Huang Maohuan
Polar-type glacier develop in a zone from the West Kunlun Mountains to the WestQilian Mountains in China, where ELA is high on the glaciers, ranging from 4 800 m a.s.l. onLaohugou Glacier No.12(in the Qilian Mountains, 39°27′N, 96°32′E)to 5 930 m a.s.l.on Chongce Ice Cap(in the West Kunlun Mountains,35°12′N, 81°06′E). The climate isextremely dry and cold in the zone.The mean annual temperature at ELA in the zone is-12.5-15.2℃, and the summertemperature is-1.1-29℃. The annual precipitation at ELA in the zone is rare and esti-mated to be 250-440 mm, for this zone being located near the Qaidam Basin and in thehinterland of Eurasia.The understanding of the development conditions of glaciers in the zone is deepenedthrough the Sino-Japanese joint glaciological expedition to the West Kunlun Mountains,1985-1987, and the Sino-American joint expedition to the Guliya Ice Cap, 1991-1992.Studies of heat and water balances on the peripheral surface of Chongce Ice Cap revealed thatthe evaporation rate is very large. The mean evaporation rate from July 23 to August 18 wasestimated as 1.36 mm d-1 and the mean melting rate was 3.52 mm d-1. Great evaporationexpendes a large amount of heat and then decreases the portion of heat used for melting, re-sulting in decreasing total mass loss.The arid climate becomes favourable for the develop-ment of glaciers.Low air temperature, with low ice temperature, causes low ablation rate with shortablation period. An ice temperature of-13.6℃ was measured at the depth of 18 m at the alti-tude of6 200 m on the Guliya Ice Cap in September 1990. The temperature at the sole, 135 mbelow the surface, under the summit of Dunde Ice Cap was measured to be-4.8℃,The low-est temperature record in China is held in the zone. Low ice temperature gives rise to refreez-ing of meltwater,forming superimposed ice. A great deal of heat is expended on ice tempera-ture rising,thus the actual ablation is decreased. Precipitation, in solid state, is concentrated in the period from May to September.Snowfall in summer increases the surface albedo, decreasing heat income,and less snowfall inwinter reduces the insulation, increasing heat loss. This precipitation regime is unfavourableto ablation.Around Kunlun Peak there are many huge and broad mountains above the equilibriumline,where the largest glacier cluster in China is formed, covering an area of 5 640 km2.
