Collaborative Research: Downstream Impacts of the South Pacific Tropical Water

对南太平洋热带水域的观测表明，在年际时间尺度上存在变化，而且几十年来盐度有增加的趋势。 由浅盐度最大值确定的SPTW在南太平洋东部形成，并在副热带环流和沿着赤道输送。 SPTW的变化可能会影响赤道地区的环流和水的性质，特别是如果盐度和温度异常没有密度补偿。 SPTW有一个明显的内部赤道路径，因此相对较短的停留时间（5-15年）和高的形成率。 因此，SPTW对赤道太平洋的贡献预计将比北太平洋的对应物更快和更强。 该项目将开始更全面地了解赤道海洋是如何通过南太平洋沃茨的俯冲而通风的，以及这种通风的可变性如何促成气候的可变性。 该项目的总体研究目标是：确定SPTW的可变性，并评估这种可变性的下游影响。 将研究SPTW变率与年际和长期大气强迫的关系。 根据SPTW变化的程度和幅度，假设热带南太平洋的下游环流和热结构将有一个动力学特征。 研究内容包括分析现有Argo漂浮剖面和WOCE/CLIVAR示踪剂（盐度、位涡、氧、CFC、SF6、氚、氦-3、14 C等）。数据，以及地球模拟器（OFES）OGCM的结果，以及估计海洋环流和气候（ECCO）的模拟被动和伴随示踪剂。 将观测结果与高分辨率大气环流模式的结果结合使用，将能够对这种变异及其对热带太平洋环流和热结构的下游影响作出全面、物理上一致的解释。 此外，模拟的被动示踪剂及其伴随物将提供明确的手段来识别SPTW路径，特别是评估中尺度涡旋和小尺度过程的影响。 SPTW对赤道潜流和赤道东太平洋的水涌有贡献，两者都与ENSO有直接关系。 对SPTW下游影响的衍生评估将增强对海洋？的作用，并提供了新的信息的年际和更长的时间尺度变率，如ENSO和PDO在太平洋的可预报性和预测。 更广泛的影响：该项目将改进用于厄尔尼诺/南方涛动和气候预测的技能;通过培训一名博士后研究员和一名研究生分析观测数据和模型产出，推进科学，同时促进教育;通过在不同学科和不同机构之间建立协作关系，加强研究和教育基础设施;利用现有的观测资料和高分辨率GCM的结果评估气候变化，造福社会。 其中一名PI参加了指导物理海洋学妇女以提高保留率的计划，并在迈阿密大学NSF预付款的执行委员会中任职。

Observations of South Pacific Tropical Water (SPTW) have revealed variability on interannual time scales and a trend of increasing salinity over several decades. SPTW identified by a shallow salinity maximum forms in the eastern South Pacific and is transported in the subtropical gyre and along the equator. Variability of SPTW may affect the circulation and water properties in the equatorial region, in particular if the salinity and temperature anomalies are not density compensated. SPTW has a significant interior equatorward pathway, and thus a relatively short (5-15 years) residence time and high formation rate. As a consequence, the contribution of SPTW to the equatorial Pacific is expected to be faster and stronger than its North Pacific counterpart. This project will initiate a more complete understanding of how the equatorial ocean is ventilated through the subduction of South Pacific waters and how variability in this ventilation contributes to climate variability. The overall research objectives of the project are: to identify variability in SPTW, and to assess downstream impacts of this variability. The relationship of SPTW variability to interannual and longer term atmospheric forcing will be investigated. Depending on the extent and magnitude of the SPTW variability, it is hypothesized that there will be a dynamical signature in the downstream circulation and thermal structure of the tropical South Pacific. The research includes the analysis of available Argo floating profiles and WOCE/CLIVAR tracer (salinity, potential vorticity, oxygen, CFC, SF6, tritium, helium-3, 14C, etc.) data, as well as results from the OGCM for the Earth Simulator (OFES), and simulated passive and adjoint tracers from the Estimating the Circulation and Climate of the Ocean (ECCO).Intellectual merit: The project will utilize all available hydrographic (mainly Argo) and tracer observations to identify the variability of SPTW. The combined use of observations with results from high-resolution GCMs will allow for a comprehensive, physically consistent interpretation of this variability and its downstream impacts on the tropical Pacific Ocean circulation and thermal structure. In addition, the simulated passive tracer and its adjoint will provide unambiguous means to identify the SPTW pathways and in particular to assess the influence of meso-scale eddies and small scale processes. The SPTW contributes to the Equatorial Undercurrent and water upwelled in the eastern equatorial Pacific, both having direct relevance to ENSO. The derived assessment of the SPTW downstream impacts will enhance the understanding of ocean?s role in climate variability, and provide new information for the predictability and prediction of interannual and longer time scale variability such as ENSO and PDO in the Pacific. Broader impacts: The project will lead to improved skills for use with ENSO and climate prediction; advance science while promoting education by the training of a postdoctoral fellow and a graduate student in the analysis of observational data and model outputs; enhance infrastructure for research and education by establishing collaborations between different disciplines and different institutions; and benefit the society by the use of existing observations and results from high-resolution GCMs to assess climate change. One of the PIs participates in the program Mentoring Physical Oceanography Women to Increase Retention, and is on the implementation committee of an NSF Advance grant to the University of Miami.