Water mass properties and exchange between the Nordic seas and the northern North Atlantic during the period 23-6 ka: Benthic oxygen isotopic evidence

Twenty benthic oxygen isotope records from different water depths in the Nordic seas and the North Atlantic are compared. During the Last Glacial Maximum, brine formation on continental shelves produced Brine Shelf Water (BSW), sinking below 1500 m in the Nordic seas. Open- ocean convection in the Nordic seas produced Glacial North Atlantic Intermediate Water (GNAIW). GNAIW overflowed the Greenland-Scotland Ridge and entrained depths above and at least partly below 2000 m in the North Atlantic. During the early deglaciation, BSW-enriched intermediate water masses in the Nordic seas were formed. These overflowed the Greenland-Scotland Ridge and influenced the North Atlantic intermediate and deepwater masses. In the Bolling-Allerod ( BA), open-ocean convection increased and produced intermediate water in the Nordic seas, with outflow to the North Atlantic. However, deep water with modern characteristics did not entrain water below 2000 m in the North Atlantic in similar amounts as during the Holocene. A new period of brine formation during the Younger Dryas transported BSW to intermediate water masses in the Norwegian Sea. There was also open-ocean convection and meridional overturning in the Nordic seas, but it was probably reduced compared to the BA. In the early Holocene and mid-Holocene, meridional overturning appears similar to that of today. Potential locations for large-scale formation of BSW might have been broad and shallow (< 200 m) areas of the North Sea, northeast of Greenland, and north of east Siberia. These settings should be favorable for BSW formation during cold periods.