading to declining retreat rates (Robertson et al (2012).Gjermundsen et al (2011) examined the change in glacier area in the central Southern Alps and found a 17% reduction in area mainly from reductions of large valley glaciers such as Hooker Glacier. Based on the nearly stagnant nature of the lower glacier and the diminished ice flow from above indicated by debris cover expansion at the purple arrow, it seems likely the retreat will continue well beyond the end of the lake but at a diminished rate.

Hooker Glacier drains into Lake Pukaki,a along with Murchison, Mueller and Tasman Glacier, where water level has been raised 9 m for hydropower purposes. Water from Lake Pukaki is sent through a canal into the Lake Ohau watershed and then through six hydropower plants of the Waitaki hydro scheme: Ohau A, B and C. Benmore, Aviemore and Waitaki with a combined output of 1340 MW. Meridian owns and operates all six hydro stations located from Lake Pūkaki to Waitaki. Reductions in glacier area in the watershed will lead to reduced summer runoff into the Lake Pukaki system (see image below)

Comparison of Hooker Glacier terminus area in 2006 (red arrow) and 2013 (yellow arrow) in Google Earth. Blue arrow indicates icebergs in 2006.

Hydropower projects below Lake Pukaki

Balfour Glacier, New Zealand Retreat 1990-2015

On November 5, 2015May 2, 2024 By mspeltoIn glacier climate change, Glacier Observations, New Zealand glacier

Balfour Glacier drains west from Mount Tasman in the Southern Alps of New Zealand. The ablation is a low slope, 8 km long debris covered tongue extending from the terminus near 800 m to 1600 m. The glacier is fed by avalanching off of Mount Tasman to the west, the southern flank of the Fox Range to the north and the northern flank of the Balfour Range to the south. Gjermundsen et al (2011) examined the change in glacier area in the central Southern Alps and found a 17% reduction in area mainly from reductions of large valley glaciers such as Balfour Glacier. The volume loss of New Zealand glaciers is reported as 36% from 1978 to 2015, from 54 cubic km to 34 cubic km.

Topographic map of Balfour Glacier area of New Zealand from http://www.topomap.co.nz/ . Blue arrows indicate flow, red arrows at 1990 terminus and yellow arrow at 2015 terminus

In 1990 the glacier ended at 700 m with a snowline at 1600 m. The lower 18 km of the Balfour Glacier is debris covered. Only the upper 8 km has snowcover. In 2015 the terminus has retrated 1250 m, the snowline is at 1800 m, with the lower 20 km debris covered. The terminus reach has continued to appear stagnant from 1990 to 2015. Balfour Glacier has not developed a significant proglacial lake at its terminus, which has limited the retreat compared to Tasman Glacier or Mueller Glacier. Google Earth indicates the retreat of stagnant debris. The main glacier meltwater outlfow issues from the glacier at the yellow arrow in 2012, 600 m above the terminus.

Landsat Analysis of 1990 above and 2015 Below of Balfour Glacier. Red arrow is at 1990 terminus and yellow arrow at 2015 terminus. The purple arrows indicate area of thinning upglacier.

2006 Google Earth image of Balfour Glacier above and 2012 image below. The red arrow is at the terminus location in 2006, the yellow arrow is at the 2012 location where the glacier stream issues from beneath the glacier. The purple arrows

Crevasse Reduction and Retreat of Salisbury Snowfield-Almer Glacier, New Zealand

On January 27, 2015January 27, 2015 By mspeltoIn Glacier Observations1 Comment

Almer Glacier is fed by the Salisbury Snowfield which also has its own terminus, and both are former tributaries to the Franz Josef Glacier. In 2007 the Almer Glacier almost reconnected with Franz Josef Glacier. The glaciers of the southern Alps have some of the highest recorded accumulation rates in their upper sections and highest ablation in the lower reaches. Anderson et al (2006), note accumulation rates exceeding 6 m on Franz Josef Glacier. This combined with the steep slopes lead to higher velocity and extensive crevassing on even smaller alpine glaciers. Purdie et al (2014) examined modern and historic length change for Franz Josef and noted a ~ 3 km loss in length since the 1800s, with the greatest retreat from 1934 and 1983, despite two periods of advance in that 50 year period. The retreat particularly since 1983 has been punctuated by advances 1983–1999 (1420 m) and 2004–2008 (280 m), with the current retreat up to 2014 being the fastest rate of retreat during the period of record. (Purdie et al , 2014). The annual end of summer snowline surveys by NIWA monitors the Salisbury Snowfield, the snowline was 140 m or more above the equilibrium altitude in 4 of the last six years and 20-30 m below the equilibrium line altitude in the other two. The net result is significant mass loss in the last six years driven by exceptional melt, driving the retreat.

