Foraminiferal accelerator mass spectrometry (AMS) 14C ages and benthic–planktonic age differences in surface-layer sediments of Labrador Sea are influenced by bioturbation and by changes in the relative abundance of foraminiferal species carrying the 14C signal. Using benthic-mixing models we demonstrate that inverse benthic–planktonic age differences can be generated when the effect of benthic mixing and abundance change exceeds apparent age differences between surface water and deep water. AMS 14C ages obtained put constraints on the timing of major paleoceanographic changes in the basin, notably on the history of the Western Boundary Undercurrent, which was clearly reinitiated during the mid-deglaciation and intensified during the last 2–3 ka.

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