The shallow limb of the Atlantic meridional overturning circulation: variability and impacts on the ocean's carbon and nutrient reservoirs

亚极地北大西洋是一个强烈的海-气相互作用导致温跃层水域转变为被称为北大西洋深水(NADW)的水团集合的区域。NADW淹没了盆地的深部和中层，并为全球变化提供了一条寻找其海洋表达的途径。转变为NADW的前体水域部分源于副热带水团，它们对亚极地涡旋的渗透被认为在时间上是不同的。控制倾覆输送及其时间变异性的基本机制仍然知之甚少，对海洋内部的热量、碳和营养物储存库的影响也是如此。为了探测海洋环流和生物地球化学性质的人为变化，我们必须加强对造成这种变化的机制的理解。 因此，拟议的工作要解决的基本问题是：决定大西洋倾覆输送时间变异性的主要机制是什么？这种变化对NADW的生物地球化学性质有什么影响？这项工作将围绕三个目标进行组织： 1.在一般环流模式中描述控制MOC变化的机制、它对人为变化的脆弱性以及它对海洋碳库和营养库的影响。 2.调查来自水文测量任务、卫星产品的观测数据以及北大西洋浮标剖面收集的近二十年数据中出现的变异性和趋势。 3.在麦吉尔建立一个项目，收集对大西洋翻转环流浅部的直接观测。这一目标包括建立一个实验室，在形成水团的恶劣海洋环境中自主收集观测数据。

The subpolar North Atlantic is a region where intense air-sea interactions cause the transformation of thermocline waters into of a collection of water masses known as North Atlantic Deep Water (NADW). The NADW floods the deep and intermediate depths of the basin and provides a pathway for global change to find its oceanic expression. The precursor waters that are transformed to become NADW stem partly from subtropical water masses, whose penetration into the subpolar gyre is thought to vary temporally. The basic mechanisms that govern the overturning transport and its temporal variability remain poorly understood, as do the implications for the ocean's interior heat, carbon, and nutrient reservoirs. In order to detect anthropogenic change in the ocean's circulation and biogeochemical properties, we must enhance our understanding of the mechanisms causing this variability. Therefore, the fundamental questions to be addressed by the proposed work are: What are the dominant mechanisms setting the temporal variability of the Atlantic overturning transport? What are the consequences of such variability on the biogeochemical properties of the NADW? The work will be organized around 3 objectives: 1. Characterize mechanisms governing variability in the MOC, its vulnerability to anthropogenic change, and its impacts on the ocean's carbon and nutrient reservoirs in a General Circulation model. 2. Investigate the variability and trends emerging in observational data from hydrographic missions, satellite products, and nearly two decades of data collected by profiling floats in the North Atlantic. 3. Build a program at McGill that will collect direct observations of the shallow limb of the Atlantic overturning circulation. This goal includes the mounting of a lab for the autonomous collection of observations in the harsh ocean environments in which water masses are formed.