Extended Data Fig. 8: Composites of the geopotential height for all four categories.

Composites of the z500 geopotential height (m) for years belonging to one of the four categories with respect to the 1950–2019 mean. Composite differences shown in Fig. 5 a represent a minus c, Fig. 5 b represents b minus d. Areas of significance are determined based on the Wilcoxon test (P-value < 0.05). The increase in frequency of the (–|+) pattern shown in d is in line with enhanced blocking conditions over Greenland.