Assessing Arctic ship navigability: Divergence between international rules and local regulations

Arctic ship navigability is affected by both international rules and local regulatory frameworks. When differences arise between the two frameworks from policy and practical perspectives, issues inevitably arise, yet they remain insufficiently addressed in the existing literature. In this study, a new framework for assessing and comparing navigability is proposed to quantify differences between international rules and local regulations, as well as between independent navigation and icebreaker escorts. Based on 2022 sea ice data, several key findings were revealed. First, the ship ice-class is identified as the dominant driver of navigability, rather than the regulatory regime, with navigability for PC6 ships quantified at only 42.7% of that for PC3 ships. Second, navigation windows are reduced by 50.5% along the Northern Sea Route (NSR) under Russian regulations and by 65.2% along the Northwest Passage (NWP) under Canadian regulations. Third, regarding local zonal divisions, the delineation of Canada’s Zone 6 is proven unreasonable, and the navigation window is set overly strictly. Finally, the navigability divergence between international rules and local regulations is reduced by 30% through icebreaker escorts, and potential risk zones are identified as being exposed by escort operations. These findings provide theoretical support and managerial insights to promote high-ice-class fleets and to revise Arctic navigation policies and regulations.