P2C2: Dry or Wet in East Asia During Heinrich Events? New Perspectives from Multiproxy Cave Records and Coupled Model Simulations

该项目旨在将大规模亚洲季风环流与末次冰期北大西洋冷却事件（即，Heinrich事件），使用一套洞穴沉积物从长江中游在中国中东部。 该项目为威廉帕特森大学的博士后研究员和丰富的本科生研究经验提供支持，威廉帕特森大学是一所以本科教学为主的大学，拥有多元化的学生群体。（美国能源部指定的西班牙裔服务机构），包括许多第一代上大学。耦合大气环流模型（CGCM）模拟表明，东亚可能会变得更加潮湿，气候变暖，然而，这些预测仍然存在很大的不确定性，这在很大程度上是由于模型模拟之间缺乏一致性。 减少这些模型偏差是现代气候科学更相关和更具挑战性的方面之一，可以为满足未来对粮食、水、能源和生物多样性的需求提供战略。对于中国中部地区局地降水变化对亚洲季风区域扰动的敏感程度，目前还缺乏一致的认识，因为对东亚中部季风的认识主要是根据新的研究，氧同位素记录可能不一定反映当地的水文气候。 因此，本项目旨在通过解决以下问题来建立一个更完整的中国中东部地区降水变化的图像：（1）洞穴沉积物替代物，如微量元素（镁，锶，钡）是否可以用来反卷积区域大气环流从当地水文在东亚地区。如果是这样，（2）这些替代替代物对中国中东部地区的水文气候有什么启示，以及解释替代物推断的变化的机制是什么。(3)代理重建与耦合大气环流模式（CGCM）的古模拟匹配程度如何？本项目的主要目标是：（1）利用长江中游4个洞穴的洞穴沉积物中的微量元素和同位素比值，重建Heinrich事件1-6期间中国中东部的水文特征：（2）利用群落地球系统模式CGCM模拟，揭示水文特征的机制;以及（3）通过直接比较洞穴沉积物伪代理时间序列（使用气候模型输出与代理系统模型（PSM）结合构建）与测量的同位素剖面，在空间和时间上进行模型-代理合成。为了实现上述目标，研究人员旨在测试以下假设：（1）尽管印度季风减弱，在海因里希事件期间，中国中部更加湿润，从而挑战了长期以来的东亚季风（EASM）（2）中国中东部地区降水偏多的主要原因是季风演变的梅雨期开始滞后。在北半球变冷期间，梅雨期到盛夏期的延迟将导致盛夏期的缩短，中国中南部的湿润将以北方的干旱为代价;（3）在Heinrich事件期间，撒哈拉/萨赫勒地区的植被死亡和随后的更高的沙尘排放影响了ITCZ的位置，从而放大了假设（2）中概述的响应;（4）将洞穴沉积物伪代用指标时间序列（由PSM生成）与东亚的实测记录进行比较，将有助于识别洞穴沉积物三角洲18-氧的主导控制因素。 它还可以允许一个更强大的评估模型的技能，并帮助更好地评估任何模型代理偏差通过突然的气候变化events.This奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的知识价值和更广泛的影响审查标准。

This project aims to disentangle large-scale Asian monsoon circulation from local hydroclimate variability during North Atlantic cooling events of the last glacial cycle (i.e., Heinrich events) using a suite of speleothems from the middle reaches of the Yangtze River in central-eastern China. The project provides support for a postdoctoral research fellow and extensive undergraduate research experience for students at William Paterson University as a primarily undergraduate teaching university with a diverse student body (Hispanic Serving Institution designated by USDOE), including many first generation to attend college.Coupled General Circulation Model (CGCM) simulations suggest that East Asia is likely to get wetter with climatic warming, yet there is still much uncertainty in these projections due in large part to the lack of agreement among model simulations. Reducing these model biases is one of the more pertinent and challenging aspects of modern climate science as a means to provide strategies to meet the future needs in food, water, energy, and biological diversity.Currently, there is a lack a consistent understanding of precisely how sensitive local rainfall variability in central China is to regional perturbations in the Asian monsoon because knowledge of the monsoon in central East Asia principally relies upon oxygen-isotope records which, according to new research, may not necessarily reflect local hydroclimate. Therefore, this project aims to build a more complete picture of local rainfall variability in central-eastern China by addressing the following questions: (1) Can speleothem proxies, such as trace elements (Magnesium, Strontium, Barium) be used to deconvolve regional atmospheric circulation from local hydrology in East Asia. If so, (2) what do these alterative proxies inform us about local hydroclimate in central-eastern China and what are the mechanisms to explain the proxy-inferred changes. (3) How well do the proxy reconstructions match the paleo-simulations from coupled general circulation models (CGCMs). The main objectives of the project include: (1) reconstruct local hydrology in central-eastern China during Heinrich events 1-6 utilizing speleothem trace elements and isotope ratios from a suite of well-dated speleothems from four caves located in the middle reaches of the Yangtze River; (2) delineate the mechanisms for the hydrologic patterns observed in the proxies using the Community Earth System Model CGCM simulations; and (3) conduct model-proxy syntheses in space and time by directly comparing speleothem pseudoproxy time series--constructed using climate model output coupled with Proxy System Models (PSMs)--with measured isotope profiles.To address the above objectives the researchers aim to test the following hypotheses: (1) Despite a weakened Indian monsoon, central China was wetter during Heinrich events thereby challenging the longstanding paradigm that the East Asian Monsoon (EASM) became weaker during North Atlantic (NA) cooling; (2) The higher rainfall in central-eastern China can best be explained by a seasonally-lagged onset of the mei-yu stage of monsoon evolution. A later onset of mei-yu to midsummer during NA cooling would have resulted in a shorter midsummer stage, leaving south-central China wet at the expense of dry conditions to the north; (3) Vegetation demise and subsequent higher dust emissions from the Sahara/Sahel regions during Heinrich events, affected the position of the ITCZ and thus amplified the response outlined in hypothesis (2); (4) Comparison of speleothem pseudoproxy time series (generated from PSMs) with measured records from East Asia will help to identify the dominant controls on speleothem delta 18-Oxygen. It may also allow a more robust assessment of model skill and help to better evaluate any model-proxy biases through abrupt climate change events.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.