Antarctic Ice Shelves Gain Mass in Summer, Not Melt—Due to Earth's Tilt

Correction: Antarctic ice shelves do not melt in summer—they accumulate ice.

❄️ Why Summer = Accumulation:

• Earth's axial tilt: In austral summer (Dec–Feb), the South Pole tilts toward the sun, but the continent's high elevation, albedo, and persistent katabatic winds keep temperatures well below freezing even at "warmest."
• Increased moisture: Warmer (relatively) air holds more moisture → heavier snowfall on coastal ice shelves.
• Net mass gain: Snow accumulation > surface melt/calving in most years/areas.

🌊 Where Melt Occurs:

• Basal melt: Warm circumpolar deep water upwells under shelves (Amundsen Sea, Bellingshausen) → thinning from below. Year-round, not seasonal.
• Peninsula: Northern Antarctic Peninsula (maritime climate) sees surface melt in summer; Larsen A/B collapse (1995/2002).

📊 Net Result:

East Antarctic shelves (Ross, Filchner-Ronne, Amery) generally gain mass. West Antarctic shelves (Thwaites, Pine Island) lose mass from below. Overall, Antarctica loses ~150 Gt/yr (net), but not from summer surface melt on shelves.