Holocene sea-surface conditions in the North Atlantic—contrasted trends and regimes in the western and eastern sectors (Labrador Sea vs. Iceland Basin (original) (raw)

2004, Quaternary Science Reviews

Two sediment cores from the Labrador Sea and one from the Iceland Basin were analysed in order to compare Holocene seasurface conditions across the northern North Atlantic. d 18 O measurements on meso-and epi-planktonic foraminifera (Neogloboquadrina pachyderma left-coiling and Globigerina bulloides), along with sea-surface condition reconstructions using transfer functions based on dinoflagellate cyst assemblages, were used to document thermohaline properties of the upper water column. At the Labrador Sea sites, a decreasing trend in sea-surface temperature following an early Holocene maximum, is observed. At the Iceland Basin site, a hiatus between 13 and 8 ka BP prevents us from documenting the entire Holocene, but a stable to slightly decreasing trend is observed from 8 ka BP onwards. Sea-surface salinity and potential density (s y ) show little variation at the Orphan Knoll site in the Labrador Sea since 7 ka BP, whereas they depict a decreasing trend at the two other sites since ca 8 ka BP. This shift in s y values suggests a progressive enhancement of Labrador Sea Water formation and a relative decrease in the Nordic seas components of the North Atlantic Deep Water (i.e., Denmark Strait Overflow Water and Norwegian Sea Overflow Water). Discrepancies are also observed with regard to millennial-frequency oscillations in sea-surface conditions. At the easternmost site, they likely match previously documented cold water pulses in the north-eastern Atlantic, whereas they do not show any clear pattern at the westernmost sites. Hence, the western and eastern areas show different behaviours with respect to both longterm and high-frequency fluctuations. r

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