Some of those other “unprecedented” melt events at Greenland ice sheet summit. Figure 2 in 1994 Science paper. Caption:
The 100-year smoothed accumulation record from the GISP2 core for the period A.D. 500 to the present. The arrows show locations of visually identified melt layers in the ice core.
Reference:
Vol. 266 no. 5191 pp. 1680-1682
DOI: 10.1126/science.266.5191.1680