Long‐Term Variability in Pliocene North Pacific Ocean Export Production and Its Implications for Ocean Circulation in a Warmer World
Long‐Term Variability in Pliocene North Pacific Ocean Export Production and Its Implications for Ocean Circulation in a Warmer World
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DOI：
10.1029/2022av000853
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发表时间：
2023-08
期刊：
影响因子：
8.4
通讯作者：
J. Abell;G. Winckler
中科院分区：
文献类型：
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作者：
J. Abell;G. Winckler
与高纬度的北大西洋不同，现代亚北极的北太平洋没有形成深水。以前有人认为，在与今天不同的气候状态中，这种二分法并没有持续下去，北太平洋深水（NPDW）的形成发生在亚北极的北太平洋，这支持了一个活跃的太平洋经向翻转环流（PMOC）。在此，我们提供了北太平洋亚北极中部横跨晚中新世至早更新世的生产力和沉积氧化还原条件的新记录。这些重建表明，在2.7-6 Ma的时间间隔内，北太平洋的出口产量大于现代，且存在时间变化。我们的时间序列，结合先前发表的上新世北太平洋动力学的数据集和模型输出，支持上新世活跃的PMOC的存在，并表明NPDW的形成特征在地球历史的这段较温暖的时期发生了变化。在考虑第四纪北太平洋海洋动力学时，深水形成时期出口产量增加的这一发现提出了一个难题，北太平洋亚北极地区的生产力在假定发生增强倾覆的间隔期间下降。考虑到上新世和第四纪北太平洋环流假说的警告，以及与海洋环流无关的其他机制，我们评估了我们的数据。由于上新世可能是近期气候的类似物，随着地球继续变暖，我们的结果和分析对我们理解未来几十年的区域和全球气候具有重要影响。
Unlike in the high‐latitude North Atlantic, no deep water is formed in the modern subarctic North Pacific. It has previously been suggested that during climate states different from today, this dichotomy did not endure, and the formation of North Pacific Deepwater (NPDW) occurred in the subarctic North Pacific, which supported an active Pacific meridional overturning circulation (PMOC). Here we provide new records of productivity and sedimentary redox conditions from the central subarctic North Pacific spanning the late Miocene to early Pleistocene. These reconstructions indicate greater‐than‐modern and temporally varying North Pacific export production across the interval of ∼2.7–6 Ma. Our time series, combined with previously published data sets and model output for Pliocene North Pacific Ocean dynamics, support the presence of an active PMOC during the Pliocene, and suggest that the characteristics of NPDW formation varied during this warmer interval of Earth's history. This finding of elevated export production at a time of deep water formation presents a conundrum when considering Quaternary North Pacific Ocean dynamics, where subarctic North Pacific productivity declines during intervals when enhanced overturning is posited to occur. We evaluate our data considering the caveats of both (i.e., Pliocene and Quaternary North Pacific circulation) hypotheses, as well as additional mechanisms unrelated to ocean circulation. Because the Pliocene is a possible analogue for near‐future climate, our results and analyses have important ramifications for our understanding of regional and global climate in the coming decades as the planet continues to warm.