Collaborative Research: Reconstructing river discharge and hydrologic variability in Panama via coral geochemistry: Implications for management of the Panama Canal

合作研究：通过珊瑚地球化学重建巴拿马河流流量和水文变化：对巴拿马运河管理的影响

• 批准号: 2002465
• 负责人: Logan Brenner
• 金额: $ 9.42万
• 依托单位: Barnard College
• 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: 2020-06-01 至 2024-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2002465&HistoricalAwards=false
• 关键词: Collaborative; Research; Reconstructing; river; discharge

Rivers and hydrology play a critical role in tropical ecosystems. They impact aspects of climate, help to sustain life, and influence societal needs such as drinking water, food security, and economics. In Panamá, a specific concern is the impact of rainfall on the functioning of the Panamá Canal. Rainfall and river discharge (Q) are strongly linked in Panamá, and they play a crucial role in the sustained success of the canal. Rainfall totals across Panamá consistently place it in the top five countries for annual rainfall, but when major droughts occur, the Panama Canal Authority places restrictions on ship traffic to conserve water so that the canal can continue to operate. Panamá has a well-known seasonal variability in precipitation, with a wet season that lasts from about May through November. However, little is known about rainfall variation on longer time scales, on the order of decades or centuries. In addition, it is not clear how El Niño events may influence Panamanian rainfall, though there are suggestions of a relationship between El Niño strength and drought severity. These questions are hard to address because instrumental data, particularly river discharge records, are short and often unreliable – we need a longer-term perspective. The chemistry of coral skeletons can preserve records of climate conditions and climate variability; these chemical records are called climate proxies. This project will use coral climate proxies to reconstruct hydrologic variability along the Pacific Coast of Panamá over the past ~300 years at near-monthly resolution. The final product will be a multi-coral, multi-proxy record that can be used to identify the frequency and strength of events such as droughts or El Niño. This project includes support for 8 female undergraduates and 1 Ph.D. student. Results from this project will be incorporated into a teaching workshop for middle and high school educators and will also be shared with water resource managers in Panamá. Many tropical nations are subjected to intense variation in precipitation with extreme seasonality. Meridional migration of the Intertropical Convergence Zone (ITCZ) is largely responsible for this variability, with northward movement during the boreal summer and a southward shift during the austral summer. In the Pacific, El Niño and other less well constrained decadal and century-scale modes of ocean- atmosphere variability also dictate regional climate. In Panamá, a country whose rainfall and river discharge (Q) are tightly coupled, understanding hydrologic variability is of the utmost importance when considering the potential impacts on the Panamá Canal, whose functioning relies solely on hydraulic head differences between the canal locks and the Gatun Lake reservoir. Therefore, the probability of anomalous hydrologic conditions, such as drought and flooding, must be well defined. However, the lack of long instrumental records of tropical hydrology (i.e.; rainfall and Q) limits our ability to develop a rigorous understanding of drought and flood recurrence intervals. These issues raise the following questions: 1) What is the relationship between El Niño Southern Oscillation and droughts and flooding in Panamá? 2) Can we identify droughts and flood years that are not related to El Niño? And 4) Has there been multi-decadal or long-term secular changes in Q in Panamá and what climatic processes are involved? Preliminary results indicate that barium/calcium (Ba/Ca) time-series data from a coral core collected in 1984 at Secas Island in the Gulf of Chiriquí (GoC) along the Pacific Coast of Panamá has a remarkably strong correlation with Q from two major nearby rivers. Given these encouraging results, we will be completing the Ba/Ca analyses of the Secas Island core back to 1707 CE and to analyze a new GoC coral core collected in 2018. The final near- monthly resolved composite Ba/Ca record of Q will extend from 2018 to 1707 CE. By pairing Ba/Ca and δ18O on the same 1mm samples we can separately evaluate salinity and sea surface temperature changes in the GoC over the last 311 years. These paleo-Q and salinity reconstructions will provide a comprehensive history of Panamanian hydroclimate that can be exploited to track protracted deviations from average conditions.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.

河流和水文学在热带生态系统中起关键作用。它们会影响气候的各个方面，帮助维持生命并影响饮用水，粮食安全和经济学等社会需求。在Panamá，一个具体的问题是降雨对Panamá运河功能的影响。降雨和河流流量（Q）在Panamá中密切相关，它们在运河的持续成功中起着至关重要的作用。帕纳马各地的降雨始终将其置于前五名国家的年度降雨中，但是当发生重大干旱时，巴拿马运河管理局将限制船舶交通限制以节约用水，以便运河可以继续运作。 Panamá在降水方面具有众多季节性差异，潮湿的季节持续时间为5月至11月。但是，关于较长的时间尺度，数十年或几个世纪的降雨变化知之甚少。此外，尚不清楚厄尔尼诺事件如何影响巴拿马的降雨，尽管有人提出了厄尔尼诺强度与干旱严重程度之间存在关系的建议。这些问题很难解决，因为仪器数据，尤其是河流排放记录，且通常不可靠 - 我们需要长期的观点。珊瑚骨骼的化学性能可以保留气候条件和气候变化的记录；这些化学记录称为气候代理。该项目将使用珊瑚气候代理在过去的300年中以接近月份的分辨率重建帕纳玛太平洋海岸的水文变异性。最终产品将是一种多孔，多核记录，可用于识别事件的频率和强度，例如干旱或厄尔尼诺现象。该项目包括支持8位女性本科生和1位博士学位的支持。学生。该项目的结果将纳入中学和高中教育者的教学研讨会，并将与Panamá的水资源经理分享。许多热带国家因极端季节性而经历降水的巨大变化。受热带收敛区（ITCZ）的子午迁移基本上是这种可变性的原因，在北方夏季向北运动，在澳大利亚夏季向南移动。在太平洋地区，厄尔尼诺现象和其他人不太受控制的十年和世纪尺度的海洋风险变异性也决定了区域气候。在Panamá，一个国家的降雨和河流排放（Q）紧密耦合，当考虑对Panamá运河的潜在影响时，了解水文变异性至关重要，Panamá运河的潜在影响仅依赖于运河锁和Gatun Lake Lake Reservoir之间的氢化头差异。因此，必须很好地定义异常水文条件（例如干旱和洪水）的概率。但是，缺乏热带水文学的长期工具记录（即降雨和Q）限制了我们对干旱和洪水复发间隔的严格理解的能力。这些问题提出了以下问题：1）埃尔尼尼诺南部振荡与帕纳马的干旱与洪水之间有什么关系？ 2）我们可以确定与厄尔尼诺无关的干旱和洪水年吗？ 4）PanamáQ中是否存在多年或长期安全变化？涉及哪些气候过程？初步结果表明，从1984年，来自帕纳马太平洋海岸沿着奇罗基海湾（GOC）收集的珊瑚核心的钡/钙（BA/CA）时间序列数据与来自两个附近两个主要河流的Q具有非常强的相关性。鉴于这些令人鼓舞的结果，我们将完成对SECAS Island Core的BA/CA分析，回到1707 CE，并分析2018年收集的新的GOC Coral Core。最终的近月份解决的Q的最终近月Q的记录将从2018年延伸至1707年。通过将BA/CA和Δ18O配对在相同的1mm样品上，我们可以在过去311年中分别评估GOC中的盐度和海面温度变化。这些古Q和盐度的重建将为巴拿马氢化气候提供全面的历史，可以探索，以跟踪受保护的偏离平均状况。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛的影响标准通过评估来获得的支持。