Asymmetries in ocean heat and carbon uptake, and effects on marine hazards

随着越来越多的热量和碳被提供给气候系统，我们需要了解海洋的未来。我们知道，海洋吸收了提供给气候系统的90%以上的额外热量，通常吸收了向气候系统排放的25%的额外碳。我们知道，海洋在决定全球平均地表变暖与向大气排放的累积碳量成正比方面起着核心作用。然而，在变暖对碳排放的这种线性依赖关系中存在很大的不确定性。减少这种不确定性是气候科学的一项紧迫任务，以便可靠地估计特定变暖目标（如《巴黎协定》设定的目标）的剩余碳预算。我们的工作表明，地表变暖与碳排放之间的模式间不确定性取决于涉及云、海洋热吸收和海洋碳吸收的气候反馈的不确定性。为了进一步了解和减少不确定性，我们需要确定构成全球气候系统响应的气候反馈、海洋热量和碳吸收的区域贡献。区域海洋如何吸收提供给气候系统的额外热量和碳，对于影响海洋灾害发生的可能性也很重要，例如海洋热浪和海洋酸化事件。因此，我们需要知道为什么一些海洋地区比全球其他地区更快地获得额外的热量或增加到气候系统中的碳。我们需要了解这种区域海洋热量和碳吸收的驱动因素。这些驱动程序的范围从1。提供给海洋的额外热量和碳是由全球海洋的稳定环流携带的，这表明额外热量和碳增加的模式在符号上是相似的；2 .海洋通过环流的时变变化驱动热量和碳增加的变化，表明额外热量和碳增加的模式可能具有相反的迹象；大气通过海气交换的差异来驱动热量和碳的变化，而云的反馈增强了亚热带的温暖异常，减弱了南大洋的温暖异常。我们需要了解这些海洋热量和碳异常的驱动因素，因为由此导致的海洋环境变化影响了海洋危害的可能性。例如，海洋热浪是指温度升高的时期，持续数周至数月，其可能性受到海洋如何吸收提供给气候系统的额外热量的区域模式的影响。温度和碳变化的结合可能会改变海洋的pH值，导致海洋酸化事件。我们需要确定海洋热浪和海洋酸化事件是否可能相互加强。最后，我们将对人为热碳异常如何控制、识别其不对称性、海洋和大气驱动因素以及对全球气候响应和海洋灾害的影响提供新的视角。这项工作直接关系到世界气候研究计划的两大挑战：“云、环流和气候敏感性”和“气候系统中的碳反馈”。

We need to understand what the future holds for the ocean, as more heat and carbon are supplied to the climate system. We know that the ocean is taking up over 90% of the extra heat supplied to the climate system and typically 25% of the extra carbon emitted to the climate system. We know that the ocean plays a central role in determining how global-mean surface warming is proportional to the cumulative amount of carbon emitted to the atmosphere. However, there are large uncertainties in this linear dependence of warming on carbon emissions. Reducing this uncertainty is an urgent task for climate science in order to reliably estimate the remaining carbon budget for specific warming targets, such as those set by the Paris Agreement.Our work has demonstrated that the inter-model uncertainty in how surface warming relates to carbon emissions depends on the uncertainties in climate feedbacks involving clouds, ocean heat uptake and ocean carbon uptake. In order to gain understanding and to reduce the uncertainties, we need to identify the regional contributions to climate feedbacks, ocean heat and carbon uptake that make up the global response of the climate system.How the regional ocean takes up the extra heat and carbon supplied to the climate system are also important in affecting the likelihood of marine hazards occurring, such as marine heatwaves and ocean acidifying events. Accordingly, we need to know why some ocean regions are gaining the extra heat or carbon added to the climate system faster than other regions over the globe. We need to understand the drivers for this regional ocean heat and carbon uptake. These drivers range from 1. The extra heat and carbon supplied to the ocean is carried by a steady circulation over the global ocean, suggesting that the patterns of extra heat and carbon gain are similar in sign to each other;2. The ocean drives changes in heat and carbon gain by time-varying changes in the circulation, suggesting that the patterns of extra heat and carbon gain may have opposing signs to each other;3. The atmosphere drives changes in heat and carbon by differences in air-sea exchange, with cloud feedbacks acting to strengthen warm anomalies in the subtropics and weaken warm anomalies in the Southern Ocean. We need to understand the drivers of these ocean heat and carbon anomalies as the resulting changes in the ocean environment affects the likelihood of marine hazards. For example, marine heatwaves are periods of enhanced temperature, lasting weeks to months, and their likelihood is affected by the regional pattern of how the ocean takes up the extra heat supplied to the climate system. The combination of temperature and carbon changes may alter the pH of the ocean leading to ocean acidifying events. We need to identify whether marine heatwaves and ocean acidifying events are likely to reinforce each other.In conclusion, we will provide a new view of how anthropogenic heat and carbon anomalies are controlled, identifying their asymmetries, the ocean and atmospheric drivers, and implications for the global climate response and marine hazards.This work is directly relevant to two Grand Challenges of the World Climate Research programme on "Clouds, circulation and climate sensitivity" and "Carbon feedbacks in the Climate system".