Quantifying the Pinatubo volcanic signal in south polar snow

Recent snow and firn core samples from South Pole contain increased sulfate (SO42-) concentrations during 1992-1994 as a result of the June 1991 Pinatubo eruption and the August 1991 Cerro Hudson eruption in Chile. Traces of Pinatubo tephra (volcanic ash) were identified in the 1993 and 1994 snow layers, supporting the conclusion that increased SO42- in 1993-1994 is from the Pinatubo eruption. Although the Pinatubo eruption preceded Hudson, its SO42- signal in south polar snow follows and is resolved from that of Hudson. The deposition of the Pinatubo SO42- aerosol was delayed due to the long transport to the high southern latitudes and its initial existence at high altitudes in the Antarctic atmosphere. Multi-year, multi-site sampling demonstrates that the volcanic signals are well preserved and spatially consistent. Measurements on 2 firn cores show that the South Pole SO42- flux from Pinatubo is 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 satellite-determined Pinatubo sulfur dioxide (SO2) emission, make it possible to link quantitatively the atmospheric aerosol mass loading from a low-latitude volcanic eruption to its signal in polar ice cores.