Early Palaeogene temperature evolution of the southwest Pacific Ocean
Early Palaeogene temperature evolution of the southwest Pacific Ocean
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DOI：
10.1038/nature08399
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发表时间：
2009-10-08
期刊：
影响因子：
64.8
通讯作者：
Brinkhuis, Henk
中科院分区：
文献类型：
--
作者：
Bijl, Peter K.;Schouten, Stefan;Brinkhuis, Henk
相对于今天，始新世早期（类似于56-53 Myr以前）的经向温度梯度异常低，赤道地区略暖(1)，但亚热带北极(2)和中纬度(3)气候温暖得多。在始新世末期（类似于34万年前），第一个主要的南极冰盖出现了（4,5），这表明主要的冷却已经发生。然而，全球向这种冰窖气候的转变仍然没有得到很好的约束，因为只有少数温度记录可以描述南方高纬度地区新生代的气候演变。在这里，我们提供了一个独特的连续的、年代地层校准良好的TEX86记录，该记录来自东塔斯曼高原（古纬度类似于南纬65度）的海洋沉积物岩心。研究表明，西南太平洋海温在始新世早期（与53 Myr前相似）高于现今热带值（约34℃），到晚始新世早期（与36 Myr前相似）逐渐降低至21℃左右。结果表明，早始新世（55 ~ 50 Myr）在赤道以下和近极地之间几乎不存在纬向海温梯度。此后，纬度梯度明显增大。理论上，如果始新世变冷主要是由大气温室气体浓度的减少所驱动(6)，那么考虑到高纬度地区的变冷更为显著，就需要额外的过程来解释热带海温的相对稳定性。
Relative to the present day, meridional temperature gradients in the Early Eocene age (similar to 56-53 Myr ago) were unusually low, with slightly warmer equatorial regions(1) but with much warmer subtropical Arctic(2) and mid-latitude(3) climates. By the end of the Eocene epoch (similar to 34 Myr ago), the first major Antarctic ice sheets had appeared(4,5), suggesting that major cooling had taken place. Yet the global transition into this icehouse climate remains poorly constrained, as only a few temperature records are available portraying the Cenozoic climatic evolution of the high southern latitudes. Here we present a uniquely continuous and chronostratigraphically well-calibrated TEX86 record of sea surface temperature (SST) from an ocean sediment core in the East Tasman Plateau (palaeolatitude similar to 65 degrees S). We show that southwest Pacific SSTs rose above presentday tropical values (to similar to 34 degrees C) during the Early Eocene age (similar to 53 Myr ago) and had gradually decreased to about 21 degrees C by the early Late Eocene age (similar to 36 Myr ago). Our results imply that there was almost no latitudinal SST gradient between subequatorial and subpolar regions during the Early Eocene age (55-50 Myr ago). Thereafter, the latitudinal gradient markedly increased. In theory, if Eocene cooling was largely driven by a decrease in atmospheric greenhouse gas concentration(6), additional processes are required to explain the relative stability of tropical SSTs given that there was more significant cooling at higher latitudes.