(Table 1) Sea surface temperature reconstruction for eastern equatorial Pacific surface sediment samples

Significant uncertainties persist in the reconstruction of past sea surface temperatures in the eastern equatorial Pacific, especially regarding the amplitude of the glacial cooling and the details of the post-glacial warming. Here we present the first regional calibration of alkenone unsaturation in surface sediments versus mean annual sea surface temperatures (maSST). Based on 81 new and 48 previously published data points, it is shown that open ocean samples conform to established global regressions of Uk'37 versus maSST and that there is no systematic bias from seasonality in the production or export of alkenones, or from surface ocean nutrient concentrations or salinity. The flattening of the regression at the highest maSSTs is found to be statistically insignificant. For the near-coastal Peru upwelling zone between 11-15°S and 76-79°W, however, we corroborate earlier observations that Uk'37 SST estimates significantly over-estimate maSSTs at many sites. We posit that this is caused either by uncertainties in the determination of maSSTs in this highly dynamic environment, or by biasing of the alkenone paleothermometer toward El Niño events as postulated by Rein et al. (2005).

东赤道太平洋过去海面温度的重建工作仍存在显著不确定性，尤其集中于冰期降温幅度与冰期后变暖的细节层面。本研究首次针对表层沉积物中的烯酮（alkenone）不饱和度与年平均海面温度（mean annual sea surface temperatures, maSST）建立区域校准关系。基于81组新测数据与48组已公开发表的数据点，研究表明开阔大洋样品符合已确立的Uk'37与maSST全球回归模型，且烯酮的产生、输出的季节变化，以及表层海水营养盐浓度、盐度均未带来系统性偏差。经统计学检验，最高maSST区间内回归曲线的平缓现象并不具备显著性。但针对南纬11°~15°、西经76°~79°的秘鲁近岸上升流区，本研究验证了此前的观测结果：多数站位基于Uk'37的海面温度估算值显著高估了maSST。我们推测，该偏差的成因可分为两类：一是该高度动态的海洋环境中maSST的测定存在不确定性；二是如Rein等人（2005）所提出的假设，烯酮古温度计（alkenone paleothermometer）偏向于记录厄尔尼诺事件。