The state of the atmospheric circulation and the associated hydroclimate in the North Atlantic during the last millennium remain the subject of considerable debate in both proxy- and model-based studies. Of particular interest in the Iberian region is the Azores High (AH) system, the southern node of the North Atlantic Oscillation (NAO), an atmospheric dipole closely tied to regional hydroclimate. Hydroclimate-sensitive proxy reconstructions from this region offer some insights into atmospheric dynamics, but large spatiotemporal gaps in these data inhibit a robust evaluation of hydroclimate variability. In this study, we present a continuous, sub-decadally-resolved composite stalagmite carbon isotopic record from three partially overlapping stalagmites from Buraca Gloriosa (BG) cave, western Portugal, situated within the center of the AH, that preserves evidence of regional hydroclimate variability from approximately 800 CE to the present. Chronologies are derived from U/Th dating and annual laminae. Stalagmite carbon isotopic values primarily reflect the amount of effective moisture and reveal generally dry conditions during the Medieval Climate Anomaly (MCA; ~ 850–1250 CE) and Modern Climate/Industrial Era (1850 CE-present), and wetter conditions during the Little Ice Age (LIA; ~ 1400–1850 CE). Multidecadal to centennial variability in the BG record and state-of-the-art last millennium climate model simulations show considerable coherence with precipitation-sensitive records from Spain and Morocco that, like BG, are strongly influenced by the intensity, size, and location of the AH. Model-proxy synthesis suggests that western Portugal was persistently dry during much of the MCA consistent with other NAO reconstructions; however, even considering age uncertainties, the apparent timing in the transition from a relatively dry MCA to a wetter LIA is spatially variable and confirms the non-stationary behavior of the AH system indicated by model output.

在过去的千年中，北大西洋的大气环流状态和相关的水文气候仍然是基于代理和基于模型的研究中相当大的争论的主题。伊比利亚地区特别令人感兴趣的是亚速尔群岛高压 (AH) 系统，它是北大西洋涛动 (NAO) 的南部节点，是与区域水文气候密切相关的大气偶极子。该地区的水文气候敏感代理重建为大气动力学提供了一些见解，但这些数据中的巨大时空差距阻碍了对水文气候变异性的稳健评估。在这项研究中，我们展示了来自葡萄牙西部 Buraca Gloriosa (BG) 洞穴的三个部分重叠的石笋的连续、亚年代际分辨的复合石笋碳同位素记录，这些石笋位于 AH 的中心，这保留了从大约公元 800 年到现在的区域水文气候变化的证据。年表来自 U/Th 测年和年度薄片。石笋碳同位素值主要反映有效水分的量，并揭示了中世纪气候异常（MCA；约公元 850-1250 年）和现代气候/工业时代（公元 1850 年至今）期间的干燥条件，以及小冰期的湿润条件年龄（LIA；~ 1400–1850 CE）。BG 记录的几十年到百年的变化以及最先进的上个千年气候模型模拟显示与西班牙和摩洛哥的降水敏感记录具有相当大的一致性，这些记录与 BG 一样受到强度、大小和位置的强烈影响啊。模型代理合成表明，在 MCA 的大部分时间里，葡萄牙西部持续干燥，这与其他 NAO 重建一致；然而，即使考虑到年龄的不确定性，从相对干燥的 MCA 过渡到较湿的 LIA 的明显时间在空间上是可变的，并证实了模型输出所表明的 AH 系统的非平稳行为。