Ventilation and mixing of surface and intermediate waters in the tropical Atlantic: perspectives from Lagrangian particles and tracers

大西洋盆地表层和中间水域的净移动是向北的：水进入非洲和南美洲南部的盆地，并在北大西洋下沉。该项目将研究向北流动的水团在到达北大西洋之前是如何在热带大西洋被改变的。了解海洋通风和混合对水性质的影响对于解释现代大西洋子午线翻转环流(AMOC)的可变性、热量输送以及预测南大洋碳吸收的变化可能如何影响北大西洋碳汇是至关重要的。这项工作也与理解热带大西洋区域的当地社会相关过程有关，例如氧气如何到达赤道大西洋西部的中心水域，以及AMOC的热输送如何影响热带辐合带的位置。更广泛的影响包括对早期职业调查员的支持、公共教育、科学劳动力培训和模型开发。粒子和示踪剂将在MOM6的两个不同的全球版本中平流60年：1/4度分辨率版本和1/8度分辨率版本。现有的程序(来自PI)在MOM6的S本地坐标系中在线平流拉格朗日粒子，通过在线执行粒子平流来创建准确的粒子轨迹。该代码将进一步开发，以包括随机平流项，以参数化次网格尺度的过程。利用各种方法，包括概率密度函数和水团转化框架，将确定巴西北部洋流与周围水域之间水性质交换的位置。转移矩阵将被用来客观地确定一个粒子在大西洋盆地从10s到10n之间最可能的路径。模型分辨率如何影响海洋粒子的路径和粒子向北移动的时间尺度将被调查。这一裁决反映了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 net movement of surface and intermediate waters in the Atlantic basin is northward: waters enter the basin south of Africa and South America, and sink in the North Atlantic. The project will examine how northward flowing water masses are modified in the Tropical Atlantic before they reach the North Atlantic. Understanding the effects of ocean ventilation and mixing on this water's properties is essential to explain modern Atlantic Meridional Overturning Circulation (AMOC) variability, heat transport, and to prediction of how changes in Southern Ocean carbon uptake might impact the North Atlantic carbon sink. This work is also pertinent to understanding local societally-relevant processes in the Tropical Atlantic region, such as how oxygen reaches central waters in the western equatorial Atlantic, and how heat transport by the AMOC affects the location of the Intertropical Convergence Zone. Broader impacts include support of an early career investigator, public education, scientific workforce training, and model development. Both particles and tracers will be advected for 60yrs in two different global versions of MOM6: a 1/4deg resolution version and a 1/8deg resolution version. Existing code (from the PI) that advects Lagrangian particles online in MOM6’s native coordinate system creates accurate particle trajectories by performing particle advection online. This code will be further developed to include a stochastic advection term to parameterize subgrid-scale processes. Using a variety of methods, including probability density functions and the water mass transformation framework, locations where water properties are exchanged between the North Brazil Current and the surrounding water will be identified. The transfer matrix will be used to objectively identify the most likely pathway of a particle from 10S to 10N in the Atlantic basin. How model resolution affects ocean particle pathways and the timescales on which particles travel northward will be investigated.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.