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首页> 外文期刊>Paleoceanography >Water mass stability reconstructions from greenhouse (Eocene) to icehouse (Oligocene) for the northern Gulf Coast continental shelf (USA)
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Water mass stability reconstructions from greenhouse (Eocene) to icehouse (Oligocene) for the northern Gulf Coast continental shelf (USA)

机译：从墨西哥湾沿岸大陆架（美国）的温室（始新世）到冰室（渐新世）的水质稳定性重建

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Shallow water mass characteristics such as temperature and density profile play a critical role in the climate system. We have developed a new method by which to reconstruct the ancient shallow water mass stability on the continental shelf using oxygen isotope variation within mollusc shells and fish otoliths and applied the method to an important interval in Earth history, the most recent transition from Greenhouse (Eocene) to Icehouse (Oligocene) climate modes. We define the slope of summer temperature (density) versus the seasonal range in temperature (density) as an indicator of water mass stability. In addition, extrapolation of the regression to zero seasonality is a proxy for temperature at the bottom of the seasonal thermocline (TBST). During the greenhouse world (the early Eocene and middle Eocene) the water mass plot shows an unstable water mass, agreeing with previous planktonic foraminiferal studies showing that temperature gradients at this time were much smaller than at present. During the middle to late Eocene transition, a substantial increase in water mass stability occurred. Significant cooling (～5°C) of the TBST at this transition indicates that the greater cooling of deeper water relative to surface water caused the increase in water mass stability. The changes in water column structure at this transition were the most likely cause of a major extinction of planktonic foraminifera from warm to cold water taxa. The late Eocene T-ΔT profile is very similar to modern profiles, suggesting that shallow water mass structure became similar to that of the modern Gulf Coastal shelf by the late Eocene. At the Eocene/Oligocene (E/O) boundary, no major change in water mass structure is identified. This agrees with the observation that no major extinction of planktonic foraminifera is found at the E/O boundary.
机译：浅水质量特征（例如温度和密度分布）在气候系统中起关键作用。我们已经开发出一种新方法，利用软体动物壳和鱼耳石中的氧同位素变化来重建大陆架上的古代浅水质量稳定性，并将该方法应用于地球历史上的一个重要区间，即最近的温室（始新世）过渡。 ）到冰屋（渐新世）气候模式。我们将夏季温度（密度）与温度（密度）的季节性范围的斜率定义为水质稳定性的指标。此外，将回归值外推到零季节性是季节性温跃层（TBST）底部温度的代表。在温室世界（始新世中期和始新世中期）中，水团图显示出不稳定的水团，这与之前的浮游有孔虫研究表明，此时的温度梯度远小于目前的情况是一致的。在始新世中期到后期，水团的稳定性大大提高。在此过渡过程中，TBST的明显冷却（〜5°C）表明，较深水相对于地表水的更大冷却导致水团稳定性增加。在此过渡过程中水柱结构的变化最可能是导致浮游有孔虫从温水到冷水类群大量灭绝的最可能原因。始新世晚期的T-ΔT剖面与现代剖面非常相似，这表明始新世晚期的浅水质量结构变得与现代墨西哥湾沿岸陆架相似。在始新世/渐新世（E / O）边界，没有发现水团结构发生重大变化。这与在E / O边界未发现浮游有孔虫大灭绝的观察结果一致。

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