Received: 04 Dec 2014 – Discussion started: 11 Mar 2015
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, although no unequivocal evidence for glacial Southern Ocean suboxia has yet been found. Here we take a novel approach by using concentrations of redox-sensitive trace metals to show that Southern Ocean sediments from two cores in the Atlantic sector were suboxic during deglaciation and the last glacial period, implying reduced ventilation and/or elevated export production that significantly altered deep water chemistry. In the Cape Basin, high concentrations of the authigenically deposited trace metal Re coincide with oldest Δ14C values at 3.8 km water depth in the Subantarctic Zone, indicating that poorest Southern Ocean ventilation occurred during the Last Glacial Maximum (~ 23–19 ka). Furthermore, trace metal results suggest that the vertical structure of the glacial Southern Ocean differed from modern deep water mass arrangement such that Lower Circumpolar Deep Water had lower O2 concentrations, and therefore was the likely reservoir of glacial CO2.
How to cite. Wagner, M. and Hendy, I. L.: Trace metal evidence for a poorly ventilated glacial Southern Ocean, Clim. Past Discuss., 11, 637–670, https://doi.org/10.5194/cpd-11-637-2015, 2015.
Trace metal (Ag, Cd, Re, Mo) concentrations in glacial-age, Atlantic sector Southern Ocean sediments that are similar to those found in modern sediments underlying oxygen minimum zones (e.g., Eastern Pacific) imply that the glacial Southern Ocean was significantly less well ventilated than present. These data point to a glacial equivalent of Lower Circumpolar Deep Water as the low-oxygen water mass, and the potential storage location of the ‘missing’ glacial CO2.
Trace metal (Ag, Cd, Re, Mo) concentrations in glacial-age, Atlantic sector Southern Ocean...