Title: Biological and Physical Dynamics of the Southern Ocean Over the Past 800,000 Years: Evidence from Micropaleontological and Geochemical Data
Abstract:
The Southern Ocean (SO) plays a major role in regulating atmospheric CO₂ concentration (p CO₂) during glacial-interglacial (G-IG) cycles through its physical and biological carbon pumps. However, the mechanisms controlling their efficiency remain poorly understood.
We first studied variations in the POC/PIC ratio (Particulate Organic Carbon/Particulate Inorganic Carbon) north of the Polar Front (PF), using micropaleontological and geochemical data from core MD04-2718 (southern Indian Ocean). Next, we studied the POC/PIC ratio at the subtropical front, using core MD97-2115 (southwestern Pacific).
The results reveal millennial fluctuations in oxygenation that are synchronous with those observed in the Pacific and Atlantic sectors of the OA. The glacial-interglacial transition is accompanied by increased oxygenation linked to enhanced ventilation driven by upwelling, whereas the deoxygenation events during MIS 11 are thought to reflect a more stagnant deep-water circulation and/or reduced air-sea O₂ exchange. In contrast to the Southern Atlantic, the southwestern Pacific exhibited relatively nutrient-poor deep waters during M12, possibly linked—as during the Last Glacial Maximum in the Southern Indian Ocean—to the convection of nutrient-poor surface waters within polynyas.
