A pronounced late Miocene cooling (LMC) from ~7 to 5.7 Ma has been documented in extratropical and tropical sea surface temperature records, but to date, available proxy evidence has not revealed a significant pCO₂ decline over this event. Here, we provide a new, high‐resolution pCO₂ proxy record over the LMC based on alkenone carbon isotopic fractionation (ε_p) measured in sediments from the South Atlantic at Ocean Drilling Program (ODP) Site 1088. We apply a recent proxy calibration derived from a compilation of laboratory cultures, which more accurately reflects the proxy sensitivity to pCO₂ changes during late Quaternary glacial‐interglacial cycles, together with new micropaleontological proxies to reconstruct past variations in algal growth rate, an important secondary influence on the ε_p. Our resulting pCO₂ record suggests an approximately twofold to threefold decline over the LMC and confirms a strong coupling between climate and pCO₂ through the late Miocene. Within this long‐term trend are pCO₂ variations on sub‐myr timescales that may reflect 400‐kyr long‐eccentricity cycles, in which pCO₂ minima coincide with several orbital‐scale maxima in published high‐resolution benthic δ¹⁸O records. These may correspond to ephemeral glaciations, potentially in the Northern Hemisphere. Our temperature and planktonic δ¹⁸O records from Site 1088 are consistent with substantial equatorward movement of Southern Ocean frontal systems during the LMC. This suggests that potential feedbacks between cooling, ocean circulation and deep ocean CO₂ storage may warrant further investigation during the LMC.

中文翻译：

---

中新世末期冷却期间减少大气中的二氧化碳

在温带和热带海表温度记录中，已记录到中新世晚期冷（LMC）从〜7到5.7 Ma，但是迄今为止，可用的替代证据尚未表明在该事件中p CO ₂显着下降。在这里，我们提供了一个新的，高分辨率的p CO ₂基于烯酮碳同位素分馏（ε在LMC代理记录_p在大洋钻探计划（ODP）站点1088从南大西洋沉积物测量我们采用最近代理）校准来自实验室文化的汇编，可更准确地反映代理对p CO _2的敏感性第四纪末期冰河-冰川间期的变化，以及新的微古生物学代理来重建藻类生长速率的过去变化，这是对εp的重要次要影响_。我们得到的p CO ₂记录表明，与LMC相比，下降了大约2到3倍，并证实了中新世晚期以来气候与p CO ₂之间存在强耦合。在这一长期趋势内，亚微米级时标上的p CO ₂变化可能反映了400 kyr长离心率周期，其中p CO ₂最小值与已发布的高分辨率底栖δ中的几个轨道级最大值一致。¹⁸ O条记录。这些可能对应于短暂的冰川，可能在北半球。我们的温度和浮游δ ¹⁸从网站1088Ø记录与LMC在南大洋锋面系统的实质性赤道运动是一致的。这表明在LMC期间，冷却，海洋环流和深海CO ₂储存之间的潜在反馈可能需要进一步研究。