Topographic Map of Salisbury Snowfield-Almer Glacier area

Here we examine changes particularly in crevassing as well as retreat of Salisbury Snowfield and Almer Glacier from 2000-2015. In the Google Earth images from 2007 and 2013 the green arrows indicate crevassed areas and the red arrows the terminus of the Almer Glacier above and Salisbury Snowfield below. The decrease in the amount of crevassing is evident at each location. This indicates not just a reduction in velocity, but in glacier thickness that is driving flow. The thinning is evident with the emergence of a bedrock knob at the pink arrow in 2013 that had been covered by crevassed ice in 2007. The red arrow indicates the terminus where the main Almer Glacier is within 75 m of the Franz Josef Glacier. By 2013 the terminus is much dirtier and is 200 m from Franz Josef Glacier. The icefall comparison image from 2007 and 2013 indicates the reduction in width and number of open crevasses, probably in depth too. This is something Jill Pelto (UMaine) has been measuring crevasses in the field on Easton Glacier in the North Cascades over the last few years to see how crevasses are changing as a glacier thins and slows (image below).

In 2014 New Zealand had a warm year and snowlines are high for early summer in January 2015 which will continue the retreat. The Landsat image from January, 2015 suggests further retreat has occurred since 2013, but given the dirty terminus, it is to hard to determine a specific amount. The retreat here follows the pattern of glaciers across the Southern Alps of New Zealand- Lyell Glacier and Tasman Glacier

2007 Google Earth image

2013 Google Earth Image.

2007-2013 icefall closeup

2015 Crevasse Assessment, Jill Pelto, North Cascades

2000 Landsat image

2015 Landsat image

Lyell Glacier retreat and separation, New Zealand

On January 17, 2014January 17, 2014 By mspeltoIn Glacier Observations2 Comments

The Lyell and Ramsay Glaciers are the northernmost substantial valley glaciers in the Southern Alps of New Zealand. Their combined run-off is the chief source of the Rakaia River. The Lyell glacier was first observed by Dr.von Haast in 1862, from Mein’s Knob (M), at the time the glacier was 9 km long and ended close to Mein’s Knob. In 1949 Lyell glacier extended east from Rangiata Col some 7 km, and Lyell Lake (L) had not yet formed. (Gage, 1951). The Lyell Glacier has been the combined flow from the easterly tributary near Rangiata Col (E) and a northern tributary, Heim Plateau (H). Here we examine Google Earth Imagery and Landsat images from 2000-2013 to identify changes in the Lyell-Heim Glacier complex.

In 2000 the Heim Glacier (H) reached onto the Lyell Lake valley floor, yellow arrow. In 2001 this is evident along with the fact that Lyell Lake is a single lake. The terminus of the Lyell Glacier is obscured by thick glacier cover, and does end near Lyell Lake at the time, the end of the blue ice of the E tributary is not indicative of the terminus location. By 2013 Heim Glacier has retreated from the Lyell Valley and no longer is connected to the Lyell Glacier. A second small lake has formed as the terminus of Lyell Glacier has melted and retreated, red arrow. The terminus of Lyell Glacier does remain buried by debris, but it is stagnant and melting away. Both the Lyell Glacier and Heim Glacier have retreated 400 m from 2000-2013. The Lyell Glacier will likely experience a more rapid retreat in the near future as the debris covered tongue melts away. The 2013 austral winter featured record warmth, and the early melt season has also been warm in New Zealand, the impact on this glacier can be assessed in March or April as the melt season ends. The NIWA snowline surveys will document the impact on glaciers across New Zealand. The glaciers of New Zealand lost 15% of thier volume from 1976-2008 (Chinn et al, 2012). The retreat is like that of most all New Zealand glaciers today, Donne Glacier, Gunn Glacier, Tasman and Murchison Glacier

