Collaborative Research: Physical mechanisms of (inter) Decadal Variability of the North Atlantic Ocean Circulation

0423975知识价值。这项研究将有助于并扩展在过去十年中发展起来的系统框架，通过详细了解海洋环流的风和热盐成分如何相互作用，来理解海洋环流的非线性动力学和不同制度。尚不清楚对风和浮力驱动的环流进行更精确的模拟，包括下坡和边界流的细节，如何影响模式解的内部年代际变率。没有这些知识，海洋环流理论将是不完整的。北大西洋环流年代际变化的物理研究将集中在低粘度极限的风和浮力驱动环流的相互作用上。最近的数值和理论研究表明，与通常用于气候研究的低分辨率模式相比，降低黏度会导致高纬度地区的平均环流、热输送模式以及深对流和下流区域的根本不同。预计这些变化将从根本上影响如何看待北大西洋环流在年代际至年代际气候变率中的作用。主要的假设是，海洋模式中黏度的降低以及伴随的边界流、海面温度、深层混合区、表面流、热输送机制和亚极环流内表面热通量的变化，将提供与北大西洋气候的年代际变率有关的海洋过程的更准确的表示。因此，对低粘度极限的研究将揭示海洋内部年代际变化的新机制。这些工具将包括应用于分层海洋模式的数值分岔方法，分辨率相对较高，以及海洋环流的直接数值模拟。更广泛的影响。这项研究的目的是更好地了解与全球气候可预测性这一具有社会意义的问题有关的时间尺度上的海洋变化。研究结果对气候变化的可预测性和海洋状态监测都很有意义。研究结果将通过主要海洋学期刊的出版物和在各种场合的介绍来传播。两个pi都有网页，将在上面描述这个研究项目，并提供结果。两位pi都是教育机构的工作人员，他们（并将继续）积极地为研究生和暑期学生（本科生）提供建议、监督和教学。本项目将培养两名现代数值方法和气候动力学方面的研究生。

0423975Intellectual Merit. This study will contribute to and extend a systematic framework that has been developed over the last decade to understand the nonlinear dynamics and different regimes of the ocean circulation, by including a detailed view on how the wind and thermohaline components of the ocean circulation interact. It is unknown how a more accurate modeling of the wind- and buoyancy-driven circulation, including details in downwelling and boundary currents, influences the internal decadal-to-interdecadal variability of the model solutions. Without this knowledge the theory of the ocean circulation will be incomplete. This study of the physics of decadal-to-interdecadal variability in the North Atlantic ocean circulation will focus on the interaction of the wind- and buoyancy-driven circulations in the low-viscosity limit. Recent numerical and theoretical studies indicate that decreasing the viscosity results in fundamentally different mean circulations, modes of heat transport, and regions of deep convection and downwelling at high latitudes compared to those in low-resolution models typically used for climate studies. It is anticipated that these changes will influence in a fundamental way how the role of the North Atlantic Ocean circulation in decadal-to-interdecadal climate variability is viewed. The main hypothesis is that the decrease in viscosity in ocean models and the concomitant changes in the boundary currents, sea surface temperature, regions of deep mixing, surface currents, mechanisms of heat transport, and the surface heat flux within the subpolar gyre, will provide a more accurate representation of oceanic processes involved in decadal-to-interdecadal variability of the North Atlantic climate. Therefore, the study of the low-viscosity limit will reveal new mechanisms of internal oceanic decadal-to-interdecadal variability. The tools will consist of numerical bifurcation methods applied to stratified ocean models at relatively high resolution and direct numerical simulations of the ocean circulation. Broader Impacts. The study is aimed at gaining a better understanding of the ocean variability on time scales relevant to the societally significant question of global climate predictability. The results will be of interest for both climate change predictability and ocean state monitoring. The results will be disseminated by publications in leading oceanographic journals, and through presentations in a variety of settings. Both PIs maintain web pages on which this research project will be described and results will be made available. Both PIs are on staff at educational institutions within which they are (and will continue to be) active in advising, supervising, and teaching graduate students and summer student fellows (undergraduates). Two graduate students will be trained under this project in modern numerical methods and climate dynamics.