The strength of meridional overturning circulation in the Nordic Seas slightly decreases by 0.4 Sv or 12% (Fig.  14 and Table  2 ), consistent with the noted expansion of winter sea-ice cover here (Fig.  13 c).

The overturning in the Nordic Seas is substantially weaker during the two events around 2.5 and 1.7 kyr BP, which are characterized by cooling over northern Europe and an increase in sea-ice cover (Fig.  14 ).

First, our simulation shows a shallower deep convection (by more than 250 m, Fig.  15 ) and weakened overturning strength (by 0.5 Sv, Fig.  14 ) in the Nordic Seas, while it is enhanced in the Labrador Sea.

This is clearly evident in the temperatures in Scandinavia and North America (Figs.  5 , 6 and Table  1 ), in the different components of the ocean circulation in the Nordic Seas (Fig.  14 and Table  2 ) and in the sea-ice evolution (Table  2 ).

The enhanced variability is most clearly expressed in the Nordic Seas region, where it culminates in two decadal-scale events that are characterized by cooling in Northern Europe (−15°C in January temperature, Fig.  5 ), negative excursions in overturning strength (−1.5 Sv, Fig.  14 ) and positive anomalies in the sea-ice extent (Fig.  12 ).