Not All Ocean Heat Transport Changes Are Created Equal

海洋热输送（OHT）的变化与海洋和大陆的气候变化有关。大西洋多年代际振荡（北大西洋平均表面温度的振荡）等信号导致欧洲上空异常的干/湿状况，被认为主要是由大西洋翻转环流和相关的OHT的盆地范围波动产生的。在OHT与异常气候条件之间联系的核心是一系列事件：OHT的变化导致海洋热含量（OHC）在大范围深度的变化，这反过来又改变了海表温度（SST）。OHT的变化最终是通过海温的这种改变来影响大气环流的。然而，必须强调的是，OHT-OHC-SST链不是系统性的。事实上，很可能大部分OHT变率只导致较弱的海温变化，因此气候影响很小。我们目前对OHT变化与气候变率之间联系的理解主要基于气候模式模拟的统计分析。我们的建议是，我们需要更好地理解这种联系背后的机制，以便能够理解有限的可用观测能告诉我们海洋对现实世界气候的影响，以及我们的气候模型是否能很好地近似后者。具体来说，我们希望解决以下几个关键问题：是什么使OHT变化在气候上变得重要，并可能与社会相关？OHT-OHC-SST链在海洋和气候模式中是否得到了恰当的表示？在与政府和企业的许多环境政策最相关的1至10年时间尺度上，对未来气候变化的预测有什么影响？为了解决这一问题，我们建议探索海洋内部动力学，限制OHT-OHC-SST链及其在气候预测系统中的表现。该项目的一个重要创新是评估OHT变化的潜在气候影响的方法，用于解释由英国资助的RAPID项目及其后续项目长达十年的经向翻转环流和相关OHT变化的观测。我们将结合对地下海洋观测（Argo数据集）和海洋再分析产品的分析，采用理想化模型（研究物理过程）和现实配置（最容易与气候模型和观测联系起来）的建模方法，以及对全球气候模型和年代际预测产品的评估。除了有助于英国资助项目的成功（如上面提到的RAPID，以及即将到来的OSNAP），这项研究还将使英国社区在评估和潜在改进英国气候模型和预测系统（UKESM1/NEMO, Met Office DePreSys）方面受益。

Changes in Ocean Heat Transport (OHT) have been associated with changes in climate over the oceans and continents. Signals such as the Atlantic Multidecadal Oscillation (an oscillation of the averaged surface temperature in the North Atlantic ocean), which drives anomalously dry/wet conditions over European, are thought to be primarily generated by basin wide fluctuations in the Atlantic Overturning Circulation and associated OHT. At the core of the link between OHT and anomalous climate conditions is a chain of events: changes in OHT result in changes in the Ocean Heat Content (OHC) over a broad range of depths, which in turn modifies the Sea Surface Temperature (SST). It is ultimately through this SST modification that the OHT changes can influence the atmospheric circulation.It has to be emphasized, however, that the OHT-OHC-SST chain is not systematic. In fact, it is likely that a large fraction of the OHT variability does only result in weak SST changes and thus little climate impact. Our current understanding of the link between OHT changes and climate variability is primarily based on statistical analyses of climate model simulations. Our proposal is that we need to understand better the mechanisms behind this link to be able to understand what the limited available observations can tell us about the ocean's impact on climate in real world, and whether or not our climate models are good approximations of the latter. Specifically, here are a few key questions that we wish to address: What makes an OHT change climatically important and potentially relevant to society? Is the OHT-OHC-SST chain properly represented in ocean and climate models? What are the implications for predictions of future climate change on the 1 to 10 year timescale of most relevance to many environmental policies of governments and businesses? To address this, we propose to explore the ocean interior dynamics that constrains the OHT-OHC-SST chain and its representation in climate prediction systems. An important innovation of the project is a methodology to evaluate the potential climate impact of OHT changes, to be used to interpret decade-long observations of the Meridional Overturning Circulation and associated OHT changes by the UK funded RAPID project and its successors.We will combine an analysis of subsurface ocean observations (Argo dataset) and ocean reanalysis products, a modeling approach with idealized models (to study physical processes) and realistic configurations (to link most readily with climate models and observations), and an evaluation of a global climate model and decadal prediction products.Besides contributing to the success of UK-funded projects (like RAPID mentioned above, but also the upcoming OSNAP), this research will also benefit the UK community in terms of evaluation and potential improvements of the UK climate models and prediction systems (UKESM1/NEMO, Met Office DePreSys).