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: 

Science 9 December 1994: Vol. 266 no. 5191 pp. 1680-1682 DOI: 10.1126/science.266.5191.1680

The Accumulation Record from the GISP2 Core as an Indicator of Climate Change Throughout the Holocene

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: 

Science 9 December 1994: 
Vol. 266 no. 5191 pp. 1680-1682 
DOI: 10.1126/science.266.5191.1680

The Accumulation Record from the GISP2 Core as an Indicator of Climate Change Throughout the Holocene