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
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
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
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
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.