Changsang Glacier, Sikkim 2 km retreat and Lake Expansion 1989-2021

On January 3, 2022April 21, 2024 By mspeltoIn Himalaya glacier retreat

Changsang Glacier in Landsat images from 1989 and 2021, illustrating a 2.05 km retreat from 1989 terminus position-red arrow to the 2021 terminus position-yellow arrow. Formation of a new lake is also evident. The snowline is marked by purple dots.

Changsang Glacier (Karda Glacier) is a valley glacier just north of Kanchengjunga, Nepal/Sikkim. A comparison of Landsat imagery from 1989 to 2021 identifies the formation of a lake at the end of the glacier.

The Changsang Glacier was reported to be retreating 22 m/year from 1976 to 2005 (Raina, 2009). Shukla et al (2018) inventoried lakes in Sikkim during the 1975-2017 period and found 35 proglacial lakes in contact with a glacier in 2017. The number and area of these lakes had increased 34% and 90% respectively during this period. One of the rapidly expanding lakes is at Changsang Glacier.

In 1989 there is no evidence of a significant lake either on top of the glacier-supraglacial or proglacial, at the end of the glacier. In 2000 there are a several small lakes beginning to develop with a combined area of 0.22 km² (Shukla et al., 2018), the snowline is at 5650-5700 m. In 2002 the supraglacial lakes are noticably more connected, and the snowline is at 5700 m in mid-December . By 2011 the main lake is 1000 meters long and has one debris covered ridge that separates it from a second lake. By 2015 the lake has expanded incorporated the second lake and is now 1600 meters long with an area of 0.70 km² . The snowline is notably high at 6000 m in mid-October . On Christmas Day 2020 the snowline is particularly high at 6100 m, reflecting the warm post-monsoon early winter period observed at Mount Everest last year (Pelto et al , 2021). In December 2021 the proglacial lake at ~5400 m is 0.93 km² and the glacier has retreated 2050 m since 1989. Lake expansion since 2015 has been slower. The lake is impounded by a 400 m wide moraine belt on the low slope valley floor beyond the lake margin, and does not appear to be a significant GLOF risk. The retreat of this glacier is similar to that of Kokthang Glacier and Middle Lhonak Glacier.

Changsang Glacier in Landsat images from 2000 and 2020 illustrating retreat from 1989 terminus position-red arrow to the 2021 terminus position-yellow arrow. Transition from small supraglacial lakes to a single proglacial Lake is evident. The snowline is marked by purple dots, which in late Deember 2020 reached 6100 m.

Changsang Glacier in Landsat images from 2002 and 2015 illustrating retreat from 1989 terminus position-red arrow to the 2021 terminus position-yellow arrow. Coalescing supraglacial lakes into a single proglacial lake is evident. The snowline is marked by purple dots which in October 2015 reached 6000 m.

Kokthang Glacier Retreat, Sikkim Himalaya, India Doubles Lake Size

On June 11, 2018April 27, 2024 By mspeltoIn India glacier retreat

Kokthang Glacier in 1988 and Feb. 2018 Landsat imagery. The red arrow indicates the 1988 terminus and the yellow arrow the upstream end of the lake beyond which the glacier has retreated in 2018. The purple dots indicate the snowline.

Kokthang Glacier drains south from the Kokthang Peak a satellite peak on the south side of the Kanchenjunga Massif, Sikkim in India, the next valley south of East Rathong Glacier. This glacier drains into the Rangit River, which hosts a 60 MW run of river Rangit Hydropower project. Here we examine changes in the glacier from 1988 to 2018. Glaciers draining east from Kanchenjunga have generally experienced substantial retreat and lake expansion (Govindha Raj et al 2013): Lhonak Glacier, Changsang Glacier etc. The exception being Zemu Glacier which has been thinning, but not retreating substantially. NASA Earth Observatory posted an article based on this blog post.

In 1988 the debris covered terminus was in a 800 m long proglacial lake, after the two main tributaries joined. The snowline was at 5500 m. In 2000 the lake has expanded significantly and only the western tributary is actively reaching the lake. The snowline in 2000 is at 5400 m. By 2005 glacier retreat of the stagnant tongue had led to a lake expansion to a length of 1300 m, Google Earth image on left below. The snowline in 2005 is at 5500 m. The eastern tributary no longer descended to the lake. By 2017 the lake had further expanded to a length of 1600 m. The glacier retreat over the 30 year period being greater than the 800 m that represent a doubling of the proglacial lake size. The glacier has now effectively retreated from the lake and only minor expansion will occur with ice cored moraine meltout. The snowline in October 2017 was at 5600 m. The snowline remained high from October to mid-winter as it had in most recent years, with the February 2018 snowline at 5600 m still. This illustrates that ablation albeit, at a slow rate, is occurring from October-mid winter.

