Millennial-scale variability in Atlantic water advection to the Nordic Seas derived from Holocene coccolith concentration records

Abundance patterns of coccolith species in two Holocene marine cores retrieved off Norway and northern Iceland are indicative of millennial-scale modulations in the flow of the main (Norwegian Atlantic Current) and secondary (North Iceland Irminger Current) branches of the North Atlantic Drift to the Nordic Seas. Long-term trends in coccolith abundance changes reflect major Holocene steps in Atlantic Water transfer to the Nordic Seas at orbital scale with important constraints on the convective activity of the Nordic Seas that leads to the formation of the precursor water mass of North Atlantic Deep Water. Millennial-scale Holocene episodes of increased advection of Atlantic waters off Norway are associated with enhanced winter precipitation over Scandinavia, increased sea-salt fluxes over Greenland, and strengthened wind over Iceland, thereby suggesting a common atmospheric forcing: the location and intensity of the westerlies and the associated changes in mid- to high-latitude pressure gradients. Our biotic data indicate an opposite pattern of Atlantic water inflow at suborbital scale between the western (Denmark) and eastern (Iceland–Scotland) straits of the northern Atlantic throughout the Holocene. This, as supported by present observational and simulated data, further highlights the role of atmospheric oscillations in the recent history of the North Atlantic-Nordic Seas water mass exchanges across the Greenland–Scotland Ridge. Such atmospheric processes are thought to explain the observed coupling between periods of excess export of arctic sea-ice to the Nordic Seas and intervals of maximum inflow of Atlantic water to the Norwegian Sea throughout the last 11 000 years.