The volume, extent and age of Arctic sea ice is in decline, yet winter sea ice production appears to have been increasing, despite Arctic warming being most intense during winter months. Several negative feedback processes help to restore Arctic sea ice volume during the winter, though previous work suggests that these mechanisms will be overwhelmed by warming in the future, leading to a fall in ice production. Here, we analyse winter ice production in the Kara and Laptev seas–sometimes referred to as Arctic “ice factories”, for their outsized role in supplying the Arctic Ocean with young sea ice. Using the Community Earth System Model’s Large Ensemble (CESM-LE), we develop a simple linear model that can explain both the forced rise and forced fall of ice production, in terms of consistent physics. We apply our linear model to observation-based estimates of the same climate variables; our reconstruction of ice production suggests that–just as in CESM-LE–we are currently passing the peak of ice production in the Kara and Laptev seas.