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.

该项目将调查以下假设：持续的北美干旱受到热带地区的持续性拉尼娜条件或降低El Nino-Southern振荡和缺乏El Ninos的差异。干旱的机制应通过详细分析工具观察期的观测和模型模拟来确定（1856年后）。这些知识将应用于在过去的千年和中新世中理解干旱，以试图将古水的变化归因于热带太平洋珊瑚记录的El Nino-Southern振荡的变化。热带太平洋海面温度将在过去1100年内估计，并使用化石珊瑚记录估算中新世，然后用于强制气候模型的集成整合。伴侣的合奏将进一步包括通过改变太阳辐照度和火山的外部强迫，以及对于中新世的轨道变化。合奏的比较将强调北美降水对外部强迫的直接影响以及埃尔尼诺 - 南方振荡的变化的相对重要性。将将模拟的水文变化与从树环记录（烹饪干旱地图集）以及二元格和历史证据中推断出的那些变化。在上一千年中，热带太平洋变化的原因将通过中间耦合模型和辅助全球循环模型进行研究，该模型将受到替代型和Orb countration countration，compurancience and courcation countration countration and obf contruciancians and obf corm off col and ob off colcan and Orb。这些模拟将在中世纪的温暖时期和小冰河时代的最低时期进行，以确定在更完整的模型中可以重现的El Nino-Southern振荡的变化，并检查全球其他地区的耦合动力学的影响。预计这项研究将提高对过去几千年中干旱机制的理解，从而提高了在水资源和农业规划中做出决定的知识基础，以期对持续干旱的未来风险进行更可靠的评估。