NOAA/WDS Paleoclimatology - Wilson et al. 2006 Coral-based Tropical Sea Surface Temperature Reconstruction

Recent large-scale palaeoclimate reconstructions of past temperature have been essentially biased to the extratropics owing to a paucity of proxy data in tropical regions. Herein we describe the first coral-based reconstruction of sea surface temperatures (SSTs) for the whole of the tropics (30°N–30°S). It was developed from 14 disparate coral records located in the Indian and Pacific oceans. Over the most replicated period, the reconstruction explains 57% of the tropical SST variance. However, the strength of this signal weakens markedly as the number of coral records decreases. The reconstruction is robust between 1850 and 1993, but some fidelity is indicated back as far as the mid 18th century. These results suggest that ambiguities in the low frequency domain of δ18O measurements can be partially overcome by pooling together multiple time series from different locations around the tropics. Agreement with simulations from two general circulation models indicates that the late 20th century is likely the warmest period in the tropics for the last 250 years, and that this recent warming can only be explained by anthropogenic forcing. The high frequency variability is dominated by the El Niño–Southern Oscillation. The reconstruction, owing to the small number of coral records, is unfortunately restricted both in time and space. Therefore we hope that this study will spur the palaeoclimate community to develop new and longer proxy series to improve the current meager data-base of temperature sensitive series in the tropics.

近年来开展的大型古气候（palaeoclimate）温度重建研究，因热带地区代用资料（proxy data）匮乏，本质上均偏向于extratropics区域。本文首次针对全球热带区域（北纬30°至南纬30°）构建了基于珊瑚的海表温度（SSTs）重建序列。该重建序列基于印度洋与太平洋海域的14条互不相同的珊瑚记录构建而成。在采样覆盖最充分的时段内，该重建序列可解释57%的热带海表温度方差。然而，随着珊瑚记录数量减少，该信号的解释能力会显著下降。该重建序列在1850年至1993年期间表现稳健，但其保真度可追溯至18世纪中叶。本研究结果表明，通过整合热带区域不同站位的多组时间序列，可部分解决δ18O（氧同位素18）测量结果在低频域内的歧义性问题。与两个大气环流模式（general circulation models）的模拟结果一致表明，20世纪晚期可能是过去250年以来热带区域最温暖的时期，且此次近代增暖仅能通过人为强迫（anthropogenic forcing）加以解释。高频变率主要受厄尔尼诺-南方涛动（El Niño–Southern Oscillation）调控。遗憾的是，由于珊瑚记录数量有限，该重建序列在时间与空间维度上均存在局限性。因此，本研究希望能够推动古气候学界（palaeoclimate community）构建更多、更长的代用序列，以改善当前热带区域对温度敏感的代用资料数据库匮乏的现状。