Paleo-sea surface temperature calculations in the equatorial east Atlantic

We present two ~270 kyr paleo-sea surface temperature (SST) records from the Equatorial Divergence and the South Equatorial Current derived from Mg/Ca ratios in the planktic foraminifer Globigerinoides sacculifer. The present study suggests that the magnesium signature of G. sacculifer provides a seasonal SST estimate from the upper ~50 m of the water column generated during upwelling in austral low-latitude fall/winter. Common to both down-core records is a glacial-interglacial amplitude of ~3°-3.5°C for the last climatic changes and lower Holocene and glacial oxygen isotope stage 2 temperatures compared with interglacial stage 5.5 and glacial stage 6 temperatures, respectively. The comparison to published SST estimates from alkenones, oxygen isotopes, and foraminiferal transfer function from the same core material pinpoints discrepancies and conformities between methods.

本研究报道了两份时长约27万年的古海水表层温度（SST）记录，分别源自赤道辐散区（Equatorial Divergence）与南赤道流（South Equatorial Current），其重建基于浮游有孔虫（planktic foraminifer）囊球抱球虫（Globigerinoides sacculifer）壳体的镁钙（Mg/Ca）比值。本研究表明，囊球抱球虫壳体的镁信号可用于估算南半球低纬度秋季/冬季上升流活动期间，水柱上部约50米处的季节性海表温度。两份岩芯记录均呈现共同特征：末次气候旋回的冰期-间冰期温度振幅约为3℃~3.5℃；全新世温度低于间冰期5.5期，而氧同位素2期冰期的温度则低于冰期6期温度。将本研究结果与已发表的、基于同一岩芯沉积物的烯酮类化合物（alkenones）、氧同位素分析及有孔虫转换函数（foraminiferal transfer function）得到的海表温度估算结果进行对比，可明确不同重建方法间的差异与一致性。