Comparison of Mg/Ca‐ and alkenone‐based sea surface temperature estimates in the fresh water–influenced Gulf of Guinea, eastern equatorial Atlantic
Comparison of Mg/Ca‐ and alkenone‐based sea surface temperature estimates in the fresh water–influenced Gulf of Guinea, eastern equatorial Atlantic
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DOI：
10.1029/2006gc001360
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发表时间：
2007-05
期刊：
影响因子：
3.7
通讯作者：
S. Weldeab;R. Schneider;P. Müller
中科院分区：
文献类型：
--
作者：
S. Weldeab;R. Schneider;P. Müller
本研究根据从赤道东大西洋几内亚湾回收的核心沉积物中的 Globigerinoides ruber 的 Mg/Ca 比率和烯酮不饱和指数 (U37K') 来比较海面温度 (SST) 估计值。基于 Mg/Ca 和 U37K′ 的海表温度估计在 21,000-14,500 年的时间间隔和全新世晚期产生了相当可比的结果。然而，全新世早期和中期的主要特征是趋势不一致，基于 Mg/Ca 的海温估计值较暖，而 U37K' 的海温估计值较冷。这种差异的海表温度趋势伴随着低海面盐度估计值（高河流径流）和生物沉积物，其特点是高生物成因蛋白石含量、低碳酸盐含量和相对较低的烯酮浓度。我们假设，全新世中期和早期重建的海表温度的差异可能表明，在一个低盐度和温暖的地表水中，溶解二氧化硅和主要是硅质浮游植物在河流输入量增加的时期，而烯酮生产者可能在寒冷的海表温度和河流二氧化硅输入量低的季节普遍存在。这项研究表明，当地水文和养分输入的变化对基于 U37K′ 的海表温度估计有很大影响，可以通过组合不同的海表温度代理来阐明这一估计。
This study presents a comparison of sea surface temperature (SST) estimates based on Mg/Ca ratios of Globigerinoides ruber and alkenone unsaturation index (U37K′) in core sediment recovered from the Gulf of Guinea, eastern equatorial Atlantic. Mg/Ca‐ and U37K′‐based SST estimates yield fairly comparable results for the time interval 21,000–14,500 years and for the late Holocene. The early and middle Holocene, however, are largely characterized by a discrepant trend, with warm Mg/Ca and cold U37K′ based SST estimates. This discrepant SST trend is accompanied by low sea surface salinity estimates (high riverine runoff) and biogenic sediment, which is characterized by high biogenic opal content, low carbonate content, and relatively low alkenone concentration. We hypothesize that the discrepancy in the reconstructed SSTs during the middle and early Holocene presumably suggests a period of elevated riverine input of dissolved silica and dominantly siliceous phytoplankton bloom in a low saline and warm surface water, while alkenone producers were likely prevalent in a season of cold SST and low riverine silica input. This study suggests that changes in the local hydrography and nutrient input have strong influence on the U37K′‐based SST estimate that may be unraveled by combining different SST proxies.