A mid-Holocene shift in Arctic sea-ice variability on the East Greenland Shelf

Abstract

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 fluxes 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 flux of calcium carbonate (TIC) thought to be derived from glacial erosion of Cretaceous calcareous mudstones. A change in the regularity and spacing of carbonate flux peaks at c. 4.7 cal. ka in JM96-1207 coincides with the onset of Neoglacial cooling in the Renland ice core δ18O record. We propose that the carbonate flux peaks between 4.7 and 0.4 cal. ka are related to sea-surface coolings associated with increased flux 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.