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首页> 外文期刊>Paleoceanography >A transient deep-sea circulation switch during Eocene Thermal Maximum 2
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A transient deep-sea circulation switch during Eocene Thermal Maximum 2

机译：始新世热量最大值2期间的瞬态深海循环开关

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Ever since its discovery, Eocene Thermal Maximum 2 (ETM2; ~53.7 Ma) has been considered as one of the "little brothers" of the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma) as it displays similar characteristics including abrupt warming, ocean acidification, and biotic shifts. One of the remaining key questions is what effect these lesser climate perturbations had on ocean circulation and ventilation and, ultimately, biotic disruptions. Here we characterize ETM2 sections of the NE Atlantic (Deep Sea Drilling Project Sites 401 and 550) using multispecies benthic foraminiferal stable isotopes, grain size analysis, XRF core scanning, and carbonate content. The magnitude of the carbon isotope excursion (0.85-1.10‰) and bottom water warming (2-2.5°C) during ETM2 seems slightly smaller than in South Atlantic records. The comparison of the lateral δ~(13)C gradient between the North and South Atlantic reveals that a transient circulation switch took place during ETM2, a similar pattern as observed for the PETM. New grain size and published faunal data support this hypothesis by indicating a reduction in deepwater current velocity. Following ETM2, we record a distinct intensification of bottom water currents influencing Atlantic carbonate accumulation and biotic communities, while a dramatic and persistent clay reduction hints at a weakening of the regional hydrological cycle. Our findings highlight the similarities and differences between the PETM and ETM2. Moreover, the heterogeneity of hyperthermal expression emphasizes the need to specifically characterize each hyperthermal event and its background conditions to minimalize artifacts in global climate and carbonate burial models for the early Paleogene.
机译：自发现以来，始新世热最大值2（ETM2;〜53.7 Ma）被视为古新世-始新世热最大值（PETM;〜56 Ma）的“小兄弟”之一，因为它显示出类似的特征，包括突然变暖，海洋酸化和生物转移。剩下的关键问题之一是这些较少的气候扰动对海洋环流和通风以及最终对生物的破坏有什么影响。在这里，我们使用多种底栖有孔虫稳定同位素，粒度分析，XRF岩心扫描和碳酸盐含量来表征东北大西洋的ETM2部分（深海钻探项目站点401和550）。 ETM2期间的碳同位素偏移（0.85-1.10‰）和底水升温（2-2.5°C）的幅度似乎比南大西洋的记录稍小。对北大西洋和南大西洋之间的横向δ〜（13）C梯度的比较表明，在ETM2期间发生了瞬时循环转换，这与PETM观察到的模式相似。新的粒度和已公布的动物数据通过表明深水流速降低而支持了这一假设。在ETM2之后，我们记录了影响大西洋碳酸盐累积和生物群落的底流明显加剧，而黏土的急剧而持久的减少则暗示了该区域水文循环的减弱。我们的发现强调了PETM和ETM2之间的异同。此外，高温表达的异质性强调了对每个高温事件及其背景条件进行特化的必要性，以使古近代早期全球气候和碳酸盐埋藏模型中的人为物最小化。

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