The ice presence significantly complicates shipping in cold regions during winter or even year-round in some polar areas. Climate change contributes to a warmer climate, resulting in more favorable ice conditions for navigation and attracting more vessels in cold regions. Efficient ice navigation requires a systemic approach, allowing for planning and analyzing future navigation under complex and changing circumstances. We developed an agent-based simulation tool for the analysis and design of sustainable winter navigation systems, considering the ice conditions, the technical parameters of ships in the traffic, parameters of ship voyages, established maritime routes in the region, and supporting infrastructure (e.g., availability and technical parameters of icebreakers, icebreaking assistance, and ice routing provided by the authorities). This paper presents an overview of the applications of our decision support tool for different regions of the Baltic Sea (e.g., modeling the Finnish-Swedish winter navigation system in the Gulf of Bothnia and winter navigation in the Estonian waters), supporting sustainable, safe, and cost-efficient shipping in ice.