Transient ocean overturning response to changes in boundary conditions.

大气和海洋之间热量和碳的交换速率强烈地影响着地球的气候。在这种情况下，海洋可以被视为一个储存大气示踪剂的巨大水库，从而调节气候。在这个过程中，海洋的作用并不仅仅是被动的。这幅图的中心是海洋经向翻转环流（MOC）。MOC设定了海洋热量和碳吸收的幅度和空间结构，并将这些示踪剂重新分配到深渊中。MOC与地表大气通量相互作用的最新进展主要集中在稳定强迫下的长期平衡解。然而，海洋很可能从未处于平衡状态，对短暂气候变化的更现实的随时间变化的反应的许多方面仍然知之甚少。这项研究计划的长期目标是通过物理和生物地球化学过程阐明海洋在短暂气候变化问题中的作用。短期目标是将重点放在孤立地对短暂性气候变化作出随时间变化的反应的三个关键方面。第一个方面涉及全球变暖条件下地表对温度异常的响应。虽然地球的大部分表面都显示出正的温度异常，但在大西洋西北部却出现了一个令人惊讶的变冷区域，称为“变暖洞”。为了了解这种结构是如何发展的，我们将研究表面风驱动环流与MOC深层路径之间的耦合相互作用。第二个方面与气候变化的极地放大有关。在全球变暖的情况下，尽管MOC变缓，大西洋暖水流入北极的流量预计会增加。为了了解海洋热输运进入北极的控制机制，我们将对北极翻转环流进行诊断，并研究河口型环流和风驱型环流之间的耦合相互作用。第三个方面与末次冰期的气候变率有关，当时发生了称为Dansgaard-Oeschger循环的气候突变。我们打算开发一个简单的预测框架，以捕捉耦合海洋-海冰相互作用的主要特征，并研究其对全球碳循环的影响。总的来说，这项工作的完成将有助于减少气候模式中与翻转环流相关的不确定性，改进海洋热输送到北极的预测，并澄清我们对控制翻转变率的关键机制的理解。通过促进气候预测的改进，这项研究将帮助加拿大气候适应政策制定者为当地居民和工业做出更明智的决策。

The rate at which heat and carbon are exchanged between the atmosphere and ocean strongly influences the Earth's climate. In this context, the ocean can be seen as a huge reservoir that stores atmospheric tracers and, as a result, regulates the climate. The ocean's role in this process is not solely passive. At the center of this picture is the ocean meridional overturning circulation (MOC). The MOC sets the amplitude and spatial structure of oceanic heat and carbon absorption and redistributes these tracers into the abyss. Recent advances the MOC's interaction with surface atmospheric fluxes has focused primarily on long-term equilibrium solutions under steady forcing. However, the ocean has most likely never been in a state of equilibrium and many aspects of the more realistic time-dependent response to transient climate change remain poorly understood. The long-term goal of this research proposal is to clarify the ocean's role in the transient climate change problem through physical and biogeochemical processes. The short-term goals are to focus on three key aspects of the time-dependent response to transient climate change in isolation. The first aspect relates to the surface response in temperature anomaly under global warming. While most of the surface of the globe shows positive temperature anomalies, a surprising region of cooling, called "warming hole", is nonetheless observed in the northwestern Atlantic. In order to gain understanding of how this structure develops, we will investigate the coupled interaction between the surface wind-driven gyres and the deeper pathways of the MOC. The second aspect relates to the polar amplification of climate change. The flux of warm Atlantic waters into the Arctic is predicted to increase under global warming despite the slowdown of the MOC. In order to understand what mechanisms control the oceanic heat transport into the Arctic, we will diagnose the Arctic overturning circulation and investigate the coupled interaction between an estuary-type circulation and a wind-driven-type circulation. The third aspect relates to climate variability during the last glacial period when abrupt climate variations, called Dansgaard-Oeschger cycles, took place. We intent to develop a simple predictive framework that captures the main characteristics of the coupled ocean-sea-ice interaction and investigate its effect on the global carbon cycle. Overall, the completion of this work will help reduce uncertainty related to the overturning circulation in climate models, improve predictions in ocean heat transport into the Arctic, and clarify our understanding of key mechanisms controlling the variability of the overturning. By contributing to improvements in climate projections, this research will help Canadian climate adaptation policy makers take more informed decisions for local populations and industry.