2000 Landsat image

2001 Landsat image

2013 Landsat image

Landsat image 2013

Google Earth image

Google earth image of terminus

Tasman Glacier Retreat Update 2013

On February 14, 2013January 27, 2015 By mspeltoIn Glacier Observations4 Comments

The New Zealand National Institute of Water and Atmospheric Research has been examining the changes in volume and snowline on New Zealand Glaciers since 1977. This survey has concluded for 2011 and 2012 that the snowline has been too high for glacier equilibrium, the glaciers are shrinking. The Tasman Glacier is evidence of this draining from the highest mountains in New Zealand. For Tasman Glacier the retreat has been ongoing, the NIWA has noted a retreat of 180 m per year on average since the 1990’s. Dykes et al (2011) note a maximum depth of 240 m, and an expansion of 0.34 square kilometers per year in area. The proglacial lake at the terminus continues to expand as the glacier retreats upvalley. The lake is deep with most of the lake exceeding 100 metes in depth, and the valley has little gradient, thus the retreat will continue. It has been noted by researchers at Massey University that the lake can expand in this low elevation valley another 9 km, and that at the current rate this will occur over two decades. This post is an update to the Tasman Glacier Retreat post of 2009 updated in 2011. Imagery of Tasman Glacier indicates the future it faces. There was no lake in 1973 and now it is more than 5.5 km long across a width of about 2 km, and 7 km long at its longest point. Here we examine four images, the 1972 topgographic map, 2000, 2012 and 2013 Landsat images and 2006 Google Earth imagery. In each image an orange and a pink arrow indicate the 2013 terminus on the east and west respectively. In the 1972 map there is no lake at the terminus of the Tasman Glacier. In 2000 the Tasman Glacier lake was 2 km long on the west side and 4.5 km along on the east side. By 2006 the lake has expanded 2.5 km on the west side and 5.5 km long in a narrow tongue on the east side. By 2013 the Lake is 5.5 km long from bank to bank. The glacier has experienced two larger calving events in recent years the first triggered by the Christchurch earthquake in February 2011 and the second on January 30, 2012. Such events can occur because the terminus has thinned to the point that the glacier terminus is more buoyant and crevasses and rifts extend through the thinner ice.

2000 Landsat Image

2006 Google Earth Image

2013 Landsat Image

The last image below is a 2012 Landsat image, the blue arrow indicates the extent to which the lake is expected to extend, the snowline in this image is at 2200 m, red arrow. The glaciers retreat is the same pattern as that of Murchison, Mueller and Hooker Glacier. 2012 Landsat Image

Douglas Neve Glacier Retreat, New Zealand

On November 23, 2012November 23, 2012 By mspeltoIn Glacier Observations

The primary portion of the Douglas Glacier was a debris covered valley tongue that is separated from the slopes feeding the terminus reach. The feeder glacier tongues, pink arrows, end on the bedrock slopes above a steep cliff and do not reach the valley glacier below, blue arrows. One section of the glacier, the furthest west portion noted by a pink arrow, the Douglas Neve flows down a steep mountains side. The bedrock slope at the base of the glacier is particularly smooth, which combined with the steep slope,, 40% grade or 22 degree slope, enhances basal sliding. On small alpine glacier the resulting high velocity leads to extensive crevassing. This crevassing can literally penetrate to the base of the glacier near the thin terminus. This leads to portions of the glacier simply separating from the rest of the glacier and avalanching down the slope or melting in place. Here we utilize Landsat images from 2000 and 2012 and Google Earth imagery from 2004 and 2009 to examine the retreat of this glacier. The sequence of images below are in order 2000, 2004, 2009 and 2012. In 2000 the terminus of the glacier terminates at a prominent bedrock fracture at 1640 meters above sea level. In 2004 the terminus still reaches this fracture. The green line in the Google Earth imagery is the 2004 terminus and the burgundy line the 2009 terminus. By 2009 the terminus has retreated 400 meters, and consists of two unsustainable narrow tongues, both less than 100 meterw side. By 2012 the two narrow tongues have been lost, resulting in a 700 m retreat from 2000 to 2012 with the terminus now at 1800 meters. As the retreat of an alpine glacier progresses crevassing typically is reduced as glacier speed declines. Here we see an increase in crevassing from 2004 above to 2009 below in the terminus area, suggesting that the retreat will continue via pieces of the glacier separating from the glacier and avalanching. This process is a much different setting, but similar in practice to ice shelf loss through rifting that reaches the critical point where the rifts lead to icebergs breaking off. At this point the terminus remains unsustainable. This retreat is similar to that of New Zealand glaciers in general as noted by the NIWA and Trevor Chinn, and examined in detail on Murchison Glacier, Mueller Glacier and Gunn Glacier

