Covariation of Deep Antarctic Pacific Oxygenation and Atmospheric CO2 during the Last 770 kyr

• Published in: Lithosphere
• Main Authors: Zheng Tang, Tiegang Li, Zhifang Xiong, Haowen Dang, Jingteng Guo
• Format: Article in Journal/Newspaper
• Language: English
• Published: GeoScienceWorld 2022
• Subjects: Geology; QE1-996.5; Antarctic; Southern Ocean; Pacific; Antarc*
• Online Access: https://doi.org/10.2113/2022/1835176; https://doaj.org/article/60743d54788b4090b1a67540a77341b4

AbstractWe present new geochemical evidence of changes in oxygenation of the deep Antarctic Pacific over the last 770 kyr. Our data are derived from redox-sensitive metals and export production proxies extracted from gravity core ANT34/A2-10 at 4217 m water depth. Our results show that oxygen levels in the deep Antarctic Zone (AZ) varied in line with the release of deeply sequestered remineralized carbon to the atmosphere during glacial–interglacial (G–IG) cycles, with lower oxygen concentrations and more carbon storage during glacial periods. Subsequent reductions in the amount of carbon stored at depth were closely associated with improved ventilation during glacial terminations. The systematic and repeated glacial-to-interglacial increases in export production in the AZ region indicate a robust pattern of enhanced Southern Ocean (SO) ventilation during interglacial periods. In addition to the decline in atmospheric CO2 caused by iron fertilization in the Subantarctic AZ (SAZ) during the latter half of the glacial progression, decreases in productivity in the central AZ suggest that the weakening of SO ventilation induced deep AZ carbon sequestration and that this might have made a continuous additional contribution to the CO2 decline from each interglacial peak to glacial maximum. Observed variations in the degree of deep oxygenation and “organic carbon pump” efficiency in the central AZ might be driven primarily by physical “ventilation” processes (i.e., overturning circulation, mixing, and/or air–sea gas exchange). Our records of abyssal oxygenation in the central AZ, which vary in concert with atmospheric CO2 levels over the last several G–IG cycles, provide strong evidence that SO ventilation plays a significant role in controlling variations in both the amount of respired carbon sequestered in the deep ocean and atmospheric CO2 concentrations on G–IG timescales. Specifically, we suggest that the “organic carbon pump” (OCP) in the SAZ and the physical ventilation processes in the AZ (the “carbon venting ...