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

最近发现的南半球超级环流（SHSG）是南部副热带环流的嵌套系统。它从塔斯曼海流出，向西输送海水，并为大西洋温盐环流的上端提供养分。亚南极模态水（SAMW）和南极中间水（AAIW）在SHSG洋间联系中起着重要作用。通过这种联系，SAMW/AAIW可以分布在三个洋盆之间。最近的分析揭示了长达20年的SHSG旋转，以及塔斯曼和阿古拉斯跨洋泄漏的增加。该项目将研究SAMW/AAIW的时变性质及其与加强的SHSG的跨洋联系。SAMW/AAIW是大体积的水团，它们吸收了大量的大气气体，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SHSG跨洋连接的两个重要水团。SHSG的增强与大气模态有关，如南环模（SAM）。然而，臭氧层的恢复预计将削弱SAM。因此，SHSG和塔斯曼和阿古拉斯泄漏是否继续加强是一个悬而未决的问题。同样未知的是，这些环流的变异性如何与SAMW/AAIW的变异性及其海洋间连通性联系起来。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，从观测得到的估计值将有助于检验模式输出。这项研究将通过在加州大学洛杉矶分校培养一名博士后，对观测数据和模型输出进行分析，从而促进教育。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，加强研究和教育的基础设施。这项工作将是第一次系统地研究当前正在加强的SHSG中SAMW/AAIW及其变异性。SAM的变率，加上Argo十多年的数据和最近模式的进展，使得研究SAMW/AAIW及其与SHSG跨洋联系的联系成为可能和及时的。总体目标是：(1)估计南亚副热带3大洋年平均SAMW/AAIW的性质和俯冲速率；(2)评估从一个南亚副热带环流向另一个南亚副热带环流输送SAMW/AAIW的量，以及它们的输送途径和体积如何随时间变化和与SHSG自旋上升的相关性；(3)探讨南亚副热带海洋水团变率的原因，特别是与浮力通量相关的变率。SHSG自旋上升和大气模式。为了实现这些目标，将分析现有的卫星和Argo数据，结果将用于海洋环流模型和模拟被动/伴随示踪剂的输出。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.