Mechanisms of Decadal Variability in the North Atlantic: The Thermohaline Circulation, Great Salinity Anomalies, and Gulf Stream Path

这项研究的目的是研究北大西洋年代际变化的物理机制。特别是，它着重探讨了这样一个假设，即大盐度异常通过对热盐环流、西部深边界流、北部再循环环流和墨西哥湾气流路径的南北移动的影响，是造成这种变化的一个重要因素。初步数值试验表明，GSA事件对年代际海洋变率的影响不亚于风强迫的变化(例如，北大西洋涛动的变率)，对年代际时间尺度的影响比温室气体增加引起的辐射和地表热通量变化的影响大得多。此外，GSA事件与温盐环流的相互作用可能导致气旋性NRG的年代际变化、墨西哥湾气流路径的南北移动，从而影响美国东海岸的气候。方法是采用数值实验和理论相结合的方法，使用简化和综合的海洋数值模型、板状海冰模型和一个简单的大气模型来研究这些问题。除了这些数值计算外，还将对GSA的性质以及它们与温盐环流的相互作用如何可能导致NGR的变化和墨西哥湾气流路径的南北移动，从而导致中纬度海洋环流的年代际变化进行理论研究。除气候变化外，拟议的研究还涉及一些长期令人感兴趣的物理-海洋学问题，即控制墨西哥湾流分离的机制、下游路径和气旋NRG的产生、GSA事件的重要性(或其他)及其对温盐环流的影响。除了增加对海洋和气候变化的基本性质和原因的了解外，这项研究还将使人们更好地了解高纬度海洋监测是否以及如何在预测和检测年代际气候变化方面是必要的。

ABSTRACTOCE-0351383The proposed research is to investigate the physical mechanisms of decadal variability in the North Atlantic ocean. Particularly, it focuses on exploring the hypothesis that Great Salinity Anomalies (GSAs) are a significant contributing factor to such variability, through their effect on the thermohaline circulation, deep western boundary current (DWBC), northern recirculation gyre (NRG) and the north-south shifts of the Gulf Stream path. Preliminary numerical experiments indicate that GSA events have as much if not more effect on decadal ocean variability than do changes in the wind forcing (e.g., variability in the North Atlantic Oscillation) and, on decadal timescales, have a much larger effect than do changes in radiative and surface heat flux changes due to increased greenhouse gases. Furthermore, the interaction between GSA events and the thermohaline circulation may lead to decadal variations of the cyclonic NRG, north-south shifts of the Gulf Stream path and thereby affect the climate of the east coast of the USA. The approach is to investigate these issues with a combination of numerical experimentation and theory, using both simplified and comprehensive numerical ocean models, coupled to slab sea-ice models and a simple model of the atmosphere. These numerical calculations will be supplemented by theoretical investigations of the nature of GSAs and how their interaction with the thermohaline circulation may lead to variations of NGR and north-south shifts of the Gulf Stream path, and hence decadal changes in the mid-latitude ocean circulation. In addition to climate variability, the proposed research addresses some physical-oceanographic problems of long-standing interest, namely the mechanism governing the Gulf Stream separation, the downstream path and the production of cyclonic NRG, and the importance (or otherwise) of the GSA events and their effect on the thermohaline circulation. In addition to an increased understanding of the fundamental nature and causes of ocean and climate variability, the research will lead to a better sense of whether and how high-latitude ocean monitoring is necessary in predicting and detecting decadal climate variability