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首页> 外文期刊>Paleoceanography >Nd isotopic structure of the Pacific Ocean 70-30 Ma and numerical evidence for vigorous ocean circulation and ocean heat transport in a greenhouse world
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Nd isotopic structure of the Pacific Ocean 70-30 Ma and numerical evidence for vigorous ocean circulation and ocean heat transport in a greenhouse world

机译：太平洋70-30 Ma的Nd同位素结构以及温室世界中剧烈的海洋环流和海洋热传输的数值证据

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The oceanic meridional overturning circulation (MOC) is a crucial component of the climate system, impacting heat and nutrient transport, and global carbon cycling. Past greenhouse climate intervals present a paradox because their weak equator-to-pole temperature gradients imply a weaker MOC, yet increased poleward oceanic heat transport appears to be required to maintain these weak gradients. To investigate the mode of MOC that operated during the early Cenozoic, we compare new Nd isotope data with Nd tracer-enabled numerical ocean circulation and coupled climate model simulations. Assimilation of new Nd isotope data from South Pacific Deep Sea Drilling Project and Ocean Drilling Program Sites 323, 463, 596, 865, and 869 with previously published data confirm the hypothesized MOC characterized by vigorous sinking in the South and North Pacific ~70 to 30 Ma. Compilation of all Pacific Nd isotope data indicates vigorous, distinct, and separate overturning circulations in each basin until ~40 Ma. Simulations consistently reproduce South Pacific and North Pacific deep convection over a broad range of conditions, but cases using strong deep ocean vertical mixing produced the best data-model match. Strong mixing, potentially resulting from enhanced abyssal tidal dissipation, greater interaction of wind-driven internal wave activity with submarine plateaus, or higher than modern values of the geothermal heat flux enable models to achieve enhanced MOC circulation rates with resulting Nd isotope distributions consistent with the proxy data. The consequent poleward heat transport may resolve the paradox of warmer worlds with reduced temperature gradients.
机译：海洋子午翻转循环（MOC）是气候系统的重要组成部分，影响热量和养分的运输以及全球碳循环。过去的温室气候间隔存在一个矛盾，因为它们的赤道极间温度梯度较弱意味着MOC较弱，但保持这些弱梯度仍需要增加极地海洋热传输。为了研究新生代早期的MOC模式，我们将Nd同位素的新数据与Nd示踪剂启用的数值海洋环流以及耦合的气候模型模拟进行了比较。来自南太平洋深海钻探项目和海洋钻探计划站点323、463、596、865和869的新Nd同位素数据与先前发布的数据进行了同化，证实了假设的MOC的特征是南太平洋和北太平洋剧烈下沉〜70至30嘛。所有太平洋Nd同位素数据的汇编表明，直到40 Ma为止，每个盆地中都有剧烈，明显和独立的倾覆环流。模拟在各种条件下一致地再现了南太平洋和北太平洋的深对流，但是使用强深海垂直混合的情况产生了最佳的数据模型匹配。强烈的混合，可能是由于深海潮汐耗散的增强，风力驱动的内波活动与海底高原之间更大的相互作用，或者高于现代的地热通量值所致。这些模型使模型获得了更高的MOC循环速率，其Nd同位素分布与代理数据。随之而来的极向热传输可能会解决温度梯度降低的世界变暖的悖论。

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