Evaluation‐Constrained Projections Reveal a Potentially Navigable Arctic by the 2030s

The rapid decline in Arctic sea ice thickness (SIT) is reshaping Arctic navigation prospects. However, large uncertainties in climate model skill hinder robust projections of future navigability. Here we evaluate SIT simulated by the CMIP6 using satellite, airborne, reanalysis, and in situ data sets across freezing and melting seasons. To better constrain projections, we develop two evaluation‐based model selection schemes. We introduce the climatological concept of a potentially navigable Arctic (PNA), defined as a state in which more than 80% of the Arctic Ocean north of 60°N exhibits SIT below 0.15 m, making most of the Arctic Ocean potentially navigable for vessels with no ice class. Compared to conventional multi‐model mean, evaluation‐based schemes project thinner SIT and earlier navigability. Under both SSP2‐4.5 and SSP5‐8.5 scenarios, PNA conditions are projected to occur in the 2030s, with the number of navigable months reaching four and six by the end of the century, respectively.