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Records of iceberg-rafting and palaeohydrography from two East Greenland shelf cores (JM96-1206/1-GC and JM96-1207/1-GC) are reported. Benthic foraminifera, stable isotopes and IRD uxes indicate a shift toward colder, lower-salinity 'polar' conditions c. 5 cal. ka. A new proxy of iceberg-rafting on the East Greenland Shelf is the ux of calcium carbonate (TIC) thought to be derived from glacial erosion of Cretaceous calcareous mudstones. A change in the regularity and spacing of carbonate ux peaks at c. 4.7 cal. ka in JM96-1207 coincides with the onset of Neoglacial cooling in the Renland ice core d 18 O record. We propose that the carbonate ux peaks between 4.7 and 0.4 cal. ka are related to sea-surface coolings associated with increased ux of polar water and sea ice in the East Greenland Current. These peaks are synchronous with sea-surface coolings interpreted from North Atlantic deep-sea cores, but additional peaks centred around 2.4 and 3.8 cal. ka in JM96-1207 suggest that the shelf site captures higher-frequency events. The data indicate that severe Arctic sea-ice events began in the Neoglacial interval, and that earlier-Holocene cool events in deep-sea records are associated with other processes, such as release of meltwater from residual glacier ice and glacial lakes.

Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic meridional overturning circulation variability, and the significance of decadal-to-centennial scale changes in Atlantic meridional overturning circulation strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning the past 1,350 years, to reconstruct changes in surface ocean circulation and climate. The water mass tracer data presented here from the North Icelandic shelf, combined with previously published data from the Arctic and subtropical Atlantic, show that surface Atlantic meridional overturning circulation dynamics likely amplified the relatively warm conditions during the Medieval Climate Anomaly and the relatively cool conditions during the Little Ice Age within the North Atlantic sector.

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