South Pole ice core record of explosive volcanic eruptions in the first and second millennia AD and evidence of a large eruption in the tropics around 535 AD

A record of explosive eruptions over the last 1830 years reconstructed from a South Pole, Antarctica, ice core extends the coverage of volcanic history to the start of the first millennium A. D. The ice core dating by annual layer counting carries an uncertainty of +/- 2% of the number of years from time markers, with the largest dating error of +/- 20 years at the bottom of the 182 m core. Several aspects of the methodology of detecting and quantifying volcanic sulfate signals in ice cores are examined in developing this record. The new record is remarkably consistent with previous South Pole records. A comparison with records from several Antarctica locations suggests that the South Pole location is among the best for ice core reconstruction of volcanic records, owing to the excellent preservation of volcanic signals at the South Pole, the relatively low and uniform sulfate background, and the moderately high snow accumulation rates which allow for dating by annual layer counting. A prominent volcanic event dated at 531(+/- 15) A. D., along with evidence from other records, indicates that an unusually large eruption took place in the tropics and was probably responsible for the mystery cloud climate episode of 536-537 A. D. The date of 536 is suggested for a prominent volcanic signal that appears in the first half of the sixth century A. D. in ice cores, which can in turn be used as a time stratigraphic marker in dating ice cores by annual layer counting or by computing average accumulation rates or layer thicknesses with such markers.