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层水的净运动是向北的：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发生变化的。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经向翻转环流（AMOC）的变异性、热输送以及预测南大洋碳吸收的变化如何影响北大西洋碳汇至关重要。这项工作也有助于理解热带大西洋地区与当地社会相关的过程，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。更广泛的影响包括支持早期职业研究者，公共教育，科学劳动力培训和模型开发。粒子和示踪剂将在两个不同的MOM6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。现有的代码（来自PI）在MOM6的原生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精确的粒子轨迹。这个代码将进一步发展，包括一个随机平流项参数化亚网格尺度过程。使用各种方法，包括概率密度函数和水团转换框架，将确定北巴西洋流与周围水域之间交换水属性的位置。传递矩阵将用于客观地确定大西洋盆地中粒子从10S到10N的最可能路径。模型分辨率如何影响海洋粒子路径和粒子向北移动的时间尺度将被研究。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 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.