Abstract The Medieval Climate Anomaly (MCA; 900–1300 AD) was the most recent period of pre-industrial climatic warming in the northern hemisphere, and thus estimations of MCA signals can illuminate possible impacts of anthropogenic climate change. Current high-resolution MCA climate signals are restricted to mid- and high-latitude regions, which confounds inferences of how the MCA impacted some global/hemispheric climate mechanisms (e.g. North Atlantic Oscillation; NAO). To address this knowledge gap, we estimate seasonally-resolved sea surface temperatures (SSTs) from the oxygen isotope composition (δ18O) of serially sampled Phorcus atratus shells from archaeological sites spanning the MCA in the Canary Islands. Twelve archaeological and six modern P. atratus shells were analyzed, and archaeological shells were dated using carbonate-target radiocarbon dating. SSTs were estimated using the published aragonite-water equilibrium fractionation equation. Modern shells showed a mean SST of 20.0 ± 1.5 °C, with a seasonal amplitude of 5.3 ± 0.9 °C. Archaeological shells exhibited a mean SST of 18.2 ± 0.7 °C, with a mean seasonal amplitude of 5.5 ± 1.0 °C. Thus, shells that span the MCA in the Canary Islands recorded SSTs that were significantly cooler than the modern (P

中文翻译：

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在北大西洋东部亚热带地区中世纪气候异常的贝壳中记录的海洋冷却

摘要 中世纪气候异常（MCA；公元 900-1300 年）是北半球工业化前气候变暖的最新时期，因此对 MCA 信号的估计可以阐明人为气候变化的可能影响。当前的高分辨率 MCA 气候信号仅限于中高纬度地区，这混淆了 MCA 如何影响某些全球/半球气候机制（例如北大西洋涛动；NAO）的推论。为了解决这一知识差距，我们从跨越加那利群岛 MCA 的考古遗址中连续采样的 Phorcus atratus 贝壳的氧同位素组成 (δ18O) 估计季节性分辨的海面温度 (SST)。分析了十二个考古和六个现代 P. atratus 贝壳，使用碳酸盐目标放射性碳测年法对考古贝壳进行测年。使用已发表的文石-水平衡分馏方程估算 SST。现代贝壳的平均海温为 20.0 ± 1.5 °C，季节性幅度为 5.3 ± 0.9 °C。考古贝壳的平均海温为 18.2 ± 0.7 °C，平均季节性幅度为 5.5 ± 1.0 °C。因此，跨越加那利群岛 MCA 的贝壳记录的海温明显低于现代（P