Collaborative Research: Reconstructing the Meridional SST Gradient and Climate Conditions of the Early Pliocene

该奖项是根据2009年《美国复苏和再投资法案》(公法111-5)提供资金的。大多数替代温度记录表明，在大约300万至500万年前的上新世早期，热带太平洋的特征是永久温暖的类似厄尔尼诺的平均状态。具体地说，沿赤道的海表面温度(SST)梯度很小或根本不存在。同时，赤道至副热带的经向SST梯度也减小，表明海洋热带暖池比现在向更远的方向延伸。尽管控制气候的外部因素，如大气二氧化碳浓度，基本上与今天相同，但这种气候条件仍然存在。这项研究的目标是生成太平洋几个关键区域的替代SST数据，使我们能够仔细重建太平洋SST的纬向分布，并研究可以解释上新世早期气候观测的机制。在生成新数据的同时，PIS将利用大气和海洋环流模式(GCMS)以及耦合GCMS的计算重建上层海洋和大气环流的热结构。这两个实验将使用两种互补的方法，有约束的和无约束的，并调查海洋垂直混合在维持类似厄尔尼诺现象和扩大暖池方面的作用。该项目的最终目标是创建一幅热带和亚热带早上新世气候的综合图景，确定有助于用耦合的GCM模拟这种状态的因素，并将上新世气候与当代气候变化联系起来。博士后研究员和研究生将获得该奖项的支持。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The majority of proxy temperature records indicate that during the early Pliocene, roughly 3 to 5 million years ago, the tropical Pacific was characterized by a permanently warm El Niño-like mean state. Specifically, the sea surface temperature (SST) gradient along the equator was very small or nonexistent. At the same time, the meridional SST gradient from the equator to the subtropics was also reduced, implying that the ocean tropical warm pool extended much farther poleward than at present. Such climate conditions persisted even though external factors that control climate, such as atmospheric CO2 concentrations, were essentially the same as today. The goal of this study is to generate proxy SST data in several critical regions of the Pacific Ocean that would enable us to carefully reconstruct the latitudinal SST distribution in the Pacific and to investigate mechanisms that can explain climate observations in the early Pliocene. In parallel with generating new data, the PIs will reconstruct the thermal structure of the upper ocean and atmospheric circulation using calculations with atmospheric and ocean General Circulation Models (GCMs), and with coupled GCMs. The coupled experiments will use two complimentary approaches, constrained and unconstrained, and investigate the role of ocean vertical mixing in maintaining El Niño-like conditions and an expanded warm pool. The ultimate goal of the project is to create a comprehensive picture of the early Pliocene climate in the tropics and subtropics, identify the factors that will facilitate modeling this state with coupled GCMs, and link the Pliocene climate to contemporary climate change. A post-doctoral researcher and graduate student will be supported with this award.