Ocean mixing and ice-sheet control of seawater 234U/238U during the last deglaciation

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Science  06 Oct 2016:
DOI: 10.1126/science.aag1015

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Seawater 234U/238U provides global-scale information on continental weathering and is vital for marine U-series geochronology. Previous evidence supports an increase in 234U/238U since the last glacial, but the timing and amplitude of its variability was poorly constrained. Here, we report two seawater 234U/238U records based on well-preserved deep-sea corals from the low latitude Atlantic and Pacific. The Atlantic 234U/238U starts to increase before major sea level rise and overshoots the modern value by 3‰ in the early deglaciation. Deglacial 234U/238U of the Pacific converges with the Atlantic after the abrupt resumption of Atlantic meridional overturning. We suggest that ocean mixing and early deglacial release of excess 234U from enhanced subglacial melt activity of the Northern Hemisphere ice sheets have driven the observed 234U/238U evolution.

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