RAPID Collaborative Research: Ground Truthing Coral Proxy Reconstructions of ENSO by Observing the 2014-15 El Nino

厄尔尼诺/南方涛动（ENSO）是全球年际气候变化的主要来源，它影响着美国和世界各地的各种重要经济部门，如渔业，农业和水资源管理。因此，了解其性质（强度，发生率，持续时间）在未来气候下可能发生的变化至关重要。最先进的气候模式预测表明，对未来厄尔尼诺/南方涛动变化的方向没有达成一致意见，仪器记录太短，无法限制厄尔尼诺/南方涛动的统计数据，因此必须利用古气候重建来建立厄尔尼诺/南方涛动的长期观测背景。在赤道太平洋中部收集的珊瑚中的同位素氧记录表明，厄尔尼诺/南方涛动现象今后可能会加强，但仍需注意：人们对厄尔尼诺/南方涛动现象对珊瑚特性的物理影响知之甚少，因为珊瑚的化学成分受到珊瑚礁环境中的水交换以及降水的影响。该项目将收集现场观测的物理条件（温度，盐度和电流）和同位素变化（海水，降水和珊瑚）在一个快速接近的事件：厄尔尼诺预计在冬季2014-15。拟议的数据集将用于验证正在进行的建模工作，创建对2014-15年厄尔尼诺事件的重新分析，目的是改善对过去厄尔尼诺事件重建记录的解释。一名博士后研究员将领导该项目，并在此过程中将扩大她的技术和科学专长。技术说明：来自珊瑚氧同位素（氧18）的古气候信息是过去气候变率数据的重要来源，为预测ENSO未来变化提供了观测基线。然而，ENSO通过平流移动、地形引起的上升流和地表通量影响氧气18：这使得使用氧气18记录与仪器记录或气候模式输出进行定量比较变得非常困难。NSF资助的一项正在进行的研究使用了新开发的同位素支持版本的区域海洋建模系统（isoROMS），表明影响氧18的过程的空间尺度可能相当小，因为代理收集地点位于近岸珊瑚礁环境中。因此，获得额外的原位数据是验证isoROMS结果和提高动力学理解的关键。厄尔尼诺事件预计在冬季2014-15提供了一个独特的机会，收集现场物理海洋学信息和同位素测量，这与isoROMS工作相结合，将提供最完整和动态一致的表征厄尔尼诺对代理网站的影响。这些结果将大大推进对现有氧18记录的解释以及气候模型验证工作。建议的数据集将是珊瑚古气候重建以及气候模型验证研究的主要资产。该项目由一位早期职业女性科学家领导，并将为她在NSF海洋科学博士后奖学金下进行的研究增加一个观察部分。这项研究将促进与来自一系列学科的同事的合作。最后，结果将用于对2014-15年厄尔尼诺事件进行重新分析，并将其作为社区资源提供。

The El Nino/Southern Oscillation (ENSO) is the dominant source of inter-annual climate variability in the world and it impacts a variety of important economic sectors in the U.S. and around the world like fisheries, agriculture and water resource management. Thus, it is vital to understand how its properties (magnitude, rate of occurrence, duration) might change under future climates. State-of-the-art climate model projections show no agreement on the direction of future ENSO changes and instrumental records are too short to constrain the statistics of ENSO, making it imperative to use paleoclimate reconstructions to establish a long-term observational context for ENSO. Record of isotopic oxygen in corals collected in the central equatorial Pacific suggests that ENSO may strengthen in the future, but a major caveat remains: the physics of the ENSO influence on the properties of corals is poorly understood, as their chemical composition is affected by water exchange in the reef environment, as well as by precipitation. This project will collect in situ observations of physical conditions (temperature, salinity,and currents) and isotopic variations (in seawater, precipitation, and corals) during a rapidly approaching event: the El Nino expected during winter 2014-15. The proposed dataset will be used to validate ongoing modeling work, create a reanalysis of the 2014-15 El Nino event with the goal of improving the interpretation of reconstructed records of past El Ninos. A post-doctoral fellow will lead the project and in the process will expand her technical and scientific expertise.Tehcnical description: Paleoclimate information from coral isotopic oxygen (Oxygen 18) is a critical source of data on past climate variability, providing an observational baseline for projections of future changes to ENSO. However, ENSO affects Oxygen 18 through advective shifts, topographically-induced upwelling, and surface fluxes: this makes it extremely difficult to use Oxygen 18 records for quantitative comparisons with instrumental records or climate model output. An ongoing NSF-funded study using a newly developed, isotope-enabled version of the Regional Ocean Modeling System (isoROMS) has shown that the spatial scale of processes affecting Oxygen 18 may be quite small, as proxy collection sites lie in nearshore reef environments. Thus, obtaining additional in situ data is critical for validating the isoROMS result and improving dynamical understanding. The El Nino event expected during winter 2014-15 provides a unique opportunity to collect both in situ physical oceanographic information and isotopic measurements, which combined with the isoROMS work would provide the most complete and dynamically consistent characterization of the El Nino influence on proxy sites to date. The results would greatly advance interpretation of existing oxygen 18 records as well as climate model validation efforts. The proposed dataset would be a major asset for studies of coral paleoclimate reconstruction as well as climate model validation. This project is led by an early career female scientist, and will add an observational component to the research she is conducting under an NSF Ocean Sciences postdoctoral fellowship. Collaborations with colleagues from a range of disciplines will be facilitated by this study. Finally, the results will be used to develop a reanalysis of the 2014-15 El Nino event, which will be provided as a resource for the community.