Ocean mixing and ice-sheet control of seawater 234U/238U during the last deglaciation.
Seawater234U/238U provides global-scale information about continental weathering and is vital for marine uranium-series geochronology. Existing evidence supports an increase in234U/238U since the last glacial period, but the timing and amplitude of its variability has been poorly constrained. Here we report two seawater234U/238U records based on well-preserved deep-sea corals from the low-latitude Atlantic and Pacific Oceans. The Atlantic234U/238U started to increase before major sea-level rise and overshot the modern value by 3 per mil during the early deglaciation. Deglacial234U/238U in the Pacific converged with that in the Atlantic after the abrupt resumption of Atlantic meridional overturning. We suggest that ocean mixing and early deglacial release of excess234U from enhanced subglacial melting of the Northern Hemisphere ice sheets have driven the observed234U/238U evolution.
Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol, UK.
Tianyu
T
Chen
Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol, UK.
Laura F
LF
Robinson
Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol, UK.
Matthew P
MP
Beasley
Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol, UK.
Louis M
LM
Claxton
Institute of Geochemistry and Petrology, Department of Earth Sciences, ETH Zürich, Zürich, Switzerland.|School of Earth and Ocean Sciences, Cardiff University, Cardiff, UK.
Morten B
MB
Andersen
School of Earth and Environment, University of Leeds, Leeds, UK.
Lauren J
LJ
Gregoire
Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, Bristol, UK.
Jemma
J
Wadham
Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
Daniel J
DJ
Fornari
Department of Geology, Colgate University, 13 Oak Drive, Hamilton, NY 13346, USA.
Karen S
KS
Harpp