Multiple peaks in sulfate concentration in ice cores have been identified as potential candidates for the ~74 ka Toba supereruption. The sulfur isotopic composition of sulfate preserved in two EPICA Antarctic ice cores, EDML and EDC, for 11 of the candidates has been analysed at high temporal resolution for mass-independent fractionation (MIF) using multi-collector inductively coupled plasma mass spectrometry. S-MIF signals preserved in volcanic sulfate are indicative of stratospheric eruptions due to sulfur aerosols being exposed to ultraviolet radiation when erupted into and above the ozone layer and subsequently undergoing photochemical reactions. Sulfur aerosols in the stratosphere will have longer residence times than those in the trop...