Paleoceanography of the North Atlantic Ocean (68°-76°N) during the past 450 ky deduced from planktic foraminifera] assemblages and stable isotopes

Polar and subpolar planktic foraminifera and the stable oxygen and carbon isotopes of Neogloboqllndrina pachyderma (s) from the Nordic seas are analyzed for the time period since oxygen isotope Stage 12, with special emphasis on interglacial time slices Stages 11,5e (Eeinian), and 1 (Holocene). A comparison of relative ("/I,) and absolute test concentratioi~sf rom two different size fractions reveals a complex downcore pattern for the morphogroup N. pnclzyderma. Ratios of small-sized N. pacllyderr?ln (s) to N. ~vrclzyderrrla (d) vary between Stage 11, the Eemian and the Holocene, due to changes ill test concentrations of N. pachydernla (s) only. As revealed in the downcore records, both coiling varieties of N, paclzydcri7zn are somehow related to each other, but the use of percent data as surface water mass proxy appears to be limited. The most doininant subpolar species, Elrborotalitn qtlinqt~eloba and Globigerinn bulloides, mainly occurred during the Holocene, the Eemian, and Stage 11. Both species are inversely related to N. pnch!jder17za (s) in that their abundai~ces steadily increased during all three interglacials. During these times, C. blllloill~s remained always restricted to the eastern area of the Nordic seas with dominant Atlantic water masses. In contrast T. qutnqllelobn exhibited a much wider distributional pattern. From stable isotopes and faunal variability it is inferred that the entire Nordic seas was covered by sea-ice during the cold seasons in Stage 11 resulting in both, highest test concentrations of N. pnchyderma (s) and highest 613C values observed tluoughout the past 450 ky. For the last two interglacials, oxygen isotope values and test coi~centrationsof T. q~li~zquelobinad icate that warmer surface waters must have prevailed in the western Iceland Sea in the Eeinian compared with any time during the Holocene time interval