The dynamics of the ocean meridional overturning circulation.

海洋经向翻转环流（MOC）在气候系统中起着关键作用：它控制着储存在深海中的热量，并有助于调节二氧化碳与大气的交换。然而，它对外部大气强迫变化的响应仍然知之甚少，也没有建立模型。在过去的二十年中，模拟MOC对气候变化的响应需要高空间分辨率。在南大洋尤其如此，必须明确解决南极环极流（ACC）周围的地转乱流。目前的计算能力允许在全球模式中对MOC进行少量的涡分辨模拟。然而，它不允许对参数空间进行更彻底的探索，例如需要完全理解控制动力学。相反，这类研究通常是使用更理想化的模型进行的。因此，在试图理解翻转环流动力学的理想化理论研究与试图准确模拟MOC并预测其对气候变化响应的更现实的环流模式（GCM）模拟之间仍然存在很大差距。本提案的总体目标是弥合这一差距。为此，我们将在GCM中应用强大的双向网格嵌套方法，以考虑更广泛的模型复杂性，并解决在MOC的先前理论研究中被忽视的关键过程的作用。我们将重点讨论制约MOC的各种边界条件，并解决以下问题：

The ocean meridional overturning circulation (MOC) plays a key role in the climate system: it controls the amount of heat stored in the deep ocean and helps regulate the exchange of CO2 with the atmosphere. Yet, its response to changes in external atmospheric forcing is still poorly understood and modeled. Over the last twenty years, it has become clear that modeling the response of the MOC to climate change requires high spatial resolution. This is especially true in the Southern Ocean, where geostrophic turbulence around the Antarctic Circumpolar Current (ACC) must be explicitly resolved. Current computing power allows for a small number of eddy-resolving simulations modeling the MOC in global models. It does not, however, allow for a more thorough exploration of the parameter space, such as is required to fully understand the governing dynamics. Instead, such studies are typically carried out using more idealized models. As a result, there still exists a very wide gap between the idealized theoretical studies that attempt to understand the dynamics of the overturning circulation and the more realistic General Circulation Model (GCM) simulations that attempt to mimic accurately the MOC and predict its response to climate change. The overall goal of this proposal is to bridge this gap. To do this, we will apply a powerful two-way grid nesting approach to a GCM in order to consider a much wider range of model complexities and address the role of key processes that have been neglected in previous theoretical studies of the MOC. We will focus on various boundary conditions constraining the MOC and address the following questions: 1) What is the role of Antarctic sea ice in partitioning the bottom water upwelling along the ACC that flows south to feed the Antarctic Bottom Water formation from that which flows north in the surface Ekman layer? 2) What is the effect of the ACC's topography-induced zonal asymmetry on the overturning circulation? 3) How does the MOC connect with the circumpolar current in a setup with multiple basins, representing the south Atlantic, Pacific and Indian Oceans? 4) Why are the waters of the West Antarctic continental shelf warming at a faster pace than waters along the rest of the Antarctic? Ultimately, the proposed research will reduce the uncertainty related to the meridional overturning circulation in the climate projections of the coming century. Our research will also improve our understanding of the mechanisms causing warming on the West Antarctic continental shelf and help reduce the uncertainty in the sea level projections.