Pathway to low-carbon arctic shipping: carbon tax thresholds and market equilibrium under climate change

Global maritime trade faces the dual challenges of climate change and the low-carbon transition. The melting of Arctic sea ice is enabling the Northeast Passage to emerge as a potential alternative to the Suez Canal Route, while carbon pricing policies continue to reshape the relative competitive advantages of these two shipping routes. Addressing the limitations of existing research—which overlooks the multi-agent game-theoretic allocation of carbon emissions, lacks dynamic policy–market feedback loops in static comparisons of heterogeneous shipping routes, and fails to adequately assess the cascading effects of carbon taxes under single-scenario analyses—this paper constructs a two-level Stackelberg game model that integrates sea ice melt scenarios with voyage-level carbon emissions accounting. It systematically characterises the ‘carbon tax–voyage speed–cost–route share–emissions’ transmission mechanism and explores the heterogeneous dynamic competition between the two shipping routes, as well as the bidirectional policy–market feedback loops, in a China–Europe scenario. The results indicate that global warming and fuel price volatility significantly influence route competitiveness through dual channels, while a differentiated carbon tax can guide the orderly reallocation of freight traffic towards the low-carbon Arctic route. The emissions reduction effect of the carbon tax exhibits a non-monotonic pattern, with an excessively low tax rate likely to stimulate shipping expansion and trigger a rebound in carbon emissions. Under a severe warming scenario, the Arctic route could account for up to 22 per cent of freight traffic, with industry emissions exceeding 630,000 metric tonnes. Climate warming lowers the threshold for effective carbon tax regulation, while the cost advantage of the Arctic Northeast Passage provides a viable pathway for the long-term implementation of low-carbon policies. This study provides theoretical guidance and quantitative evidence for low-carbon governance in maritime transport, China–Europe shipping route planning, and the commercial development of the Arctic Northeast Passage.