Southern Ocean Biological Pump Role in Driving Holocene Atmospheric CO₂: Reappraisal

Changes in Southern Ocean biological pump efficiency are frequently invoked as a source of glacial/interglacial CO 2 variability. It was recently suggested that Southern Ocean biological pump weakening also contributed to Holocene CO 2 increase. Here we test the causes and downstream effects of biological pump inefficiency during the Holocene. We first provide evidence that a southward shift of the South Westerly Winds, was likely the cause of increasing upwelling in the Southern Ocean leading to local biological pump weakening as reflected in fossil‐bound δ 15 N. We then introduce a series of ultra‐high resolution (6 m/ky) productivity records from the Chilean Margin to determine the fate of Southern Ocean nutrients. A compilation of records from Pacific sites supports export and complete consumption of preformed Southern Ocean nutrients, which might have reduced the contributions of Southern Ocean marine source to the Holocene increase in atmospheric CO 2 .