Antarctic ice cores reveal a glacial climate state during Marine Isotope Stage 3 (MIS-3; 57–29 ka) punctuated by millennial-scale warming events and pulses of CO₂. This study further explores how changes in Southern Ocean carbon cycling contributed to these millennial-scale fluctuations in climate. Evidence from South Atlantic sediment cores suggests that warming events were associated with decreased dust-borne iron flux, reduced export production, and increased upwelling from the deep Southern Ocean (SO). These processes are considered to have contributed to rising atmospheric CO₂ during periods of rapid warming_. Here we investigate whether the same processes occurred in the southwest Pacific sector of the SO at TAN1106-28. We show that reduced New Zealand glaciation and localized iron limitation in the southwest Pacific led to reduced export production during millennial-scale warming events. Decreases in foraminifera-bound δ¹⁵N during all MIS-3 warming events may reflect increased nutrient supply by upwelling. Increased calcium carbonate flux during MIS-3 warming events likely reflects coccolithophore production in response to sea surface temperatures, which, would increase carbonate counter pump strength and reduce CO₂ sequestration. Concomitant decreases in bottom water oxygen, inferred from redox-sensitive U and Mn sediment concentrations, and increases in the ¹⁴C age of deep waters, suggest that old, nutrient-rich waters influenced southwest Pacific middepth waters during warming events. This signature may reflect an expansion of Pacific Deep Water into the SO during warming. Taken together, our multi-proxy data set reveals that the southwest subantarctic Pacific acted as a source of CO₂ during millennial-scale warming events of MIS-3.

中文翻译：

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海洋同位素阶段 3（57-29 ka）期间亚南极太平洋千禧年尺度的碳通量变化

南极冰芯揭示了海洋同位素第 3 阶段（MIS-3；57-29 ka）期间的冰川气候状态，其间夹杂着千年规模的变暖事件和 CO ₂脉冲。这项研究进一步探讨了南大洋碳循环的变化如何导致这些千年规模的气候波动。来自南大西洋沉积物岩心的证据表明，变暖事件与尘埃铁通量减少、出口产量减少以及南大洋深处上升流增加有关。这些过程被认为导致了快速变暖时期大气中CO _{2的上升。}在这里，我们调查 TAN1106-28 的 SO 西南太平洋区域是否发生了相同的过程。我们表明，新西兰冰川作用的减少和西南太平洋的局部铁限制导致千禧年规模的变暖事件期间出口产量的减少。在所有 MIS-3 变暖事件期间，有孔虫结合的 δ ¹⁵ N 的减少可能反映了上升流导致的营养供应增加。 MIS-3 变暖事件期间碳酸钙通量的增加可能反映了响应海面温度的颗石藻生产，这将增加碳酸盐反泵强度并减少CO ₂封存。根据氧化还原敏感的 U 和 Mn 沉积物浓度推断，底层水氧含量减少，并且深水¹⁴ C 年龄增加，表明古老的、营养丰富的水域在变暖事件期间影响了西南太平洋中深水域。这一特征可能反映了变暖期间太平洋深水向SO 的扩张。综上所述，我们的多代理数据集揭示了西南亚南极太平洋在 MIS-3 千年规模变暖事件期间充当了 CO _{2的来源。}