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首页> 外文期刊>Paleoceanography >Simulating Pliocene warmth and a permanent El Ni?o-like state: The role of cloud albedo
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Simulating Pliocene warmth and a permanent El Ni?o-like state: The role of cloud albedo

机译：模拟上新世温暖和永久性的厄尔尼诺现象：云的反照率

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Available evidence suggests that during the early Pliocene (4-5 Ma) the mean east-west sea surface temperature (SST) gradient in the equatorial Pacific Ocean was significantly smaller than today, possibly reaching only 1-2?C. The meridional SST gradients were also substantially weaker, implying an expanded ocean warm pool in low latitudes. Subsequent global cooling led to the establishment of the stronger, modern temperature gradients. Given our understanding of the physical processes that maintain the present-day cold tongue in the east, warm pool in the west and hence sharp temperature contrasts, determining the key factors that maintained early Pliocene climate still presents a challenge for climate theories and models. This study demonstrates how different cloud properties could provide a solution. We show that a reduction in the meridional gradient in cloud albedo can sustain reduced meridional and zonal SST gradients, an expanded warm pool and warmer thermal stratification in the ocean, and weaker Hadley and Walker circulations in the atmosphere. Having conducted a range of hypothetical modified cloud albedo experiments, we arrive at our Pliocene simulation, which shows good agreement with proxy SST data from major equatorial and coastal upwelling regions, the tropical warm pool, middle and high latitudes, and available subsurface temperature data. As suggested by the observations, the simulated Pliocene-like climate sustains a robust El Ni?o-Southern Oscillation despite the reduced mean east-west SST gradient. Our results demonstrate that cloud albedo changes may be a critical element of Pliocene climate and that simulating the meridional SST gradient correctly is central to replicating the geographical patterns of Pliocene warmth.
机译：现有证据表明，在上新世早期（4-5 Ma），赤道太平洋的东西平均海表温度（SST）梯度明显小于今天，可能只有1-2？C。子午海温梯度也大大减弱，这意味着低纬度地区的海洋暖池扩大了。随后的全球冷却导致建立了更强的现代温度梯度。考虑到我们对维持当今东部冷舌，西部温暖池以及由此形成的强烈温度差异的物理过程的理解，确定维持早期上新世气候的关键因素仍然对气候理论和气候模式构成挑战。这项研究证明了不同的云属性如何提供解决方案。我们表明，反照率云中子午梯度的减小可以维持子午和纬向海温梯度的减小，海洋中暖池的扩大和热分层的增加以及大气中哈德利和沃克环流的减弱。进行了一系列假设的修改过的云反照率实验之后，我们得出了上新世模拟，该模拟与来自主要赤道和沿海上升流地区的代理SST数据，热带暖池，中高纬度以及可用的地下温度数据很好地吻合。正如观测结果所表明的那样，尽管东西向SST平均梯度减小，但模拟的上新世状气候仍保持了强劲的厄尔尼诺-南方涛动。我们的结果表明，云的反照率变化可能是上新世气候的关键因素，正确模拟子午海温梯度对复制上新世温暖的地理模式至关重要。

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