1000 years of explosive volcanism recorded at the South Pole

Cataclysmic volcanic eruptions generally disturb the global atmosphere markedly for around 2 years. During that time, long-life volcanic products (mainly H₂SO₄), stored in the stratosphere gradually return to the troposphere. Antarctic snow may be subsequently contaminated and acid signals recorded. The recovery of these signals along Antarctic ice cores provides a history of past volcanic events, most often of global, but sometimes of just regional, significance. Several physical and chemical techniques have been used to analyse a 1000-year ice core drilled near Amundsen-Scott Base. Acid and ultrafine ash deposits of volcanic origin have been carefully investigated. 23 major volcanic eruptions have been detected, dated and tentatively identified. The results have been compared with similar Antarctic and Greenland records. The amount of volcanic sulfate deposited in Antarctic snow, calculated and averaged over the last millennium, is, however, minor (13% of the total sulfate) in comparison with that of the marine biogenic source. The 19th century was the period of the millennium most seriously disturbed by global explosive volcanic activity. The chlorine cycle, as recorded in Antarctic ice, seems to be little affected even by such a large event as Tambora, 1815.