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Shifts in Phytoplankton Composition and Stepwise Climate Change During the Middle Miocene
Paleoceanography and Paleoclimatology ( IF 3.5 ) Pub Date : 2020-08-19 , DOI: 10.1029/2020pa003915
J. Henderiks 1 , M. Bartol 1 , N. Pige 1, 2 , B.‐Th. Karatsolis 1 , B. C. Lougheed 1
Affiliation  

The abundance and composition of modern phytoplankton are primarily related to equator‐to‐pole temperature gradients and global ocean circulation, which in turn determine the availability of nutrients in the photic zone. The nutricline is found at greater depths in warm, tropical waters, whereas more vigorous surface mixing in higher latitudes (seasonally) enhances nutrient availability and primary productivity. Ocean temperatures were ~7°C higher during the middle Miocene Climatic Optimum (MCO; ~16.9–14.7 million years ago, Ma), which was followed by Antarctic glaciation and global cooling during the middle Miocene Climate transition (MMCT; 14.7–13.8 Ma). Four decades ago, Haq (1980, https://doi.org.10.2307/1485353) already related migration patterns of low‐latitude versus high‐latitude calcareous nannoplankton in the Atlantic Ocean to major climatic fluctuations during the Miocene. Here, we detail and discuss the macroevolutionary patterns and processes across the middle Miocene (~16.5–11 Ma) at five deep sea sites on a north‐south transect in the Atlantic Ocean (57°N to 28°S). We show that the major cooling step toward the modern “icehouse” world impacted coccolithophore communities at all latitudes. Contrary to previous observations suggesting that tropical sites showed little change and that midlatitudes were the most sensitive recorders of climate change across the MMCT, we show that all sites recorded a marked diversification and increase in abundance of reticulofenestrids. Global cooling and related increased meridional overturning circulation are implicated as likely forcings for this macroevolutionary step toward establishing modern coccolithophore communities that are dominated by eurythermal and eurytrophic species such as Emiliania huxleyi.

中文翻译:

中新世中期浮游植物组成的变化和气候的逐步变化

现代浮游植物的丰度和组成主要与赤道到极点的温度梯度和全球海洋环流有关,这反过来又决定了光合带养分的可用性。在温暖的热带水域中发现的营养成分更深,而在较高纬度(季节性)中更剧烈的地表混合提高了养分的利用率和初级生产力。在中新世中期(MCO;〜16.9-1470万年前,Ma),海洋温度升高了约7°C,随后在中新世中期(MMCT; 14.7-13.8Ma),南极冰期和全球变冷。 )。四十年前,哈克(Haq,1980,https://doi.org.10。2307/1485353)已经将大西洋中低纬度和高纬度钙质浮游纳米藻的迁移模式与中新世期间的主要气候波动相关联。在这里,我们详细讨论了中大西洋中新世(〜16.5-11 Ma)在大西洋南北横断面(57°N至28°S)的五个深海站点的宏观演化模式和过程。我们表明,迈向现代“冰屋”世界的主要降温步骤影响了各个纬度的球石藻群落。与以前的观察结果相反,热带地区的气候变化几乎没有变化,中纬度地区是整个MMCT中最敏感的气候变化记录者,我们发现所有站点都记录了明显的多样性,网状雌蕊的数量增加了。
更新日期:2020-08-19
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