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

8200年前，一场灾难性的冰川融化水涌入拉布拉多海，扰乱了大西洋的环流，使北大西洋地区陷入了一个多世纪的寒冷条件，并影响了全球气候。一些气候模型表明，广大的热带雨带可能会因这种扰动而向南移动，这对于理解如果海洋变暖扰乱海洋循环，未来气候可能会如何变化具有重要意义。然而，热带地区82000年前的降雨量几乎没有重建，这使得基于模型的预测很难得到证实。为了弥补这一数据缺口，该项目将根据位于现代热带雨带南北边缘的帕劳和加拉帕戈斯群岛湖泊沉积物的化学变化，重建热带太平洋的降雨量变化。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期的降雨量变化，以响应北大西洋融化水的增加，其规模与8200年前事件期间的估计类似。将为密克罗尼西亚高中教师举办讲习班，并在科斯雷(密克罗尼西亚)举办体验式学习课程。来自华盛顿大学的学生将与高中教师合作，根据他们的经验进行实地练习和创建课程活动。降雨量将根据帕劳和加拉帕戈斯湖泊放射性碳测年沉积物中微藻类脂Dinosterol的氢同位素比率进行重建。将通过重复测量、沉积物岩心、湖泊和岛屿来实现对氢同位素信号区域性质的信心。所有9个长度在2-15米之间的沉积物岩芯都已收集完毕，大多数都有初步的放射性碳年代学。对于每个岩心的7000-9000年前的时间间隔，提出了25-40年的时间分辨率，其厚度范围为50-250厘米。每个核的全新世剩余时间将以250-500年的分辨率产生氢同位素数据，以便将8200年前的任何一次漂移置于全新世的背景下。对这些降雨重建的解释，包括它们的全球背景，将得到利用同位素启用的社区地球系统模型的模拟的帮助，这些模拟是用真实的融水通量强迫到拉布拉多海的。由于模型对热带太平洋降雨对淡水强迫的响应差异很大，我们的降雨重建将为这些模型提供一个关键基准，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，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.