Stable oxygen isotope record from a high-latitude reef off Western Australia@en

A core from a coral colony of Porites lutea was analysed for stable oxygen isotopic composition*. A 200-year proxy record of sea surface temperatures from the Houtman Abrolhos Islands off west Australia was obtained from coral delta18O. At 29°S, the Houtman Abrolhos are the southernmost major reef complex of the Indian Ocean. They are located on the path of the Leeuwin Current, a southward flow of warm, tropical water, which is coupled to Indonesian throughflow. Coral delta18O primarily reflects local oceanographic and climatic variability, which is largely determined by spatial variability of the Leeuwin Current. However, coherence between coral delta18O and the current strength itself is relatively weak. Evolutionary spectral and singular spectrum analyses of coral delta18O demonstrate a high variability in spectral composition through time. Oscillations in the 5-7-y, 14-15-y, and quasi-biennial bands reflect teleconnections of local sea surface temperature (SST) to tropical Pacific climate variability. Deviations between local (coral-based) and regional (instrument) SST contain a cyclic component with a period of 15 y. Coral delta18O suggests a rise in SST by 0.6°C since AD 1944, consistent with available instrumental SST records. A long-term warming by 1.4°C since AD 1795 is inferred from the coral record.本研究对取自澄黄滨珊瑚（Porites lutea）群落的一份珊瑚岩心开展了稳定氧同位素组成分析*。科研人员从西澳大利亚州外海的霍特曼·阿布洛霍斯群岛的珊瑚δ¹⁸O序列中，重建得到一段时长200年的海表温度（Sea Surface Temperature, SST）代用记录。该群岛地处南纬29°，是印度洋最南端的大型礁体复合体，位于勒温海流（Leeuwin Current）的流经路径之上；这支向南输送暖性热带海水的海流与印度尼西亚贯穿流存在耦合关系。珊瑚δ¹⁸O主要反映局地海洋与气候变率，而此类变率在很大程度上由勒温海流的空间变异所主导。不过，珊瑚δ¹⁸O与海流强度本身的相关性相对较弱。对珊瑚δ¹⁸O开展的演化频谱与奇异谱分析结果显示，其频谱组成随时间呈现出显著的变异性。5~7年、14~15年以及准两年周期的振荡信号，反映了局地海表温度与热带太平洋气候变率之间的遥相关关系。局地（基于珊瑚重建）与区域（仪器观测）海表温度之间的偏差，存在一个周期为15年的周期性分量。珊瑚δ¹⁸O记录显示，自公元1944年以来，海表温度上升了0.6℃，这与已有的仪器观测海表温度记录相符。基于该珊瑚记录可推断，自公元1795年以来，海表温度已出现1.4℃的长期增温。