Changes in sea ice and future accessibility along the Arctic Northeast Passage

Retreating Arctic sea ice under rapid warming is projected to continue. A new transarctic route, the Northeast Passage (NEP), may open in the near future, with considerable impacts on global shipping transportation. Comprehensive research on the past changes in sea ice in September and future accessibility along the NEP is essential. In this investigation, an unstructured-grid model was used for accurate fitting to the irregular coastal boundary, and accessibility was assessed under two different shared socioeconomic pathways (SSPs) and two vessel classes with the Arctic transportation accessibility model from 2021-2050. Significant warming was presented in the deep layer in the Arctic seas along the NEP in recent decades (1988-2016), with a distinct band on the outer edge of the abyssal zone. The positive anomaly of seawater temperature moved westward and increased notably in coastal areas, which made sea ice disappear, and the area was dominated by the negative anomaly in the last decade. The NEP is projected to be navigable for open water ships in September from 2021 to 2025, which would extend to August-October during 2025-2050 under both SSP2-4.5 and SSP5-8.5. In ad-dition, Polar Class 6 ships would be capable of crossing the NEP from August to December during 2021-2025 and from July to December during 2026-2050. The Vilkitsky Strait and Dmitrii Laptev Strait, which are close to the coast, have higher accessibility than the Shokalskiy Strait and Sannikov Strait, especially in the next five years.