Future navigability of Arctic sea routes: High-resolution projections of the Arctic Ocean and Sea Ice decline

1 The rapid Arctic summer sea ice reduction in the last decade has lead to debates in the 2 maritime industries whether one could expect an increase in cargo transportation in the region. 3 After a dramatic drop in Arctic maritime transport in the 1990s and 2000s, the number of 4 vessels sailing along the Northern Sea Route (NSR) increased from 4 in 2010 to 71 in 2013, 5 before declining to 53 in 2014. Shipping data shows a reduction in average sailing time from 6 of ca. 20 days in 1990s to 11 days in 2012-2013, attributed to easing sea ice conditions along 7 the Siberian coast. However, the economic risk of exploiting the Arctic routes is substantial. It 8 lies in the uncertainty of the length of the navigation season, and in changes in sea ice and 9 ocean, and requires robust environmental predictions. Here a detailed high-resolution future 10 projection of ocean and sea ice forced with the RCP8.5 IPCC emission scenario is used to 11 examine navigability of the Arctic sea routes. In summer, opening of large areas of the 12 Arctic Ocean previously covered by pack ice to the wind and surface waves leads to the 13 Arctic pack ice cover evolving into the Marginal Ice Zone (MIZ). In winter, Arctic sea ice 14 extent decreases to 14.8 million km in the 2030s and to 8.8 million km by the end of the 21 15 century. Using the projected sea ice and ocean model data and the Arctic Transport 16 Accessibility Model, the summer season sailing times along the Arctic North Pole Route 17 (NPR) in the mid 21 century are estimated to be of 13-17 days, which makes the this route as 18 fast as the NSR. The new emerging state of the Arctic Ocean features large areas of ice-free 19 ocean, fragmented and thinner sea ice, stronger winds, ocean currents and waves. It presents 20 new challenges for resources mining and transportation in the Arctic and for forecasting. 21