Collaborative Research: Water mass variability and connectivity in a strengthening Southern Hemisphere Super-Gyre

最近发现的南半球超级涡旋(SHSG)是一个嵌套的南半球副热带涡旋系统。它横扫出塔斯曼海，将水向西输送，并为大西洋温盐环流的上端提供营养。次南极模式水(SAMW)和南极中间水(AAIW)是SHSG洋际联系的重要组成部分。通过这一连接，SAMW/AAIW可以在三个大洋盆地之间分配。最近的分析揭示了长达20年的SHSG旋转，以及大洋间塔斯曼和阿古拉斯岛泄漏的增加。该项目将研究SAMW/AAIW的时变性质以及它们与加强的SHSG的海洋间联系。SAMW/AAIW是大量的水团，会吸收大量的大气气体，这些气体对生命和气候都很重要--比如氧气和二氧化碳。它们是参与SHSG大洋间连接的两个重要水团。SHSG的增强与大气模式有关，例如南环空模式(SAM)。然而，预计臭氧层的恢复将削弱SAM。因此，SHSG以及塔斯曼和阿古拉斯的泄漏是否会继续加强是一个悬而未决的问题。同样未知的是，这些环流的可变性如何与SAMW/AAIW及其海洋间连通性的可变性联系起来。数据和模型将用于评估南部环流的连通性及其与大气模式(SAM、厄尔尼诺南方涛动(ENSO)和印度洋偶极子(IOD))的相关性。此外，观测值的估计值将有助于模型产出的检验。这项研究将通过培训加州大学洛杉矶分校的博士后研究员分析观测数据和模型输出来促进教育。它将通过建立不同学科(物理和化学海洋学)和不同机构(加州大学洛杉矶分校和迈阿密大学)之间的合作来加强研究和教育的基础设施。这项工作将是目前正在加强的SHSG中对SAMW/AAIW及其变异性的第一次系统研究。SAM的可变性，加上十多年的ARGO数据和最近的模式进展，使得研究SAMW/AAIW及其与SHSG海洋间连接的联系成为可能和及时。总体目标是：(1)估计SAMW/AAIW在三个南部副热带海洋的年平均性质和俯冲率，(2)评估有多少SAMW/AAIW从一个南部副热带气旋输送到另一个，其路径和体积输送如何随时间变化并与SHSG自旋有关，以及(3)探索南部副热带海洋水团变化的原因，特别注意与浮力通量、SHSG自旋和大气模式有关的变异性。为了实现这些目标，将分析现有的卫星和ARGO数据，结果将用于为海洋环流模型和模拟的被动/伴随示踪剂的输出提供信息。该奖项反映了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。

The recently identified Southern Hemisphere Super-Gyre (SHSG) is a nested system of the southern subtropical gyres. It sweeps out of the Tasman Sea, transports waters westward, and feeds the upper limb of the Atlantic thermohaline circulation. The Sub-Antarctic Mode Water(SAMW) and Antarctic Intermediate Water (AAIW) are prominently involved in the SHSG inter-ocean connection. Through this connection, the SAMW/AAIW can be distributed among the three ocean basins. Recent analysis has revealed a two-decade-long SHSG spin-up, and an increase in the inter-ocean Tasman and Agulhas Leakages. The project will study the time-varying nature of SAMW/AAIW and their inter-ocean link to a strengthening SHSG. The SAMW/AAIW are large volume water masses that take up substantial quantities of atmospheric gases, which are important for life and climate - such as oxygen and CO2. They are two significant water masses that are involved in the inter-ocean connection of the SHSG. Strengthening of SHSG has been correlated to atmospheric modes, e.g., Southern Annular Mode (SAM). However, recovery of the ozone layer is predicted to weaken the SAM. Thus, whether the SHSG and the Tasman and Agulhas Leakages continue strengthening or not is an open question. Also unknown is how variability in these circulations link to variability in SAMW/AAIW and their inter-ocean connectivity. Data and models will be used to assess connectivity of the southern gyres and their correlations with atmospheric modes (SAM, El Nino Southern Oscillation (ENSO), and Indian Ocean Dipole (IOD)). In addition, estimates from the observations will be useful as tests for model outputs. The research will promote education by the training of a postdoctoral fellow at UCLA in the analysis of observational data and model outputs. It will enhance infrastructure for research and education by establishing collaborations between different disciplines (physical and chemical oceanography) and different institutions (UCLA and University of Miami).This work would be the first systematic study of the SAMW/AAIW and their variability in a presently strengthening SHSG. Variability in the SAM, together with over a decade of Argo data and recent model advances make study of the SAMW/AAIW and their link to the SHSG inter-ocean connection possible and timely. The overall objectives are: (1) To estimate the annually averaged SAMW/AAIW properties and subduction rates in the three southern subtropical oceans, (2) To evaluate how much of the SAMW/AAIW is transported from one southern subtropical gyre into another, and how their pathways and volume transports vary with time and correlate with the SHSG spin-up, and (3)To explore the causes of water mass variability in the southern subtropical oceans with particular attention to variability associated with buoyancy fluxes, the SHSG spin-up and atmospheric modes. To achieve these objectives, available satellite and Argo data will be analyzed, and the results will be used to inform output from ocean general circulation models and simulated passive/adjoint tracers.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.