The highly productive northern Bering and Chukchi marine shelf ecosystem has long been dominated by strong seasonality in sea-ice and water temperatures. Extremely warm conditions from 2017 into 2019—including loss of ice cover across portions of the region in all three winters—were a marked change even from other recent warm years. Biological indicators suggest that this change of state could alter ecosystem structure and function. Here, we report observations of key physical drivers, biological responses and consequences for humans, including subsistence hunting, commercial fishing and industrial shipping. We consider whether observed state changes are indicative of future norms, whether an ecosystem transformation is already underway and, if so, whether shifts are synchronously functional and system wide or reveal a slower cascade of changes from the physical environment through the food web to human society. Understanding of this observed process of ecosystem reorganization may shed light on transformations occurring elsewhere.

长期以来，高产的白令和楚科奇海域海洋生态系统一直以海冰和水温旺季为主导。从2017年到2019年，极端温暖的天气-包括在所有三个冬季整个区域的冰覆盖减少-甚至与最近的其他温暖年份相比也有明显变化。生物指标表明，这种状态变化可能会改变生态系统的结构和功能。在这里，我们报告了对关键物理驱动器，生物学反应和对人类的后果的观察，包括生计狩猎，商业捕鱼和工业运输。我们考虑观察到的状态变化是否表示未来的规范，生态系统的转型是否已经在进行，如果是，转变是同步发生的功能，还是整个系统的变化，还是揭示了从物理环境到食物网络再到人类社会的一系列缓慢变化。对这一观察到的生态系统重组过程的了解可能会为其他地方发生的转变提供启示。