Mueller Glacier retreat Lake Expansion, New Zealand

On December 20, 2011March 13, 2014 By mspeltoIn Glacier Observations5 Comments

Volume loss in New Zealand glaciers is dominated by 12 large glaciers. The NIWA glacier monitoring program has noted that volume of ice in New Zealand’s Southern Alps has decreased 5.8 cubic kilometres, more than 10% in the past 30 years. More than 90% of this loss is from 12 of the largest glaciers in response to rising temperatures over the 20th century. Three of these glaciers are the Tasman, Mueller and Hooker Glacier. Mueller and Hooker Glacier are one valley west of the Tasman Glacier and end in the same valley ending just 3 km apart. Description of the retreat and the role of glacier lakes in accelerating the reteat of Tasman Glacier is discussed in detail in Dykes et al (2011). If we look back to the 1972 Mount Cook Map no lakes are evident at the terminus of Hooker (H), Mueller (M) or Tasman Glacier(T), pink dots indicate terminus location, top image. In 2011 the Landsat image illustrates that this has become a new lake district, bottom image.. Mueller Glacier drains the eastern side of Mount Sefton, Mount Thompson and Mount Isabel. The lower section of the glacier is debris covered in the valley reach from the terminus at 1000 m to 1250 m. A comparison of the Mueller Glacier in a sequence of three Landsat images below from 2000 (top), 2004 (middle) and 2011 (bottom), indicates that the lake at the end of Hooker Glacier had developed by 2000. The lake at the end of the Mueller Glacier was just forming length of 400 meters. By 2004 the Mueller Glacier Lake had expanded to a length of 700 meters. By 2011 the lake had reached 1400 meters in length. The 1000 meter retreat from 2000-2011 will continue in the future as the lower section is stagnant. . A closer look at the lower Mueller Glacier indicates that the lower 2 km is stagnant as indicated by the formation of supraglacial lakes and considerable surface roughness (green arrow) that does not occur when a glacier is active and moving. The glacier has been fed by three different glaciers flowing off of Mount Sefton. Two of them Tuckett and Huddlesoton (pink arrow) are no longer delivering significant ice to the Mueller, only modest avalanching now spills onto the Mueller Glacier. Only the Frind Glacier (yellow arrow) is contributing to the Mueller Glacier. The result is that the end of truly active ice is at the purple arrow, this will develop into the terminus of the Mueller Glacier. In the 2011 image of the glacier the yellow-burgundy arrow indicates the snowline on the Frind Glacier is at 1900 meters, yielding too small of an accumulation zone to support the valley tongue of the Mueller Glacier. This is similar to the situation on nearby Murchison Glacier. Further the lack of ice connection from Huddleston and Tuckett Glaciers to Mueller is again evident, pink arrow. The lake will continue to expand through minor calving and downwasting. The lake has not been surveyed, but seems to lack the depth at the current terminus of Tasman Lake where calving can be more important.

Gunn Glacier Retreat, lake expansion, New Zealand

On December 8, 2011December 8, 2011 By mspeltoIn Glacier Observations

Gunn Glacier is a small cirque glacier that lies beneath Mount Gunn. A lake has formed recently and is continuing to expand. The 2000 based map of the area published in 2010, does not show a lake, but does at the terminus indicate a small water body surrounded by snow. The New Zealand NIWA has monitored the snowline of New Zealand glaciers over the last 15 years and monitored the volume and area loss of these glaciers including Tasman and Donne Glacier, other like Murchison Glacier are also retreating. On Gunn Glacier the key factor is that four of the last 11 years NIWA has observed that the glacier has lost nearly all of its snowcover indicating a glacier without a persistent accumulation zone (Pelto, 2010). The glacier area has been reduced by 40% from its 1972 mapped area. The 2006 imgery in Google Earth indicates a number of new icebergs adrift in the lake. The lake is now 300 meters across. A view of the cirque indicates a number of bare rock patches on upper sections of the glacier (bottom image), indicating a lack of a consistent accumulation zone. This glacier is thin and without a consistent accumulation it cannot survive (Pelto, 2010). The largest glacier section has an area of 0.2 square kilometers in 2006. The continued expansion of rock areas amidst the glacier and of the lake will lead to the loss of this glacier in the next two decades with a continuation of current climate.

Murchison Glacier Retreat Increasing

On February 22, 2011March 8, 2011 By mspeltoIn Glacier Observations6 Comments

Murchison Glacier drains southeast from the Mount Cook region, one valley east of Tasman Glacier. The end of the glacier terminates in a lake that is rapidly developing as the glacier retreats. This retreat will become rapid as 2010 imagery indicates other proglacial lakes have now developed 3.5 km above the actual terminus. These lakes are at a higher elevation and may not endure but do help increase ablation, and in the image below show a glacier that is too narrow to provide flow to the lower 3.5 km. The increased retreat has been forecast by the NIWAand Dykes et al (2009) This lower section is debris covered, stagnant, relatively flat and will not survive long. The demise of the lower section of this glacier will parallel that of Tasman Glacier. The glacier has retreated 2200 meters from the moraines at the south end of the lake. There was not a lake in the 1972 map of the region. A comparison of 2006 and 2010 imagery indicates the decrease in glaciated area in the lake basin. The bottom image is from NASA after the Feb. 2011 earthquake near Christchurch that led to a major calving event of a portion of the rotten stagnant terminus reach of the Tasman Glacier. There is no evident calving event from Murchison Glacier. The lake on the western margin of the valley, separated from the main lake has since April 2010 expanded notably . The glacier still has a significant accumulation area above 1650 m to survive at a smaller size. The lower debris covered tongue is 6 km long and extends from the terminus at 1050 meters to 1200 meters, a very low gradient to supply healthy flow from the accumulation area. The ongoing retreat is triggered by warming and a rise in the snowline in the New Zealand Alps observed by the NIWA .