QUANTIFYING THE PINATUBO VOLCANIC SIGNAL IN SOUTH POLAR SNOW

Recent snow and firn core samples from South Pole contain increased su lfate (SO42-) concentrations during 1992-1994 as a result of the June 1991 Pinatubo eruption and the August 1991 Cerro Hudson eruption in Ch ile. Traces of Pinatubo tephra (volcanic ash) were identified in the 1 993 and 1994 snow layers, supporting the conclusion that increased SO4 2- in 1993-1994 is from the Pinatubo eruption. Although the Pinatubo e ruption preceded Hudson, its SO42- signal in south polar snow follows and is resolved from that of Hudson. The deposition of the Pinatubo SO 42- aerosol was delayed due to the long transport to the high southern latitudes and its initial existence at high altitudes in the Antarcti c atmosphere. Multi-year, multi-site sampling demonstrates that the vo lcanic signals are well preserved and spatially consistent. Measuremen ts on 2 firn cores show that the South Pole SO42- flux from Pinatubo i s 10.9 +/- 1.2 kg km(-2) over 2.2 years, while the Hudson flux is 3.2 +/- 0.6 kg km(-2) in 1.1 years. These results, when combined with sate llite-determined Pinatubo sulfur dioxide (SO2) emission, make it possi ble to link quantitatively the atmospheric aerosol mass loading from a low-latitude volcanic eruption to its signal in polar ice cores.