The persistent high snowline through much of the year leads to continued thinning and retreat of the lower glacier. The high snowlines have been seen in the Mount Everest area and on Gangotri Glacier. The upper glacier continues to retain snowcover indicating the glacier can survive current climate.

Kokthang Glacier in 2000 and 2017 Landsat imagery. The red arrow indicates the 1988 terminus and the yellow arrow the upstream end of the lake beyond which the glacier has retreated in 2018. The purple dots indicate the snowline.

Google Earth imagery from 2005 and 2014 of Kokthang Glacier.

Gurudongmar Glacier Retreat and Teesta River Hydropower, Sikkim

On May 2, 2017April 29, 2024 By mspeltoIn India glacier retreat

Gurudongmar Glacier draining ton Gurudongmar Lake B in Landsat images from 1996 and 1998 and Sentinel image from 2016.Red arrow is the 1996 terminus and yellow arrow the 2016 terminus.Point M indicates a terminal moraine belt, impounding the lake

Teesta Urja Limited is this month finishing the 1200 MW Teesta Stage III hydro power project on. The project is a run of the river scheme in the North Sikkim district. The dam is at the Chugthang Village just below the confluence of the Lachen River and Lachung River and the power house is 15 km downstream at Singhik. The project utilizes the fall of head in the River course, of about 800 meters between these two villages. This project is a part of overall development of Teesta basin being undertaken by Sikkim Government. The project is run of the river designed to generate 5,214 Million kWh (units) annually in 90 per cent dependable year, as per the information provided. This project adds to the existing hydropower on the Teesta River, such as the 510 MW Teesta V, also highly dependent on glacier runoff. The area of lake “B” in the Gurudongmar Cho Complex has increased nearly 4 times between 1965 and 1989. The significant increase in the areas of lakes “B” and adjacent “C” is a clear indicator of the glacier retreat/melt. Between 1989 and 2010, Gurudongmar Cho “B” has grown by one-sixth of its size in 1989 (Kumar and Prabhu, 2012). An inventory of Sikkim glacier lakes shows the existence of 320 glacial lakes, 85 are new ones in the study area compared to 2003 inventory, due to the ongoing retreat (Govindha Raj et al, 2012).

Like all glaciers in this region Gurudongmar Glacier is a summer accumulation type glacier. This means that the glacier receives most ~80% of its snowfall during the summer monsoon. This is also the period when ablation low on the glacier is highest. Following the summer monsoon which ends in early September there is a transition period with some colder storm events where the snowline drops. Than from November-February is the dry winter monsoon with limited precipitation. Thus, strange compared to most glaciers as winter proceeds often the lower glacier remains snow free. Here we examine 1996 to 2016 Landsat and Sentinel images to identify change. In 1996 the glacier terminates in the lake, just where the lake narrows significantly. In 1998 the terminus remains at the same location, the shading better identifies the calving front. Point M is the wide and stable moraine belt that impounds the lake. This suggests a limited GLOF risk. By 2016 the terminus has retreated 600 m since 1987 through a narrow lake extension. The glacier terminus based on the icefall that almost reaches the terminus, is nearing the upglacier end of the lake. This should lead to a reduction in the retreat rate. The retreat distance is substantial given the length of the glacier is 25% of the 1996 glacier length of 2.4 km. The retreat of this glacier is similar to that of other glaciers in the basin such as Middle Lhonak Glacier, South Lhonak Glacier and Changsang Glacier.

Google Earth image of Gurudongmar Glacier, indicating terminus location. Note icefall almost reaching shore.

Google Earth image from 2004 indicating s, terminus position in 2014 yellow arrow and icefall purple arrow.

Google Earth image from 2014 indicating glacier flow blue arrows, terminus position yellow arrow and icefall purple arrow.

