Seasonal differences in snow chemistry from the vicinity of Mt. Everest, central Himalayas

During August and September 1998, fresh snow samples were collected in the East Rongbuk (ER) Glacier on the northern slope of Mt. Everest over an elevation range 5800-6500 m. Three snowpits were sampled in the ER glacier at an elevation of 6400, 6500, and 6500 m in August 1998, May 2000 and October 2002, respectively. Snow chemical data from fresh snow and snowpit samples from the ER Glacier are shown to be consistent with earlier results reported by other researchers from the vicinity of Mt. Everest. Among major ions, Ca2+ has the most striking seasonal differences: non-monsoon snow Ca2+ concentration is one order of magnitude higher than monsoon value. A large seasonal difference characterizes fresh snow SO42- but does not seem to persist in snowpit samples probably as a consequence of post-depositional ion elution. Non-monsoon snow Na+, K+ and Cl- are close to two times higher than monsoon snow for both fresh snow and snowpit samples. Magnesium has distinct seasonal variations in snowpit samples and a fourfold higher concentration in non-monsoon snow than that in monsoon snow. Seasonal differences in major chemical composition in snow over the Mt. Everest region provide a definitive indicator for precisely dating ice cores and as a consequence are essential in reconstructing the history of climate change and atmospheric chemistry in this region. (C) 2004 Elsevier Ltd. All rights reserved.