The Atlantic Meridional Overturning Circulation (AMOC) helps regulate the transport and storage of a large reservoir of heat and carbon, and therefore plays an essential role in climate change past and present. Authigenic uranium deposition in deep-sea sediments is a sensitive redox tracer that can shed light on bottom water oxygen, carbon storage and, in certain circumstances, water mass distributions in the deep ocean.
In this project, I combined new and published authigenic uranium data to reconstruct oxygenation since the last ice age in the east and west basins of the North Atlantic Ocean. Overall, the glacial deep North Atlantic was less well oxygenated compared to the Holocene, suggesting a higher ocean carbon inventory and important contribution to the global sequestration of CO2. We find that lower oxygen levels occurred in the deepest locations in the western basin, while substantially lower-oxygen waters were present throughout the northeast Atlantic. Our findings indicate that lower oxygen levels and correspondingly greater carbon storage were persistent features of the last glaciation and deglaciation in the deep North Atlantic Ocean, particularly in the eastern basin. This zonal emphasis may be related to the longer residence time and farther advance in the east of deep waters originating from the Southern Ocean.
This project is now published as an invited review at Quaternary Science Reviews (https://doi.org/10.1016/j.quascirev.2022.107914).