Himalayan Glacier Change Index

On July 13, 2014July 16, 2014 By mspeltoIn Glacier Observations2 Comments

Himalaya Range Glacier Change Below is a list of individual glaciers in the Himalaya that illustrate what is happening glacier by glacier. In addition to the individual sample glaciers we tie the individual glaciers to the large scale changes of approximately 10,000 glaciers that have been examined in repeat satellite image inventories. In the Himalayan Range, stretching from the Karokaram Range in NW India east south east to the border region of Bhutan and China, detailed glacier mapping inventories, from GLIMS: (Global Land Ice Measurements from Space), ICIMOD (International Centre for Integrated Mountain Development), ISRO ( Indian Space Research Organisation) and Chinese National Committee for International Association of Cryospheric Science (IACS) of thousands of glaciers have indicated increased strong thinning and area loss since 1990 throughout the the Himalayan Range. The inventories rely on repeat imagery from ASTER, Corona, Landsat, IKONOS and SPOT imagery. It is simply not possible to make observations on this number of glaciers in the field. This is an update to the assessment by Pelto (2012) in the BAMS State of the Climate, which was the source of a Skeptical Science article as well

Kali Gandaki Headwaters, Nepal——–Ngozumpa Glacier, Nepal

Khumbu Glacier, Nepal ———— West Barun Glacier, Nepal

Imja Glacier, Nepal ——– Nobuk Glacier, Nepal

Lumding Glacier, Nepal———-

Milam Glacier, India———— Samudra Tupa, India

Ratangrian Glacier, India———– Khatling Glacier, India

Satopanth Glacier, India———- Durung Drung Glacier, India

Gangotri Glacier, India———— Warwan Basin, India

Sara Umaga Glacier, India—– Malana Glacier, India

Jaonli Glacier, India——– Kalabaland Glacier, India

Jaundhar Barak, India———– Burphu Glacier, India

Changsang Glacier, Sikkim—– Zemu Glacier, Sikkim

South Lhonak Glacier, Sikkim——North Lhonak Glacier, Sikkim

Theri Kang Glacier, Bhutan———-Luggi Glacier, Bhutan

Mangde Chu Glacier, Bhutan——–Thorthormi Glacier, Bhutan

Menlung Glacier, Tibet———- Yejyumaro Glacier, Tibet

Lumding Glacier, Tibet—- Rongbuk Glacier, Tibet

Sepu Kangri, China———– Longbasba Glacier, Tibet

Jiongla Glacier, Tibet———- Bode Zanbo Headwaters, Tibet

Zayul Chu Headwaters, Tibet— Boshula Glaciers, Tibet

Matsang Tsanpo Gl, Tibet—– Reqiang Glacier, Tibet

In Garhwal Himalaya, India, of 58 glaciers examined from 1990-2006 area loss was 6% (Bhambri et al, 2011). They also noted the number of glaciers increased from 69 (1968) to 75 (2006) due to the disintegration of ice bodies. Examination of 466 glaciers in the Chenab, Parbati and Baspa Basin, India found a 21% decline in glacier area from 1962 to 2004 (Kulkarni, 2007). Glacier fragmentation was also observed in this study, which for some fragments represents a loss of the accumulation area, which means the glacier will not survive (Pelto, 2010). The India glacier inventory (ISRO, 2010) identified glacier area losses and frontal change on 2190 glaciers and found an area loss rate of 3.3% per decade and 76% of glaciers retreating. (Kulkarni, 2014) reports on Indian Himalyan glaciers that 79 of 80 with terminus change records have been receding.

In the Nepal Himalaya area loss of 3808 glaciers from 1963-2009 is nearly 20% (Bajracharya et al., 2011). The Langtang sub-basin is a small northeast-southwest elongated basin, tributary of Trishuli River north of Kathmandu and bordered with China to the north. The basin contained 192 km2 of glacier area in 1977, 171 km2 in 1988, 152 km2 in 2000 and 142 km2 in 2009. In 32 years from 1977 to 2009 the glacier area declined by 26% (Bajracharya et al., 2011). In the Khumbu region, Nepal volume losses increased from an average of 320 mm/yr 1962-2002 to 790 mm/yr from 2002-2007, including area losses at the highest elevation on the glaciers (Bolch et al., 2011). The Dudh Koshi basin is the largest glacierized basin in Nepal. It has 278 glaciers of which 40, amounting to 70% of the area, are valley-type. Almost all the glaciers are retreating at rates of 10–59 m/year and the rate has accelerated after 2001 (Bajracharya and Mool, 2009). ICIMOD (2013) completed an inventory of Nepal glaciers and found a 21% decline in area from the 1970’s to 2007/08. ICIMOD has developed an map viewer application for examining the changes through time.

