Collaborative Research: Tropical Forcing of Hydrological Variations Over North America during the Last Millennium

合作研究：上个千年北美水文变化的热带强迫

• 批准号: 0500275
• 负责人: Amy Clement
• 金额: $ 21.14万
• 依托单位: University of Miami
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-10-01 至 2009-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0500275&HistoricalAwards=false
• 关键词: Collaborative; Research; Tropical; Forcing; Hydrological

This project will investigate the hypothesis that persistent North American droughts are forced by persistent La Nina conditions in the tropics or by reduced variance of the El Nino-Southern Oscillation and an absence of El Ninos. The mechanisms of drought are to be worked out by detailed analysis of observations and model simulations of the period of instrumental observations (post 1856). This knowledge will be applied to understanding drought over the last millennium and in the mid-Holocene in an attempt to attribute the paleohydrological variations to changes in the El Nino-Southern Oscillation recorded by tropical Pacific corals. Tropical Pacific sea surface temperatures will be estimated for periods within the last 1100 years and for the mid-Holocene using fossil coral records and then used to force ensemble integrations of a climate model. Companion ensembles will further include external forcing by altered solar irradiance and volcanism and, for the mid-Holocene, orbital changes. Comparison of the ensembles will highlight the relative importance for North American precipitation of the direct impact of external forcings and the changes in the El Nino-Southern Oscillation. Simulated hydrological variations will be compared to those inferred from tree ring records (the Cook Drought Atlas) and limnological, geomorphological and historical evidence.The causes of the tropical Pacific changes over the last millennium will be investigated using an intermediate coupled model and a coupled global circulation model which will be subjected to changes in solar irradiance, volcanism and orbital configuration. These simulations will be conducted for the Medieval Warm Period and the Maunder Minimum period of the Little Ice Age, to ascertain if the changes in the El Nino-Southern Oscillation simulated by the intermediate model are reproducible in a more complete model, and to examine the impacts of coupled dynamics in other regions of the globe. This research is expected to improve the understanding of the mechanisms of drought over the last few millennia, improving the knowledge base upon which decisions in water resource and agricultural planning are made, with a view to offering a more reliable assessment of the future risks of persistent drought.

该项目将调查一种假设，即持续的北美干旱是由于热带持续的拉尼娜条件或由于厄尔尼诺-南方涛动的减少和厄尔尼诺的存在而造成的。干旱的机制将通过对观测的详细分析和仪器观测期间(1856年后)的模型模拟来确定。这一知识将用于理解过去一千年和全新世中期的干旱，试图将古水文变化归因于热带太平洋珊瑚记录的厄尔尼诺-南方涛动的变化。热带太平洋海面温度将使用化石珊瑚记录估计过去1100年和中全新世期间的温度，然后用于强制气候模型的整体积分。伴星组合将进一步包括太阳辐射变化和火山活动造成的外部强迫，以及全新世中期的轨道变化。这些集合的比较将突出外部强迫的直接影响和厄尔尼诺-南方涛动的变化对北美降水的相对重要性。模拟的水文变化将与从树木年轮记录(库克干旱地图集)以及湖泊、地貌和历史证据推断的结果进行比较。将使用一个中间耦合模式和一个耦合全球环流模式来研究热带太平洋在过去一千年中变化的原因，该模式将受到太阳辐射、火山活动和轨道结构的影响。这些模拟将针对中世纪暖期和小冰期的蒙德最小时期进行，以确定中间模式模拟的厄尔尼诺-南方涛动的变化是否可以在更完整的模式中重现，并检查耦合动力学在全球其他地区的影响。这项研究预计将增进对过去几千年干旱机制的了解，改善水资源和农业规划决策所依据的知识基础，以期对未来持续干旱的风险提供更可靠的评估。