Arctic Sea Ice Changes and Future Access for Marine Navigation

As part of the Arctic Climate Impact Assessment, projected changes of Arctic sea ice coverage through the 21st century have been evaluated in the context of potential enhancements of navigation opportunities in the Arctic. The evaluation is based on monthly fields of sea ice from simulations by five different global climate models, forced by the conservative B2 scenario of increasing greenhouse gas concentrations. Regionally and seasonally varying bias-corrections based on the models' simulations of present-day ice coverage were applied to the projected sea ice coverage. The greenhouse warming reduces sea ice coverage in all models, especially during the summer, although there is considerable range among the retreats projected by the different models. The five-model mean decrease of sea ice coverage projected for 2100 is approximately 60% in September (ranging among models from 9% to 100%) and approximately 15% in March (ranging among models from 11% to 18%). One model projects an ice-free Arctic during summer in the 2070-2090 time slice, while three other models lose most of their summer ice by that time. The seasonality of the retreat (largest in summer) is consistent with trends in observed sea ice coverage over the past several decades. As a case study for enhanced navigational opportunities, we have focused on the Eurasian Arctic, where the Northern Sea Route is the established Arctic marine transport system. By the 2070-2090 time slice, the navigation season in the Laptev and East Siberian Seas is projected to lengthen by an average (over the five models) of 60-90 days, although the lengthening ranges from only 10 days in the model with the smallest retreat to as much as 100 days in the model with the greatest ice retreat. In most of the model simulations, the retreating ice continues to interact with the northern tip of Severnaya Zemlya, implying a reliance on a transit route through Vilkitski Strait between the Kara and Laptev Seas.