An inventory of 308 glaciers in the Nam Co Basin, Tibet, noted an increased loss of area for the 2001-2009 period, 6% area loss (Bolch et al., 2010). Zhou et al (2009) looking at the Nianchu River basin southern Tibet found a 5% area loss. 1990-2005. In the Pumqu Basin, Tibet an inventory of 999 glacier from the 1974 & 1983 to 2001 indicated the loss of 9% of the glacier area and 10% of the glaciers disappeared (Jin et al, 2005). The high elevation loss is also noted in Tibet on Naimona’nyi Glacier which has not retained accumulation even at 6000 meters. This indicates a lack of high altitude snow-ice gain (Kehrwald et al, 2008).

A new means of assessing glacier volume is GRACE, which cannot look at specific changes of individual glaciers or watersheds. In the high mountains of Central Asia GRACE imagery found mass losses of -264 mm/a for the 2003-2009 period (Matsuo and Heki, 2010). This result is in relative agreement with the other satellite image assessments, but is at odds with the recent global assessment from GRACE, that estimated Himalayan glacier losses at 10% of that found in the aforementioned examples for volume loss for the 2003-2010 period (Jacobs et al, 2012). At this point the detailed glacier by glacier inventories inventories of thousands of glaciers are better validated and illustrate the widespread significant loss in glacier area and volume, though not all glaciers are retreating. This page will continue to be updated as new inventory data is published and new individual glaciers are examined herein. Yao et al (2012) in an examination of Tibetan glaciers observed substantial losses of 7090 glaciers. Bolch et al (2012) in a report on the “State and Fate of Himalayan Glaciers” noted that most Himalayan glacier are losing mass and retreating at rates similar to the rest of the globe. ICIMOD has also developed an application illustrating changes of glaciers in Bhutan.

Middle Lhonak Glacier Retreat, Sikkim, India

On January 6, 2014January 6, 2014 By mspeltoIn Glacier Observations1 Comment

“Middle” Lhonak Glacier is an unnamed glacier between North Lhonak and South Lhonak Glacier near the border of the state of Sikkim in India and Nepal, red arrow on first map. I have previously reported on the retreat of South Lhonak Glacier whose retreat has led to a significant proglacial lake expansion and nearby Changsang Glacier. Here we examine landsat and Google Earth imagery from 2000-2013. Like all glaciers in this region Middle Lhonak Glacier is a summer accumulation type glacier. This means that the glacier receives most ~80% of its snowfall during the summer monsoon. This is also the period when ablation low on the glacier is highest. Following the summer monsoon which ends in early September there is a transition period with some colder storm events where the snowline drops. Than from November-February is the dry winter monsoon with limited precipitation. Thus, strange compared to most glaciers as winter proceeds often the lower glacier remains snow free. The pre-monsoon season from March-May features increasing precipitation, temperature and rising snowlines. The glacier drains into the Teesta River, which has several existing and many proposed hydropower projects, mostly run-of-river with minor dams.
Map of Region

Weather records from Pyramid station at 5000 m in Nepal indicating the peak temperature and precipitation occurring in summer monsoon.
Proposed hydropower

In 2000 and 2001 Middle Lhonak Glacier ends in a proglacial lake at the yellow dot. The pink dot indicates a small peninsula in the lake. The green dot indicates a bare rock area that separates two arms of the glaciers. The green arrow indicates where the two arms of the glacier join. By 2005 the glacier had retreated from the yellow dot, but the two arms of the glacier still connected, green arrow. In 2006 a higher resolution image from Google Earth indicates the 300-400 m retreat since 2000 of the glacier. The two glacier arms still join, green arrow, though barely. There is a substantial icefall that begins at 5800-5900 m, as noted by red arrows. Above the icefall the glacier is almost always snowcovered, but the icefall the glacier often remains snow free for much of the year at around 5700 meters. This will be explored further in a sequence of 2013 images below the terminus change sequence. In 2013 the two arms of the glacier have separated, the green dot bare rock area has greatly expanded and the glacier terminus has retreated 500-600 m since 2000.
Landsat image 2000

Landsat image 2001

Landsat image 2005

Google Earth image 2006

Landsat Image 2013

A series of images below indicate the snowline in a period from October 12, 2013-December, 21 2013. On October 21 the snowline is at the last bend above the terminus at 5650 m. By November 21 the snowline has shifted little. By December 1 the snowline has begun to rise to 5700 m. The rise has continued to 5750 by December 21. The lake at the terminus remains unfrozen.

