Projections of Arctic sea ice conditions and shipping routes in the twenty-first century using CMIP6 forcing scenarios

The accelerated decline in Arctic sea ice in recent decades suggests the possibility of future trans-Arctic shipping routes linking the Atlantic and Pacific oceans, with significant implications for the global economy. We present a projection of Arctic sea ice conditions and shipping activities during the 21st century based on 16 CMIP6 models calibrated to remove spatial biases. The multimodel ensemble mean shows that the Arctic is likely to be ice-free in September by 2076 and 2055 under the SSP2-4.5 and SSP5-8.5 scenarios, respectively, whereas the extent of sea ice is >2 x 10(6)km(2)throughout the 21st century under the SSP1-2.6 scenario. The Arctic sea ice in September thins over time, leading to a reduction in the area with an ice thickness >120 cm (i.e. the threshold over which sea ice is inaccessible to Type A vessels) by 34-100% by the late 21st century (2086-2100) under the three scenarios. Given the declines in the extent and thickness of sea ice, the most commonly traversed route along the North West Passage tends to migrate from the southern to the northern route during the 21st century. The optimum route along the Northern Sea Route shifts northward with time, with the Transpolar Sea Route becoming available. Quantitatively, the maritime accessibility to Type A vessels via the Transpolar Sea Route increases from similar to 6.7, 4.2 and 2.1% in 2021-2035 to 14.7, 29.2 and 67.5% in 2086-2100 under the SSP1-2.6, SSP2-4.5 and SSP5-8.5 scenarios, respectively. The season for trans-Arctic shipping extends from 5 to similar to 7.5 (9) months by the late 21st century under the SSP1-2.6 (SSP2-4.5) scenario and the Arctic becomes navigable all year round under the SSP5-8.5 scenario. These findings may aid in developing strategic planning by governments for the Arctic and providing strategic advice for the global maritime industry.