Nss SO4 peaks are classified as volcanic eruptions if two criteria are
fulfilled: 1) the maximum peak concentration exceeds one standard
deviation above the mean (N1550 ppb) and 2) the nss SO4
background increases above the median concentration of 375 ppb
for at least 10 yrs. These conditions are satisfied during five events in the
record. The volcanic eruptions identified in the VLG record are: Agung
(1963 AD), Krakatau (1883 AD), Tambora (1816 AD), Huayanaputina
(1601 AD), and "Unkown" (1259 AD) (Fig. 2). The 1259 ADeruption has
been recorded in Antarctic and Arctic ice cores and is the largest
eruption in Antarctic records in the past millennium (Oppenheimer,
2003; Stothers, 2000) and hence provides a particularly well constrained
age benchmark. The EPICA-DML record identified 26 eruptions
over the same time period. However most volcanic peaks, in addition to
the five identified in the VLG record, are of lower amplitude (with
the exception of the Kuwae eruption, 1458 AD) andmight be present in
the VLG record too, but are masked by the much higher ss SO4 input to
the site