Early Pliocene increase in thermohaline overturning: A precondition for the development of the modern equatorial Pacific cold tongue
Early Pliocene increase in thermohaline overturning: A precondition for the development of the modern equatorial Pacific cold tongue
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DOI：
10.1029/2008pa001645
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发表时间：
2010-06
期刊：
影响因子：
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通讯作者：
S. Steph;R. Tiedemann;M. Prange;J. Groeneveld;M. Schulz;A. Timmermann;D. Nürnberg;C. Rühlemann
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文献类型：
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作者：
S. Steph;R. Tiedemann;M. Prange;J. Groeneveld;M. Schulz;A. Timmermann;D. Nürnberg;C. Rühlemann
揭开地球气候从温暖的上新世早期的“类似厄尔尼诺状态”转变为现代类似“拉尼娜主导状态”的过程，目前是科学界面临的挑战。最近，上新世的气候变化与大约300万年前的海洋温跃层浅化以及地球最终过渡到两极冰窖世界有关。本文提出了上新世代用数据和气候模式结果，表明上新世气候转换的时间更早，强迫机制链也不同。我们表明，在480万至400万年前，由中美洲海道逐渐关闭引发的北大西洋经向翻转环流的增加，引发了热带温跃层的全面浅滩化。这为从温暖的东赤道太平洋到现代赤道冷舌状态的转变提供了先决条件，比先前的假设早了大约100万年。自~ 360万至350万年前以来，北半球冰川作用的增强导致信风的增强，从而放大了低纬度地区的上升流和生物生产力。
Unraveling the processes responsible for Earth’s climate transition from an “El Nino–like state” during the warm early Pliocene into a modern‐like “La Nina–dominated state” currently challenges the scientific community. Recently, the Pliocene climate switch has been linked to oceanic thermocline shoaling at ∼3 million years ago along with Earth’s final transition into a bipolar icehouse world. Here we present Pliocene proxy data and climate model results, which suggest an earlier timing of the Pliocene climate switch and a different chain of forcing mechanisms. We show that the increase in North Atlantic meridional overturning circulation between 4.8 and 4.0 million years ago, initiated by the progressive closure of the Central American Seaway, triggered overall shoaling of the tropical thermocline. This preconditioned the turnaround from a warm eastern equatorial Pacific to the modern equatorial cold tongue state about 1 million years earlier than previously assumed. Since ∼3.6–3.5 million years ago, the intensification of Northern Hemisphere glaciation resulted in a strengthening of the trade winds, thereby amplifying upwelling and biogenic productivity at low latitudes.