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Collaborative Research: Testing the Indian Ocean El Nino Hypothesis

合作研究：检验印度洋厄尔尼诺假说

基本信息

批准号：
1903478
负责人：
Pedro Di Nezio
金额：
$ 39.89万
依托单位：
University of Texas at Austin
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-08-01 至 2020-09-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1903478&HistoricalAwards=false
关键词：
Collaborative Research Testing Indian Ocean

项目摘要

This research will explore whether the Indian Ocean could sustain climate variability resembling El Nino under continued greenhouse warming. Testing this hypothesis is important because the activation of such a mode could drive large changes in year-to-year variability and hydrological extremes over the densely populated Indian Ocean rim. This mode of climate variability has not been observed in historical data, and therefore paleoclimate reconstructions are required to study conditions that favor its emergence, its spatial characteristics, and the ability of climate models to simulate it realistically. According to climate simulations, the activation of this mode depends on the state of the Indian Ocean, which currently does not exhibit upwelling nor has a shallow thermocline (the zone of the ocean water-column where temperatures rapidly decrease with depth) -- features needed to support strong, large-scale interactions between the ocean and atmosphere. Paleoclimate records indicate that these features could have existed in the geological past, particularly during the Last Glacial Maximum, roughly 19,000-21,000 years before present, albeit with cooler average conditions. Accordingly, simulations indicate greater cooling in the eastern Indian Ocean concurrent with strong upwelling and a shallow thermocline, which is reflected in the paleo-data as an altered basin-wide (east-west) temperature gradient. Preliminary data also reveal greatly increased seasonal and year-to-year temperature variations in this region, consistent with a state favoring stronger air-sea interactions. Climate simulations of this interval show that this increase in variability could have been caused by the activa- tion of the hypothesized "Indian Ocean El Nino". Throughout this project, the researchers will further test this hypothesis by generating new datasets of seasonal and year-to-year climate variability as well as investigating new model simulations that will help determine whether, and when, this mode will emerge in the future.This project builds on preliminary model-data investigations that indicate dramatically intensified seasonal and interannual climate variability in the eastern Indian Ocean during the Last Glacial Maximum. These data suggest that changes in oceanic conditions similar to those predicted for the future could cause the emergence of a presently unobserved mode of climate variability in the Indian Ocean that resembles modern El Nino in the Pacific. In order to test this hypothesis, the researchers will develop new paleoclimate datasets and model analyses to explore climate variability in the Indian Ocean under altered conditions. The proposed new paleodata will isolate seasonality and thermocline depth signatures and thus more rigorously test the "Indian Ocean El Nino" hypothesis. Advanced model-proxy comparison techniques using existing and new model simulations from the Paleoclimate Modelling Intercomparison Project (PMIP) will be developed to perform additional tests. Historical observations and model simulations will be analyzed to determine whether this mode is distinct from present-day climate variability, and address questions related to its precursors and background conditions under which it can become active. These questions will also be explored using existing and new climate model simulations from the Coupled Model Intercomparison Project (CMIP). These simulations will be used to assess uncertainties regarding the potential activation of the "Indian Ocean El Nino" in the near future. Constraints from the model-proxy comparison will be used to determine whether these uncertainties could be reduced. Further broader impacts include student and postdoc training, and support for a new faculty member at the University of Arizona.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.

这项研究将探讨在温室效应持续变暖的情况下，印度洋是否能够维持类似厄尔尼诺现象的气候变化。验证这一假设很重要，因为这种模式的激活可能会导致人口稠密的印度洋沿岸的年际变化和水文极端情况发生巨大变化。这种气候变率模式在历史资料中没有观测到，因此需要古气候重建来研究有利于其出现的条件、空间特征以及气候模式真实模拟它的能力。根据气候模拟，这种模式的激活取决于印度洋的状态，目前印度洋没有上升流，也没有浅层温跃层（海洋水柱的区域，温度随深度迅速下降）——这些特征需要支持海洋和大气之间强烈的、大规模的相互作用。古气候记录表明，这些特征可能存在于过去的地质时期，特别是在末次冰期，大约在距今19,000-21,000年前，尽管平均条件较冷。因此，模拟表明东印度洋更大的降温，同时伴有强烈的上升流和浅层温跃层，这在古数据中反映为整个盆地（东西）温度梯度的改变。初步数据还显示，该地区的季节性和年际温度变化大大增加，与倾向于更强的海气相互作用的状态相一致。对这段时间的气候模拟表明，这种变率的增加可能是由假设的“印度洋厄尔尼诺”的激活引起的。在整个项目中，研究人员将通过生成新的季节和年度气候变化数据集以及研究新的模型模拟来进一步验证这一假设，这些模型模拟将有助于确定这种模式是否以及何时会在未来出现。本项目建立在初步模式数据调查的基础上，这些调查表明，在末次盛冰期，东印度洋的季节和年际气候变化急剧加剧。这些数据表明，海洋条件的变化类似于对未来的预测，可能导致印度洋出现一种目前未观测到的气候变化模式，类似于太平洋的现代厄尔尼诺现象。为了验证这一假设，研究人员将开发新的古气候数据集和模型分析，以探索印度洋在改变条件下的气候变化。新提出的古数据将分离季节性和温跃层深度特征，从而更严格地检验“印度洋厄尔尼诺”假说。将开发先进的模式-代理比较技术，利用来自古气候模拟比对项目（PMIP）的现有和新模式模拟来进行额外的测试。将对历史观测和模式模拟进行分析，以确定这种模式是否不同于当今的气候变率，并解决与它的前体和背景条件有关的问题，在这些条件下，它可能变得活跃。这些问题也将利用来自耦合模式比对项目（CMIP）的现有和新的气候模式模拟来探讨。这些模拟将用于评估在不久的将来“印度洋厄尔尼诺”潜在激活的不确定性。来自模型-代理比较的约束将用于确定这些不确定性是否可以减少。更广泛的影响包括学生和博士后培训，以及为亚利桑那大学的一名新教员提供支持。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。