Exposure to extreme events is a major concern in coastal regions where growing human populations and stressed natural ecosystems are at significant risk to such phenomena. However, the complex sequence of processes that transform an event from notable to extreme can be challenging to identify and hence, limit forecast abilities. Here, we show an extreme heat content event (i.e., a marine heatwave) in coastal waters of the northern Gulf of Mexico resulted from compounding effects of a tropical storm followed by an atmospheric heatwave. This newly identified process of generating extreme ocean temperatures occurred prior to landfall of Hurricane Michael during October of 2018 and, as critical contributor to storm intensity, likely contributed to the subsequent extreme hurricane. This pattern of compounding processes will also exacerbate other environmental problems in temperature-sensitive ecosystems (e.g., coral bleaching, hypoxia) and is expected to have expanding impacts under global warming predictions.

暴露于极端事件是沿海地区的一个主要问题，在这些地区，不断增长的人口和紧张的自然生态系统面临此类现象的重大风险。然而，将事件从显着转变为极端的复杂过程序列可能难以识别，因此限制了预测能力。在这里，我们展示了墨西哥湾北部沿海水域的极端热含量事件（即海洋热浪），这是由热带风暴和大气热浪的复合效应引起的。这一新发现的产生极端海洋温度的过程发生在 2018 年 10 月飓风迈克尔登陆之前，并且作为风暴强度的关键因素，可能促成了随后的极端飓风。