The frequency of heatwaves in the Arctic is on the rise under global warming. These occurrences not only profoundly impact the local ecological environment but also exert remote effects on East Asia and even the global climate. Yet, there exists a noticeable dearth of research focus on Arctic compound daytime-nighttime heatwaves, limiting our comprehension of Arctic climate dynamics. We investigated the occurrence and extinction mechanism for compound daytime-nighttime heatwaves in the Barents–Kara Sea (BKS) during the boreal autumn and explored their association with the sea ice variability. Our results show that a significant dipole pattern appears in the geopotential height two days before the occurrence of compound daytime-nighttime heatwaves in the BKS during autumn, characterized by a negative anomaly centered over Greenland and a positive anomaly centered over the BKS. A robust southerly anomaly in the middle of this dipole pattern facilitates the continuous inflow of warm, moist air from the Atlantic Ocean to the BKS. Both the strong intrusion of moisture and the transport of heat (positive temperature advection) driven by the large-scale atmospheric circulation increase downward latent heat flux, sensible heat flux and net longwave radiation. These factors collectively increase the near-surface temperature over the BKS, ultimately leading to the occurrence of compound daytime-nighttime heatwaves in this region of the Arctic. The extinction of compound daytime-nighttime heatwaves in the BKS is a result of the weakening of the transport of heat and intrusion of water vapor caused by changes in the large-scale circulation. The intrusion of water vapor and the transport of heat significantly reduce the sea ice concentration in most of the BKS. This reduction in sea ice persists for an additional day after the termination of compound daytime-nighttime heatwaves in the BKS. A process of positive atmospheric temperature feedback on a sub-monthly scale may potentially influence the maintenance of compound daytime-nighttime heatwaves in the BKS during the boreal autumn.

中文翻译：

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北秋季巴伦支海-喀拉海复合昼夜热浪机制及其与海冰变化的关系


在全球变暖的背景下，北极地区热浪发生的频率不断增加。这些事件不仅深刻影响当地生态环境，也对东亚乃至全球气候产生深远影响。然而，对北极复合昼夜热浪的研究明显缺乏，限制了我们对北极气候动态的理解。我们研究了北秋季巴伦支海-喀拉海（BKS）复合昼夜热浪的发生和消退机制，并探讨了它们与海冰变化的关系。结果表明，秋季BKS昼夜复合热浪发生前两天，位势高度出现显着的偶极子模式，其特征是以格陵兰岛为中心的负异常和以BKS为中心的正异常。该偶极子模式中部的强劲南风异常促进了温暖潮湿的空气从大西洋持续流入BKS。水汽的强烈侵入和大范围大气环流驱动的热量输送（正温平流）都增加了向下的潜热通量、感热通量和净长波辐射。这些因素共同增加了BKS上空的近地表温度，最终导致北极该地区出现昼夜复合热浪。 BKS地区昼夜复合热浪的消失是大范围环流变化导致热量输送减弱和水汽侵入的结果。水蒸气的侵入和热量的传输显着降低了大部分 BKS 的海冰浓度。 在BKS的昼夜复合热浪结束后，海冰的减少还会持续一天。亚月尺度的正大气温度反馈过程可能会影响北方秋季期间 BKS 复合昼夜热浪的维持。