Implications of seawater Mg/Ca variability for Plio-Pleistocene tropical climate reconstruction
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- 作者：Martí ; n Medina-Elizalde ; David W. Lea ; Matthew S. Fantle
- 关键词：Pliocene ; Pleistocene ; greenhouse forcing ; CO<sub>2sub> ; SSTs ; warm pool ; cold tongue ; alkenones ; foraminiferal Mg/Ca ; seawater Mg/Ca
- 刊名：Earth and Planetary Science Letters
- 出版年：2008
- 出版时间：30 May 2008
- 年：2008
- 卷：269
- 期：3-4
- 页码：585-595
- 全文大小：1401 K
文摘
Recent reconstructions of Mg and Ca concentrations of seawater indicate that seawater Mg/Ca changed significantly over the last 5 million years (Ma). Tropical sea surface temperature (SST) records for the last 5 Ma based on foraminiferal Mg/Ca paleothermometry assume constant seawater Mg/Ca. These SST records suggest that average equatorial Pacific SSTs remained thermally stable from 5 to 2 Ma, after which significant cooling occurred only in the eastern equatorial Pacific. This study examines the implications of adjusting available equatorial Pacific SST records based on Mg/Ca paleothermometry to account for the inferred past variations of seawater Mg/Ca. The results suggest that both the cold and the warm regions of the equatorial Pacific were much warmer during the early Pliocene (30–31 °C), and that both regions experienced a marked cooling from ![]()
src=""http://www.sciencedirect.com/scidirimg/entities/223c.gif"" alt=""not, vert, similar"" title=""not, vert, similar"" border=""0""> 4 Ma to ![]()
src=""http://www.sciencedirect.com/scidirimg/entities/223c.gif"" alt=""not, vert, similar"" title=""not, vert, similar"" border=""0""> 1 Ma. This new interpretation of foraminiferal Mg/Ca creates a discrepancy with alkenone unsaturation-based SST records from the eastern equatorial Pacific, which might be due to either overestimation of changes in past seawater Mg/Ca or to factors affecting the interpretation of the U<sup>K'sup><sub>37sub> index. The adjusted SST records are consistent with the hypothesis that higher levels of greenhouse gases maintained the warmth of the early Pliocene.