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

合作研究：热带太平洋对8200年前突发气候变化事件的反应

• 批准号: 2002364
• 负责人: Julian Sachs
• 金额: $ 45.64万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-10-01 至 2024-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2002364&HistoricalAwards=false
• 关键词: Collaborative; Research; Response; Tropical; Pacific

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.

8200年前，冰川融化的灾难性爆发进入拉布拉多海，破坏了大西洋的循环，使北大西洋地区陷入了一个多世纪的寒冷条件，并在全球范围内影响气候。一些气候模型表明，巨大的热带雨带可能会响应这种扰动而向南转移，这对于理解如果温暖的海洋破坏了海洋循环，这对理解气候可能会在未来发生变化具有重要意义。然而，从跨越8,2000年的时间间隔的热带中，很少有降雨的重建，因此很难确认基于模型的预测。为了解决这个数据差距，该项目将重建热带太平洋的降雨变化，从帕劳湖沉积物的化学变化以及位于现代热带雨带的北部和南部边缘的加拉帕戈斯群岛的化学变化。这项研究将包括气候模型模拟，阐明了帕劳和加拉帕戈斯预期的降雨变化，以响应北大西洋上的融水，大小与8200年期间估计的降雨量相似。将在科斯拉（Microneia）（Microneia）的专家学习中为密克罗尼亚高中教师举行一个研讨会。华盛顿大学的学生将与高中教师合作，并根据他们的经验进行课程活动。降雨将从来自Palau和Galápagos的湖泊的放射性碳年代沉积物中的微藻脂质害油的氢同位素比重建。通过复制测量，沉积物核，湖泊和岛屿的复制，将对氢同位素信号的区域性质信心。所有九个九个沉积物核的长度范围为2-15 m，并且大多数都具有初始的放射性碳年代。对于每个核心的7,000-9，000年间隔，提出了25 - 40年的临时分辨率，厚度从50-250 cm厚度。每个核心的全新世的其余时间将在250-500年的分辨率下产生的氢同位素数据，以便在全新世的背景下将8200倍的游览中的任何一个放置。这些降雨重建的解释，包括它们的全球背景，将通过以启用同位素的社区地球系统模型的模拟来帮助，该模型被迫使用现实的融合水磁通量到拉布拉多海。因为模型在热带太平洋降雨对淡水强迫的反应方面存在很大分歧，所以我们的降雨重建将为这些模型提供关键的基准，并有助于限制热带对突然AMOC中断反应的机制。该奖项反映了NSF的法定任务，并通过评估基金会的MERITIAL和BRODIT构成了基金会的支持。