Antarctica's ice proves little. Desert status depends on how little precipitation arrives, not how much water already sits on the ground, which makes Earth's largest desert an immense freshwater store rather than a geographical contradiction. The distinction is simple. Across roughly fourteen million square kilometers, a continent buried in ice receives remarkably little new moisture, especially in its interior.
Cold is the gatekeeper. Because water vapor pressure falls sharply with temperature, Antarctica's frigid atmosphere can contain little moisture, leaving the high interior with less than fifty millimeters of precipitation annually, measured as liquid water. Snowfall still counts, though. Deserts commonly receive less than about 250 millimeters annually, although classification methods vary and Antarctica's coastal areas can receive substantially more snowfall than its interior. Dryness also works invisibly. Through sublimation, ice changes directly into water vapor without first melting, removing some surface snow even where temperatures remain below freezing.
Storage changes the arithmetic. Where snowfall exceeds losses, successive layers bury and compress earlier snow into ice, allowing a small annual input to build an enormous reserve because melting remains limited across much of the continent. The totals dwarf appearances. Antarctica holds about seventy percent of Earth's freshwater and roughly ninety percent of its ice, quantities that describe accumulated storage rather than present precipitation or readily available drinking water. Scarcity and abundance coexist. Beneath a sky that delivers little, the ice sheet preserves what has not yet escaped, a white vault whose contents say almost nothing about the generosity of its ceiling.
