One‐To‐One Coupling Between Southern Ocean Productivity and Antarctica Climate.

The Southern Ocean is supposed to play a crucial role in influencing atmospheric CO2 concentrations. However, the dynamic relationships among the rate of Southern Ocean upwelling, atmospheric CO2 concentration, and Antarctic climate at millennial timescales remain unclear. Here, we present high‐resolution color reflectance component b* and natural gamma radiation from the southern Scotia Sea sector of the Southern Ocean to reconstruct productivity over the past 160 ka. We find that these two independent productivity proxies, reflecting the signal of nutrient supply in this region, captured millennial‐scale upwelling that covaried in timing with Heinrich Stadials and Antarctic warming events, supporting the bipolar seesaw mechanism. The one‐to‐one coupling of variability between productivity and atmospheric CO2 concentrations reveals that the upwelling is closely linked to atmospheric CO2 and climate change. Plain Language Summary: The Southern Ocean's physical and associated biogeochemical processes play important roles in influencing atmospheric CO2 and climate change. In this study, we investigate temporal changes in productivity in the Antarctic Zone of the Southern Ocean by color reflectance component b* and natural gamma radiation data over the past 160 ka. We find that millennial‐scale productivity variability, which reflects the rate of upwelling in this region, corresponds to millennial‐scale variations in Antarctic temperature and atmospheric CO2 concentration over the past 160 ka. These tight couplings could imply that Southern Ocean upwelling is involved in atmospheric CO2 fluctuation and climate change. Key Points: Change in productivity at Site U1537 reflects the degree of upwelling in the Antarctic Zone of the Southern OceanThe millennial‐scale productivity peaks correspond to the Antarctic Isotope Maximum events that coincided with the Heinrich Stadials or Dansgaard‐Oeschger events in GreenlandThe rate of upwelling and atmospheric CO2 concentrations are positively correlated during the Heinrich Stadials [ABSTRACT FROM AUTHOR]