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: 2002467
• 负责人: Braddock Linsley
• 金额: $ 33.83万
• 依托单位: Columbia University
• 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=2002467&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.

河流和水文在热带生态系统中起着至关重要的作用。它们影响气候的各个方面，有助于维持生命，并影响饮用水、粮食安全和经济等社会需求。在帕纳马，一个特别令人关切的问题是降雨对帕纳马运河功能的影响。在帕纳马，降雨和河流流量(Q)密切相关，它们对运河的持续成功起着至关重要的作用。巴拿马的总降雨量一直是年降雨量排名前五的国家之一，但当发生重大干旱时，巴拿马运河管理局会对船只交通进行限制，以节约用水，使运河能够继续运营。PanAma的降水量有众所周知的季节性变化，雨季从大约5月持续到11月。然而，人们对较长时间尺度上、几十年或数百年量级的降雨量变化知之甚少。此外，目前尚不清楚厄尔尼诺事件可能如何影响巴拿马的降雨量，尽管有迹象表明厄尔尼诺强度与干旱严重程度之间存在关系。这些问题很难解决，因为工具数据，特别是河流流量记录，都很短，而且往往不可靠--我们需要更长远的视角。珊瑚骨骼的化学成分可以保存气候条件和气候变异性的记录；这些化学记录被称为气候代用品。该项目将使用珊瑚气候指标，以近月分辨率重建近300年来帕纳马太平洋沿岸的水文变化。最终产品将是一个多珊瑚、多代理记录，可用于识别干旱或厄尔尼诺等事件的频率和强度。该项目包括对8名女本科生和1名博士生的支持。该项目的成果将纳入初中和高中教育工作者的教学讲习班，还将与帕纳马的水资源管理人员分享。许多热带国家的降水量变化剧烈，具有极强的季节性。热带辐合带(ITCZ)的经向迁移是造成这种变化的主要原因，北部夏季向北移动，南部夏季向南移动。在太平洋，厄尔尼诺现象和其他限制较少的海洋-大气变化的十年和世纪尺度模式也决定了区域气候。在帕纳马这个降雨量和河流流量(Q)紧密相连的国家，在考虑对帕纳马运河的潜在影响时，了解水文变化是至关重要的，因为它的运行完全依赖于运河船闸和加通湖水库之间的水头差。因此，必须很好地定义干旱和洪水等异常水文条件的概率。然而，缺乏热带水文学的长期仪器记录(即降雨量和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)厄尔尼诺南方涛动与巴拿马的干旱和洪水之间有什么关系？2)我们能识别出与厄尔尼诺无关的干旱和洪水年份吗？4)帕纳马的Q是否存在多年或长期的长期变化，涉及哪些气候过程？初步结果表明，1984年在帕纳马太平洋沿岸奇里奎湾(Goc)的塞卡斯岛(Secas Island)采集的珊瑚岩芯中的钡/钙(BA/Ca)时间序列数据与附近两条主要河流的Q有很强的相关性。鉴于这些令人鼓舞的结果，我们将完成回到公元1707年的塞卡斯岛岩芯的Ba/Ca分析，并分析2018年收集的一个新的Goc珊瑚岩芯。Q的最终近月分辨综合记录将从2018年延长到1707年。通过在相同的1 mm样品上配对BA/Ca和δ18O，我们可以分别评估过去311年来GOC的盐度和海温变化。这些古Q和盐度重建将提供巴拿马水气候的全面历史，可以用来追踪长期偏离平均条件的情况。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。