The mid‐to‐late Miocene is proposed as a key interval in the transition of the Earth's climate state toward that of the modern‐day. However, it remains a poorly understood interval in the evolution of Cenozoic climate, and the sparse proxy‐based climate reconstructions are associated with large uncertainties. In particular, tropical sea surface temperature (SST) estimates largely rely on the unsaturated alkenone U^k₃₇ proxy, which fails to record temperatures higher than 29˚C, the TEX₈₆ proxy which has challenges around its calibration, and Mg/Ca ratios of poorly preserved foraminifera. We reconstruct robust, absolute, SSTs between 13.5 Ma and 9.5 Ma from the South West Indian Ocean (paleolatitude ∼5.5˚S) using laser‐ablation inductively coupled‐plasma mass spectrometer microanalysis of glassy planktic foraminiferal Mg/Ca. Employing this microanalytical technique, and stringent screening criteria, permits the reconstruction of paleotemperatures using foraminifera which although glassy, are contaminated by authigenic coatings. Our absolute estimates of 24–31°C suggest that SST in the tropical Indian Ocean was relatively constant between 13.5 and 9.5 Ma, similar to those reconstructed from the tropics using the U^k₃₇ alkenone proxy. This finding suggests an interval of enhanced polar amplification between 10 and 7.5 Ma, immediately prior to the global late Miocene Cooling.

中文翻译：

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琉璃有孔虫的激光烧蚀ICP-MS分析之后的中新世中期气候变迁后的热带海面温度

提议将中晚期至中新世作为地球气候状态向现代气候状态转变的关键间隔。然而，在新生代气候的演变过程中，它仍然是一个人们所知甚少的区间，而基于稀疏代理的气候重建也伴随着巨大的不确定性。特别是，热带海表温度（SST）估计很大程度上取决于不饱和烯酮U ^k ₃₇替代物，该替代物未能记录到高于29˚C的温度，即TEX ₈₆代理在校准以及保存不良的有孔虫的Mg / Ca比方面面临挑战。我们使用激光消融电感耦合等离子体质谱仪对玻璃状板状有孔虫的Mg / Ca进行了微分析，从西南印度洋（古纬度〜5.5˚S）重建了介于13.5 Ma和9.5 Ma之间的坚固，绝对的SST。采用这种微观分析技术和严格的筛选标准，可以使用有孔虫来重建古温度，而有孔虫虽然是玻璃状的，但会被自生涂层污染。我们对24-31°C的绝对估计表明，热带印度洋的SST在13.5至9.5 Ma之间相对恒定，类似于使用U ^k ₃₇从热带地区重建的结果。烯酮代理。这一发现表明，在全球晚中新世冷却即将来临之前，极化放大作用的增强间隔在10到7.5 Ma之间。