Superimposed ice in glacier mass balance on the Tibetan Plateau

The relations between mass balance and meltwater refreezing were examined on the basis of glaciological observations carried out in summer 1993 on Xiao Dongkemadi Glacier, Tanggula Mountains, central Tibetan Plateau. On this glacier, a part of meltwater refreezes at the snow/ice interface as superimposed ice. The amount of superimposed ice formation was determined by both meltwater supply and temperature condition of the glacier. Snow-layer thickness on the glacier ice body is less than 2 m, even in the higher accumulation zone. About 60% of meltwater generated in the accumulation zone for the period May-September was trapped at the snow/ice interface by refreezing, and was not discharged out of the glacier. About 26% of accumulated snow to the glacier surface was replaced on the snow/ice interface by refreezing in the accumulation zone. These facts indicate that superimposed ice formation is quite significant for water retention in glaciers under low-precipitation conditions.