Imja glacier dead-ice melt rates and changes in a supra-glacial lake 1989-1994, Khumbu Himal, Nepal: danger of lake drainage

Melt rates of the dead ice in front of "Imja Glacier Lake" varied between 0.1 and 2.7 m/yr during the period 1989-1994. A maximum in excess of 5.0 m/yr occurred where the ice surface had been submerged by lake water before 1994. The lake level fell from 5,022 m a.s.l. in 1984 to about 5,017 m in 1989, and to about 5,007 m in 1994. This decrease is attributed to melt of dead ice along the outflow; thus there is less danger of collapse of the lateral moraines. Instead, the rapid melting is expected to cause the lake to expand westward, that is towards the terminal moraine. "Imja Glacial Lake" was 0.69 km20.69 km2, with maximum dimensions of 1,450 × 600 m by the winter of 1992. This rapid expansion in area is due to melting of the glacier at the east (upper) end of the lake. Nevertheless, if the melt rate is sustained the western shoreline could migrate to the edge of the terminal moraine in little more than 7 years. Immediate action to lower the lake level below the level of the spillway is needed.