Trace metal evidence for a poorly ventilated glacial Southern Ocean

Trace metal evidence for a poorly ventilated glacial Southern Ocean Glacial benthic δ13C and Δ14C measurements from the Atlantic Ocean have been interpreted to indicate the existence of a poorly ventilated Southern Ocean with greater CO2 and nutrient contents compared to present. Enhanced storage of CO2 in the deep ocean predicts that oxygen concentrations should have declined at the same time—a prediction increasingly supported by evidence for oxygen depletion in the glacial Southern Ocean. Here we take a novel approach by using a suite of redox-sensitive trace metals (Ag, Cd, Re and Mo) to show that Southern Ocean sediments from two cores in the Atlantic sector were suboxic during and prior to deglaciation, implying changes to ocean circulation and/or elevated export production that significantly altered deep water chemistry. In the Cape Basin, enrichments of the authigenically deposited trace metal Re are comparable to those found in oxygen minimum zones, pointing to substantial decreases in oxygenation. Furthermore, trace metal results suggest potential spatial heterogeneity in the glacial Southern Ocean, and a more complicated oceanographic and oxygenation history than has previously been assumed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Quaternary Science Reviews Elsevier

Trace metal evidence for a poorly ventilated glacial Southern Ocean

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Publisher
Elsevier
Copyright
Copyright © 2017 Elsevier Ltd
ISSN
0277-3791
eISSN
1873-457X
D.O.I.
10.1016/j.quascirev.2017.06.014
Publisher site
See Article on Publisher Site

Abstract

Glacial benthic δ13C and Δ14C measurements from the Atlantic Ocean have been interpreted to indicate the existence of a poorly ventilated Southern Ocean with greater CO2 and nutrient contents compared to present. Enhanced storage of CO2 in the deep ocean predicts that oxygen concentrations should have declined at the same time—a prediction increasingly supported by evidence for oxygen depletion in the glacial Southern Ocean. Here we take a novel approach by using a suite of redox-sensitive trace metals (Ag, Cd, Re and Mo) to show that Southern Ocean sediments from two cores in the Atlantic sector were suboxic during and prior to deglaciation, implying changes to ocean circulation and/or elevated export production that significantly altered deep water chemistry. In the Cape Basin, enrichments of the authigenically deposited trace metal Re are comparable to those found in oxygen minimum zones, pointing to substantial decreases in oxygenation. Furthermore, trace metal results suggest potential spatial heterogeneity in the glacial Southern Ocean, and a more complicated oceanographic and oxygenation history than has previously been assumed.

Journal

Quaternary Science ReviewsElsevier

Published: Aug 15, 2017

References

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