Long-term ventilation changes of Subpolar Mode Waters in the North Atlantic Ocean and its impact on the oxygen distribution

海洋通风是一个将氧气和二氧化碳等物质从海洋表面转移到海洋内部的过程，在那里它们主要沿着环流路径传播。在气候变化导致的海洋变暖中，密度分层增加，导致通风减少和氧气损失，特别是在副极地区域。在副极地北大西洋，副极地模态沃茨（SPMWs）是在副极地环流的气旋性环流之后的冬末对流期间形成的。它们参与了大西洋翻转环流（AMOC）的上层流动，并提供了大部分最终转化为北大西洋深层水（NADW）的几个组成部分的水，这是AMOC的寒冷，深层部分。因此，了解这些水团如何受到通风变化的影响将有助于我们更好地了解AMOC的变化。这项建议的目标是：1）调查过去五十年来通风变化对SPMW形成和这些水团所占体积的影响，2）调查SPMW性质的长期变化，特别关注氧变化，3）评估SPMW与改变通气年龄和氧气利用率（OUR）之间的关系更好地区分驱动海洋氧气变化的三个主要机制：海气交换、环流和海洋生物，并利用高分辨率模型的结果分析驱动观测到的变化的机制。

Ocean ventilation is a process that transfers properties, such as oxygen and carbon dioxide from the surface into the ocean interior where they are propagating following mainly the circulation pathways. In a warming ocean as a result of climate change, density stratification increases leading to reduced ventilation and loss of oxygen, particularly in the subpolar region. In the subpolar North Atlantic Ocean, Subpolar Mode Waters (SPMWs) are formed during late winter convection following the cyclonic circulation of the subpolar gyre. They participate in the upper flow of the Atlantic overturning circulation (AMOC) and provide much of the water that is eventually transformed into several components of the North Atlantic Deep Water (NADW), the cold, deep part of the AMOC. Thus, understanding how these water masses are affected by ventilation changes will help us to better understand the variability in the AMOC. The objectives of this proposal are: 1) investigate the effect of ventilation changes on the formation of SPMWs and on the volume occupied by these water masses over the last five decades, 2) investigate the long-term variability of SPMW properties with a particular focus on the oxygen variability, 3) evaluate the relationship within the SPMW with respect to changing ventilation ages and oxygen utilization rate (OUR) to better distinguish between the three main mechanisms driving the oxygen changes in the ocean: air-sea gas exchanges, circulation and marine biology and utilize the output of a high resolution model to analyse the mechanisms driving the observed changes.