Collaborative Research: Downstream Impacts of the South Pacific Tropical Water

对南太平洋热带水（SPTW）的观测揭示了其在年际时间尺度上的变化和几十年来盐度增加的趋势。SPTW形成于南太平洋东部一个浅层盐度极大区，在副热带环流中沿赤道输送。SPTW的变率可能影响赤道地区的环流和水性质，特别是在盐度和温度异常没有密度补偿的情况下。SPTW具有明显的内赤道通道，因而具有较短的停留时间（5-15年）和较高的形成速率。因此，SPTW对赤道太平洋的贡献预计将比北太平洋的贡献更快、更强。该项目将使人们更全面地了解赤道海洋是如何通过南太平洋水域的俯冲而通风的，以及这种通风的变化是如何导致气候变化的。该项目的总体研究目标是：确定SPTW的变异性，并评估这种变异性对下游的影响。将研究SPTW变率与年际和长期大气强迫的关系。根据SPTW变率的程度和幅度，假设热带南太平洋的下游环流和热结构将存在动力特征。研究包括分析现有Argo漂浮剖面和WOCE/CLIVAR示踪剂（盐度、位涡度、氧、CFC、SF6、氚、氦-3、14C等）数据，以及OGCM对地球模拟器（OFES）的结果，以及模拟海洋环流和气候（ECCO）的被动和伴随示踪剂。智力优势：该项目将利用所有可用的水文（主要是Argo）和示踪观测来确定SPTW的可变性。将观测结果与高分辨率gcm的结果相结合，可以对这种变率及其对热带太平洋环流和热结构的下游影响进行全面、物理一致的解释。此外，模拟的被动示踪剂及其伴随物将提供明确的方法来识别SPTW途径，特别是评估中尺度涡流和小尺度过程的影响。SPTW对赤道潜流和赤道东太平洋上涌有贡献，两者都与ENSO有直接关系。对SPTW下游影响的衍生评估将增进对海洋的认识？并为太平洋ENSO和PDO等年际和更长时间尺度变率的可预测性和预测提供新的信息。更广泛的影响：该项目将提高ENSO和气候预测的使用技能；通过培养一名博士后和一名研究生对观测数据和模型输出进行分析，在促进科学发展的同时促进教育；通过建立不同学科和不同院校之间的合作，加强研究和教育的基础设施；并通过利用现有观测和高分辨率gcm的结果来评估气候变化，从而造福社会。其中一名pi参与了“指导物理海洋学女性以增加保留率”项目，并担任美国国家科学基金会向迈阿密大学提供的高级资助的执行委员会成员。

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.