Key Points

• Corrected NOAA snow records indicate Northern Hemisphere autumn snow cover is declining rather than increasing.
• The snow-loss finding strengthens evidence for snow-albedo feedback and Arctic amplification.
• Satellite hydrology studies show Arctic river runoff is changing unevenly across basins, not moving in one consistent direction.
• Freshwater delivery to the Arctic Ocean remains a major variable for sea ice, salinity, circulation, and northern ecosystems.
• Remote sensing remains essential because many Arctic regions lack dense ground-based measurements.
• Polar satellite missions continue to be used for ice-sheet mass tracking, sea-level projections, and risk planning.