October 12 2013 Landsat

November 21, 2013 Landsat

December 1, 2013 Landsat

December 21, 2013 Landsat

Changsang Glacier Retreat and Lake Formation, Sikkim

On December 22, 2012February 8, 2013 By mspeltoIn Glacier Observations3 Comments

Changsang Glacier is a valley glacier just north of Kanchengjunga, the third highest peak, in Sikkim. A comparison of Landsat imagery from 1989 to 2012 identifies the formation of a lake at the end of the glacier. The red arrow indicates the downvalley end of the lake that will develop, the green arrow the upvalley end. In 1989 there is no evidence of a lake either on top of the glacier, supraglacial or proglacial, at the end of the glacier. In 2000 there are a several small lakes beginning to develop. In the 2006 Google Earth imagery the lake is 700 meters long with several other developing smaller lakes. By 2011 the main lake is 1000 meters long and has one debris covered ridge that separates it from a second lake. By 2012 the lake has expanded incorporated the second lake and is now 1500 meters long. The Changsang Glacier was reported to be retreating 22 m/year from 1976 to 2005 (Raina, 2009). In Sikkim 26 glaciers examined were retreating at an average rate of 13.02 m per year from 1976 to 2005 (Raina, 2009) is following the same path as South Lhonak Glacier just to the north and Zemu Glacier just to the south. Zemu Glacier to the south is fed by a higher accumulation zone, and has not been retreating as fast, but it should be anticipated that a lake will form near its terminus.

A closeup view of the terminus area in 2006 indicates the main lake and several smaller lakes that will join the main lake by 2012. The purple arrow indicates the outlet river from beneath stagnant debris covered ice. The orange arrows indicate the extent of the developing lake by 2012.

South Lhonak Glacier, Retreat Sikkim

On May 8, 2012February 8, 2013 By mspeltoIn Glacier Observations

The South Lhonak Glacier drains east from Lhonak Peak into Sikkim from the Nepal-Sikkim border. The glacier begins at the border at 6500 meter and ends in a lake at 5200 meters. In 1933 the Mount Everest Expedition led by Eric Shipton explored the area. They traversed across the border and down the Lhonak Glacier finding only moraine covered cover glacier and no lake. Comparison of Landsat and Google Earth images from 2000-2011 indicate the expansion of the lake as the glacier has retreated. The first three are Landsat images from 2000 (top), 2010 (middle) and 2011 (bottom), indicating the expansion of the lake and glacier retreat. 2013 Update A paper just published in Current Science by K. Babu Govindha Raj1, S.N. Remya andK. Vinod Kumar reports on this lake expanding by 1.9 km due to glacier retreat from 1962-2008.

The next set of three are from Google Earth with a Landsat image from 2000 overlain in GE (top), 2006 GE image (middle) and 2010 GE image (bottom). The 2010 terminus is marked by green line, 2006 orange line and 2000 magenta line. The glacier retreated 350 meters from 2000 to 2006 and 250 meters from 2006-2010. The net 600 meter retreat for the decade is 60 m/per year. The 2006 image has red arrows indicating the large moraine behind which the lake has formed, and which Shipton found the glacier pressed up against. The retreat from 1933-2010 is at least 1800 meters. Clearly the retreat in the last decade is much more rapid than previous. The specific hazard is identified by Babu Govindha Raj et al (2013), the lake outburst probability is a very high value of 42% and peak discharge estimated at 586 m3/s. The retreat fits the pattern of other glaciers in the area reported by Raina (2008) and including Zemu Glacier and Changsang Glacier. In Sikkim 26 glaciers examined were retreating at an average rate of 13.02 m per year from 1976 to 2005. An example of this kind of retreat from Bhutan is Theri Kang Glacierand Changsang Glacier in Sikkim is another example.
A closeup examination of the terminus region of the Lhonak Glacier indicates a well incised supraglacial stream (on surface of glacier), indicating relative stagnation. Three areas where debris cover has protected the underlying ice leading to a prominent ridge on the glacier,(light blue arrows) again an indicator of stagnation. Finally the magenta arrow identifies a side stream valley that adjacent to the glacier and lower than the glacier, another indication of stagnation.