Observed Climatology and Formation Mechanisms of Sea Fog Along the Trans‐Arctic Shipping Routes

Abstract As Arctic sea ice rapidly melts, trans‐Arctic shipping routes are emerging with significant economic value and potentially reshaping global shipping patterns. The safety of ships navigating along these routes will be severely threatened by low visibility caused by Arctic sea fog. Here, we utilize ship and coastal site observations spanning 1979–2023 to investigate the climatological features and mechanisms of Arctic sea fog from June to September. We find that the Northern Sea Route (NSR, along the Russian coast) experiences a mean fog frequency of 20.0%, significantly higher than the 11.5% fog frequency observed along the Northwest Passage (NWP, along the Canadian coast). Fog frequency shows null correlation with sea ice but a strong negative correlation (−0.80) with surface air temperature. The lower mean surface air temperature in the NSR region enhances relative humidity and atmospheric stability, which are conducive to fog formation and maintenance. We further reveal that fog formation mechanisms differ between the NSR and NWP. Along the NSR, fog is usually advection fog, associated with upper boundary layer warming and moistening; in contrast, along the NWP, fog is typically radiation fog linked to near‐surface cooling. Our study highlights the distinct fog frequency and dominant mechanisms along the different trans‐Arctic shipping routes, thereby establishing observed reference for the model validation of simulating Arctic sea fog.