The onset of modern-like Atlantic meridional overturning circulation at the Eocene-Oligocene transition: Evidence, causes, and possible implications for global cooling
The onset of modern-like Atlantic meridional overturning circulation at the Eocene-Oligocene transition: Evidence, causes, and possible implications for global cooling
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DOI：
10.1002/2017gc006826
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发表时间：
2017-06-01
影响因子：
3.5
通讯作者：
Erez, Jonathan
中科院分区：
文献类型：
--
作者：
Abelson, Meir;Erez, Jonathan
来自整个大西洋和南大洋（大西洋区）的底栖 O-18 的汇编显示，在始新世和渐新世期间，O-18 (O-18) 的盆间梯度发生了两次重大跳跃：一次约为 40 Ma，第二次伴随着始新世-渐新世过渡 (EOT) 的同位素事件，大约为 33.7 Ma 前。从之前发布的环流模型和代理中，我们表明第一次 O-18 跳跃反映了与原始南极环极流 (ACC) 相关的南极洲的热隔离。第二个标志着半球间北源环流的开始，类似于现代大西洋经向翻转环流（AMOC）。类 AMOC 环流的开始稍早于 EOT（100-300 kyr），正如我们之前从南大洋和南大西洋 DSDP/ODP 站点发布的 O-18 和 C-13 的高分辨率剖面图所示。这些事件与北欧海域和北大西洋之间的反河口环流的开始同时发生，该环流始于 EOT 周围，可能与格陵兰-苏格兰海岭的加深有关。我们认为，虽然浅层原始ACC为南半球深海对流提供了能量，但半球间北部环流单元的出现是由于北欧反河口环流驱动下北大西洋深水形成的EOT显着增强。半球间北源环流单元的出现可能促进了EOT全球变冷。 通俗总结 始新世-渐新世转变是新生代期间主要的突变气候事件，标志着向冰室世界迈出的重要一步。我们表明，这种转变是向大西洋经向翻转环流（AMOC）世界的转变，并且稍微早于这种转变。因此，这可能是这种气候变化的一个主要因素。
A compilation of benthic O-18 from the whole Atlantic and the Southern Ocean (Atlantic sector) shows two major jumps in the interbasinal gradient of O-18 (O-18) during the Eocene and the Oligocene: one at approximate to 40 Ma and the second concomitant with the isotopic event of the Eocene-Oligocene transition (EOT), approximate to 33.7 Ma ago. From previously published circulation models and proxies, we show that the first O-18 jump reflects the thermal isolation of Antarctica associated with the proto-Antarctic circumpolar current (ACC). The second marks the onset of interhemispheric northern-sourced circulation cell, similar to the modern Atlantic meridional overturning circulation (AMOC). The onset of AMOC-like circulation slightly preceded (100-300 kyr) the EOT, as we show by the high-resolution profiles of O-18 and C-13 previously published from DSDP/ODP sites in the Southern Ocean and South Atlantic. These events coincide with the onset of antiestuarine circulation between the Nordic seas and the North Atlantic which started around the EOT and may be connected to the deepening of the Greenland-Scotland Ridge. We suggest that while the shallow proto-ACC supplied the energy for deep ocean convection in the Southern Hemisphere, the onset of the interhemispheric northern circulation cell was due to the significant EOT intensification of deepwater formation in the North Atlantic driven by the Nordic antiestuarine circulation. This onset of the interhemispheric northern-sourced circulation cell could have prompted the EOT global cooling.Plain Language Summary The Eocene-Oligocene transition is the major abrupt climatic event during the Cenozoic, which marks the major step to the icehouse world. We show that this transition is a shift to a world with Atlantic meridional overturning circulation (AMOC) and slightly preceded this transition. Thus, possibly was a major factor in this climatic shift.