Thirty-year history of glacier melting in the Nepal Himalayas

Abstract

Two net balance records of neighboring glaciers under different conditions are analyzed to extract temporal variations in glacier melting in the Himalayas. Significant melt was observed every year at one site (wet site), whereas no melt occurred at the second site because of its high elevation (dry site). Accumulation at the wet site of a glacier is estimated from the dry site neighboring another glacier through a measured precipitation record for a short time period. The difference between the estimated accumulation and the net balances at the wet site is obtained as the "melt index, which represents the glacier melting conditions. The melt index with an interannual timescale is significant as a climatic proxy at high elevation since no relationship between stable isotopes and temperature is established and few long-term temperature records are available at high elevations in the Himalayas. The melt index showed a decadal fluctuation with a major amplitude never reported in previous studies with respect to temperature and ice cores analyses in the Himalayas. Ice cores from a site where significant melt occurs every year have not been considered available in reconstructing past climates since climatic signals in ice were disturbed by meltwater infiltration. However, we suggest a new approach to glean temperature information by a combination of wet and dry cores, not obtainable from a good-quality ice core alone. Copyright 2006 by the American Geophysical Union.