Collaborative Research: Response of the Tropical Pacific to the Abrupt Climate Change Event 8,200 Years Ago

8,200年前，一场灾难性的冰川融水涌入拉布拉多海，扰乱了大西洋环流，使北大西洋地区陷入寒冷状态长达世纪，并影响了全球气候。一些气候模式表明，巨大的热带雨带可能会因这种扰动而向南移动，这对于理解如果变暖的海洋破坏海洋环流，未来气候可能如何变化具有重要意义。然而，几乎没有关于8,2000年前热带地区降雨量的重建，这使得很难证实基于模型的预测。为了弥补这一数据缺口，该项目将根据位于现代热带雨带北方和南方边缘的帕劳和加拉帕戈斯湖沉积物的化学变化，重建热带太平洋的降雨变化。这项研究将包括气候模型模拟，阐明帕劳和加拉帕戈斯群岛预计的降雨量变化，以应对北大西洋增加的融水，其规模与8 200年前事件期间估计的规模相似。将在科斯雷（密克罗尼西亚）为密克罗尼西亚的高中教师沿着一个经验学习班。来自华盛顿大学的学生将与高中教师合作，进行实地练习，并根据他们的经验创建课程活动。 将根据帕劳和加拉帕戈斯湖放射性碳定年沉积物中微藻脂甾醇的氢同位素比率重建降雨量。将通过重复测量、沉积物岩心、湖泊和岛屿来确定氢同位素信号的区域性质。收集了所有9个沉积物岩心，长度从2米到15米不等，大多数都有最初的放射性碳年代学。每个岩芯的厚度在50-250厘米之间，其7000 - 9000年前的时间分辨率为25-40年。每个岩芯中全新世时期的剩余部分将有250-500年分辨率的氢同位素数据，以便将8,200年前的任何一次偏移置于完整的全新世背景下。这些降雨重建的解释，包括其全球范围内，将有助于模拟与同位素启用社区地球系统模型被迫与现实的融水通量拉布拉多海。由于模型在热带太平洋降雨对淡水强迫的响应方面存在很大差异，我们的降雨重建将为这些模型提供一个关键的基准，并有助于限制热带地区对AMOC突然中断的反应机制。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

A catastrophic outburst of glacial meltwater into the Labrador Sea 8,200 years ago disrupted Atlantic Ocean circulation, plunging the North Atlantic region into cold conditions for more than a century and impacting climate globally. Some climate models indicate that the vast tropical rain bands may shift south in response to such a perturbation, which has important implications for understanding how the climate might change in the future if a warming ocean disrupts ocean circulation. Yet few reconstructions of rainfall exist from the tropics that span the 8,2000-year-ago time interval, making it difficult to confirm the model-based predictions. To remedy this data gap this project will reconstruct rainfall changes in the tropical Pacific from chemical variations in lake sediments in Palau and the Galápagos that lie on the northern and southern edges of the modern tropical rain band. The research will include climate model simulations elucidating the rainfall changes expected in Palau and the Galápagos in response to a meltwater addition to the North Atlantic similar in size to that estimated during the 8,200-year-ago event. A workshop will be held for Micronesian high school teachers along with an experiential learning coarse in Kosrae (Micronesia). Students from the University of Washington will work with high school teachers and conduct field exercises and create curricular activities based on their experiences. Rainfall will be reconstructed from hydrogen isotope ratios of the microalgal lipid dinosterol in radiocarbon-dated sediments from lakes in Palau and the Galápagos. Confidence in the regional nature of the hydrogen isotope signals will be achieved through replication of measurements, sediment cores, lakes, and islands. All nine sediment cores, which range in length from 2-15 m, have been collected, and most have initial radiocarbon chronologies. A temporal resolution of 25-40 yr is proposed for the 7,000-9,000-year-ago interval of each core, which ranges in thickness from 50-250 cm. The remainder of the Holocene period in each core will have hydrogen isotope data produced at 250-500-yr resolution in order to place any of the 8,200-yr-ago excursions in the context of the full Holocene. Interpretations of these rainfall reconstructions, including their global context, will be aided by simulations with the isotope-enabled Community Earth System Model forced with realistic meltwater fluxes to the Labrador Sea. Because models diverge widely in their response of tropical Pacific rainfall to freshwater forcing, our rainfall reconstructions will provide a critical benchmark for these models and help constrain the mechanisms by which the tropics respond to abrupt AMOC disruptions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.