Atmospheric Synoptic Variability and Pacific Ocean Biogeochemistry in the Current and Future Climate (SyVarBio)

基于地球系统模型（ESMs）的预测表明，如果全球表面变暖以目前的速度继续下去，海洋环境将在未来100年内发生巨大变化。与东部边界上升流系统（EBUSs）功能变化相关的热带“最低氧带”（OMZs）的未来扩展将对海洋生态系统和气候产生重大的区域和全球后果。控制氧气水平和上升流生产力的主要机制之一是风驱动的海洋环流。水运和地表浮力通量不仅取决于时间平均风的强度，而且还取决于高频大气天气变率（ASV）的大小，特别是与热带气旋、风暴、强对流模式等极端事件有关。虽然时间平均分量和高频分量都将在未来气候中发生变化，但ASV变化的具体影响目前被忽视。SyVarBio的目标是：i)通过在最先进的大气-海洋-生物地球化学耦合模型框架下进行专门的灵敏度实验，了解ASV和时间平均风的变化在影响海洋生物地球化学循环和海洋生物地球化学中的相对作用。大尺度和中尺度实验将使用欧洲海洋模型核（NEMO）框架进行，并将利用基尔气候模式系统先前模拟的场。将把区域重点放在东热带北太平洋的哥斯达黎加热穹窿，这是一个生物多样性热点，靠近热带辐合带，位于世界上最广阔的OMZ；ii)研究ASV是否在一系列esm中得到了真实的体现，以及未来氧水平和生产力的变化在多大程度上与ASV的变化相关。在耦合模型比较项目第6阶段（CMIP6）的背景下进行的模拟的子样本将使用统计工具和机器学习技术进行分析。SyVarBio项目将这两个目标结合起来，通过对现有模型数据库进行对比分析，并进行过程研究，将有助于填补ASV在当前和未来气候中对太平洋热带和亚热带环流以及生物地球化学循环调节的重要性方面的知识空白。

Projections based on Earth system models (ESMs) suggest that the ocean environment will dramatically change in the next 100 years should global surface warming continue at the present rate. A future expansion of the tropical “Oxygen Minimum Zones” (OMZs) associated with changes of the functioning of the Eastern Boundary Upwelling Systems (EBUSs) will have major regional and global consequences for the marine ecosystems and the climate. One of the main mechanisms controlling the oxygen levels and the upwelling productivity is the wind-driven ocean circulation. The water transport and the surface buoyancy fluxes depend not only on the intensity of the time-averaged winds but also on the magnitude of the high-frequency Atmospheric Synoptic Variability (ASV), in particular related to extreme events such as tropical cyclones, storms, strong convective patterns. While both time-averaged and high-frequency components will change in a future climate, the specific impacts of a change in ASV are currently overlooked. The objectives of SyVarBio are to: i) understand the relative roles of changes in ASV and time-averaged winds in impacting marine biogeochemical cycles and OMZs by performing dedicated sensitivity experiments with a state-of-art coupled atmosphere – ocean – biogeochemical modeling framework. Large-scale and mesoscale experiments will be performed using the Nucleus for European Modeling of the Ocean (NEMO) framework and will make use of previously simulated fields by the Kiel Climate Model System. A regional focus will be given to the Costa Rica thermal dome in the Eastern Tropical North Pacific, a biodiversity hotspot located close to the Intertropical Convergence Zone and in the most extended OMZ of the world; ii) investigate whether the ASV is realistically represented in a suite of ESMs and to which extent future changes in oxygen levels and productivity are related to changes in ASV. A subsample of simulations performed in the context of the Coupled Model Intercomparison Project phase 6 (CMIP6) will be analyzed using statistical tools and machine learning techniques. By combining these two objectives, involving a process study complemented by an intercomparison analysis of an existing model database, the project SyVarBio will help filing in a knowledge gap regarding the importance of the ASV in the modulation of the Pacific Ocean tropical and subtropical circulation and biogeochemical cycles in the current and future climate.