An unprecedented warm sea surface temperature (SST) anomaly event, namely, the Blob, occurred in the northeast Pacific during the winter (October–January) of 2013/2014, causing substantial economic and ecological impacts. Here, we explore the driving forces of the Blob from both atmospheric and oceanic perspectives and show that the Blob primarily resulted from weak wintertime cooling due to the reduced air-sea heat flux transfer from the ocean to the atmosphere and the reduced horizontal advection of cold water in the upper ocean. Both mechanisms were attributed to an anomalous high-pressure system over the study region. Specifically, the anomalous air-sea heat flux, which was dominated by turbulent heat flux anomalies, was mainly induced by the increased air temperature (i.e., with a contribution of approximately 70%) and the weakened wind speed associated with the high-pressure system. The reduced horizontal heat advection was mainly due to the weakened winds acting on the ocean temperature meridional gradient. Using a regional ocean numerical model with different experimental runs, we evaluated the contributions of air temperature and wind drivers to the Blob at both the surface and subsurface of the ocean. The Blob was absent when the model was forced by climatology-air-temperature. Both the SST and integrated ocean heat content (OHC, 0–150 m) decreased, and the mixed layer depth (MLD) was deeper than that in the control run forced by real atmospheric conditions. In the climatology-winds experiment, obvious warm anomalies still existed, which were similar to but weaker than the control run. The SST (OHC) and MLD values in the climatology-winds run were between those of the climatology-air-temperature run and the control run. Compared to former studies that attribute the formation of the Blob to an anomalous air-sea heat flux and horizontal advection mainly induced by reduced winds, our study demonstrates that anomalous warm air temperatures played a more important role in its formation.

2013/2014 年冬季（10 月至 1 月）东北太平洋发生了史无前例的暖海表温度 (SST) 异常事件，即 Blob，造成了重大的经济和生态影响。在这里，我们从大气和海洋的角度探索了 Blob 的驱动力，并表明 Blob 主要是由于从海洋到大气的海气热通量传递减少以及冷水平平流减少导致的冬季冷却较弱造成的海洋上层的水。这两种机制都归因于研究区域的异常高压系统。具体而言，以湍流热通量异常为主的海气热通量异常主要是由气温升高（即 贡献率约为 70%) 以及与高压系统相关的风速减弱。水平热平流减少主要是由于风作用于海洋温度经向梯度减弱。我们使用具有不同实验运行的区域海洋数值模型，评估了气温和风驱动因素对海洋表面和地下 Blob 的贡献。当模型受到气候学气温的影响时，Blob 不存在。SST 和综合海洋热含量（OHC，0-150 m）均降低，混合层深度（MLD）比实际大气条件强制的控制运行更深。在气候-风实验中，仍然存在明显的暖异常，与对照运行相似但较弱。气候-风运行中的 SST (OHC) 和 MLD 值介于气候-气温运行和控制运行之间。与以往的研究将 Blob 的形成归因于异常的海气热通量和主要由风减少引起的水平平流相比，我们的研究表明异常暖空气温度在其形成中发挥了更重要的作用。