Impacts of 1.5℃ global warming on hydrological conditions of navigation along the Northern Sea Route and Northwest Passage

Arctic navigability is crucial to the global economy and landscape,while there is an omission in understanding how Arctic navigability changes as a function of 1.5℃ of the Paris Agreement.This study investigated the impact of 1.5℃ global warming above the preindustrial level on sea ice conditions and accessibility of the Northern Sea Route(NSR)and Northwest Passage(NWP)with the Polar Operational Limit Assessment Risk Indexing System and new risk demarcation criteria.The Arctic is colder on the Canadian side than on the European side under 1.5℃ warming.Sea ice is mostly less than three years old,and the younger,thinner and less concentrated ice is mainly in the seas along the NSR.Ships above Polar Class(PC)6 might be unimpeded along two passages all the year.Besides,the NSR and NWP have great potential for PC6 ships in October-December,while it is only the NSR for PC7 ships.Caution is still required when navigating the western East Siberian Sea,its surrounding straits,and the Parry Channel.These changes in hydrological conditions are important for global shipping,and this work is helpful for supporting coordinated international decision-making.

Variation of sea ice and perspectives of the Northwest Passage in the Arctic Ocean

The continued warming of the Arctic atmosphere and ocean has led to a record retreat of sea ice in the last decades.This retreat has increased the probability of the opening of the Arctic Passages in the near future.The Northwest Passage(NWP)is the most direct shipping route between the Atlantic and Pacific Oceans,producing notable economic benefits.Decadal variations of sea ice and its influencing factors from a high-resolution unstructured-grid finite-volume community ocean model were investigated along the NWP in 1988-2016,and the accessibility of the NWP was assessed under shared socioeconomic pathways(SSP245 and 585)and two vessel classes with the Arctic transportation acces-sibility model in 2021-2050.Sea ice thickness has decreased with increasing seawater temperature and salinity,especially within the Canadian Arctic Archipelago(CAA)in 1988-2016,which has facilitated the opening of the NWP.Complete ship navigation is projected to be possible for polar class 6 ships in August-December in 2021-2025,after when it may extends to July under SSP585 in 2026-2030,while open water ships will not be able to pass through the NWP until September in mid-21st century.The navigability of the NWP is mainly affected by the ice within the CAA.For the accessibility of the Parry Channel,the west part is worse than that of the eastern part,especially in the Viscount-Melville Sound.

Arctic sea ice variation in the Northwest Passage in 1979-2017 and its response to surface thermodynamics factors

Sea ice conditions in the Canadian Arctic Archipelago(CAA)play a key role in the navigation of the Northwest Passage(NWP).Limited by observed sea ice thickness data,the research of temporal and spatial variation of sea ice in the NWP is insufficient.Based on the observed sea ice concentration and simulated thickness data,the temporal and spatial characteristics of sea ice concentration,extent and thickness from 1979 to 2017 in the NWP of the CAA were studied.The more specific pathways of the northern and southern routes of the NWP were evaluated.Against the background of the rapid retreat of Arctic sea ice,the 39-year observed sea ice concentration and extent of the NWP exhibited a relatively large decreasing trend in summer and fall,while heavy sea ice conditions were maintained in winter and spring,with slightly increasing trend in some subregions.The sea ice thickness in most subregions of the NWP showed a decreasing trend,with exception of Lancaster Sound.The sea ice thickness was larger along the northern route than the southern routes.The significant correlation(p<0.05)between sea ice and surface air temperature(SAT)and sea surface temperature(SST)in the NWP suggested that the surface thermodynamic factors had a greater impact on sea ice in the summer and fall,and the variations of sea ice concentration were more closely correlated with the surface thermodynamic factors than sea ice thickness.The SST had a higher correlation with sea ice concentration than SAT,while SAT exhibited a higher correlation with sea ice thickness than SST.The remaining sea ice concentration and thickness in the fall,associated with the summer and fall SAT and SST,contributed to the formation of sea ice in the following winter and spring.The heat content and mixed layer depth were also be considered as the vertical thermodynamic factors to the sea ice condition in the NWP.

Accessibility in key areas of the Arctic in the 21st mid-century

The navigation potential of the Arctic has improved with the rapid retreat of sea ice under continuous warming.The comprehensive evaluation of Arctic accessibility for low ice-breaking ships(civil use)in the mid-century is important to support coordinated international decision-making.In this study,the hydrological conditions and navigation potential in key areas and crucial straits along the Northern Sea Route(NSR)and Northwest Passage(NWP)were assessed under Shared Socioeconomic Pathways(SSPs)using the Polar Operational Limit Assessment Risk Indexing System.The results showed that the most critical areas for navigation in the mid-century(2046-2055)are the waters around the New Siberian Islands and within the Parry Channel.Arctic navigability improves from SSP1-2.6 to SSP2-4.5 to SSP5-8.5,and the accessibility for PC7 ships under SSP2-4.5 is even better for OW ships under SSP5-8.5.The route on the north side of the New Siberian Islands is a relatively good choice within the NSR,and the southern route has a better navigation potential than the Parry Channel within the NWP.In addition,the accessibility of the Dmitri Laptev Strait is better than that of the Sannikov Strait at a monthly scale,although the latter has more navigable days.However,there is little difference in accessibility between the eastern and western parts of the Parry Channel.The best nav-igation potential through the above straits is in September for ordinary ships,and the optimal time window is delayed and extended for PC7 ships.The results can serve as references for policy-making and navigation planning in the Arctic.