March 11, 2010

Urumqihe Glacier, China Separation and Retreat

Posted by Mauri Pelto

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.