Coral Sr/Ca records from Bonaire Holocene corals@en

Proxy reconstructions of tropical Atlantic sea surface temperature (SST) that extend beyond the period of instrumental observations have primarily focused on centennial to millennial variability rather than on seasonal to multidecadal variability. Here we present monthly-resolved records of Sr/Ca (a proxy of SST) from fossil annually-banded Diploria strigosa corals from Bonaire (southern Caribbean Sea). The individual corals provide time-windows of up to 68 years length, and the total number of 295 years of record allows for assessing the natural range of seasonal to multidecadal SST variability in the western tropical Atlantic during snapshots of the mid- to late Holocene. Comparable to modern climate, the coral Sr/Ca records reveal that mid- to late Holocene SST was characterised by clear seasonal cycles, persistent quasi-biennial and prominent interannual as well as inter- to multidecadal-scale variability. However, the magnitude of SST variations on these timescales has varied over the last 6.2 ka. The coral records show increased seasonality during the mid-Holocene consistent with climate model simulations indicating that southern Caribbean SST seasonality is induced by insolation changes on orbital timescales, whereas internal dynamics of the climate system play an important role on shorter timescales. Interannual SST variability is linked to ocean-atmosphere interactions of Atlantic and Pacific origin. Pronounced interannual variability in the western tropical Atlantic is indicated by a 2.35 ka coral, possibly related to a strengthening of the variability of the El Niño/Southern Oscillation throughout the Holocene. Prominent inter- to multidecadal SST variability is evident in the coral records and slightly more pronounced in the mid-Holocene. We finally argue that our coral data provide a target for studying Holocene climate variability on seasonal and interannual to multidecadal timescales, when using further numerical models and high-resolution proxy data.延伸至仪器观测时段之外的热带大西洋海表温度（SST）代用重建研究，此前多聚焦于百年至千年尺度的气候变率，而非季节至多年代际尺度的变异性。本文基于加勒比海南部博奈尔岛（Bonaire）的化石年纹层珊瑚（Diploria strigosa），重建了月分辨率的Sr/Ca（海表温度代用指标）记录。单块珊瑚可提供最长68年的时间序列窗口，总记录时长共计295年，可用于评估全新世中晚期多个时段内，热带大西洋西部海域季节至多年代际尺度SST变率的自然波动范围。与现代气候特征一致，珊瑚Sr/Ca记录显示，全新世中晚期的SST具有清晰的季节周期、持续的准两年周期波动，以及显著的年际、年代际至多年代际尺度变率。然而，上述时间尺度下的SST变化幅度在过去6.2千年间存在波动。珊瑚记录显示，全新世中期的季节变率有所增强，这与气候模型模拟结果相契合——模型表明加勒比海南部的SST季节变率由轨道尺度下的太阳辐射变化驱动，而气候系统内部动力过程在更短时间尺度上发挥关键作用。年际尺度的SST变率与大西洋及太平洋源地的海气相互作用密切相关。一块年代为2.35千年的珊瑚记录显示，热带大西洋西部存在显著的年际变率，这可能与全新世以来厄尔尼诺-南方涛动（El Niño/Southern Oscillation）变率的增强有关。珊瑚记录中清晰呈现出显著的年代际至多年代际SST变率，且在全新世中期这一特征更为突出。综上，本研究的珊瑚数据可为后续结合数值模型与高分辨率代用资料开展的全新世季节、年际至多年代际尺度气候变率研究提供参照基准。