The role of sea ice in the climate response after the 536 and 540 CE volcanic eruptions hasbeen investigated through MPI-ESM simulations with imposed volcanic forcing. There is aclear response in the Arctic sea-ice cover to the volcanic forcing. The largest sea-ice areaanomalies are found in the summer/autumn following each of the eruptions, when it is foundto be up to 1.6*1012m2(24%) larger relative to the mean of the pre-industrial control run.There is a large spatial variability both in the sea-ice response and the surface temperatureanomalies. The strongest surface cooling is found in the Arctic, where the mean temperatureanomaly reaches -4.0oC after each of the eruptions, compared to a minimum of -1.5oC and-2.0oC in the NH mean after the 536 and 540 CE eruptions respectively. A prominent patternof negative temperature anomalies is found along the sea-ice edge. The most anomaloussea-ice cover is found in the Barents Sea and the Labrador Sea. The timing and spatialdistribution of surface temperature anomalies after the eruptions is more consistent withchanges in the sea-ice cover and subsequent modification of ocean currents, than with the decreased insolation directly or the dynamical response of the atmosphere.