Ribuktse Glacier drains east from 6200 m peaks along the Nepal-China border. The glacier ends in a lake that drains into Ribuktse Tso, the Yarlung Tsangpo (Zangbo), which becomes the Brahmaputra River. The Zangmu hydropower project is being constructed on the river, it is a 510 MW project. Here we examine Landsat and Google Earth imagery from the 1991-2014 period. This is a region where Li et al (2011) noted that increasing temperature, especially at altitude, the fronts of 32 glaciers have retreated, mass losses of 10 glaciers have been considerable, glacial lakes in six regions have expanded and melt water discharge of four basins has also increased. Neckel et al (2014) examined changes in surface elevation of the glaciers and found this region lost 0.44 m/year from 2003 to 2009.
Google Earth image
In 1991 the glacier ends in a proglacial lake at the red arrow, the yellow arrow is the 201 terminus. The lake at an elevation of 5050 m is 1.1 km long and 600 m wide. The purple arrow indicates two tributaries that connect to the larger valley glaciers. By 1998 the lake has expanded. The tributary to the glacier to the north of Ribuktse has separated from the main glacier. In 2000 and 2001 the tributary to the Ribuktse Glacier is still connected to the main glacier. The terminus continues to retreat with lake expansion. By 2005 the lake is 1.8 km long and the tributary is no longer visibly in contact with the main glacier at the purple arrow. In 2014 the terminus has retreated 800 m since 1991, the lake is 1.9 to 2 km long and the tributary has significantly separated form the main glacier. At the glacier just to the north the tributary separation from the valley glacier has led to a new glacier lake developing by 2011. There is little evidence of calving from Ribuktse Glacier. The retreat of the low slope glacier tongue in the proglacial lake lacking calving will continue at a slow rate. The high elevation of the glacier terminus area limits the magnitude of ablation on the glacier tongue. The retreat follows the pattern of the Yemayndrung Glacier just to the south, Durung Drung Glacier, India, Reqiang Glacier, China and Matsang Tsanpo Glacier, China which are in a similar climate setting. This area did get an unusual heavy October snowfall from Cyclone Hudhud this week.
1991 Landsat image
1998 Landsat image
2000 Landsat image
2001 Landsat image
2005 Google Earth image
2014 Landsat image
2011 Google Earth image
The Hailuogou Glacier has retreated 1.8 km during the 20th century. This glacier drains southeast from Gongga Shan beginning at 7500 m and extending to a debris covered terminus at 3000 m. The first image is a map from Li et al (2010).The glacier has been the focus of an ongoing research program by the Laboratory of Cryospheric Sciences, Chinese Academy of Sciences, Lanzhou, China and Nagoya University, Japan. This glacier is a summer accumulation type glacier fed largely by the summer monsoon. The glacier feeds the Dadu River. which eventually joins the Yangtze River. The Dadu River has a series of hydropower plants that fed in part by the glaciers of Gongga Shan. The Pubugou Hydropower Station has a total generating capacity is 3,300 MW, Gongzui Hydropower Station 600 MW and Tongjiezi Hydropower Station 700 MW and the still under construction Dagangshan Hydropower Station 2600 MW. The main changes in the Hailuogou Glacier are the continued thinning of the ablation zone, not terminus retreat of the heavily debris covered terminus. The terminus is at 3000 meters (T), the debris cover dominates to 3400 m. The glacier continues with a low slope to the base of the icefall (I) at 3800 m. Through the icefall the elevation rises above the equilibrium line at 4900 meters (ELA). The thick debris cover insulates the underlying ice slowing the melting. Zhang et al(2010) indicate that thinning and retreat have both accelerated since 1989. The images from Google Earth below are from 2002. The glacier area has been reduced by 0.8 square kilometers over the last 44 years, but more importantly has thinned by 1.1 meters/year in the ablation zone (Pan et al, 2011). In the second image the red arrow indicates the start of the debris cover, and the blue arrow where the river emerges at the terminus. The beginning of the debris cover is noted (DC)(top image), the green arrow indicates where the glacier becomes stagnant and the debris cover is quite thick, the red arrow the terminus, where the glacial river emerges from below the glacier. In the closeup the blue arrows indicate the thick debris covered glacier area and red arrow the terminus where the river emerges. . The retreat rate was 13 meters/year from 1966-1989 and 27 m/year from 1998-2008. They also report a significant reduction in glacier velocity in the ablation zone. This is an indication of increasing stagnation of the terminus area, that will lead to continued downwasting and retreat. The glacier is responding to a temperature warming as noted at the Gongga Alpine Ecosystem Observation and Research Station of the Chinese Ecological Research Network, during 1966–2009, the mean annual temperature at the research station has been increasing by 0.15 to 0.21 C/decade. Two examples of the developing hydropower on the Dadu River fed by the glaciers of Gongga Shan are below with the Dagangshan Hydropower Station, 40 km downstream, top image and Pubugou Hydropower Station, 100 km downstream bottom image.
Urumqi No. 1 or Urumqihe No.1 Glacier is in the Tian Shan Range of China. The Tain Shan Glaciological Research Station nearby, has led to this being the most closely observed glacier in China over the last 50 years. The glacier’s elevation ranges from 3740 meters to 4500 meters in 2005 the glacier had an area of 1.8 km2 (WGMS, 2010). In 1993 it separated into a larger east branch and a west branch. Since 1988 glaciological measurements are carried out for both branches separately (WGMS, 2010). The first image below is from Nozuma Takeuchi, Chiba University, Japan The second is from the WGMS submitted by Tobias Bolch in 2006.
The dryness and inhospitable nature of the region is evident. What is also evident is the limited snow extent on the glacier in the upper image of the east branch of the glacier. Both glacier branches are seen below, they joined in the foreground outwash plain region just 13 years before this image was taken. This region is one of the most continental areas of the world, dominated by polar and continental air masses from the Arctic and central Asia from autumn through spring, causing very low temperatures and little precipitation. During the summer months monsoonal air masses account for two thirds of the annual precipitation. This makes the Urumqi a summer accumulation type glacier, unusual outside of the Himalayan region, where peak accumulation on the upper part of the glacier and peak ablation on the lower part of the glacier, take part simultaneously in summer.
The regional increase of average air temperature of 0.7 C from 1987 to 2000 in north-western China has led to significant glacial mass losses, including a loss of 12 meters in glacier thickness on Urumqi Glacier in the last 35 years. The Average annual precipitation measured on the glacier is 600 to 700 mm relatively low for a glacier, an indicator of the continental climate. Most glaciers north of the immediate southern boundary with India and Pakistan, in China belong to the continental type and react slower to climate change than glaciers in warmer and wetter environments. The annual temperature at the equilibrium line is -8 to -9 C, the soils around the glacier feature permafrost. Runoff has been observed in the Urumqi River basin and has increased by 30% from 1983-2006. Comparison of runoff from glacier and non-glacier basins indicate a much larger change, change of 150%-200% in glacierized basins over the last 50 years. This is due to enhanced melting of the glacier, providing runoff that had been in long term frozen storage.
The mass balance is assessed at specific points indicated in the first figure below, 45 locations which is a higher than typical density 25 point per km2. The second figure is the contoured result of these measurements in terms of the snow-ice (measured in water equivalent units) gained or lost across the glacier. In this particular year the area of snow cover for both glacier branches is about 33% this is much less than the 65% needed for equilibrium on this glacier leading to a negative balance in 2006-07 of -650 mm (WGMS,2010). The mass loss fits the global pattern and cumulative mean of glaciers reporting to the WGMS. The mass balances losses have continued to increase each decade.